Osmosis, Diffusion, and Osmotic Pressure Flashcards
What is diffusion?
the movement of molecules due to random motion
net movement of molecules across a membrane will
passively diffuse across a membrane from high
concentration to low concentration until equilibrium is
reached
the random movement (diffusion) continues!
What is a key concept of both osmosis and diffusion?
molecules are moving in both directions
What is osmosis?
the diffusion of water, for example across a membrane
Describe how water moves into and out of a cell.
by passive diffusion, but it can move into a cell more readily by facilitated diffusion using protein channels called aquaporins
What is osmotic pressure?
a build-up of pressure that results from the continuous diffusion of water across the cell membrane into the cells
What happens when osmotic pressure continues to build-up?
cell membrane might be able to expand a little, but then it will burst
What can help prevent osmotic lysis?
cell wall
How can cells prevent swelling in hypotonic solutions?
due to osmosis, for example water can
leave the cell
What do bacteria do to combat osmotic pressure in hypotonic environments?
use a ‘net’ like cell wall called
peptidoglycan, to surround the cytoplasm
What do cell walls around bacterial cells do?
help to counteract osmotic pressure build up due to osmosis
What do vacuoles in plant cells do?
exert hydrostatic pressure on the cell walls and provide rigidity to the plant cell
What does dehydration do to plant cells?
collapses the vacuoles, relives the hydrostatic pressure, and results in wilting
What is the cell wall?
a rigid structure that surrounds the plasma membrane and resists cell expansion when the cell takes in water
maintains cell shape in some organisms
