methane-oxidizing organelle

A cytoplasmic, membrane-bounded compartment found within Methanotrophic bacteria that contains enzymes and electron transfer proteins for methane catabolism. This structure is analogous to the thylakoid of Cyanobacteria and the anammoxosome of anaerobic ammonium oxidation organisms.


cleavage apparatus septin structure

biolink:CellularComponent biolink:AnatomicalEntity biolink:OrganismalEntity biolink:BiologicalEntity biolink:NamedThing biolink:PhysicalEssence biolink:SubjectOfInvestigation biolink:ThingWithTaxon biolink:PhysicalEssenceOrOccurrent

Any of a series of structures composed of septins and septin-associated proteins localized to the cleavage plane which are involved in cytokinesis.


lytic vacuole within protein storage vacuole

A membrane-bounded compartment containing crystals of phytic acid and proteins characteristic of a lytic vacuole, found within a storage vacuole.


ciliary cap

An intracellular compartmentalized cilium structure found in insect spermatids which is bounded by a membrane derived from the invagination of the cell membrane that remains associated with the primary cilium as it is internalized. The ciliary cap is maintained at the end of the axoneme distal to the centriole and is separated from the cytosolic axoneme/cytoplasm by a putative transition zone, which may extend into the ciliary cap, and include a structure at the base of the ciliary cap termed the ring centriole.


host extracellular space

The space within a host but external to the plasma membrane of host cells, e.g. within host bloodstream.


female germline ring canal inner rim

A proteinaceous actin-rich layer of the insect ovarian ring canal that forms subcortically to the outer rim. The electron dense inner rim accumulates after the final mitotic division of each germline syncytia, and contains actin, a phosphotyrosine protein, and a number of cytoskeletal proteins.


cortical layer of collagen and cuticulin-based cuticle extracellular matrix

The cuticle layer that lies directly beneath the lipid-containing epicuticle. The cortical layer contains collagens and insoluble, non-collagenous cuticulins and is characterized by a distinct annular pattern consisting of regularly spaced annular ridges delineated by annular furrows. An example of this component is found in Caenorhabditis elegans.


ascospore-type prospore

An immature spore undergoing development. The spore usually consists of nucleic acid, prospore membrane(s) that encase the nucleic acid, and ultimately a cell wall that covers the membrane(s). This type of spore is observed in ascospore-forming fungi.


exosporium

The outermost layer of a bacterial endospore, which is loosely attached and located outside of the endospore coat. It is generally composed of protein, carbohydrate, and perhaps lipid.


mitotic actomyosin contractile ring

A cytoskeletal structure composed of actin filaments, myosin, and myosin-associated proteins that forms beneath the plasma membrane of many cells, including animal cells and yeast cells, in a plane perpendicular to the axis of the mitotic spindle, i.e. the cell division plane. Ring contraction is associated with centripetal growth of the membrane that divides the cytoplasm of the two future daughter cells. In animal cells, the mitotic contractile ring is located inside the plasma membrane at the location of the cleavage furrow. In budding fungal cells, e.g. mitotic S. cerevisiae cells, the mitotic contractile ring forms beneath the plasma membrane at the mother-bud neck before mitosis.


multiple synapse bouton

A single axon terminal bouton making contact onto two or more dendritic spines protruding either from a single dendrite or from multiple dendrites.


cellular bud membrane

The portion of the plasma membrane surrounding a cellular bud.


intracellular organelle lumen

An organelle lumen that is part of an intracellular organelle.


microbody lumen

The volume enclosed by the membranes of a microbody.


extracellular core region of desmosome

The desmosomal part containing the desmosomal cadherins, desmogleins and desmocollins, that establish contact and adhere to neighboring cells in a Ca2+-dependent manner.


amyloplast starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter, and located in amyloplasts. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


host cell wall

The rigid or semi-rigid envelope lying outside the host cell membrane of plant, fungal, and most prokaryotic cells, maintaining their shape and protecting them from osmotic lysis. In plants it is made of cellulose and, often, lignin; in fungi it is composed largely of polysaccharides; in bacteria it is composed of peptidoglycan.


plastid intermembrane space

The region between the inner and outer lipid bilayers of the plastid envelope.


mating projection tip membrane

The portion of the plasma membrane surrounding a mating projection tip.


rhabdomere microvillus membrane

The portion of the plasma membrane surrounding a microvillus of a rhabdomere.


spore inner membrane

The membrane surrounding the spore core (endospore core) that separates it from its external environment.


cell wall

The rigid or semi-rigid envelope lying outside the cell membrane of plant, fungal, most prokaryotic cells and some protozoan parasites, maintaining their shape and protecting them from osmotic lysis. In plants it is made of cellulose and, often, lignin; in fungi it is composed largely of polysaccharides; in bacteria it is composed of peptidoglycan; in protozoan parasites such as Giardia species, it's made of carbohydrates and proteins.


host cellular component

Any cellular component of a host cell. The host is an organism in which another organism, for instance a parasite or symbiont, spends part or all of its life cycle and from which it obtains nourishment and/or protection.


mitochondrial inner boundary membrane

The portion of the mitochondrial inner membrane that is not invaginated to form cristae. The inner boundary membrane lies parallel to the outer membrane.


macropinocytic cup cytoskeleton

The part of the cortical actin cytoskeleton that forms part of a macropinocytic cup.


bacterial-type flagellum basal body, MS ring

One of the rings of the bacterial-type flagellar basal body; a double-flanged ring that anchors the basal body to the cytoplasmic membrane.


pilus

A proteinaceous hair-like appendage on the surface of bacteria ranging from 2-8 nm in diameter.


pairing center

A special chromosome region located towards one end of a chromosome that contains dispersed copies of short, repetitive DNA sequences and functions as a cis-acting element essential for presynaptic homologous chromosome pairing and chromosome-nuclear envelope attachment.


nucleomorph

A small, vestigial nucleus found in some plastids that derive from a eukaryotic endosymbiont. Observed in chlorarachniophytes and cryptomonads, which acquired their plastids from a green and red alga respectively.


Gram-positive-bacterium-type cell wall

A layer of peptidoglycan found outside of the cytoplasmic membrane. The peptidoglycan is relatively thick (20-80nm) and retains the primary stain of the Gram procedure, thus cells appear blue after Gram stain. The cell walls often contain teichoic acids (acidic anionic polysaccharides) bound to the peptidoglycan. Examples of this component are found in Gram-positive bacteria.


microsporocyte nucleus

The nucleus of the microsporocyte. The microsporocyte is a diploid cell in which meiosis will occur, resulting in four microspores. A microspore is a spore that, in vascular plants, gives rise to a male gametophyte.


division septum

A cell septum which forms as part of the division site and functions in the compartmentalization of a cell into two daughter cells at division. A division septum spans a cell and does not allow exchange of organelles or cytoplasm between compartments.


ensheathing process

A cell projection (often from glial cells such as Schwann cells) that surrounds an unmyelinated axon or cell soma.


microbody

Cytoplasmic organelles, spherical or oval in shape, that are bounded by a single membrane and contain oxidative enzymes, especially those utilizing hydrogen peroxide (H2O2).


bacterial outer membrane vesicle

A spherical, bilayered proteolipid vesicle released from gram-negative bacterial outer membranes.


type I terminal bouton

Terminal inflated portion of the axon of a glutamatergic neuron, containing the specialized apparatus necessary to release neurotransmitters that will induce the contraction of muscle. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it.


fungal-type cell wall

A rigid yet dynamic structure surrounding the plasma membrane that affords protection from stresses and contributes to cell morphogenesis, consisting of extensively cross-linked glycoproteins and carbohydrates. The glycoproteins may be modified with N- or O-linked carbohydrates, or glycosylphosphatidylinositol (GPI) anchors; the polysaccharides are primarily branched glucans, including beta-linked and alpha-linked glucans, and may also include chitin and other carbohydrate polymers, but not cellulose or pectin. Enzymes involved in cell wall biosynthesis are also found in the cell wall. Note that some forms of fungi develop a capsule outside of the cell wall under certain circumstances; this is considered a separate structure.


multiple synapse bouton, contacting multiple dendrites

A single axon terminal bouton making contact onto two or more dendritic spines protruding from multiple dendrites.


host cell membrane pore complex

Any small opening in a host cell membrane that allows the passage of gases and/or liquids, composed of host proteins.


mitotic nuclear bridge midzone

The central region of a mitotic nuclear bridge, distal to the main portions of the daughter nuclei.


pellicular membrane

The portion of the plasma membrane surrounding the pellicle, a structure enclosing some parasite cells such as certain apicomplexa and Euglenozoa. These membranes are associated with an infrastructure of microtubules, microfilaments, and other organelles.


polytene chromosome ectopic fiber

A thread-like connection joining two regions of ectopically paired polytene chromosomes.


right ventral basal body

Any ciliary basal body that is part of a right ventral flagellum found in Giardia species (trophozoite stage).


microneme membrane

The lipid bilayer surrounding a microneme.


phragmoplast

The phragmoplast is a plant cell specific cytoplasmic structure composed of cytoskeletal polymers, membranes, and associated cytosolic proteins that functions as the focused secretory module for assembling the cell plate.


chloroplast inner membrane

The inner, i.e. lumen-facing, lipid bilayer of the chloroplast envelope; also faces the chloroplast stroma.


envelope

A multilayered structure surrounding all or part of a cell; encompasses one or more lipid bilayers, and may include a cell wall layer; also includes the space between layers.


ventral surface of cell

The surface of a migrating cell that is in contact with the substratum or cell layer.


glycocalyx

A carbohydrate rich layer at the outermost periphery of a cell.


micronucleus

A membrane-bounded organelle of ciliated protozoan cells that contains a diploid copy of the cell's complete genome. Sections of contiguous sequence in the macronucleus are often interrupted by internal eliminated sequences (IES), and may be permuted, in micronuclei. Genic transcription is not found in micronuclei. Some ciliate species may contain multiple micronuclei per cell.


bacterial-type flagellum basal body, proximal rod

The portion of the central rod of the bacterial-type flagellar basal body that is proximal to the cell membrane; the proximal rod connects the distal rod to the flagellar motor.


plant-type cell wall

A more or less rigid stucture lying outside the cell membrane of a cell and composed of cellulose and pectin and other organic and inorganic substances.


chrorion micropyle

A single cone-shaped specialization that forms an opening in the egg chorion that allows sperm entry into the egg prior to fertilization.


pirellulosome

A cytoplasmic structure found in bacterial phyla Planctomycetes and Verrucomicrobia containing a condensed nucleoid and ribosomes and surrounded by an intracytoplasmic membrane. It is surrounded by ribosome-free cytoplasm, in a compartment called the paryphoplasm.


dinoflagellate antapex

The anterior most point of a dinoflagellate hypocone.


glycosome

A membrane-bounded organelle found in organisms from the order Kinetoplastida that houses the enzymes of glycolysis.


plasmodesmatal cytoplasmic sleeve

The space between the plasma membrane and the desmotubule of a plasmodesma.


concave side of sperm head

The concave part of the late spermatid head or spermatozoon head that forms the ventral portion of the head, particularly in some rodent species.


microsporidian-type endospore

The middle layer in a microsporidian spore wall that lies under the exospore and outside the plasma membrane, containing chitin and proteins.


actin wave

A cellular anatomical entity that is part of the actin cytoskeleton and results in a wave-like propagation of actin networks. It consists of dynamic structures traveling on the ventral (substrate-attached) side of the cell during cell migration, cytokinesis, adhesion and neurogenesis.


type II terminal bouton

Terminal inflated portion of the axon of a non-glutamatergic neuron, containing the specialized apparatus necessary to release neurotransmitters at a regulatory synapse. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it.


periarbuscular membrane

A host-derived membrane surrounding the symbiont arbuscule during symbiosis.


dinoflagellate apex

The anterior most point of a dinoflagellate epicone.


symbiont-containing vacuole membrane

The lipid bilayer surrounding a symbiont-containing vacuole, derived from both the host and symbiont.


ciliary microtubule quartet

A set of four specialized microtubules that originates from the basal bodies and wraps around the ciliary pocket membrane, likely supporting its distinct flask shape.


scintillon

A body present in the cytoplasm of some dinoflagellates, which is the source of bioluminescence; emits light on acidification in the presence of oxygen.


P3 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P3 peroxisomes are formed by fusion of P1 and P2 peroxisomes, and are distinguished from the other subforms on the bases of buoyant density and protein content.


surface coat of collagen and cuticulin-based cuticle extracellular matrix

An electron dense, amorphous envelope that comprises the outermost layer of the cuticle. The surface coat is loosely apposed to the epicuticle, has distinct biochemical properties, is synthesized by cells other than the underlying hypodermis, and is labile. In addition to serving as a lubricant to protect against abrasion and dehydration, the surface coat may also play important roles in infection and immune evasion. An example of this component is found in Caenorhabditis elegans.


nuclear envelope adjacent to nuclear pore complex

The region of the nuclear envelope situated in close proximity to a nuclear pore complex.


rod photoreceptor disc lumen

The volume enclosed by the membrane of a rod photoreceptor cell disc membrane.


leaflet of membrane bilayer

Any of the two layers of lipid molecules that constitute a membrane.


host cell endomembrane system

A collection of membranous structures involved in transport within the host cell. The main components of the endomembrane system are endoplasmic reticulum, Golgi bodies, vesicles, cell membrane and nuclear envelope. Members of the endomembrane system pass materials through each other or though the use of vesicles. The host is defined as the larger of the organisms involved in a symbiotic interaction.


extrinsic component of periplasmic side of cell outer membrane

The component of the cell outer membrane consisting of gene products and protein complexes that are loosely bound to periplasmic surface, but not integrated into the hydrophobic region.


nucleus leading edge

The area of a motile nucleus closest to the direction of movement.


dendritic knob

The terminal swelling of an apical dendrite of a ciliated olfactory receptor neuron. Each knob gives rise to 5 to 20 long delicate nonmotile cilia, which extend into the mucus covering the sensory epithelium.


chloroplast stroma

The space enclosed by the double membrane of a chloroplast but excluding the thylakoid space. It contains DNA, ribosomes and some temporary products of photosynthesis.


perforation plate

A cell wall part that is the part of a wall of a vessel member and bears one or more openings (perforations).


pathogen-containing vacuole lumen

The enclosed volume within the sealed membrane of a pathogen-containing vacuole.


sperm glycocalyx

The carbohydrate rich layer at the outermost periphery of a sperm cell.


type I pilus

A short filamentous structure on the surface of a bacterial cell distinguished from other pili by their D-mannose-sensitive agglutinatination of erythrocytes. In E. coli, type I pili consist of a short tip fibrillum made up of the adhesin protein (FimH) and two minor subunits (FimG and FimF) that is joined to the pilus rod, a homopolymer of ~1000 FimA subunits.


amyloplast membrane

Either of the lipid bilayers that surround an amyloplast and form the amyloplast envelope.


polytene chromosome weak point

A region of the polytene chromosome where the diameter is considerably decreased, probably resulting from local differences in chromosome organization.


cyanelle stroma

The space enclosed by the double membrane of a cyanelle.


chloroplast membrane

Either of the lipid bilayers that surround a chloroplast and form the chloroplast envelope.


cluster of actin-based cell projections

A cell part consisting of multiple, closely packed actin-based cell projections.


proplastid stroma

The space enclosed by the double membrane of a proplastid.


ciliary shaft

The mid part of a cilium between the ciliary base and ciliary tip that extends into the extracellular space.


intracellular immature spore

A cell or part of the cell that constitutes an early developmental stage of a spore, a small reproductive body that is highly resistant to desiccation and heat and is capable of growing into a new organism, produced especially by certain bacteria, fungi, algae, and nonflowering plants.


rhoptry

A large, club-shaped secretory organelle that forms part of the apical complex of an apicomplexan parasite, and consists of a bulbous body and a narrow electron-dense neck that extends through the conoid at the apical tip of the parasite. The rhoptry necks serve as ducts through which the contents of the rhoptries are secreted after attachment to the host has been completed and at the commencement of invasion. Rhoptry proteins function in the biogenesis and host organellar association of the parasitophorous vacuole.


cortical endoplasmic reticulum lumen

The volume enclosed by the membranes of the cortical endoplasmic reticulum.


gerontoplast stroma

Any plastid stroma that is part of a gerontoplast.


spindle pole body

The microtubule organizing center in fungi; functionally homologous to the animal cell centrosome.


pilus tip

The pointed extremity furthest from the cell of a pilus.


subpellicular network

A mechanically stable cytoskeletal structure associated with the cytoplasmic face of the pellicle and surrounding the microtubule-based cytoskeleton.


hydrogenosome lumen

The volume enclosed by the hydrogenosome membrane.


intermediate layer of spindle pole body

Structure between the central and outer plaques of the spindle pole body.


primary cell wall

A plant cell wall that is still able to expand, permitting cell growth. Primary cell walls contain more pectin than secondary walls and no lignin is present.


S-layer

A crystalline protein layer surrounding some bacteria.


half bridge of spindle pole body

Structure adjacent to the plaques of the spindle pole body.


glycoprotein network

An extracellular matrix part that consists of cross-linked glycoproteins.


acidocalcisome

An electron-dense acidic membrane-bounded organelle which contains a matrix of pyrophosphate and polyphosphates with bound calcium and other cations.


endoplasmic reticulum cisternal network

A subcompartment of the endoplasmic reticulum consisting of flattened, disc-shaped domains known as cisternae. These are typically found close to the nucleus and are generally more prominent in secretory cells.


host cell junction

A plasma membrane part that forms a specialized region of connection between two host cells or between a host cell and the host extracellular matrix. At a host cell junction, anchoring proteins extend through the host plasma membrane to link cytoskeletal proteins in one cell to cytoskeletal proteins in neighboring cells or to proteins in the extracellular matrix.


outer plaque of spindle pole body

One of three laminate structures that form the spindle pole body; the outer plaque is in the cytoplasm.


plastid membrane

Either of the lipid bilayers that surround a plastid and form the plastid envelope.


host cell late endosome membrane

The lipid bilayer surrounding a host cell late endosome.


chloroplast starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter, and located in chloroplasts. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


endexine

The inner part of the exine, which stains.


acroblast

A cone-shaped structure in the head of a spermatozoon, which is formed by the coalescence of Golgi fragments following the completion of meiosis. The acroblast is situated adjacent to the acrosomal vesicle.


haustorium

A projection from a cell or tissue that penetrates the host's cell wall and invaginates the host cell membrane.


organelle

Organized structure of distinctive morphology and function. Includes the nucleus, mitochondria, plastids, vacuoles, vesicles, ribosomes and the cytoskeleton, and prokaryotic structures such as anammoxosomes and pirellulosomes. Excludes the plasma membrane.


inner plaque of mitotic spindle pole body

One of three laminate structures that form the mitotic spindle pole body; the inner plaque is in the nucleus.


extraorganismal space

The environmental space outside of an organism; this may be a host organism in the case of parasitic and symbiotic organisms.


cofilin-actin rod

A cellular structure consisting of parallel, hexagonally arranged actin tubules, comprising filamentous actin and disulfide cross-linked cofilin multimers.


pectic matrix

The gel-like pectin matrix consists of the interlinked acidic and neutral pectin networks that are further cross-linked by calcium bridges. Pectins consist largely of long chains of mostly galacturonic acid units (typically 1,4 linkages and sometimes methyl esters). Three major pectic polysaccharides (homogalacturonan, rhamnogalacturonan I and rhamnogalacturonan II) are thought to occur in all primary cell walls.


bounding membrane of organelle

The lipid bilayer that forms the outer-most layer of an organelle.


acidocalcisome membrane

The lipid bilayer surrounding an acidocalcisome.


organellar chromatophore intermembrane space

The region between the inner and outer lipid bilayers that surround an organellar chromatophore.


type Is terminal bouton

Terminal inflated portion of the axon of a glutamatergic neuron, containing the specialized apparatus necessary for the phasic release neurotransmitters that will induce the contraction of muscle. Type Is terminal boutons are smaller than type Ib terminal boutons.


plasmodesmatal plasma membrane

The portion of the plasma membrane surrounding a plasmodesma.


basal labyrinth

A region in the lower half of some cells formed from extensive infoldings of the basal plasma membrane; includes cytoplasm adjacent to the infolded membrane.


basal layer of collagen and cuticulin-based cuticle extracellular matrix

The layer of cuticle most closely apposed to the hypodermal cells. The morphology of the basal layer varies with life stage. In adult C. elegans animals, the basal layers is comprised of three sublayers: two fibrous layers whose fibers run in clockwise and counter-clockwise directions meeting one another at a 60 degree angle, and an amorphous basal layer that lies underneath the fibrous layers and directly contacts the hypodermis. In C. elegans dauer and L1 larval stage animals, the basal layer is characterized by a striated pattern that appears to derive from interwoven laminae. An example of this component is found in Caenorhabditis elegans.


macronucleus

A membrane-bounded organelle of ciliated protozoan cells that contains polyploid copies of a portion of the cell's complete genome. Transcription of genes occurs in macronuclei. Some ciliate species may contain multiple macronuclei per cell.


ventral disc crossbridge

Structure horizontally linking adjacent microribbons of the ventral disc in Giardia species (trophozoite stage). The composition of crossbridges is not fully known yet.


host cell rough endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell rough endoplasmic reticulum.


host cell endosome membrane

The lipid bilayer surrounding a host cell endosome.


cyanelle intermembrane space

The region between the inner and outer lipid bilayers of the cyanelle envelope; includes the peptidoglycan layer.


longitudinal side of cell surface

The side of the cell parallel to the zygotic axis.


metaphase plate

The intracellular plane, located halfway between the poles of the spindle, where chromosomes align during metaphase of mitotic or meiotic nuclear division.


tectum

The layer of sexine which forms a roof over the columella, granules or other infratectal elements.


type IV pilus

A short filamentous structure on the surface of a bacterial cell distinguished from other pili by post-translational N-methylation of the pilin monomers.


lysosomal glycocalyx

The polysaccharide-based coating on the inner side of a lysosomal membrane. It may be involved in protecting the membrane from digestion by lysosomal enzymes.


fusome

A large intracellular spectrin-rich structure that has been found in insect germline cells and mammalian hematopoietic cells. The fusome is an elongated, branched structure, formed from the spherical spectrosome organelle.


periplasmic space

The region between the inner (cytoplasmic) and outer membrane (Gram-negative Bacteria) or cytoplasmic membrane and cell wall (Fungi and Gram-positive Bacteria).


left tetrad

Set of four basal bodies found in Giardia species (trophozoite stage). It comprises the left lateral basal body pair and the left middle basal body pair (i.e. the anterior, ventral, caudal and posteriolateral basal bodies located to the right of the left nucleus of the trophozoite when viewed dorsally).


cyanelle membrane

Either of the lipid bilayers that surround a cyanelle and form the cyanelle envelope.


bacterial-type flagellum motor

A transmembrane complex embedded in the cytoplasmic membrane which is the motor force, or torque, generator of the bacterial-type flagellum. The motor consists of a membrane-anchored rotor complex surrounded by one or more stator complexes in the cytoplasmic membrane. The stator consists of a hetero-hexameric complex of 2 membrane proteins, A and B, with stoichiometry A4B2. Examples are the H+ driven MotA-MotB stator complex of Escherichia coli and Salmonella enterica, and the Na+ driven PomA-PomB stator complex of Vibrio and Shewanella species. The rotor complex consists of a membrane-anchored ring and the motor switch complex, which controls the direction of flagellar rotation.


extrachromosomal DNA

DNA structures that are not part of a chromosome.


host cell postsynaptic membrane

A postsynaptic membrane that is part of a host cell. A postsynaptic membrane is a specialized area of membrane facing the presynaptic membrane on the tip of the nerve ending and separated from it by a minute cleft (the synaptic cleft). Neurotransmitters transmit the signal across the synaptic cleft to the postsynaptic membrane.


mating projection tip

The apex of the mating projection in unicellular fungi exposed to mating pheromone; site of polarized growth.


spindle envelope

An organelle envelope that surrounds the chromosomes and the central part of the spindle apparatus during mitosis and meiosis; observed in many invertebrates. The spindle envelope consists of membrane layers, called parafusorial membranes, derived from endoplasmic reticulum membrane; in male meiosis it forms during prometaphase and persists until early in the ensuing interphase.


non-growing cell tip

A cell tip at which no growth takes place. For example, in fission yeast the cell end newly formed by cell division does not grow immediately upon its formation, and lacks actin cytoskeletal structures.


starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


host cell smooth endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell smooth endoplasmic reticulum.


photoreceptor proximal connecting cilium

The proximal region of the photoreceptor connecting cilium is similar to the transition zone of unspecialized primary cilia and houses several major transition zone complexes, including NPHP, MKS, and RPGR.


Woronin body

Peroxisome-derived dense-core vesicle that seals septal pores upon hyphal lysis to prevent excessive cytoplasmic loss. It is specific to several genera of filamentous ascomycetes.


meiotic spindle pole body

The microtubule organizing center that forms as part of the meiotic cell cycle; functionally homologous to the animal cell centrosome.


Isp3 layer of spore wall

The outermost layers of the spore wall, as described in Schizosaccharomyces pombe.


spine mat

A configuration of neuron spines found on ciliary ganglion neurons in the embryonic and adult brain consisting of patches of closely spaced spines lying flat against the soma.


DIM/DIP cell wall layer

A section of the Actinobacterium-type cell wall composed of (phenyl)phthiocerol, phthiodiolone, phthiotriol dimycocerosate, diphthioceranate and other compounds.


ciliary pro-basal body

The cilary pro-basal body is an immature, partially assembled form of a ciliary basal body found next to the basal body of a cilium. Pro-basal bodies are not capable of nucleating a cilium. As the cell progresses through the cell cycle, continuing assembly will convert the pro-basal body into a mature basal body that is capable of nucleating a cilium.


plastid stroma

The proteinaceous ground substance of plastids.


rhoptry lumen

The volume enclosed by the rhoptry membrane.


plasma membrane respirasome

A respiratory chain located in the plasma membrane of a cell; made up of the protein complexes that form the electron transport system (the respiratory chain), associated with the plasma membrane. The respiratory chain complexes transfer electrons from an electron donor to an electron acceptor and are associated with a proton pump to create a transmembrane electrochemical gradient.


left posteriolateral basal body

Any ciliary basal body that is part of a left posteriolateral flagellum found in Giardia species (trophozoite stage).


dendriole

Small dendrites that makes up a brush structure found as the terminal specialization of a dendrite of a unipolar brush cell (UBC).


plasma membrane of growing cell tip

Any plasma membrane part that is part of a growing cell tip.


spongiome

A cellular anatomical entity which is a network of tubules and vessicles and is part of the contractile vacuole complex. It is involved in the discharge of water externally. One of its functions is osmoregulatory.


Golgi stack lumen

The volume enclosed by any of the membranes of the thin, flattened cisternae that form the central portion of the Golgi complex.


antipodal cell nucleus

The nucleus of an antipodal cell, one of three cells of the embryo sac in angiosperms, found at the chalazal end of the embryo away from the point of entry of the pollen tube, and its descendents.


pollen wall

The wall surrounding a mature pollen grain; a multilayered structure consisting of a pectocellulosic intine surrounded by a sporopollenin-based exine, which itself contains two layers, the inner nexine and the outer sexine.


host cell part

Any constituent part of a host cell. The host is defined as the larger of the organisms involved in a symbiotic interaction.


cellular bud tip

The end of a cellular bud distal to the site of attachment to the mother cell.


slime layer

A slime layer is an easily removed, diffuse, unorganized layer of extracellular material that surrounds a cell. Specifically this consists mostly of exopolysaccharides, glycoproteins, and glycolipids.


DNA replication termination region

A chromosomal region that contains fork pausing elements influencing the progression and merging of DNA replication forks.


host cell envelope

An envelope that surrounds a bacterial host cell and includes the host cytoplasmic membrane and everything external, encompassing the host periplasmic space, host cell wall, and host outer membrane if present.


satellite fibril

An axoneme part that is found in the flagella of mammalian sperm and is located in the middle piece between the outer dense fibers (on the concave side of outer dense fibers as seen in cross-section).


chitosan layer of spore wall

The second outermost layer of the spore wall, as described in Saccharomyces.


presynaptic grid

A hexagonal array of electron dense particles attached to the cytoplasmic face of the presynaptic membrane.


ciliary pocket collar

A constriction site at the junction of the plasma, flagellar and flagellar pocket membranes where the flagellum emerges from the cell body. Observed in some unicellular eukaryotic species such as Chlamydomonas, Giardia and Trypanosoma.


rod bipolar cell terminal bouton

A specialized region of the axon terminus portion of a rod bipolar axon. A rod bipolar cell is a neuron found in the retina and having connections with rod photoreceptor cells and neurons in the inner plexiform layer.


vascular endothelial glycocalyx

The carbohydrate-rich layer lining the vascular endothelium connected to the endothelium through a variety of molecules, mainly proteoglycans and glycoproteins. These form a network in which soluble molecules, either plasma- or endothelium-derived, are incorporated.


host cell membrane

Double layer of lipid molecules as it encloses host cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins. The host is defined as the larger of the organisms involved in a symbiotic interaction.


capsule

A protective structure surrounding some fungi and bacteria, attached externally to the cell wall and composed primarily of polysaccharides. Capsules are highly organized structures that adhere strongly to cells and cannot be easily removed. Capsules play important roles in pathogenicity, preventing phagocytosis by other cells, adherance, and resistance to dessication.


bacterial-type flagellum hook-filament junction

The region of the bacterial-type flagellum where the hook and filament meet.


C bouton

Synaptic bouton found in spinal cord on the soma and proximal dendrites of motor neurons.


plastid thylakoid lumen

The volume enclosed by a plastid thylakoid membrane.


sporoplasm

The complex infective apparatus corresponding to the central mass of cytoplasm within a spore that is injected into a host cell by various parasitic microorganisms.


nexine

The inner, non-sculptured part of the exine which lies below the sexine.


ring centriole

A ring-like structure observed at the base of the ciliary cap of insect spermatids. This structure may anchor the axoneme to the ciliary cap membrane and/or act as a diffusion barrier, proposed to be analogous to the annulus of mammalian sperm flagellum.


meiotic actomyosin contractile ring

A cytoskeletal structure composed of actin filaments, myosin, and myosin-associated proteins that forms beneath the plasma membrane of many cells, including animal cells and yeast cells, in a plane perpendicular to the axis of the meiotic spindle, i.e. the cell division plane. Ring contraction is associated with centripetal growth of the membrane that divides the cytoplasm of the two future daughter cells. In animal cells, the meiotic contractile ring is located inside the plasma membrane at the location of the cleavage furrow. In fungal cells, the meiotic contractile ring forms beneath the plasma membrane of the prospore envelope in preparation for completing cytokinesis.


stromule

Thin filamentous structure extending from the surface of all plastid types examined so far, including chloroplast, proplastid, etioplast, leucoplast, amyloplast, and chromoplast. In general, stromules are more abundant in tissues containing non-green plastids, and in cells containing smaller plastids. The primary function of stromules is still unresolved, although the presence of stromules markedly increases the plastid surface area, potentially increasing transport to and from the cytosol. Other functions of stromules, such as transfer of macromolecules between plastids and starch granule formation in cereal endosperm, may be restricted to particular tissues and cell types.


ventral disc lateral crest

Fibrillar repetitive structure surrounding the ventral disc edge in Giardia species (trophozoite stage). The composition of the lateral crest is not fully known yet.


prospore membrane leading edge

The region of the prospore membrane that extends to surround the spore nucleus; coated with specific proteins that are thought to play a role in prospore membrane organization.


smooth muscle dense body

Electron-dense region associated with a smooth muscle contractile fiber.


unicellular trichome branch

A cell projection part that is a branch of a unicellular trichome.


peptidoglycan-based cell wall

A protective structure outside the cytoplasmic membrane composed of peptidoglycan (also known as murein), a molecule made up of a glycan (sugar) backbone of repetitively alternating N-acetylglucosamine and N-acetylmuramic acid with short, attached, cross-linked peptide chains containing unusual amino acids. An example of this component is found in Escherichia coli.


An organelle arrangement comprised of the following elements: a mitochondrion positioned near the presynaptic membrane; an electron-dense mitochondrial plaque adjacent to the outer mitochondrial membrane that faces the presynaptic membrane; filament-like elements appearing to link the mitochondrial plaque to a cell-cell junction region (sometimes termed punctum adherens); tubular or vesicular-appearing membrane (also called vesicular chain) interposed among the filaments. Mitochondrion-associated adherens complexes were initially described in the dorsal horn of the spinal cord. They are found in calyces and other large terminals of the auditory brainstem, and in a variety of mammalian species including humans.


mitochondrial intracristal space

The space bounded by the mitochondrial cristae membranes, continuous with the intermembrane space.


attachment organelle

A membrane-bounded extension of the cell, originally characterized in Mycoplasma species, that contains an electron-dense core that is part of the cytoskeleton and is oriented lengthwise and ends distally in a bulbous knob (terminal button). Required for adherence to host cells and involved in gliding motility and cell division.


cell septum edging

The cell wall material that surrounds the septum in fungal cells.


external encapsulating structure

A structure that lies outside the plasma membrane and surrounds the entire cell or cells. This does not include the periplasmic space.


ventral disc dorsal microribbon

Trilaminar structure extending perpendicularly into the cytoplasm along the length of ventral disc microtubules in Giardia species (trophozoite stage). Constituents of dorsal microribbons (also called dorsal ribbons or microribbons) include alpha-coiled-helix proteins approximately 29 to 38 kDa in size. These proteins line the edges of the microribbons but are not found in microtubules. Tubulins are not found in microribbons.


porosome

A permanent cup-shaped structure at the cell plasma membrane in secretory cells. Following a secretory stimulus, secretory vesicles transiently dock and fuse at the base of porosomes and release intravesicular contents dictated by the turgor pressure generated from the swelling of secretory vesicles.


organelle lumen

The internal volume enclosed by the membranes of a particular organelle; includes the volume enclosed by a single organelle membrane, e.g. endoplasmic reticulum lumen, or the volume enclosed by the innermost of the two lipid bilayers of an organelle envelope, e.g. nuclear lumen.


left middle basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the caudal and posteriolateral basal bodies located to the right of the left nucleus of the trophozoite when viewed dorsally.


median body

A non-membrane bound, semi-organized microtubule array of unknown function found in Giardia species (trophozoite stage). It is located on the dorsal side of the trophozoite, slightly posterior to the ventral disc.


mononeme

A secretory organelle that forms part of the apical complex; a small, threadlike structure located is close proximity to the subpellicular microtubules. Its contents include a rhomboid protease (PfROM1 in Plasmodium falciparum) that moves from the lateral asymmetric localization to the merozoite apical pole and the posterior pole upon release of merozoites from schizonts.


glyoxysome

A specialized form of peroxisome that contains the enzymes of the glyoxylate pathway. The glyoxysome is found in some plant cells, notably the cells of germinating seeds.


preprophase band

A dense band of microtubules, 1-3 pm wide, that appears just beneath the cell membrane before the start of cell division in the cells of higher plants. It precedes the onset of prophase and then disappears as mitosis begins, yet it somehow determines the plane of orientation of the new cell plate forming in late telophase and marks the zone of the parental cell wall where fusion with the growing cell plate ultimately occurs.


inner plaque of spindle pole body

One of three laminate structures that form the spindle pole body; the inner plaque is in the nucleus.


mating projection septin band

A septin band, i.e. a diffuse ring composed of a series of septin bars running parallel to the long axis of the cell, located at the neck of a shmoo (mating projection).


phagocytic cup base

The older part of the phagocytic cup where the actin cytoskeleton disassembles, allowing early incoming and outgoing vesicular trafficking.


apical complex

A group of cytoskeletal structures and associated membrane-bounded organelles found at the anterior end of adult obligate intracellular protozoan parasites in the phylum Apicomplexa. The apical complex is involved in attachment to and penetration of the host cell, and in parasite proliferation.


ocelloid

Eye-like subcellular structure found in dinoflagellates (a large group of single-celled eukaryotes). Consists of subcellular analogues to a cornea, lens, iris, and retina. Ocelloids are built from pre-existing organelles, including a cornea-like layer made of mitochondria and a retinal body made of anastomosing plastids.


exoneme

A dense granule-like organelle of the apical complex of merozoites, released into the parasitophorous vacuole, mediating protease-dependent rupture and parasite exit from the infected erythrocyte.


hyphal membrane

A host-derived membrane surrounding the symbiont hypha during infection.


bacterial-type flagellum filament cap

The proteinaceous structure at the distal tip of the bacterial-type flagellar filament.


magnetosome lumen

The volume enclosed by the membrane of a magnetosome.


primary cell septum

A cell septum that forms following nuclear division.


subplasmalemmal coating

Electron dense material observed coating the cytoplasmic face of the plasma membrane in certain regions of a neuron, e.g., the axon initial segment; the nodal membrane at the Node of Ranvier.


medial cortical node

A component of the cell division site that contains the mid1, cdr2, wee1, klp8, and blt1 proteins, and is involved in contractile ring localization. Medial cortical node complexes appear as cortical dots in the middle of the cell during interphase, and function to recruit other ring components in early mitosis.


reservosome matrix

A matrix composed of planar membranes, vesicles and lipid inclusions within the reservosome.


cortical dynamic polarity patch

A region of the cell cortex that contains a higher concentration of growth polarity factors than the surrounding cortex and that changes position over time. An example is found in fission yeast cells during early mating, in which the GTPase Cdc42 dynamically to discrete zones within the cortex prior to shmoo formation.


centrosomal core

The core region of the centrosome, a layered structure containing proteins, surrounded by the centrosomal corona. The core duplicates once per cell cycle at the G2/M transition when two outer layers form the mitotic spindle poles.


stereocilia coupling link

A structure involved in coupling stereocilia to one another in sensory hair cells There are four morphologically distinct types: tip links, horizontal top connectors, shaft connectors and ankle links. Tip links and horizontal top connectors are the only inter-stereocilia links associated with mature cochlea, whereas ankle links appear during development of the auditory hair bundle.


outer dense plaque of desmosome

The desmosomal part containing plakoglobins, plakophilins, the N-termini of desmoplakins, as well as the cytoplasmic tails of the desmosomal cadherins, which together attach the plaque to the plasma membrane.


organellar chromatophore thylakoid lumen

The volume enclosed by an organellar chromatophore thylakoid membrane.


etioplast membrane

Either of the lipid bilayers that surround a etioplast and form the etioplast envelope.


hyphal cell wall

The cell wall surrounding a fungal hypha.


host intracellular region

That space within the plasma membrane of a host cell.


retrotransposon nucleocapsid

A complex of the retrotransposon RNA genome, reverse transcriptase, integrase, and associated molecules required for reproduction and integration of the retrotransposon into the host genome; the main structural molecule of the nucleocapsid is often a gag protein homolog.


mitochondrial membrane scission site

The site on the mitochondrial membrane where the separation of a single continuous mitochondrial membrane into two membranes occurs as a final step in mitochondrial fission.


acidocalcisome lumen

The volume enclosed by the membranes of an acidocalcisome.


basolateral cytoplasm

The region of the cytoplasm located at the basolateral side of the cell. Used in reference to animal polarized epithelial cells.


deep fiber

Inward projections of the cytoskeletal structures of the oral apparatus, which form a fiber that extends past the cytostome into the cytoplasm.


plant-type vacuole lumen

The volume enclosed within the vacuolar membrane of a vacuole that retains the same shape regardless of cell cycle phase. An example of this is found in Arabidopsis thaliana.


bacterial-type flagellum secretion apparatus

A part of the bacterial-type flagellum that is located at the cytoplasmic side of the MS ring and composed of six membrane proteins (FlhA, FlhB, FliP, FliQ, FliR, and FliO, or orthologs thereof) and three soluble proteins (FliI, FliH, and FliJ, or orthologs thereof) in the cytoplasm. It is responsible for secretion of flagellar type III protein substrates, including the proteins of the flagellar rod, hook, and filament.


annuli extracellular matrix

The extracellular matrix that is a regularly spaced circumferential ridge present in the cortical region of the cuticle. Annuli are delineated by annular furrows and are present throughout the cuticle with the exception of lateral regions where longitudinal alae are present.


basal pole of outer hair cell

The end of the outer hair cell which receives and transmits neural signals.


arbuscule

Highly branched symbiont haustoria within host root cortex cells, responsible for nutrient exchange.


host peribacteroid fluid

The soluble material inside the peribacteroid membrane, but outside of the bacteroid, within a bacteroid-containing symbiosome of a host cell.


plasma membrane of cell tip

The portion of the plasma membrane surrounding the cell tip.


apoptotic body

A vesicle containing parts of a dying cell. Apoptotic bodies can be formed during the execution phase of the apoptotic process, when the cell's cytoskeleton breaks up and causes the membrane to bulge outward. These bulges may separate from the cell, taking a portion of cytoplasm with them, to become apoptotic bodies. These are then engulfed by phagocytic cells, and their components recycled. Apoptotic bodies may range in size from 0.8 to 5um.


host cell endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell endoplasmic reticulum.


mitotic nuclear bridge midzone membrane domain

A nuclear membrane part at the midzone of the mitotic nuclear bridge. The midzone forms a bulge that is enriched in nuclear pores that lack baskets.


microbody membrane

The lipid bilayer surrounding a microbody.


right anterior basal body

Any ciliary basal body that is part of a right anterior flagellum found in Giardia species (trophozoite stage).


extrinsic component of cell outer membrane

The component of the cell outer membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.


central cylinder

A scaffolding structure present within the inner region of the ciliary transition zone. The central cylinder lies between the outer doublet and inner singlet microtubules.


polar nucleus

Either of two nuclei located centrally in a flowering plant embryo sac that eventually fuse to form the endosperm nucleus.


mitotic actomyosin contractile ring, proximal layer

The region of the mitotic actomyosin ring adjacent to the plasma membrane where membrane bound scaffolds are located.


mating projection actin fusion focus

A focus at the mating projection tip where the cell wall is degraded during conjugation with cellular fusion. Actin filaments form an aster-like structure from this location.


external side of cell wall

The side of the cell wall that is opposite to the side that faces the cell and its contents.


early recombination nodule

An electron dense structure that is associated with meiotic chromosomes in leptotene or zygotene during meiosis I.


bacterial-type flagellum basal body, distal rod, L ring

One of the rings of the bacterial-type flagellar basal body; anchors the basal body to the outer membrane.


right posteriolateral basal body

Any ciliary basal body that is part of a right posteriolateral flagellum found in Giardia species (trophozoite stage).


gut granule lumen

The lumen of a gut granule, a lysosome-related organelle contained within the intestinal cells of the nematode C. elegans.


protein storage vacuole lumen

The volume enclosed by the protein storage vacuole membrane.


plasmodesmatal desmotubule

A tightly wound cylinder of membrane that is located within the plasmodesmal pore and runs the length of the plasmodesma. The desmotubule likely provides a rigid stability to plasmodesmata and confers a fixed diameter and pore size to the plasmodesmal canal, and is linked to the endoplasmic reticulum in each of the adjacent cell.


smooth endoplasmic reticulum lumen

The volume enclosed by the membranes of the smooth endoplasmic reticulum.


sexine

The outer, sculptured layer of the exine, which lies above the nexine.


septal periplasm

The region between the plasma membrane and the cell wall, as found in organisms such as filamentous fungi.


noradrenergic synapse

A synapse that uses noradrenaline as a neurotransmitter.


symplast

The interconnected cell membranes and intracellular regions of a plant. The interconnections occur via the plasmodesmata.


endoplasmic reticulum subcompartment

A distinct region of the endoplasmic reticulum.


xanthophore

A chromatophore containing yellow pigment.


secondary cell septum

Cell wall structures composed of linear polysaccharides which are deposited at both sides of the primary septum at 90 degrees to the primary septum.


mitotic nuclear bridge stalk

Either of the regions of a mitotic nuclear bridge proximal to the main portion of each daughter nucleus. The nuclear envelope in the stalk regions is depleted of nuclear pore complexes.


right nucleus

One of the two nuclei found in Giardia species (trophozoite stage). It is located on the right side of the cell when viewed from the dorsal side.


dityrosine layer of spore wall

The outermost layer of the spore wall, as described in Saccharomyces.


yolk

The cytoplasmic part that serves as a nutrient reserve or energy source for the developing embryo.


basal ring of apical complex

An electron dense ring at the most posterior position of the apical complex, from which the subpellicular microtubules originate; formed during an invasive life cycle stage of an apicomplexan parasite.


chromoplast intermembrane space

The region between the inner and outer lipid bilayers of a chromoplast envelope.


basal pole of neuron

Portion of a neuron cell soma closest to the point where the basilar dendrite emerges.


rough endoplasmic reticulum cisterna

A subcompartment of the rough endoplasmic reticulum consisting of lumenal expansion into a flattened, disc-shaped cavity.


mitotic actomyosin contractile ring, distal actin filament layer

The region of the mitotic actomyosin ring containing actin filaments and cross linkers, myosin motors, and connections to the plasma membrane through the intermediate layer. It is further from the plasma membrane than the intermediate layer which it is adjacent to.


organelle envelope lumen

The region between the inner and outer lipid bilayers of an organelle envelope.


dendritic branch point

The part of a dendritic tree where it branches, giving rise to a dendritic branch.


fungal-type vacuole lumen

The volume enclosed within the vacuolar membrane of a vacuole, the shape of which correlates with cell cycle phase. An example of this structure is found in Saccharomyces cerevisiae.


prospore membrane spindle pole body attachment site

The region of the prospore membrane to which the spindle pole body (SPB) is anchored; the prospore membrane extends from the SPB attachment site to surround the spore nucleus.


right middle basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the caudal and posteriolateral basal bodies located to the left of the right nucleus of the trophozoite when viewed dorsally.


medial layer of collagen and cuticulin-based cuticle extracellular matrix

The fluid-filled cuticle layer that lies between the cortical and basal layers and is characterized by the presence of regularly spaced columnar struts that lie on either side of the annular furrows and link the two surrounding layers. In C. elegans, a defined medial layer is found only in adult animals.


cell septum

A structure composed of peptidoglycan and often chitin in addition to other materials. It usually forms perpendicular to the long axis of a cell or hypha and grows centripetally from the cell wall to the center of the cell and often functions in the compartmentalization of a cell into two daughter cells.


host cell presynaptic membrane

A specialized area of membrane of the host axon terminal that faces the plasma membrane of the host neuron or muscle fiber with which the axon terminal establishes a synaptic junction; many host synaptic junctions exhibit structural presynaptic characteristics, such as conical, electron-dense internal protrusions, that distinguish it from the remainder of the axon plasma membrane.


somatic ring canal

A stable intercellular bridge between somatic cells. Examples include the intercellular bridges between ovarian follicle cells in insects and between imaginal disc cells in insects.


type III terminal bouton

Terminal inflated portion of the axon of a non-glutamatergic neuron, containing the specialized apparatus necessary to release neurotransmitters at a regulatory synapse. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it. Type III terminal boutons are larger than type II ones.


bacterial extracellular vesicle

Small membrane vesicle (< 1 um) that buds off a prokaryotic cell plasma membrane, able to carry proteins, phospholipids, lipopolysaccharides, nucleic acids, viruses, and more. Important in intercellular communication and pathogenesis; can exist within host cells.


dinoflagellate antapical horn

A horn-shaped dinoflagellate antapex found in thecate species.


epicuticle of collagen and cuticulin-based cuticle extracellular matrix

A lipid-containing layer of cuticle that lies between the cortical layer and the surface coat. An example of this component is found in Caenorhabditis elegans.


muscle cell postsynaptic specialization

A postsynaptic specialization that is part of a neuromuscular junction.


right lateral basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the anterior and ventral basal bodies located to the left of the right nucleus of the trophozoite when viewed dorsally.


sperm individualization complex

A macromolecular complex that includes cytoskeletal components and part of the cell membrane. Forms at the nuclear end of a male germline syncytium, or cyst, and translocates the over the length of the syncytium in the course of sperm individualization. Each complex contains an array of 64 investment cones, one per nucleus, that move synchronously along the spermatogenic cyst.


chloroplast thylakoid lumen

The cavity enclosed within the chloroplast thylakoid membrane. An example of this component is found in Arabidopsis thaliana.


cell envelope

An envelope that surrounds a bacterial cell and includes the cytoplasmic membrane and everything external, encompassing the periplasmic space, cell wall, and outer membrane if present.


curli

A proteinaceous extracellular fiber, produced by an enteric bacterium, that is involved in surface and cell-cell contacts that promote community behavior and host colonization.


actin rod

A cellular structure consisting of parallel, hexagonally arranged actin tubules, comprising filamentous actin and associated proteins. Actin rod structures are found in diverse organisms, having been observed in spores of Dictyostelium discoideum, Drosophila melanogaster oocytes, as well as in numerous animal cells under stress conditions.


nucleoplasmic periphery of the nuclear pore complex

Nucleoplasm situated in close proximity and peripheral to a nuclear pore complex.


plastid inner membrane

The inner, i.e. lumen-facing, lipid bilayer of the plastid envelope; also faces the plastid stroma.


organelle subcompartment

A compartment that consists of a lumen and an enclosing membrane, and is part of an organelle.


cellularization cleavage furrow invagination front

The base of the cellularization invagination or cleavage furrow most distal to the original multi-nucleate cell or syncytium plasma membrane.


suberin network

An extracellular matrix part that consists of fatty acid-derived polymers, including both aromatic and aliphatic components. The suberin network is found in specialized plant cell walls, where it is laid down between the primary wall and plasma membrane, forms protective and wound-healing layers, and provides a water-impermeable diffusion barrier.


elaioplast stroma

The space enclosed by the double membrane of an elaioplast.


plant-type vacuole membrane

The lipid bilayer surrounding a vacuole that retains the same shape regardless of cell cycle phase. The membrane separates its contents from the cytoplasm of the cell. An example of this component is found in Arabidopsis thaliana.


prospore contractile ring

A contractile ring, i.e. a cytoskeletal structure composed of actin filaments and myosin, that forms beneath the plasma membrane of the prospore envelope in meiotic cells in preparation for completing cytokinesis.


mesosome

An intracellular, often complex, membranous structure, sometimes with additional membranous lamellae inside, found in bacteria. They are associated with synthesis of DNA and secretion of proteins.


septin band

A diffuse ring composed of a series of septin bars that run parallel to the long axis of the cell. This type of septin structure has been observed in a number of locations associated with polarized grown and/or deposition of new membrane, but not with cytokinesis, such as at the shmoo (mating projection) neck, at the junction between the mother cell and the germ tube (hypha) of a fungal cell growing filamentously.


bacterial-type flagellum basal body, C ring

Cytoplasmic ring located at the base of the bacterial-type flagellar basal body; acts as a rotor; includes three switch proteins, which generate torque and can change their conformational state in a bimodal fashion, so that the motor direction can switch between clockwise and counterclockwise.


extrinsic component of thylakoid membrane

The component of a thylakoid membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.


membrane-enclosed lumen

The enclosed volume within a sealed membrane or between two sealed membranes. Encompasses the volume enclosed by the membranes of a particular organelle, e.g. endoplasmic reticulum lumen, or the space between the two lipid bilayers of a double membrane surrounding an organelle, e.g. nuclear envelope lumen.


cyst wall

The specialized envelope lying outside the cell membrane of a cyst. A cyst is a resting or dormant stage of a microorganism, usually a bacterium or a protist or rarely an invertebrate animal, that helps the organism to survive in unfavorable environmental conditions. In protists such as protozoan parasites alternating cystic- and non-cystic stages, the cyst wall is usually composed of carbohydrates and proteins.


inner membrane pellicle complex

A membrane structure formed of two closely aligned lipid bilayers that lie beneath the plasma membrane and form part of the pellicle surrounding an apicomplexan parasite cell.


orthogonal array

Square array of closely spaced intramembrane particles, 4-6 nm in size, that form supramolecular aggregates found in the plasma membrane of astrocytes, skeletal muscle and epithelial cells. They have been shown to contain aquaporins (water channels).


endospore cortex

A layer surrounding a bacterial endospore found inside the outer endospore membrane, but outside the membrane surrounding the endospore core. It consists of peptidoglycan of a different chemical nature than that found in vegetative cell walls which results in less cross-linking of peptidoglycan.


half bridge of mitotic spindle pole body

Structure adjacent to the plaques of the mitotic spindle pole body.


post-anaphase microtubule array

A cytoskeletal part that consists of an array of microtubules and associated molecules that forms at the end of anaphase, and in which microtubules are nucleated from an equatorial microtubule organizing center.


host cell periplasmic space

The region between the inner (cytoplasmic) and outer host membrane (Gram-negative Bacteria) or inner host membrane and host cell wall (Fungi).


gas vesicle shell

The proteinaceous structure surrounding a gas vesicle.


root hair tip

The tip portion of an outgrowth of a root epidermal cell.


anammoxosome

An intracytoplasmic membrane-bounded compartment in anaerobic ammonium oxidation (anammox) bacteria, is the site of anammox catabolism.


P4 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P4 peroxisomes are distinguished from the other subforms on the bases of buoyant density and protein content.


outer plaque of mitotic spindle pole body

One of three laminate structures that form the mitotic spindle pole body; the outer plaque is in the cytoplasm.


extracellular organelle

Organized structure of distinctive morphology and function, occurring outside the cell. Includes, for example, extracellular membrane vesicles (EMVs) and the cellulosomes of anaerobic bacteria and fungi.


host caveola

A small pit, depression, or invagination, such as any of the minute pits or incuppings of the host cell membrane formed during pinocytosis, that communicates with the outside of a host cell and extends inward, indenting the host cytoplasm and the host cell membrane. Such caveolae may be pinched off to form free vesicles within the host cytoplasm. The host is defined as the larger of the organisms involved in a symbiotic interaction.


unicellular trichome apex

A cell projection part that is the apical most portion of a unicellular trichome.


lateral shield

Region of the ventral side of the cell body found in Giardia species (trophozoite stage). It is located posterior on either side of the ventral groove; the upper boundary is the ventral disc, and the lower boundary is marked by the posteriolateral flagella.


plasma membrane-derived chromatophore

A pigment-bearing structure that is derived from the cytoplasmic membrane, sometimes consisting of simple invaginations and sometimes a complete vesicle. This component is found in certain photosynthetic bacteria and cyanobacteria.


organelle envelope

A double membrane structure enclosing an organelle, including two lipid bilayers and the region between them. In some cases, an organelle envelope may have more than two membranes.


ascus membrane

A double layer of lipid molecules that surrounds an ascus, a capsule containing the sexual spores in some fungi.


spine apparatus membrane

The lipid bilayer surrounding the spine apparatus.


synaptonemal structure

A proteinaceous scaffold found between homologous chromosomes during meiosis.


old growing cell tip

A cell tip which has existed for at least one complete cell cycle, and at which polarized growth occurs. For example, in fission yeast the cell end that existed prior to cell division grows immediately after division, and contains a distinctive complement of proteins including actin cytoskeletal structures.


intine

The innermost of the major layers of the pollen grain wall which underlies the exine and borders the cytoplasm.


cellular bud neck

The constriction between the mother cell and daughter cell (bud) in an organism that reproduces by budding.


microsporidian-type exospore

The dense, protein rich outermost layer of a microsporidian spore wall that lies above the endospore.


rDNA protrusion

Any of the tandem arrays of rDNA localized at the periphery of the nucleus and protruding into the nucleolus, and associated proteins. May be visible as a single or double spot by DAPI staining.


microneme lumen

The volume enclosed by the microneme membrane.


Casparian strip

Region of plant cell wall specialised to act as a seal to prevent back leakage of secreted material (analogous to tight junction between epithelial cells). Found particularly where root parenchymal cells secrete solutes into xylem vessels. The barrier is composed of suberin; a fatty substance, containing long chain fatty acids and fatty esters, also found in the cell walls of cork cells (phellem) in higher plants.


rhoptry neck

Narrow, electron-dense part of the rhoptry that extends through the conoid at the apical tip of an apicomplexan parasite. The rhoptry neck serves as a duct through which the contents of the rhoptry are secreted after attachment to the host has been completed and at the commencement of invasion.


podosome core

The F-actin-rich core of an adhesion structure characterized by formation upon cell substrate contact and localization at the substrate-attached part of the cell.


exine

The outer layer of the pollen grain wall which is composed primarily of sporopollenin.


magnetosome membrane

The lipid bilayer surrounding a magnetosome.


conoid

A spiral cytoskeletal structure located at the apical end of the apical complex in some apicomplexan parasites. Fibers form a left-handed spiral, and are comprised of tubulin protofilaments organized in a ribbon-like structure that differs from the conventional tubular structure characteristic of microtubules.


polar ring of apical complex

An electron dense ring at the most anterior position of the apical complex, from which the conoid fibers originate; formed during an invasive life cycle stage of an apicomplexan parasite.


hydrogenosomal membrane

The lipid bilayer surrounding a hydrogenosome.


cleavage furrow leading edge

The 'trough' of the cleavage furrow. This is the part of the cleavage furrow closest to the contractile ring.


external side of fungal-type cell wall

The side of the fungal-type cell wall that is opposite to the side that faces the cell and its contents.


mitosome

A double-membrane-bounded organelle that functions in iron-sulfur protein maturation; evolutionarily derived from mitochondria. The mitosome has been detected only in anaerobic or microaerophilic organisms that do not have mitochondria, such as Entamoeba histolytica, Giardia intestinalis and several species of Microsporidia. These organisms are not capable of gaining energy from oxidative phosphorylation, which is normally performed by mitochondria.


bilobe structure

A cytoskeletal structure in some kinetoplastid species linking the structures of the ciliary pocket collar and the flagellum attachment zone (aka cilium attachment zone).


actin filament branch point

The part of an actin filament where the structure forks.


hydrogenosome

A spherical, membrane-bounded organelle found in some anaerobic protozoa, which participates in ATP and molecular hydrogen formation.


symbiont-containing vacuolar space

The space between a symbiont plasma membrane and the symbiont-containing vacuole membrane.


endonuclear canal

A membrane-bound structure present in the nucleus of a spermatozoon. There is variation in the number of endonuclear canals between sperm of different organisms, and some species lack these structures altogether. The endonuclear canal may provide a supporting role for the sperm nucleus, and originates during spermiogenesis from an invagination of the nuclear envelope.


presynaptic active zone dense projection

Electron dense projection extending from the cytomatrix into the cytoplasm on which synaptic vesicles are tethered.


etioplast prolamellar body

A three dimensional regular lattice found in etioplasts. It is composed of a continuous system of tubules but when exposed to light the symmetrical arrangement is rapidly lost as tubules become pinched off into two dimensional sections of lattice. These for perforated sheets of membrane that move apart, extend and increase, finally establishing the typical granal and intergranal lamellae of the mature chloroplast.


Hechtian strand

An extended membranous thread which firmly connects the plasma membrane to the cell wall during plasmolysis such that the plasma membrane does not separate from the cell wall completely.


platelet dense tubular network lumen

The volume enclosed by the membranes of the platelet dense tubular network.


cytostome

Stable, specialized structure for the ingestion of food by the cell into phagosomes.


endosperm protein body

A membrane-bounded plant organelle found in the developing endosperm, contains storage proteins.


bacterial-type flagellum basal body, distal rod, P ring

One of the rings of the bacterial-type flagellar basal body; anchors the basal body to the peptidoglycan layer.


extrinsic component of external side of cell outer membrane

The component of a cell outer membrane consisting of gene products and protein complexes that are loosely bound to its external surface, but not integrated into the hydrophobic region.


bacterial biofilm matrix surface

The external part of the biofilm matrix, a structure lying external to bacterial cells. A biofilm is an aggregate of surface-associated bacteria, and the biofilm matrix is the envelope of polymeric substances that surrounds the bacteria.


extrachromosomal circular DNA

Circular DNA structures that are not part of a chromosome.


adventitious septum

A cell septum whose formation is independent of nuclear division.


neural crest-derived structure

biolink:AnatomicalEntity biolink:OrganismalEntity biolink:BiologicalEntity biolink:NamedThing biolink:PhysicalEssence biolink:SubjectOfInvestigation biolink:ThingWithTaxon biolink:PhysicalEssenceOrOccurrent

An anatomical structure that develops from the neural crest.


ectoderm-derived structure

An anatomical structure that develops (entirely or partially) from the ectoderm.


structure with developmental contribution from neural crest

An anatomical structure that has some part that develops from the neural crest.


mesoderm-derived structure

An anatomical structure that develops (entirely or partially) from the mesoderm.


endoderm-derived structure

An anatomical structure that develops (entirely or partially) from the endoderm.


chemical entity

A chemical entity is a physical entity of interest in chemistry including molecular entities, parts thereof, and chemical substances.


main group molecular entity

A molecular entity containing one or more atoms from any of groups 1, 2, 13, 14, 15, 16, 17, and 18 of the periodic table.


virus tail, baseplate

Multiprotein component at the distal (head) end of the virus tail to which fibers of tailed viruses may be attached.


polyatomic entity

Any molecular entity consisting of more than one atom.


viral inner capsid

The inner layer of a double or triple concentric icosahedral capsid. Inner capsids are part of reoviridae and cystoviridae virions.


viral nucleocapsid

The complete protein-nucleic acid complex that is the packaged form of the genome in a virus particle.


virus tail, tip

The basal end of the virus tail, which is used by the virus to attach to the host cell.


virus tail

Part of the virion that may be used to recognize, attach and inject the viral genome and accessory proteins into the host cell.


virus tail, tube

The internal tube of the contractile tails of some viruses. The virus tail tube is the channel for DNA ejection into the host cytoplasm.


icosahedral viral capsid, collar

A small disk located at the base of some icosahedral virus capsids.


virus tail, fiber

The fibrous region of the virus tail used to scan, recognize and attach to the host cell.


virion nucleoid

The region of a virion in which the nucleic acid is confined.


virion membrane

The lipid bilayer surrounding a virion.


icosahedral viral capsid, spike

A short structure attached to an icosahedral virion capsid, and used for attachment to the host cell.


viral procapsid

A stable empty viral capsid produced during the assembly of viruses.


icosahedral viral capsid, neck

A region of constriction located below the head and above the tail sheath of viruses with contractile tails (Myoviridae).


virus tail, shaft

The tube of the non-contractile tails of some viruses.


viral outer capsid

The outer layer of a double or triple concentric icosahedral capsid. Outer capsids are part of reoviridae and cystoviridae virions.


molecular entity

Any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer etc., identifiable as a separately distinguishable entity.


virion component

Any constituent part of a virion, a complete fully infectious extracellular virus particle.