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| An optical instrument with lenses that refract (bend) visible light to magnify images of specimens. |
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| 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. |
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| scanning electron microscope |
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| A microscope that uses an electron beam to scan the surface of a sample to study details of its topography. |
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| transmission electron microscope |
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| A microscope that passes an electron beam through very thin sections and is primarily used to study the internal ultrastructure of cells. |
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| The disruption of a cell and separation of its parts by centrifugation. |
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| The semifluid portion of the cytoplasm. |
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| A dense region of DNA in a prokaryotic cell. |
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| The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane. |
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| The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition. |
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| The chromosome-containing organelle of a eukaryotic cell. |
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| The double membrane in a eukaryotic cell that encloses the nucleus, separating it from the cytoplasm. |
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| A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. |
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| The complex of DNA and proteins that makes up a eukaryotic chromosome. |
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| 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. |
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| 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. |
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| The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles. |
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| A sac made of membrane in the cytoplasm. |
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| rough endoplasmic reticulum |
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| That portion of the endoplasmic reticulum studded with ribosomes. |
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| smooth endoplasmic reticulum |
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| That portion of the endoplasmic reticulum that is free of ribosomes. |
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| 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. |
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| A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists. |
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| 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). |
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| A membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell. |
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| An organelle in eukaryotic cells that serves as the site of cellular respiration. |
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| 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). |
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| The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle. |
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| One of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts). |
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| 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. |
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| A flattened membranous sac inside a chloroplast. They exist in an interconnected system in the chloroplast and contain the molecular “machinery” used to convert light energy to chemical energy. |
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| A stack of membrane-bounded thylakoids in the chloroplast. Grana function in the light reactions of photosynthesis. |
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| A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant. |
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| An organelle containing enzymes that transfer hydrogen (H2) from various substrates to oxygen (O), producing and then degrading hydrogen peroxide (HO). |
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| A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions. |
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| 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. |
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| 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. |
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| A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments. |
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| Structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center. They have two centrioles. |
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| A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern. They have a pair of centrioles. |
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| A long cellular appendage specialized for locomotion. Like motile cilia, eukaryotic ones have a core with nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of the plasma membrane. Prokaryotic ones have a different structure. |
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| A short cellular appendage containing microtubules. A motile one 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 one is usually nonmotile and plays a sensory and signaling role; it lacks the two inner microtubules (the “9 + 0” arrangement). |
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| A eukaryotic cell structure consisting of a 9 + 0 arrangement of microtubule triplets. It may organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole. |
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| 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. |
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| A type of protein filament that acts as a motor protein with actin filaments to cause cell contraction. |
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| A cellular extension of amoeboid cells used in moving and feeding. |
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| 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. |
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| An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell. |
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| A type of intercellular junction in animal cells that prevents the leakage of material between cells. |
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| A type of intercellular junction in animal cells that functions as a rivet. |
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| A type of intercellular junction in animals that allows the passage of materials between cells. |
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