Term | Definition |
cell | Basic unit of structure and organization of all living organisms. |
cell theory | States that (1) organisms are made up of one or more cells; (2) cells are the basic unit of life; (3) all cells come only from other cells. |
plasma membrane | Flexible, selectively permeable boundary that helps control what enters and leaves the cell. |
eukaryotic cell | A cell or unicellular organism with membrane bound nucleus and organelles; generally larger and more complex. |
nucleus | The central membrane-bound organelle that manages cell function and contains DNA in eukaryotic cells |
organelles | Specialized internal cell structures that carry out specific cell functions such as protein synthesis or energy production. |
prokaryotic cell | Microscopic, unicellular organism without a nucleus or other membrane bound organelles. |
selective permeability | Property of the plasma membrane that allows it to control movement of substances into or out of the cell |
phospholipid bilayer | Plasma membrane layers composed of phospholipid molecules arranged with polar heads facing the outside and nonpolar tails facing the inside. |
transport protein | Protein that moves substances or wastes through the plasma membrane |
fluid mosaic model | A plasma membrane with components constantly in motion, sliding past one another within the lipid bilayer |
cytoplasm | Semifluid material inside the cell's plasma membrane |
cytoskeleton | Supporting network of protein fibers that provide a framework for the cell |
nucleolus | The site of ribosome production within the nucleus |
ribosome | Simple cell organelle that manufactures protein |
endoplasmic reticulum | Highly folded membrane system in eukaryotic cells that is the site for protein and lipid synthesis |
golgi apparatus | Flattened stack of membranes that modifies, sorts, and packages proteins into vesicles and transports them to other organelles or out of the cell. |
vacuole | Membrane-bound vesicle for temporary storage of materials such as food, enzymes and wastes. |
centriole | Organelle that plays a role in cell division and is made of microtubules |
lysosome | Vesicle that uses enzymes to digest excess or worn-out cellular substances |
chloroplast | Double-membrane organelle that captures light energy and converts it to chemical energy through photosynthesis |
mitochondrion (mitochondria) | Membrane-bound organelle that converts fuel into energy (ATP) that is available to the rest of the cell. |
cell wall | The rigid barrier that surrounds the outside of the plasma membrane that provides support and protection (plants, fungi and prokaryotes) |
cilium (cilia) | Short, hairlike projection that functions in cell movement |
flagellum (flagella) | Long, tail-like projection with whip-like or propeller motion that helps a cell move. |
diffusion | Net movement of particles from an area of higher concentration to an area of lower concentration |
dynamic equilibrium | Condition of continuous, random movement of particles but no overall change in concentration of materials |
facilitated diffusion | Passive transport of ions and small molecules across the plasma membrane by transport proteins |
osmosis | Diffusion of water across a selectively permeable membrane |
hypotonic solution | A solution that has a lower concentration of solute outside than inside the cell, causing water to flow into the cell by osmosis |
isotonic solution | A solution with the same concentration of water and solutes as inside a cell, resulting in no net movement of water. |
active transport | Energy-requiring process by which substances cross the plasma membrane against a concentration gradient |
hypertonic solution | A solution that has a higher concentration of solute outside than inside a cell causing water to leave the cell by osmosis. |
endocytosis | Energy-requiring process by which large substances from the outside environment can enter a cell. |
exocytosis | Energy-requiring process by which a cell expels wastes and secretes substances at the plasma membrane |