Chapter 12: Membrane Structure and Function

Question 1

Name some of the features common to all membranes:

Answer 1

1. asymmetric: bilayers are different
2. amphipathic: hydrophobic and hydrophilic
3. non-covalent assemblies
4. fluid structures
5. electrically polarized (inside is negative)
6. composition: lipids, unique proteins, carbohydrates
7. structure: sheetlike, closed boundaries, two molecules thick
8. proteins mediate transfer molecules and information across the membrane

Question 2

What conditions are required for simple diffusion?

Answer 2

1. small
2. lipophilic
3. with the concentration gradient

Question 3

Integral membrane protein:

Answer 3

interacts tightly with the membrane interior

Question 4

Peripheral membrane protein:

Answer 4

interacts with the border of a membrane

Question 5

Channel:

Answer 5

allows rapid movement of molecules down a gradient across a membrane

Question 6

Passive transport:

Answer 6

facilitated diffusion

Question 7

Active transport:

Answer 7

movement against a concentration gradient

Question 8

Na+-K+ ATPase:

Answer 8

inhibited by digitalis

Question 9

Secondary transporter:

Answer 9

uses the energy of one gradient to create another

Question 10

Antiporter and Symporter:

Answer 10

A– molecules moving in opposite directions

S– molecules moving in the same direction

Question 11

Ion channel:

Answer 11

can be voltage gated or ligand gated