movement of molecules + water

simple diffusion

passive movement of molecules from an area of high concentration to an area of low concentration through a partially permeable membrane down a concentration gradient

3 factors that influence rate of diffusion

-concentration gradient; steeper → faster

-thickness of exchange surface; thicker surface = longer distance

-surface area; larger → more space for diffusion to take place → faster

facilitated diffusion?

passive movement of molecules down their gradients through either carrier or channel proteins to get from one side of the membrane to the other

carrier proteins

use ATP to change shape in order to allow molecules to pass through

channel proteins

form hydrophilic tunnels through the membrane to allow molecules to pass through

osmosis

passive movement of water from an area of high water potential to an area of low water potential down a gradient across a partially permeable membrane

water potential of pure water

o

isotonic solutions are…

2 solutions with the same water potential

plant cell observations in hypertonic solution

-vacuole shrinks

-cell becomes flaccid

-cell plasmolyses

• cell membrane pulls from wall

plant cell observations in hypoonic solution

-vacuole swells

-cytoplasm pushes against cell wall and membrane

-cell becomes turgid

active transport?

active process using carrier proteins (and atp) in which molecules move from an area of low concentration to an area of high concentration against a gradient across a partially permeable membrane

what is a cotransporter?

a carrier proteins that binds to 2 molecules at one time

animal cell observations in hypertonic solution

cell shrinks

animal cell observations in hypotonic solution

cell bursts

rate of active transport is dependant on…

-number of carrier proteins; more → faster

-speed of each protein; faster proteins → faster rate

-rate of respiration; faster → more atp available → faster rate

endocytosis

active process in which large substances pass through the membrane

describe how endocytosis occurs

-cell surrounds the substance

-the plasma membrane folds around substance, and pinches off

-cell engulfs substance and forms a vesicle in the cells interior

describe how exocytosis occurs

-substance in vesicles moves towards membrane

-vesicle fuses with the plasma membrane

contents will either be:

• released out of cell

• inserted into the membrane

what is exocytosis

active process in which large substances leave a cell