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cell theory

idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells


photograph of the view through a microscope


part of a cell with a specific job to do

plasma membrane

defines the boundary of the cell and regulates the traffic of chemicals between the cell and its surroundings


houses the cell's genetic material in the form of DNA


consists of various organelles suspended in a fluid

cell wall

protects the plant cell and maintains its shape

prokaryotic cell

cell lacking a nucleus and most other organelles

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


the net movement of the particles of a substance from where they are more concentrated to where they are less concentrated



selectively permeable membrane

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

passive transport

transport of a substance across a cell membrane by diffusion

facilitated diffusion

transport proteins provide a pathway for certain molecules to pass


the passive transport of water across a selectively permeable membrane


the solution with the higher concentration of solute


the solution with the lower solute concentration


solutions in which the concentrations of solute are equal

active transport

when a cell expends energy to move molecules or ions across a membrane


small membrane sacs that specialize in moving products into, out of, and within a cell


process by which vesicles release their contents outside the cell


process by which a cell takes material into the cell within vesicles that bud inward from the plasma membrane

nuclear envelope

surrounds the nucleus


contains the parts that make up organelles called ribosomes


clusters of proteins and nucleic acids assembled from components made in the nucleolus

endoplasmic reticulum

within the cytoplasm of a cell, an extensive network of membranes

golgi apparatus

an organelle that modifies, stores, and routes proteins and other chemical products to their next destinations


large membrane-bound sacs


membrane-bound sacs that contain digestive enzymes that can break down macromolecules


photosynthetic organelles found in some cells of plants and algae


site where cellular respiration occurs


the main energy source that cells use for most of their work

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