Cell Membrane and Transport

Question 1

What is a biological membrane?

Answer 1

Consist of continuous double layer of lipid molecules where membrane proteins are embedded

Question 2

What is clinical significance of understanding cell membrane transport?

Answer 2

Predict which drugs can penetrate specific tissues or compartments such as BBB penetration

Question 3

Mechanisms of absorption from GI tract

Answer 3

1. Passive Diffusion (Simple and facilitated) - No energy required
2. Active Transport - Energy required through hydrolysis of ATP
3. Endocytosis/ Exocytosis
4. Paracellular Transport - No energy required

Question 4

Simple Diffusion VS Facilitated Diffusion (transport)

Answer 4

1. Simple Diffusion
   - HydroPHOBIC (small lipid soluble drugs) that can diffuse into lipoidal matrix of membrane
2. Facilitated Diffusion
   - HydroPHILIC (water soluble drugs) that moves through aqueous pores/channels
   - Carrier Mediated Transport - Carries ions, nutrients, metabolites, transmitters and drugs

Question 5

Active Transport

Answer 5

Carrier-mediated transport with transmembrane proteins for lipid insoluble drugs, ions, nutrients, metabolites, transmitters etc that requires hydrolysis of ATP for energy

Question 6

Endocytosis VS exocytosis transport

Answer 6

1. Endocytosis (no energy)
   - Cells taking in substances from OUTSIDE the cell by engulfing into a vesicle
   - immune cells
2. Exocytosis (no energy)
   - Cells shifts materials from INSIDE cells to extracellular space
   - Aerobic respiration - Cells produces CO2 and H2O which are removed

Question 7

Paracellular Transport

Answer 7

Epithelial tight junction permeability
- Independent tight junction regulation affecting mucosal permeability
- BBB - restricts movement of drugs due to tight junctions
- Epithelial damage - leaky tight junctions in Heart failure patients, causing sacral and pedal edema