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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

micrograph

photograph of the view through a microscope

organelle

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

nucleus

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

cytoplasm

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

diffusion

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

equilibrium

balance

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

osmosis

the passive transport of water across a selectively permeable membrane

hypertonic

the solution with the higher concentration of solute

hypotonic

the solution with the lower solute concentration

isotonic

solutions in which the concentrations of solute are equal

active transport

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

vesicles

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

exocytosis

process by which vesicles release their contents outside the cell

endocytosis

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

nuclear envelope

surrounds the nucleus

nucleolus

contains the parts that make up organelles called ribosomes

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

vacuoles

large membrane-bound sacs

lysosomes

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

chloroplasts

photosynthetic organelles found in some cells of plants and algae

mitochondria

site where cellular respiration occurs

ATP

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

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