In Class Questions

Question 1

Given the carbon skeletons below, order the fatty acids
from lowest to highest melting point.
i 20:0
ii 20:4(D5,8,11,14 )
iii 14:0
iv 18:1(D9)

Answer 1

ii,iv,iii,i

Question 2

What is the advantage of storing fat as triacylglycerols instead of free fatty acids?

Answer 2

Due to the ester linkage, triacylglycerols are more hydrophobic than fatty acids and can be stored more densely.

Question 3

FRAP (Fluorescence Recovery After Photobleaching) can be used to observe lateral diffusion of lipids within the plane of a membrane. As shown in A, lipids can diffuse spontaneously within this lateral plane. Would you expect lipids to also move spontaneously across the plane of the membrane from one leaflet to another as shown in B? Why or why not?

Answer 3

No. Vertical movement across the membrane requires moving a polar charged head group across the hydrophobic interior of the bilayer. This is an endergonic process.

Question 4

Consider the structure of cholesterol. Would you expect the presence of cholesterol to promote the L o state or the L d state?

Answer 4

This is dependent on lipid composition. Cholesterol interacts with unsaturated fatty acids promoting the L o state. Cholesterol interacts with saturated fatty acids promoting the L d state.

Question 5

. How is a cholesterol ester distinct from
cholesterol? What is the function of cholesterol esters

Answer 5

Cholesterol esters are no longer amphipathic enough to function within membranes. They are
transported within lipoprotein particles and stored

Question 6

During times of starvation, what is the predominant fate of fatty acids within VLDL?

Answer 6

Myocytes. Energy is needed and fat is the primary form of stored energy

Question 7

After a carbohydrate rich meal, what is the predominant fate of fatty acids within VLDL?

Answer 7

Adipocytes. Energy needs are satisfied so fat is stored as TAG within adipocytes