RDN Nutritional Biochemistry 3

Question 1

Which lipoprotein is primarily responsible for transporting dietary fat from the intestine to peripheral tissues?

Accepted Answer

Chylomicrons

Answer

Chylomicrons are assembled in intestinal enterocytes and transport dietary triglycerides, cholesterol, and fat-soluble vitamins via the lymphatic system to peripheral tissues.

Question 2

Pyruvate dehydrogenase complex requires five cofactors; which of the following is NOT one of them?

Accepted Answer

Pyridoxal phosphate (PLP)

Answer

The pyruvate dehydrogenase complex uses TPP, lipoic acid, FAD, NAD+, and CoA (derived from pantothenic acid) as cofactors, but does NOT require pyridoxal phosphate (PLP/B6).

Question 3

In the context of iron absorption, what effect does ascorbic acid (vitamin C) have?

Accepted Answer

Converts ferric (Fe3+) to ferrous (Fe2+) form, enhancing absorption

Answer

Vitamin C reduces dietary non-heme iron from the ferric (Fe3+) to the more soluble ferrous (Fe2+) form, which is the form transported by DMT-1 across the intestinal epithelium.

Question 4

Which enzyme converts arachidonic acid into prostaglandins and thromboxanes?

Accepted Answer

Cyclooxygenase (COX)

Answer

Cyclooxygenase (prostaglandin H synthase) catalyzes the conversion of arachidonic acid into prostaglandin H2, the precursor for all prostaglandins and thromboxanes via the COX pathway.

Question 5

What is the net ATP yield from complete oxidation of one molecule of glucose via glycolysis, TCA cycle, and oxidative phosphorylation?

Accepted Answer

30-32 ATP

Answer

Using current P/O ratios (2.5 for NADH, 1.5 for FADH2), complete glucose oxidation yields approximately 30-32 ATP, lower than the older textbook value of 36-38.

(RDN) Registered Dietitian Nutritionist Practice Test

(RDN) Registered Dietitian Nutritionist Practice Test

RDN Nutritional Biochemistry 3