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cell theory

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


photograph of the view through a microscope

plasma membrane

thin outer boundary which defines the boundary of the cell and regulates the traffic of chemicals between the cells and its surroundings.


houses the cells genetic material in the form of DNA


entire region of the cell between the nucleus and the plasma membrane

cell wall

protects the plant cell and maintains its shape *only plant cells have a cell wall.

prokaryotic cell

lacks a nucleus and most other organelles ex. bacteria

eukaryotic cell

has a nucleus surrounded by its own membrane, and has other internal organelles bounded by membranes. ex. plants, fungi, prosists, and animal


loves water.


doesnt like water, doesnt interact with water

phospholipid bilayer

"sandwich" of molecules which surround the organelle wall.

fatty acid tails = HYDROPHOBIC


PROTEINS embedded in the phospholipid bilayer.



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


or balance

selectively permeable membrane

allows some substances to cross the membrane more easily then others and blocks the passage of some substances altogether. this is PASSIVE TRANSPORT.

passive transport

diffusion across a membrane, because no energy is needed to do this. *high concentration to low concentration

facilitated diffusion

transport proteins provide a pathway for certain molecules to pass. (facilitate = to help)


passive transport over a selectively permeable membrane


a solution with higher concentration


a solution that is said to have lower concentration


solutions in which the concentrations of the solute are equal are said to be isotonic.

active transport

a process when a cell expands energy to move molecules or ions across a membrane. during active transport a specific protein pumps a solute across a membrane, usually the opposite direction in which diffusion travels. LOW CONCENTRATION --> HIGH CONCENTRATION


larger particles are packages in vesicles in order to move through the membrane.


exiting the products from the cell by fusing with the plasma membrane and spilling its contents out of the cell.


reverse process of exocytosis, takes material into a cell within vesicles that bud inward from the plasma membrane

nuclear envelope

surrounds the nucleus in a pair of membranes, substances made in the nucleus move into the cell's cytoplasm through tiny holes or pores in the nuclear envelope.


contains the parts that make up organelles called ribosomes.


proteins are constructed in a cell by ribosomes, "workers"

endoplasmic reticulum

within the cytoplasm of a cell is an extensive network of membranes, produces and enormous amount of molecules. main manufacturing and transportation facilities in the celll factory.

rough ER

has ribosomes lined on the outside of the membrane., ribosomes produce proteins, also produce proteins which are packaged in vesicles.

smooth ER

lack ribosomes but builds lipid molecules.

the golgi apparatus

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


in the cytoplasm which are large membrane-bound sacs, they store undigested nutrients.


membrane bound sacs which contain digestive enzymes that can break down such macromolecules as proteins, nucleic acids and polysaccharides.


they are in eukaryotic cells, and sites where cellular respiration occurs. In this process it releases energy from sugars and certain other organic molecules and then uses it in the formation of another organic molecule called ATP.

ATP (adenosine triphosate)

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

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