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the theory that (1) all organisms are composed of cells, (2) the cell is the basic unit of organization of organisms, (3) all cells come from preexisting cells
firm, fairly rigid structure located outside the plasma membrane of plants, fungi, most bacteria, and some protists; provides support and protection
the center of the atom which contains the protons and neutrons; in cells, structure that contains the cell's genetic material (DNA) and controls the cell's activities
thin, hollow cylinders made of protein that provide structural support for eukaryotic cells
organelle in eukaryotic cells with a series of highly folded membranes surrounded in cytoplasm; site of cellular chemical reactions; can either be rough (with ribosomes) or smooth (without ribosomes)
organelle in eukaryotic cells with a system of flattened tubular membranes; modifies proteins and sends them to their appropriate destinations
organelles that contain digestive enzymes; digest excess or worn out organelles, food particles, and engulfed viruses or bacteria
organelles that, like mitochondria, are surrounded by a double membrane and contain their own DNA.
long, thin, whip-like structures, with a core of microtubules, that enable some cells to move
short, numerous, hairlike projections composed of pairs of microtubles; frequently move in a wavelike motion; aid in feeding and locomotion
chlorophyll-containing cell organelles found in the cells of green plants and some protists; capture light energy from the sun, which is converted to chemical energy in food molecules
in animal cells, a pair of small cylindrical structures composed of microtubles that duplicate during interphase and move to opposite ends of the cell during prophase
clear, gelatinous fluid in eukaryotic cells that suspends the cell's organelles and is the site of numerous chemical reactions
net, random movement of particles from an area of higher concentration to an area of lower concentration, eventually resulting in even distribution
the concentration of molecules will be the same throughout the space the molecules occupy
diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal
pathway provided by transport proteins that helps certain molecules pass through a membrane
transport of a substance (as a protein or drug) across a cell membrane against the concentration gradient
process in which extensions of cytoplasm surround and engulf large particles and take them into the cell
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