Biology Chapter 6

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33 terms

cell theory

generalization that all living things are composed of cells, and that cells are the basic unit of structure and function in living things

micrograph

photograph of the view through a microscope

organelle

part of a cell with a specific function

plasma membrane

thin outer boundary of a cell that regulates the traffic of chemicals between the cell and its surroundings

cytoplasm

region of a cell between the nucleus and the plasma membrane

eukaryotic cell

cell with a nucleus (surrounded by its own membrane) and other internal organelles

phospholipid bilayer

two layer "sandwich" of molecules that surrounds a cell

diffusion

new movements of the particles of a substance from where they are more concentrated to where they are less concentrated

equilibrium

point at which the number of diffusing molecules moving in one direction is equal to the number of moving in the opposite direction

selectively permeable membrane

membrane that allows some substances to pass more easily than others and blocks the passage of some substances altogether

passive transport

diffusion across a membrane requiring only the random motion of molecules with no energy expended by the cell

facilitated diffusion

pathway provided by transport proteins that helps certain molecules pass through a membrane

hypotonic

having a lower concentration of solute than another solution

hypertonic

having a higher concentration of solute than another solution

osmoisis

passive transport of water across a selectively permeable membrane

active transport

movement of molecules across a membrane requiring energy to be expended by the cell

vesicles

small membrane-bound sac that functions in moving products into, out of, and within a cell

exocytosis

process of exporting proteins from a cell by a vesicle fusing with the plasma membrane

endocytosis

process of taking material into a cell within vesicles that bud inward from the plasma membrane

nuclear envelope

double membrane that surrounds a cell nucleus

nucleolus

ball-like mass of fibers and granules in a cell nucleus

ribosomes

cluster of proteins and nucleic acids that constructs proteins in a cell

endoplasmic reticulum

network of membranes within a cell's cytoplasm that produce a variety of molecules

Golgi apparatus

cellular organelle that modifies, stores, and routes cell products

vacuoles

membrane-bound sac that buds from the endoplasmic reticulum or the Golgi apparatus

lysosomes

membrane-bound sac containing digestive enzymes that can break down proteins, nucleic acids, and polysaccharides

chloroplasts

organelle found in some plant cells and certain unicellular organisms where photosynthesis takes place

mitochondria

cellular organelles where cellular respiration occurs

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

microtubules

straight, hollow tube of proteins that gives rigidity, shape, and organization to a cell

microfilaments

solid rod of protein, thinner than a microtubule, that enables a cell to move or change shape

flagella

long, thin, whip-like structure, with a core of microtubules, that enable some cells to move

cilia

short structures containing bundles of microtubules that move a cell through its surroundings or move fluid over the cell's surface

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