Membrane Transport

Question 1

What are hydrophobic molecules that need to cross the cell membrane?

Answer 1

O₂, CO₂, N₂, benzene

Question 2

What are small, uncharged, polar, molecules that need to cross the cell membrane?

Answer 2

H₂O, urea, glycerol

Question 3

What are large, uncharged, polar molecules that need to cross the cell membrane?

Answer 3

Glucose and sucrose

Question 4

What are some ions that need to cross the cell membrane?

Answer 4

H⁺, Na⁺, HCO₃^-, K⁺, Ca²⁺, Cl^-, Mg²⁺

Question 5

What are the two major classes of membrane transport proteins?

Answer 5

Transporters and channels

Question 6

What do transporters do?

Answer 6

Bind the specific solute to be transported and undergo a series of conformational changes to transfer the bound solute across the membrane.

Question 7

What do channels do?

Answer 7

They form aqueous pores that extend across the lipid bilayer; when open, these pores allow specific solutes to pass through them and thereby cross the membrane.

Question 8

What type of transport do channels allow?

Answer 8

**Passive **transport or facilitated diffusion

Question 9

What influence passive transport?

Answer 9

The **concentration **gradient and the electrochemical gradient

Question 10

What type of transport move substances against their concentration/electrochemical gradient?

Answer 10

Active transport

Question 11

Each type of ____________ has one or more specific binding sites for its solute (__________). It transfers the _________ across the lipid bilayer by undergoing reversible ______________ changes that alternately expose the _________-_________ site first on one side of the membrane and then the other.

Answer 11

Each type of transporter has one or more specific binding sites for its solute (substrate). It transfers the substrate across the lipid bilayer by undergoing reversible **conformational **changes that alternately expose the **substrate-binding **site first on one side of the membrane and then the other.

Question 12

What are the three ways of driving active transport?

Answer 12

1. Coupled transporter
2. ATP-driven pump
3. Light-driven pump

Question 13

What do coupled transporters do?

Answer 13

Couple the uphill transport of one solute across the membrane to the downhill transport of another

Question 14

What do ATP-driven pumps do?

Answer 14

Couple uphill transport to the hydrolysis of ATP

Question 15

What do light-driven pumps do?

Answer 15

Couple uphill transports to an input of energy from light

Question 16

What are the three types of transporter-mediated movement?

Answer 16

1. **Uniport **(uni-: one)
2. **Symport **(sym-: together)
3. Antiport (anti-: against)