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| Plastids | membrane-enclosed organelles found in the cells of some protists and almost all plants; includes chloroplasts, chromoplasts, and leucoplasts |
| Chromoplasts | plastids that contain pigments other than chlorophyll |
| Endosymbiosis | a condition in which the organism lives inside the cell of another to the benefit of both |
| Diffusion | the movement of molecules or particles from an area of greater concentration to an area of lesser concentration |
| Concentration gradient | the difference in concentration between a region of greater concentration and one of lesser concentration |
| Facilitated diffusion | a process by which certain molecules diffuse quickly across a cell membrane |
| Osmosis | diffusion of water across a semipermiable membrane from a region of high concentration of water to a region of low concentration of water |
| Osmotic pressure | the increase in pressure resulting from the low flow of water in osmosis |
| Isotonic solution | a solution that contains the same concentration of dissolved substances as does a living cell placed in it |
| Hypertonic solution | a solution whose concentration of solutes is higher than that of a cell placed in it |
| Plasmolysis | the shrinking of cytoplasm resulting from loss of water by osmosis in a cell placed in a hypertonic solution |
| Hypotonic solution | a solution that contains a lower concentration of dissolved substances than that of a cell placed in it |
| Passive transport | a process by which materials move across cell membranes without the expenditure of cellular energy |
| Active transport | a process in which the movement of materials across a cell membrane requires the expenditures of energy |
| Endocytosis | the process of transporting material into a cell by means of a vesicle |
| Phagocytosis | the process in which large particles or small organisms are ingested into a cell |
| Exocytosis | the movement of materials out of the cell by the reverse of endosytosis |
| Tissue | in multicellular organisms, a group of cells that are similar and organized into a functional unit; usually integrated with other tissues to form an organ |
| Epithelial tissues | the tissues that cover body surfaces and line body cavities and organs |
