Chapter 12- Memranes

Question 1

Common attributes to membranes

Answer 1

• Sheetlike, only two molecules thick, form closed boundaries. Thickness of most is between 60-100 A
• consist of mainly lipids and proteins. They also contain carbohydrates that are linked to lipids and proteins
• hydrophilic and hydrophobic moieties; these lipid bilayers are barriers to the flow of polar molecules
• non covalent, asymmetric, fluid structures, electrically polarized such that the inside is negative

Question 2

Membrane fluidity

Answer 2

Controlled by fatty acid composition and cholesterol content

Cholesterol is the key modulator of membrane fluidity in animals

Question 3

What is the driving force for membrane formation

Answer 3

The hydrophobic effect

Question 4

Arrange the following substances in order of increasing permeability: glucose, glycerol, Cl-, indole, tryptophan

Answer 4

Cl- is the least permeable bc it is charged and is in ionic form

Glucose is next because it is polar

Tryptophan because it is A zwitterion (contains both positive and negative groups)

Glycerol is less polar than the above

Indole is the most permeable bc it lacks ionic groups and only contains 1 polar group