Lec 6: Membrane Transport

Question 1

Membrane Transport Importance: (5)

Answer 1

1. ) Nutrients – move into cells
2. ) Wastes – move out of cells
3. ) Ionic balance
4. ) Electrical balance (resting membrane potential)
5. ) Regulatory molecules – certain hormones

Question 2

~20% of all genes in E. coli are involved in

Answer 2

membrane transport

Question 3

Types of membrane transport: (3)

Answer 3

1. ) Simple Diffusion
2. ) Facilitated Diffusion
   - Carrier mediated
   - Channel mediated
3. ) Active Transport
   - Direct (1)
   - Indirect (2)

Question 4

• Simple Diffusion =
• Driven by? =
• Always proceeds towards…
• Diffusion across cell
• Membranes is limited to =

Answer 4

= Movement from region of high to low concentration
= concentration gradient
…a decrease in free energy of the system (delta G < 0)
= Small, Non-polar
(Example: O2 , CO2)

Question 5

Factors that influence diffusion rates across membranes: (3)

Answer 5

1. ) Solute size
2. ) Polarity
3. ) Solute charge

Question 6

(1. Solute size)
- ______ molecules diffuse faster
- What can freely diffuse across membranes?

Answer 6

• Smaller

- Uncharged, non-polar molecules with MW up to ~100

Question 7

(2. ) Polarity)
- _______ molecules diffuse faster
- The ______ the polarity the faster the diffusion

Answer 7

• Non-polar

- lower

Question 8

(3. ) Solute charge)
- Lipid bilayer is highly impermeable to…
- Ions are charged, therefore…
- Requires energy to…

Answer 8

• …ions
• …associated with a shell of hydration (water molecules attracted to the charged ion)
• …remove the shell of hydration (break hydrogen bonds), which would be needed to allow the ion to enter into the hydrophobic layers of the membrane