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| cell | the basic units of all forms of life |
| cell theory | one of the fundamental concepts of biology. All living things are composed of cells. Cells are the basic units of structure and function in living things. New cells are produced from existing cells. |
| cell membrane | the thin flexible barrier around the cell |
| cell wall | the strong layer around the cell membrane |
| nucleus | a large structure that contains the cell's genetic material and controls the cell's activities |
| cytoplasm | the material inside the cell membrane, not including the nucleus |
| prokaryote | contain a cell membrane and cytoplasm but no nuclei |
| eukaryote | cells that contain a nucleus, a cell membrane and cytoplasm along with other specialized structures called organelles |
| organelle | specialized structures that perform important cellular functions |
| chromatin | the granular material visible within the nucleus of a cell |
| chromosome | distinct threadlike structures containing the genetic information that is passed from one generation of cells to the next |
| nucleolus | a small dense region inside the nuclei |
| nuclear envelope | the double membrane layer that surrounds the nucleus |
| cytoskeleton | a network of protein filaments that helps the cell to maintain its shape |
| microtubule | hollow tubes of protein about 25 nanometers in diameter that maintain the cell shape and can also serve as tracks along which organelles are moved |
| microfilament | long, thin fibers that function in the movement and support of the cell |
| ribosome | small particles made of RNA and protein |
| endoplasmic reticulum | the organelle in which components of the cell membrane are assembled and some proteins are modified |
| Golgi apparatus | a stack of membranes in the cell in which enzymes attach carbohydrates and lipids to proteins |
| lysosome | a cell organelle filled with enzymes needed to break down certain materials in the cell |
| vacuole | a cell organelle that stores materials such as water, salts, proteins, and carbohydrates |
| chloroplast | an organelle found in the cells of plants and some other organisms that uses energy from sunlight to make energy-rich food molecules by photosynthesis |
| mitochondrion | the cell organelle that releases energy from stored food molecules |
| lipid bylayer | a double-layered sheet that forms the core of nearly all cell membranes |
| concentration | the mass of solute in a given volume of solution (mass/volume) |
| diffusion | the process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated |
| selective permeability | the property of biological membranes that allows only certain substances to pass through them |
| osmosis | diffusion of water through a selectively permeable membrane |
| facilitated diffusion | movement of specific molecules across cell membranes through protein channels |
| active transport | an energy-requiring process that moves material across a cell membrane against a concentration difference |
| endocytosis | the process by which a cell takes material into the cell by infolding of the cell membrane |
| phagocytosis | a process in which extensions of cytoplasm surround and engulf large particles and take them into the cell |
| exocutosis | the process by which a cell releases a large amounts of material |
| cell specialization | separate roles for each type of cell in multicellular organisms |
| tissue | a group of similar cells that perform a particular function |
| organ | a group of tissues that work together to perform closely related functions |
| organ system | a group of organs that work together to perform a specific function |
