Term | Definition |
Cell Theory | The theory that states that all living things are made up of cells, that cells are the basic units of organisms, that each cell in a multicellular organism has a specific job, and that cells come only from existing cells. |
Cytoplasm | The region of the cell within the membrane that includes the fluid, the cytoskeleton, and all of the organelles except the nucleus |
Organelle | One of the small bodies that are found in the cytoplasm of a cell and that are specialized to perform a specific function |
Prokaryotic Cell | Cell that does not have a nucleus or other membrane-bound organelles |
Eukaryotic Cell | Cell that has a nucleus and other membrane-bound organelles |
Cytoskeleton | The cytoplasmic network of protein filaments that plays an essential role in cell movement, shape, and division |
Nucleus | In a eukaryotic cell, a membrane-bound organelle that contains the cell's DNA and that has a role in processes such as growth, metabolism, and reproduction |
Endoplasmic Reticulum | A system of membranes that is found in a cell's cytoplasm and that assists in the production, processing, and transport of proteins and in the production of lipids |
Ribosome | A cell organelle composed of RNA and protein; the site of protein synthesis |
Golgi Apparatus | A cell organelle that helps make and package materials to be transported out of the cell |
Vesicle | A small cavity or sac that contains materials in a eukaryotic cell; forms when part of the cell membrane surrounds the materials to be taken into the cell or transported within the cell |
Mitochondrion | In eukaryotic cells, the cell organelle that is surrounded by two membranes and that is the site of cellular respiration, which produces ATP |
Vacuole | Organelle that is used to store materials, such as water, food, or enzymes, that are needed by the cell |
Lysosome | Organelle that contains enzymes |
Centriole | Small cylinder-shaped organelle made of protein tubes arranged in a circle; aids mitosis |
Cell Wall | Rigid structure that gives protein, support, and shape to cells in plants, algae, fungi, and bacteria |
Chloroplast | An organelle found in plant and algae cells where photosynthesis occurs |
Cell Membrane | Double-layer of phospholipids that forms a boundary between a cell and the surrounding environment and controls the passage of materials into and out of a cell |
Phospholipid | A lipid that contains phosphorous and that is a structural component in cell membranes |
Fluid Mosaic Model | Model that describes the arrangement and movement of the molecules that make up a cell membrane |
Selective Permeability | Condition or quality of allowing some, but not all, materials to cross a barrier or membrane |
Receptor | Protein that detects a signal molecule and performs an action in response |
Passive Transport | The movement of substances across a cell membrane without the use of energy by the cell |
Diffusion | The movement of particles from regions of higher density to regions of lower density |
Concentration Gradient | A difference in the concentration of a substance across a distance |
Osmosis | The diffusion of water or another solvent from a more dilute solution (of a solute) to a more concentrated solution (of the solute) through a membrane that is permeable to the solvent |
Isotonic | Solution that has an equal concentration of dissolved particles compared with another solution |
Hypertonic | Describes a solution whose solute concentration is higher than the solute concentration inside a cell |
Hypotonic | Describes a solution whose solute concentration is lower than the solute concentration inside a cell |
Facilitated Diffusion | The transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins |
Active Transport | The movement of chemical substances, usually across the cell membrane, against a concentration gradient; requires cells to use energy |
Endocytosis | The process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell |
Phagocytosis | Uptake of a solid particle into a cell by engulfing the particle |
Exocytosis | The process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out |