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19 terms

Cells and Their Environment

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passive transport
movement across the cell membrane that does not require energy from the cell
concentration gradient
Difference in concentration of a substance
Equilibrium
condition in which the concentration of a substance is equal throughout a space
diffusion
movement of a substance from an are of high concentration to an are of lower concentration caused by the random motion of particles
osmosis
diffusion of water through a selectively permeable membrane
hypertonic solution
solution that causes a cell to shrink because of osmosis
hypotonic solution
solution that causes a cell to swell because of osmosis
isotonic solution
solution that produces no change in cell volume because of osmosis
ion channel
doughnut-shaped transport protein with a polar pore through which ions can pass
carrier proteins
transport protein that binds to a specific substance on one side of the cell membrane, carry the substance across the cell membrane, and release it on the other side
Facilitated Diffusion
passive transport because it moves substances down their concentration gradient without using the cell's energy
active transport
the transport of a substance across the cel membrane against its concentration gradient
sodium potassium pump
transports three sodium ions out of a cell and two potassium ions into the cell
endocytosis
movement of a substance into a cell by a vesicle
exocytosis
movement of a substance by a vesicle to the outside of a cell
Receptor Protein
protein that binds to a specific signal molecule enabling the cell to respond to the signal molecule
second messengers
acts as a signal molecule in the cytoplasm
What needs to happen between cells during communication
signal molecules that bind to receptor proteins on cells
When a signal molecule binds to a receptor protein, how does the cell change?
-enables specific ions to cross the cell membrane
-causing the formation of a second messenger
-speeding up chemical reactions inside the cell