transport new

Question 1

4 factors effecting diffusion rate

Answer 1

Temperature:
- increasing temperature increases diffusion rate.
- increase in kinetic energy > more movement/vibration > particles spread out more
Concentration difference:
- the steeper the concentration gradient the faster the rate of diffusion.
SA:Volume ratio:
- the bigger the surface area to volume ratio the quicker the diffusion rate will be.
- in organisms with a small SA:vol ratio, the diffusion rate will not be enough to help maintain the demand for nutrients/oxygen
Thickness of the membrane:
- low thickness> low diffusion distance > higher rate of diffusion.
- high thickness > high diffusion distrance > low rate of diffusion.

Question 2

equation for rate of diffusion

Answer 2

rate of diffusion=
(surface area x concentration gradient) / distance of which diffusion occurs

Question 3

what are two solutions with the same water potential called?
what are two solutions with different water potentials called?

Answer 3

same water potential = isotionic

If they have different water potentials the higher one is called hypotonic and the lower one is called hypertonic

Question 4

what happens to animal cells if the water potential of an external solution is higher/lower

Answer 4

higher:
- water moves in
- cells swell and burst
- cytolysis- they split

lower:
- water moves out
- cell is crenated (wrinkled)

Question 5

what happens to plant cells if the water potential of an external solution is higher/lower

Answer 5

higher:
- water moves into cell
- cell becomes turgid as vacuole swells

lower:
- water moves out of cell
- cell becomes plasmolysed (cytoplasm shrinks)

Question 6

what is solution potential and what is pressure potential

Answer 6

solution potential
- cytoplasm contains solutes which make up the solute potential
- solute potential is always negative
pressure potential
- wall of the cell exerts a pressure on the cell contents which provides a pressure potential.
- pressure potential stops water from entering a cell
- pressure potential is always positive

Question 7

what is the equation for overall water potential

Answer 7

overall water potential= solute potential + pressure potential

Question 8

how do carrier proteins release energy for active transport

Answer 8

• there is an ATP binding site
• this allows the hydrolysis of ATP into ADP + Pi
  (Pi= inorganic phosphate ions)
• this releases energy

Question 9

what is endocytosis

Answer 9

• materials are brought into the cell by the formation of vesicles
• requires ATP to move the vesicles along the microtubule tracks

Question 10

exocytosis

Answer 10

• use of vesicles to transport materials out of the cell.
• vesicles bind with the cell surface membrane
• because the membrane is fluid, it parts and lets the contents of the vesicle out.
• requires ATP to move the vesicles along the microtubule tracks

Question 11

what is pinocytosis and phagocytosis

Answer 11

Pinocytosis
- absorption of liquids by endocytosis
Phagocytosis
- absorption of solids by exocytosis