#3 Transport Across Cell Membranes

concentration gradient

- difference in concentration of a substance on two sides of a membrane

passive transport

- doesn't require energy - the movement of particles through a cell membrane without the use of cellular energy; includes diffusion, osmosis, and facilitated diffusion.

endocytosis

- form of active transport - process where a cell engulfs materials with a portion of the cell's plasma membrane and releases the contents inside of the cell.

exocytosis

- form of active transport - process where a cell releases a particle by enclosing the particle in a vesicle that then moves to the cell surface and fuses with the cell membrane

osmosis

- form of passive transport - the diffusion of water through a selectively permeable membrane

diffusion

- form of passive transport - the movement of molecules from an area of higher concentration to an area of lower concentration. - ex. how oxygen enters the body and carbon dioxide leaves the body

facilitated diffusion

- form of passive transport - transportation of molecules across a plasma membrane with the concentration gradient with the aid of carrier (transport) proteins - ***requires proteins***

sodium potassium pump

- most famous example of active transport - moves sodium outside of the cell and potassium inside the cell by using ATP

active transport

- requires energy - the movement of particles from an area of low concentration to an area of high concentration that uses energy provided by ATP - ***needs ATP***

co-transport

- transport across a cell membrane in which movement of one substance relies on the movement of another in same or opposite direction.

hypertonic

- when comparing two solutions, referring to the one with a greater solute concentration.

hypotonic

- when comparing two solutions, referring to the one with a lower solute concentration.

isotonic

- when two solutions contain equal concentrations of solutes.