One of several formed bodies with specialized functions, suspended in the cytoplasm of eukaryotic cells.
A microscope that focuses an electron beam through a specimen, resulting in resolving power a thousandfold greater than that of a light microscope. A transmission electron microscope (TEM) is used to study the internal structure of thin sections of cells. A scanning electron microscope (SEM) is used to study the fine details of cell surfaces.
The disruption of a cell and separation of its organelles by centrifugation.
A machine that spins test tubes at the fastest speeds to separate liquids and particles of different densities.
The semifluid portion of the cytoplasm.
A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.
A dense region of DNA in a prokaryotic cell.
The entire 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, thereby regulating the cell's chemical composition.
(1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.
A netlike array of protein filaments that maintains the shape of the nucleus.
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists as a mass of very long, thin fibers that are not visible with a light microscope.
A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins.
(plural, nucleoli) A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes.
A cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of rRNA and protein molecules, which make up two subunits.
That portion of the endoplasmic reticulum that is free of ribosomes.
That portion of the endoplasmic reticulum studded with ribosomes.
An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.
A protein covalently attached to a carbohydrate.
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum.
A tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell.
A membrane-enclosed bag of hydrolytic enzymes found in the cytoplasm of eukaryotic cells.
A type of endocytosis involving large, particulate substances.
A membranous sac formed by phagocytosis.
A membranous sac that helps move excess water out of the cell.
A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the cell sap.
(plural, mitochondria) An organelle in eukaryotic cells that serves as the site of cellular respiration.
An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
(plural, cristae) An infolding of the inner membrane of a mitochondrion that houses the electron transport chain and the enzyme catalyzing the synthesis of ATP.
One of a family of closely related plant organelles, including chloroplasts, chromoplasts, and amyloplasts (leucoplasts).
A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
(plural, grana) A stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis.
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
A microbody containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions.
Material present in the cytoplasm of all eukaryotic cells, important during cell division; the microtubule-organizing center.
(plural, flagella) A long cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules, ensheathed in an extension of plasma membrane.
(plural, cilia) A short cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of plasma membrane.
A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.
A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists. In plant cells, the wall is formed of cellulose fibers embedded in a polysaccharide-protein matrix. The primary cell wall is thin and flexible, whereas the secondary cell wall is stronger and more rigid and is the primary constituent of wood.
The substance in which animal tissue cells are embedded consisting of protein and polysaccharides.
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.