Any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells.
Light microscope (LM)
An optical instrument with lenses that refract visible light to magnify images of specimens.
Electron microscope (EM)
A microscope that uses magnets to focus an electron beam on or through a specimen, resulting in resolving power a thousandfold greater than that of a light microscope.
Scanning electron microscope (SEM)
A microscope that uses an electron beam to scan the surface of a sample to study details of its topography.
Transmission electron microscope (TEM)
A microscope that passes an electron beam through very thin sections and is primarily used to study the internal ultrastructure of cells.
The disruption of a cell and separation of its parts by centrifugation.
The semifluid portion of the cytoplasm.
A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes.
A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria and archaea) are called prokaryotes.
A dense region of DNA in a prokaryotic cell.
The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane.
The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.
The double membrane in a eukaryotic cell that encloses the nucleus, separating it from the cytoplasm.
A netlike array of protein filaments lining the inner surface of the nuclear envelope; it helps maintain the shape of the nucleus.
A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins. (A bacterial chromosome usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded).
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.
A specialized structure in the nucleus, consisting of chromatin regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmic site of rRNA synthesis and ribosomal subunit assumably.
An RNA molecule that functions as an enzyme, catalyzing reaction during RNA splicing.
The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or but the transfer of membranous vesicles; includes the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles.
A sac made of membrane in the cytoplasm.
Endoplasmic reticulum (ER)
An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.
That portion of the endoplasmic reticulum that is free of ribosomes.
That portion of the endoplasmic reticulum studded with ribosomes.
A protein with one or more carbohydrates covalently attached to it.
A tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cells.
An organelle in eukaryotic cells consisting of stacks of flat membraneous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncelluse carbohydrates.
A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.
A type of endocytosis in which large particulate substances are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells).
A membranous sac formed by phagocytosis of macro-organisms or particles to be used as food by the cell.
A membranous sac that helps move excess water out of certain freshwater protists.
A membraneous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
An organelle in eukaryotic cells that serves as the site of cellular respiration.
An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
An organelle containing enzymes that transfer hydrogen from various substrates to oxygen producing and then degrading hydrogen peroxide.
An infolding of the inner membrane of a mitochondrion that houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthesize)
The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the critic acid cycle.
One of a family of closely related organelles that includes chloroplasts, chromoplasts amyloplasts (leucoplasts). Plastids are found in cells of photosynthetic organisms.
A flattened membranous sac inside a chloroplast. Thylakoids exist in an interconnected system in the chloroplast and contain the molecular "machinery" used to convert light energy to chemical energy.
A stack of membrane-bounded thylakoids in the chloroplast. Grana function in the light reactions of photosynthesis.
A microscopic pore surrounded b guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant.
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.
A protein that interacts with cytoskeletan elements and other cell components, producing movement of the whole cell or parts of the cell.
A hollow rod composed of tubulin proteins that make up part of the cytoskeleton in all eukaryotic cells and is found in cilia ad flagella.
A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern. A centrosome has a pair of centrioles.
A long cellular appendage specialized for locomotion. Like motile cila, eukaryotic flagella have a core with nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of the plasma membrane. Prokaryotic flagella have a different structure.
A short cellular appendage containing microtubules. A motile cilium is specialized for locomotion and is formed from a core of nine outer doublet microtubules and two inner single microtubules (the "9 + 2" arrangement) ensheathed in an extension of the plasma membrane. A primary cilium is usually nonmotile and plays a sensory and signaling role; it lacks the two inner microtubules (the "9 + 0" arrangement).
A eukaryotic cell structure consisting of a 9 + 0" arrangement of microtubule triplets. The basal body may organize the microtubule assembly of a cilium of flagellum and is structurally very similar to a centriole.
In cilia and flagella, a large contractile protein extending from one microtubule doublet to the adjacent doublet. ATP hydrolysis drives changes in dynein shape that lead to bending of cila and flagella.
A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also known as an actin filament.
A globular protein that links into chains, two of which twist helically about each other, forming microfilaments (actin filaments) in muscle and other kinds of cells.
A type of protein filament that acts as a motor protein with actin filaments to cause cell contraction.
A cellular extension of amoeboid cells used in moving and feeding.
A circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.
A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments.
A protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists. Polysaccharides such as cellulose (in plants and some protists), chitin (in fungi) and peptidoglycan (in bacteria) are an important structural component of cell walls.
Primary cell wall
In plants, a relatively thin and flexible layer first secreted by a young cell.
In plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells.
Secondary cell wall
In plants, a strong and durable matrix often deposited in several laminated layers for cell protection and support.
Extracellular matrix (ECM)
The substance in which animal cells are embedded, consisting of protein and polysaccharides synthesized and secreted by cells.
A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom.
A glycoprotein consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells. A proteoglycan man consist of up to 95% carbohydrate.
A glycoprotein that helps animal cells attach to the extracellular matrix.
In animal cells, a transmembrane receptor protein that interconnects the extracellular matrix and the cytoskeleton.
An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.
Structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center. A centrosome has two centrioles.