Lecture 3 Questions Flashcards Preview

Biochemistry > Lecture 3 Questions > Flashcards

Flashcards in Lecture 3 Questions Deck (7)
Loading flashcards...
1

Explain why lengthening the hydrocarbon chain in a fatty acid will lower the CMC.

With more hydrophobic surface to sequester, the association energy increases.

2

Examine the steric and polarity characteristics of a phospholipid. Suggest how its bilayer forming properties might change if the headgroup were twice as wide, or if the chains were ¼ as long relative to the long axis of the lipid.

Bilayer formation depends on the area of the chains and headgroup being similar, so increasing the area of the headgroup could destabilize it, resulting in micelle formation. This effect has been observed in a few cases. Shortening the chains will, at some point, alter the balance of polarity and result in greater water solubility, as has been observed experimentally.

3

A lipid vesicle is made from palmitoyloleoylphosphatidylcholine, and is 1000Å in diameter measured from bilayer center to bilayer center.
Calculate the number of lipid molecules in the vesicle, assuming an area per lipid of 75 square angstroms at the boundary of the hydrophobic region.

The Hydrophobic region is about 30A thick, so the inner leaflet is 985 A in diameter, ad the outer leaflet is 1015 A in diameter. Calculate the sum of the areas and divide by 75.

4

A lipid vesicle is made from palmitoyloleoylphosphatidylcholine, and is 1000Å in diameter measured from bilayer center to bilayer center. If the diameter is only 300Å, calculate how many lipids are in the inner and outer monolayers, respectively.

Same approach, but the diameters are 285 A and 315A.

5

A lipid vesicle is made from palmitoyloleoylphosphatidylcholine, and is 1000Å in diameter measured from bilayer center to bilayer center. Using the literature, find the diameter of a synaptic vesicle, measured from bilayer centers.

Fill in

6

A lipid vesicle is made from palmitoyloleoylphosphatidylcholine, and is 1000Å in diameter measured from bilayer center to bilayer center. Speculate on the problem of fusing two small vesicles, given that lipids do not easily flip from one surface to the other.

Since the areas are different, fusing the vesicles will produce a strain that needs to be resolved by balancing the areas. There are enzymes that do this (flippases).

7

Water soluble vitamins must be taken every day, but hydrophobic vitamins may remain in the body for months after ingestion. Propose an explanation for the disparity.

Hydrophobic vitamins ("fat-soluble") accumulate in the fatty tissues of the body, and leach out slowly. Some drugs are fat soluble, and so clearance can also be slow.