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| an optical instrument with lenses that refract (bend) visible light to magnify images and project them into a viewer's eye or onto photographic film. |
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| an increase in the apparent size of an object. |
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| a measure of the clarity of an image; the ability of an optical instrument to show two-objects as seperate. |
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| the theory that all living things are composed of cells and that all cells come from other cells. |
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| an instrument that focuses an electron beam through, or onto the surface of, a specimen. An electron microscope achieves a thousandfold greater resolution than a light microscope; the most powerful EM can distinguish objects as mslal as 0.2 nm. |
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| scanning electron microscope (SEM) |
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a microscope that uses an electron beam to study the surface architecture of a cell or other specimen. |
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| transmission electron microscope (TEM) |
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| a microscope that uses an electron beam to study the internal structure of thinly sectioned specimens. |
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| a type of cell lacking a membrane-enclosed nucleus and other membrane-enclosed organelles; found only in the domains Bacteria and Archaea. |
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| a type of cell that has membrane-enclosed nucleus and other membrane-enclosed organelles. All organisms except bacteria and archaea are composed of eukaryotic cells. |
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| the thin layer of lipids and proteins that sets a cell off from its surroundings and acts as a selective barrier to the passage of ions and molecules into and out of the cell; consists of a phospholipid bilayer in which are embedded molecules of protein and cholesterol. |
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| a cell organelle consisting of RNA and protein organized into two subunits and functioning as the site of protein synthesiss in the cytoplasm. The ribosomal subunits are constructed in the nucleolus. |
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| the region in a prokaryotic cell consisting of a concentrated mass of DNA. |
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| a protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists; protects the cell and helps maintain its shape. |
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| a sticky layer that surrounds the bacterial cell wall, protects the cell surface, and sometimes helps glue the cell to surfaces. |
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| a short protection on the surface of a prokaryotic cell that helps the prokaryote attach to other surfaces. Specialized sex pili are used in conjugation to hold the mating cells together. |
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| a long surface protection that propels a prokaryotic cell through its liquid environment; totally different from the flagellum of a eukaryotic cell. |
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| everything inside a cell between the plasma membrane and the nucleus; consists of a semifluid medium and organelles. |
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| a structure with a specialized function within a cell. |
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| the chemical activities of cells. |
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(1) an atom's central core, containing protons and neutrons. (2) the genetic control center of a eukaryotic cell. |
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| the combination of DNA and proteins that constitutes chromosomes; often used to refer to the diffuse, very extended form taken by the chromosomes when a eukaryotic cell is not dividing. |
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| a threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. Chromosomes consist of chromatin. |
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| a double membrane, perforated with pores, that encloses the nucleus and separates it from the rest of the eukaryotic cell. |
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| a structure within the nucleus of a eukaryotic cell where ribosomal RNA is made and assembled with proteins to make ribosomal subunits; consists of parts of the chromatin DNA, RNA transcribed from the DNA, and proteins imported from the cytoplasm. |
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| a network of membranous organelles that partition the cytoplasm of eukaryotic cells into functional compartments. Some of the organelles are structurally connected to each other, whereas others are structurally separate but functionally connected by the traffic of membranous vesicles between them. |
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| endoplasmic reticulum (ER) |
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| an extensive membranous netwrok in a eukaryotic cell, continuous with the outer nuclear membrane and composed of ribosome-studdded (rough) and ribosome-free (smooth) regions. |
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smooth endoplasmic reticulum (smooth ER) |
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| a network of interconnected membranous tubules in a eukaryotic cell's cytoplasm. Smooth ER lacks ribosomes. Enzymes embedded in the smooth ER membrane function in the synthesis of certain kinds of molecules, such as lipids. |
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rough endoplasmic reticulum (rough ER) |
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a network of interconnected membranous sacs in a eukaryotic cell's cytoplasm. Rough ER membranes are studded with ribosomes that make membrane proteins and secretory proteins. The rough ER constructs membrane from phospholipids and proteins. |
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| a protein (such as an antibody) that is secreted by a cell. |
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| a macromolecule consisting of one or more polypeptides linked to short chains of sugars. |
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| a tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell. The vesicle buds from the endoplasmic reticulum or Golgi and eventually fuses with another membranous organelle or the plasma membranes, releasing its contents. |
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| an organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum. |
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| a digestive organelle in eukaryotic cells; contains hydrolytic enzymes that digest the cell's food and wastes. |
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| a membrane-enclosed sac, part of the endomembrane system of a eukaryotic cell, having diverse functions. |
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| a membrane-enclosed sac occupying most of the interior of a mature plant cell, having diverse roles in reproduction, growth, and development. |
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| an organelle found in plants and photosynthetic protists. Enclosed by two concentric membranes, a chloroplast absorbs sunlight and uses it to power the synthesis or organic food molecules (sugars). |
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| a thick fluid enclosed by the inner membrane of a chloroplast. Sugars are made in the stroma by the enzymes of the Calvin cycle. |
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| a stack of hollow disks formed of thylakoid membrane in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis. |
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| an organelle in eukaryotic cells where cellular respiration occurs. Enclosed by two concentric membranes, it is where most of the cell's ATP is made. |
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| one of the two fluid-filled internal compartments of the mitochondrion. The intermembrane space is the narrow region between the inner and outer membranes. |
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| the fluid contained within the inner membrane of a mitochondrion. |
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| a fold of the inner membrane of a mitochondrion. Enzyme molecules embedded in cristae make ATP. |
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| a meshwork of fine fibers in the cytoplasm of a eukaryotic cell; includes microfilaments, intermediate filaments, and microtubules. |
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| the thinnest of the three main kinds of protein fibers making up the cytoskeleton of a eukaryotic cell; a solid, helical rod composed of the globular protein actin. |
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| an intermediate-sized protein fiber that is one of the three main kinds of fibers making up the cytoskeleton of eukaryotic cells. Intermediate filaments are ropelike, made of fibrous proteins. |
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| the thickest of the three main kinds of fibers making up the cytoskeleton of a eukaryotic cell; a straight, hollow tube made of globular proteins called tubulins. Microtubules from the basis of the structure and movement of cilia and flagella. |
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| a short appendage that propels some protists through the water and moves fluids across the surface of many tissue cells in animals. In common with eukaryotic flagells, cilia have a 9 + 2 arrangement of microtubules covered by the cell's plasma membrane. |
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| a protist generation (protozoan) that moves by means of one or more flagella. |
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| a eukaryotic cell organelle consisting of a 9 + 0 arrangement of microtubule triplets; may organize the microtubule assembly of a cilium or flagellum; structurally identical to a centriole. |
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| a structure in an animal cell composed of microtubule triplets arranged in a 9 + 0 pattern. An animal cell usually has a pair of centrioles within each of its centrosomes. |
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| plasmodesma, plural: plasmodesmata |
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| an open channel in a plant cell wall, through which strands of cytoplasm connect from adjacent walls. |
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| a substance in which the cells of an animal tissue are embedded; consists of protein and polysaccharides. |
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| a junction that binds tissue cells together in a leakproof sheet. |
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| a junction that connects tissue cells to each other (or to an extracellular matrix) and allows materials to pass from cell to cell. |
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| a channel between adjacent tissue cells through which water and other small molecules pass freely. |
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