A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
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 ______s.
Structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center. A ______ has two centrioles.
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.
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, _______ exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.
A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each _______ consists of one very long DNA molecule and associated proteins. (A bacterial _______ usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded.) See also chromatin.
A membranous sac that helps move excess water out of certain freshwater protists.
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 synthase).
The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane.
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.
A type of intercellular junction in animal cells that functions as a rivet.
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.
A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with _____ ______ (protists, plants, fungi, and animals) are called eukaryotes.
extracellular matrix (ECM)
The substance in which animals cells are embedded, consisting of protein and polysaccharides synthesized and secreted by cells.
A type of intercellular junction in animals that allows the passage of materials between cells.
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.
A stack of membrane-bounded thylakoids in the chloroplast. ______ function in the light reactions of photosynthesis.
A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animals cells and some protists.
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 hollow rod composed of tubulin proteins that make up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella.
The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.
An organelle in eukaryotic cells that serves as the site of cellular respiration.
A dense region of DNA in a prokaryotic cell.
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 assembly. See also ribosome.
1) An atom's central core, containing protons and neutrons. 2) The chromosome-containing organelle of a eukaryotic cell. 3) A cluster of neurons.
Any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells.
The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.
An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.
A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus.
That portion of the endoplasmic reticulum studded with ribosomes.
That portion of the endoplasmic reticulum that is free of ribosomes.
Within the chloroplast, the dense fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
A flattened membranous sac inside a chloroplast. ______s exist in an interconnected system in the chloroplast and contain the molecular "machinery" used to convert light energy to chemical energy.
A type of intercellular junction in animal cells that prevents the leakage of material between cells.
A membrane-bounded vesicle whose function varies in different kinds of cells.
A sac made of membrane in the cytoplasm.