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 | a cell that does not have a nucleus or cell organelles; an example is a bacterial cell |
eukaryotic cell | a cell that has a nucleus enclosed by a membrane, multiple chromosomes, and a mitotic cycle |
cytoskeleton | the cytoplasmic network of protein filaments that plays an essential role in cell movement, shape, and division |
nucleus | in physical science, an atom's central region, which is made up of protons and neutrons |
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 apparatius | 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 | a fluid-filled vesicle found in the cytoplasm of plant cells or protozoans |
lysosome | a cell organelle that contains digestive enzymes |
centriole | an organelle that is active during mitosis |
cell wall | a rigid structure that surrounds the cell membrane and provides support to the cell |
chromoplast | an organelle found in plant and algae cells where photosynthesis occurs |
cell membrane | a phospholipid layer that covers a cell’s surface and acts as a barrier between the inside of a cell and the cell’s environmen |
phospholipid | a lipid that contains phosphorus and that is a structural component in cell membranes |
fluid mosaic model | |
selective permeability | |
receptor | a specialized sensory nerve that responds to specific types of stimuli |
passive transport | the movement of substances across a cell membrane without the use of energy by the cell |
defusion | |
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 | |
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 | the process by which a cell engulfs large particles or whole cells, either as a defense mechanism or as a means to obtain food |
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 |