3B Passive Transport

Question 1

Diffusion/Simple Diffusion (define/characterise)

Answer 1

• Kinetic energy (energy a particle or body possess due to motion) = the passive movement of molecules from an area of high concentration to an area of low concentration (down the concentration gradient)
• Faster = greater difference between inter and extra cellular environments + high temps)

Question 2

Passive Transport

Answer 2

Requires no energy

Question 3

Diffusion/Simple Diffusion (molecules that can freely diffuse across plasma membrane)

Answer 3

1. Polarity (non-polar + uncharged + hydrophobic molecules) (e.g. O2, H2, CO2)
2. Size (small molecules) (e.g. water)

Question 4

Facilitated diffusion (define + define key terms (e.g. Protein channel/carrier)

Answer 4

Passive movements of molecules down their concentration gradient through a membrane-bound protein (e.g. protein - channel (pores that let specific substances through the membrane/ Protein Carrier (binds to transported substance - conformational change - substance pushed down concentration gradient + on another side of membrane - Returns to original shape after substance has been transported)

Question 5

Facilitated diffusion (molecules that can use a membrane-protein due to not being able to freely diffuse across the membrane) (e.g.)

Answer 5

1. Polarity (polar + charged + hydrophilic molecules) (e.g. ions)
2. Size (large molecules) (e.g. glucose)

Question 6

Osmosis (define + purpose)

Answer 6

Define the net Passive movement of water from an area of high water concentration to an area of low water concentration (hypotonic solution to hypertonic solution)

Purpose: Speed (many solutes cannot easily cross the plasma membrane) using aquaporins sometimes

Question 7

Osmosis (tonicity - hypertonic + hypotonic + isotonic)

Answer 7

1. Tonicity

Measures the relative
concentration of solutes on
either side of a semipermeable
membrane

2. Hypotonic solutions

Higher solute concentrations + lower solvent concentration (water) outside of cell = Water moving out of the cell to dilute the higher solute concentrations existing in the hypertonic solution

3. Hypotonic Solution

Lower solute concentration + high solvent concentration (water) outside of the cell = water moving into the cell to dilute the higher solvent concentration in the cell

4. Isotonic solution = no net movement of water (rate of water moving out of the cell = the rate of water moving into the cell)

Question 8

Osmosis (tonicity effect on cells in the solutions explained above)

Answer 8

1. Hypotonic Solution

• Since water is moving into the cell to dilute the higher solute concentration there = lysed (plasma membrane breaks - animal cell) + turgid (swollen) - plant cell)

2. Hypertonic Solution

• Since water is moving outside of the cell to dilute the higher solute concentration there = shrivelled (animal cell - shrinking) + Plasmolysed (plant cell - weak + sagging plasma membrane from water loss)

3. Isotonic solution

Animal cell - remains normal

Plant cell - flaccid state (not firm)