movement of substance

Question 1

Define diffusion

Answer 1

Diffusion is the new movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient

Question 2

Factors affecting rate of diffusion

Answer 2

• Concentration gradient (steeper)
• Diffusion distance shorter
• Surface area to volume ratio
• Lighter the mass of solute
• Temperature (higher temperature = more kinetic energy so increased rate of diffusion)

Question 3

Define Osmosis

Answer 3

Net movement of water molecules from a region of higher water potential to a higher of lower water potential though a partially permeable membrane, down a water potential gradient

Question 4

Define Water potential

Answer 4

Measure the tendency of water to move from one place to another

Question 5

Factors affecting rate of osmosis

Answer 5

• Water potential gradient
• Surface area to volume ratio
• Distance the water molecules need to move

Question 6

When is water potential gradient formed

Answer 6

Partially permeable membrane separates 2 solutions of g different water potentials

Question 7

What solution has a higher water potential

Answer 7

Dilute solution has a higher water potential than a concentrated solution

Question 8

RBS (animal cell) in concentrated solution

Answer 8

Cell sap has a higher water potential than surrounding solution. Water molecules leave the cell by osmosis. Membranes of the cell forms little spikes. Cell shrinks and becomes dehydrated. Cell dies eventually.

Question 9

RBS (animal cell) in dilute solution

Answer 9

Cell sap has a lower water potential than surrounding solution. Water molecules enter the cell by osmosis. Animal cell does not have cell wall to prevent over expansion of cell membrane. Cell bursts

Question 10

Plant cell in concentrated solution

Answer 10

Cell sap has a higher water potential than surrounding solution. Water molecules leave the cell by osmosis. Cell and vacuole decreases in size and becomes flaccid. Cytoplasm shrinks away from the cell wall and cell is plasmolyse.

Question 11

Plant cell in a dilute solution

Answer 11

Cell sap has a lower water potential than surrounding solution. Water molecules enter the cell by osmosis. Vacuole increases in size. Cell wall prevents over expansion of cell membrane by exerting an opposing pressure. When cell is fully turgid, further entry of water is prevented.