Movement through cell membranes Flashcards
3 processes that move substances through cell membranes
diffusion
osmosis
active transport
diffusion definition
the movement of a substance from an area of high concentration to an area of low concentration
a passive process
why does diffusion not require energy?
because it moves substances ALONG the concentration gradient
what type of substances move by diffusion
liquids and gases
1 example of animal diffusion
0₂ and CO₂ between the air in the alveoli and the blood capillaries
1 example of diffusion in plants
H₂O vapour moving out of leaves and stems via stomata
osmosis definition
the movement of water molecules from a region of high water concentration to a region of low water concentration through a semi-permeable membrane
what type of process is osmosis
a passive process
what category does osmosis fall into
diffusion
selectively-permeable membrane
a membrane that allows free passage of some molecules and prevents the passage of others
advantage of a selectively permeable membrane
substances can be let in or substances can be let out or substances can be kept out or substances can be kept in
if a cell is surrounded by a solution of higher water concentration
water moves in by osmsos
if a cell is surrounded by a solution of lower water concentration
water moves out by osmosis
a cell is surrounded by a solution of the same water concentration
it stays the same
turgor or turgor pressure
the pressure of the cell contents on the cell wall
3 things that turgor does in plants
gives them
shape
strength
support (in woody stems and leaves)
what happens if there is no turgor in a cell
it becomes flaccid (limp)
what happens if there is no turgor in a plant
it wilts
plasmolysis
the shrinking of the cell contents due to the loss of water by osmosis
1 plant example of osmosis
absorption of water by germinating seeds
1 animal example of osmosis
absorption of water in the intestine
why does sugar or salt prevent food decaying
the microorganisms lose water by osmosis as there is a low water concentration outside. they become plasmolysed and die
osmoregulation
the maintanence of the water-salt balance in body fluids in organisms
the osmoregulatory organs in humans
kidneys
the osmoregulatory organs in amoeba
the contractile vacuoles
active transport
the movement of substances across a membrane against a concentration gradient that requires energy
1 plant example of active transport
absorbtion of minerals by root epidermal cells
1 animal example of active transport
reabsorption of glucose, amino acids and salt into the nephron of the kidney
to demonstrate osmosis in an artificial membrane
what is the membrane called
visking tubing
to demonstrate osmosis in an artificial membrane
what do you first do with the visking tubing
tie a knot at one end
to demonstrate osmosis in an artificial membrane
what do you fill the visking tubing with?
strong sucrose solution
to demonstrate osmosis in an artificial membrane
what do you fill the control with
distilled water
to demonstrate osmosis in an artificial membrane
result for real experiment 2
turgidity increases
mass increases
to demonstrate osmosis in an artificial membrane
result for control 2
turgidity unchanged
mass unchanged
