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MCAT Organic Question — Triacylglycerides

Triacylglycerides consist of

I. a ribose backbone

II. a glycerol backbone

III. three phosphodiester linkages

IV. three ester linkages

a) I and III

b) II only

c) II and III

d) II and IV


Triacylglycerides consist of a glycerol backbone bonded to three fatty acids. The bond between each acid and the glycerol is an ester group. Phosphodiester linkages are found in DNA.

a) I and III, incorrect, Glycerol, not ribose, forms the backbone of triacylglycerides.

b) II only, incorrect, There are three ester linkages in addition to the glycerol backbone.

c) II and III, incorrect, Phosphodiester linkages are found in DNA not triacylglycerides.

d) II and IV, correct. Phospholipids contain two ester linkages between the glycerol backbone and the two fatty acid tails, and one ester linkage between glycerol and the phosphate group.

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