D2.3 Water Potential (SL)

Question 1

Define “diffusion”

Answer 1

passive net movement of molecules from regions of high concentration to low concentration

Question 1

Describe what happens at equilibrium

Answer 1

• absolute zero → no movement
  
  • -273.15°C / 0K
• at zero: net movement = 0
  
  • one comes across, the others go back
  • no change in concentration → both regions have same concentration

Question 2

Explain brownian motion

Answer 2

The random movement of particles

Question 3

Describe the terms included in the definition of diffusion

Answer 3

passive: requires no energy

net: overall movement (all molecules are moving all the time in all directions)

high to low: down a concentration gradient

Question 4

Define “facilitated diffusion”

Answer 4

the passive net movement of particles from regions of high concentration to low concentration, through a selectively permeable membrane, facilitated by carrier proteins

(some parts of the membrane is hydrophilic, some parts are hydrophobic)

Question 5

Explain what are carrier/channel proteins

Answer 5

integral globular proteins in the plasma membrane that allow some molecules to pass through

Question 6

Channel proteins are ____ to their molecules

Answer 6

channel proteins are specific to their molecules, determined by the polar (or charged) regions on the proteins

Question 7

Is facilitated diffusion passive or active

Answer 7

facilitated diffusion is down a concentration gradient, therefore it is passive

Question 8

Why does facilitated diffusion have a plateau

Answer 8

has a plateau: cells have limiting factors (e.g. surface area to volume ratio), limit in the number of channel proteins

Question 9

Is facilitated diffusion faster or slower compared to (simple) diffusion

Answer 9

facilitated diffusion is much faster

Question 10

What are aquaporins

Answer 10

hole made of special proteins to allow water to go through

Question 11

Define “osmosis” (SL version)

Answer 11

passive net movement of water molecules from regions of low solute concentration to high solute concentration, through a partially/selectively permeable membrane

Question 12

Using erythrocytes as an example, describe hypotonic and hypertonic solutions

Answer 12

• if solution is hypertonic → osmotic flow out of cell
  
  • rbc have higher water potential
  • hypertonic solution: has a lower water potential & cells will lose water
• if solution is hypotonic → osmotic flow into cell
  
  • kills the animal cell

Question 13

Using a plant cell as an example, what happens to the plant cell

Answer 13

turgid/normal plant cell —flaccid→ plasmolysed (cell membrane detaches from cell wall)

Question 14

What does isotonic refer to

Answer 14

no net movement of water moving in or out