Forces Acting Across Membranes

Question 1

What is meant by the membrane being “dynamic”?

Answer 1

Constantly changing, being broken down or formed etc.

Question 2

What are integral membrane proteins?

Answer 2

Membrane proteins that are imbedded in the membrane

Question 3

List 4 examples of integral membrane proteins

Answer 3

• Enzymes
• Transporter proteins
• Ion channels
• Receptors

Question 4

What are peripheral proteins?

Answer 4

Proteins on the membrane but not imbedded. They aren’t amphipathic

Question 5

What’s peripheral proteins most common function?

Answer 5

Enzymes connected to integral membrane proteins.

Question 6

Name two membranes that differ greatly in membrane protein content

Answer 6

• Schwann cells (18%)

- Mitochondria (70%)

Question 7

What do molecules need to be to diffuse across the membrane?

Answer 7

• Small
• Uncharged
• Lipophilic

Question 8

How do voltage gated channels open in response to a change in potential difference?

Answer 8

The electrical potential acts on charged regions which causes a conformational change

Question 9

What is the electrochemical gradient?

Answer 9

The fact that the concentration of ions in the cell also changes the potential difference, this can affect the movement of ions (positive ions don’t want to move to the overall positive side.)

Question 10

Describe carrier mediated facilitated transport?

Answer 10

• molecule complementary to receptor binds

- Conformational change in receptor, moves molecule into the cell.

Question 11

Define osmolarity

Answer 11

Measure of solute concentration, e.g. 1mole of glucose has an osmolarity of 1 osmole/L

Question 12

Why does 1M of NaCl have an osmolarity of 2osmol/L

Answer 12

It dissociates into 1M of Na and 1M of Cl

Question 13

Isosmotic?

Answer 13

Equal numbers of both non penetrating and penetrating solutes on both sides of the membrane

Question 14

Isotonic

Answer 14

Equal numbers of non penetrating solutes on each side of the membrane