INSTRUCTIONS: -ANSWER EACH QUESTION IN 1 PARAGRAPH. EACH ANSWER CANNOT EXCEED MO

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INSTRUCTIONS:
-ANSWER EACH QUESTION IN 1 PARAGRAPH. EACH ANSWER CANNOT EXCEED MORE THAN HALF A PAGE.
-PROVIDE TWO REFERENCES FOR EACH ANSWER (NO WIKIPEDIA!). USE A CITATION FORMAT OF YOUR CHOICE AND BE CONSISTENT.

1. (a) Discuss the permeability of biological membranes as a function of hydrophilicity / lipophilicity of solute molecules. (b) Discuss the permeability of biological membranes as a function of a solute molecule size. (c) What is the approximate molecular weight above which the permeation of water-soluble substances by diffusion occurs at negligible rates? (d) How do water-soluble molecules that are much larger than this cut-off enter and leave the cell?

2. The poison cyanide acts by binding irreversibly to one of the components of the electron transport chain, blocking its action. As a result, the entire electron transport process comes to a screeching halt and the cells lose 94% of their ATP-producing capacity. Considering the types of cellular activities that depend on energy expenditure, what would be the consequences of cyanide poisoning?

3. Briefly discuss gene therapy and describe 2 potential clinical applications.

Explanation / Answer

1) Biological membranes is made up of phospholipids, glycolipids and cholesterol. The major component of the membrane are phospholipids which are amphipathic. The phospolipid molecules are arranged in two layers. The hydrophobic fatty acid chains are linked to phosphate containing hydrophilic head. Hydrophobic tails are buried in the interior of the membrane and the polar head groups are exposed on both sides.

a) Biological membrane is a selectively permeable membrane. Hydrophobic molecules can readily cross the membrane by dissolving in the hydrophobic core of the lipid bilayer.

b) Smaller and more hydrophobic the molecule, the greater is the permeability across the biological membrane. This process is known as simple diffusion.

c) The permeability of biological membranes by diffusion is neglible for water soluble molecules that have molecular weight more than 200.

d) Larger particles with a molecular weight of more than 200 will pass through the biological membranes with the help of carrier proteins and protein channels present in the lipid bilayer of the membranes.

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