| A | B |
|---|
| cell theory | generalization that all living things are composed of cells, and that cells are the basic unit of structure and function in living things |
| micrograph | photograph of the view through a microscope |
| organelle | part of a cell with a specific function |
| plasma membrane | thin outer boundary of a cell that regulates the traffic of chemicals between the cell and its surroundings |
| nucleus | in a cell, the part that houses the cell's genetic material in the form of DNA |
| cytoplasm | region of a cell between the nucleus and the plasma membrane |
| cell wall | strong wall outside a plant cell's plasma membrane that protects the cell and maintains its shape |
| prokaryotic cell | cell lacking a nucleus and most other organelle |
| eukaryotic cell | cell with a nucleus (surrounded by its own membrane) and other internal organelles |
| phospholipid bilayer | two-layer "sandwich" of molecules that surrounds a cell |
| diffusion | net movement of the particles of a substance from where they are more concentrated to where they are less concentrated |
| equilibrium | point at which the number of diffusing molecules moving in one direction is equal to the number moving in the opposite direction |
| selectively permeable membrane | membrane that allows some substances to pass more easily than others and blocks the passage of some substances altogether |
| passive transport | iffusion across a membrane requiring only the random motion of molecules with no energy expended by the cell |
| facilitated diffusion | pathway provided by transport proteins that helps certain molecules pass through a membrane |
| osmosis | passive transport of water across a selectively permeable membrane |
| hypertonic | having a higher concentration of solute than another solution |
| hypotonic | having a lower concentration of solute than another solution |
| isotonic | having a solute concentration equal to that of another solution |
| active transport | movement of molecules across a membrane requiring energy to be expended by the cell |
| vesicle | small membrane-bound sac that functions in moving products into, out of, and within a cell |
| exocytosis | process of exporting proteins from a cell by a vesicle fusing with the plasma membrane and spilling the proteins outside the cell |
| endocytosis | process of taking material into a cell within vesicles that bud inward from the plasma membrane |
| nuclear envelope | double membrane that surrounds a cell nucleus ( |
| nucleolus | ball-like mass of fibers and granules in a cell nucleus |
| ribosome | cluster of proteins and nucleic acids that constructs proteins in a cell |
| endoplasmic reticulum | network of membranes within a cell's cytoplasm that produces a variety of molecules |
| Golgi apparatus | cellular organelle that modifies, stores, and routes cell products |
| vacuole | membrane-bound sac that buds from the endoplasmic reticulum or the Golgi apparatus |
| lysosome | membrane-bound sac containing digestive enzymes that can break down proteins, nucleic acids, and polysaccharides |
| chloroplast | organelle found in some plant cells and certain unicellular organisms where photosynthesis takes plac |
| mitochondria | cellular organelles where cellular respiration occurs |
| ATP | (adenosine triphosphate) main energy source that cells use for most of their work |
| microtubule | straight, hollow tube of proteins that gives rigidity, shape, and organization to a cell |
| microfilament | solid rod of protein, thinner than a microtubule, that enables a cell to move or change shape |
| flagella | long, thin, whip-like structures, with a core of microtubules, that enable some cells to move |
| cilia | short structures projecting from a cell and containing bundles of microtubules that move a cell through its surroundings or move fluid over the cell's surface |
