| Term | Definition |
|---|
| spontaneous generation | a popular belief in the 19th century that living organisms can come from non-living things |
| plasma membrane | a phospholipid bilayer that surrounds a cell and serves as a barrier between the cell and its surroundings |
| aqueous | water-based |
| cytosol | the liquid part of the contents of a cell |
| eukaryote | an organism consisting of one or more cells that contain a membrane-enclosed nucleus |
| eukaryotic cell | a cell that possesses a membrane-enclosed nucleus |
| prokaryote | a unicellular organism that does not have a membrane-enclosed nucleus |
| prokaryotic cell | a cell that lacks a membrane-enclosed nucleus |
| organelle | a component of eukaryotic cells that carries out a specific function |
| nucleus | a membrane-enclosed organelle that contains most of the genetic material in a eukaryotic cell |
| endoplasmic reticulum | a network of membranes near the nucleus that plays an important role in the transport of components needed for protein synthesis |
| golgi apparatus | an organelle that sorts, modifies, and packages proteins for transport within a cell or to other cells |
| lysosome | an organelle that contains digestive enzymes to break down carbohydrates, fats, and proteins |
| mitochondrion | an organelle that is the main site of energy conversion through cellular respiration |
| cell wall | a rigid structure that surrounds the plasma membrane of plant cells and some bacteria in order to provide support for the cell |
| chloroplast | an organelle that is the main site of photosynthesis in plant cells |
| vacuole | a large membrane-enclosed sac in plant cells that stores large molecules and toxic substances |
| chromosome | a combination of DNA and protein that is visible in a cell during cell division |
| chromatin | a combination of DNA and protein that appears as a mass of long thin fibers in a non-dividing cell |
| nuclear envelope | a double membrane structure that surrounds the nucleus |
| nuclear pore | a small perforation in the nuclear envelope that connects the cytoplasm with the interior of the nucleus |
| nucleolus | a large structure within a eukaryotic nucleus that makes the structures involved in protein synthesis |
| histone | an abundant protein which forms the nucleosome on the DNA in eukaryotic chromosomes |
| nucleosome | bead-like structure in eukaryotic chromatin, composed of a short length of DNA wrapped around a core of histone proteins |
| cell fractionation | a laboratory technique that uses a centrifuge to separate cytoplasmic organelles from one another |
| freeze fracture | a laboratory technique that is used to study the structure of the plasma membrane |
| in vitro | "in glass"; refers to cells or procedures carried out in the laboratory, as in a glass petri dish or test tube |
| magnification | the apparent enlargement of an object by an optical device such as a microscope |
| resolution | the measurement of the clarity of an image; the minimum distance that two very close points can be viewed as separate objects |
| cytoskeleton | the structural support system on the inside of a cell |
| microfilaments | a component of the cytoskeleton that is made from actin proteins |
| microtubules | a component of the cytoskeleton that is made from tubulin proteins |
| intermediate filaments | a component of the cytoskeleton that is made from keratin proteins |
| flagellum | a structure made of microtubules that enables cells to move using a whip-like action |
| cilia | short, hair-like structures made of microtubules that enable movement of cells or movement of materials outside a cell |
| pseudopod | an extension of a cell's cytoplasm that enables it to crawl along a surface; literally "false feet" |
| cytoplasmic streaming | a circular motion of the cytosol that enables substances to move through the cell more quickly |
| passive transport | a transport process that does not require energy |
| diffusion | the movement of molecules from an area of high concentration to an area of low concentration |
| facilitated diffusion | a form of diffusion that requires the assistance of a transport protein |
| selectively permeable | a barrier that enables some molecules or substances to cross a membrane, but not others |
| osmosis | the diffusion of water through a selectively permeable membrane |
| cytoplasm | the entire contents of a cell, other than the nucleus |
| isotonic | having the same concentration of solutes as another solution |
| hypotonic | having a lower concentration of solutes than another solution |
| hypertonic | having a higher concentration of solutes than another solution |
| active transport | a transport process that requires energy |
| endocytosis | the process of taking in large molecules by pinching off a portion of the plasma membrane |
| binary fission | a process of cell division in prokaryotes in which each daughter cell receives a copy of the cell's chromosome |
| cell cycle | the life cycle of a cell that consists of distinct growth and division phases in eukaryotes |
| M phase | the phase of the cell cycle that includes mitosis and cytokinesis |
| interphase | that portion of the cell cycle when the cell is not actively dividing |
| daughter cell | one of two genetically identical cells that result from cell division |
| cytokinesis | the division of cytoplasm in M phase of the cell cycle |
| prophase | the first step of mitosis |
| metaphase | the second step of mitosis |
| anaphase | the third step of mitosis |
| telophase | the fourth and final step of mitosis |
| G1 phase | the first gap phase in the cell cycle; the first subphase of interphase that occurs immediately following M phase |
| S phase | the second subphase of interphase, where DNA synthesis occurs |
| G2 phase | the second gap phase in the cell cycle; the third subphase of interphase that occurs immediately before the cell reenters M phase |
| G0 phase | a resting phase in the cell cycle that can occur near the end of G1 phase |
| contact inhibition | a process that stops additional cell growth when cells become crowded |
| cancer | the uncontrolled growth of cells that results when cells lose their ability to respond correctly at checkpoints in the cell cycle |
| tumor | a mass of cells within normal tissue that arises when a cell no longer responds properly to the cell cycle checkpoint signals |
| mutation | a change in the sequence of DNA |
| mutagen | a substance that can cause a change in a DNA sequence |
| sister chromatids | two daughter strands of a replicated chromosome joined at the middle by a centromere |
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