Cell Transport Process

Question 1

Describe the structure of the cell membrane.

Answer 1

Composed of phospholipids, cholesterol and proteins. Completely surroundedby cell contents (boundary). Proteins may be integral or peripheral.

Question 2

What are the functions of the cell membrane?

Answer 2

1. Barrier
2. Communication (provides area for contact)
3. Provides receptors for chemicals
4. Controls movement of substences into and out of cell.
5. Selectively permeable

Question 3

In brief, how do lipophilic substances cross the cell membrane?

Answer 3

Lipiphillic substances cross the cell membrane through bilayer by diffusion as membrane is permeable

Question 4

In brief, how do lipophobic substances cross the cell membrane?

Answer 4

Lipophobic substances cannot cross bilayer through diffusion as it is not permeable and is repulsed by lipid tails.

It uses aquaporins and channels to move water and proteins respectively. (may be passive or active)

Question 5

Describe those factors affecting Fick’s law of Diffusion.

Answer 5

Rate of diffusion = SA*Conc.grad*Membperm/membthicknes

• Lipid solubility
• Molecular size
• cell membrane thickness
• conc. gradient
• membrane surface area
• composition of lipid bilayer

Question 6

The Na+-K+ pump is said to be “electrogenic”. What does this mean and what does it relate to?

Answer 6

Na+K+ pump is electrogenic meaning it contributes to establishing the resting membrane potential of its cell. (3Na+ out 2K+ in, therefore imbalance in transfer alowing membrane potential to be negative.