Question

1. Which of the following functions of vitamin B-12 is not related to the functions of folate?

A. Maintaining myelin sheaths

B. Transfer of methyl groups

C. Homocysteine metabolism

D. DNA synthesis

2. Plants _______.

A. are a rich source of vitamin B-12

B. are not sources of vitamin B-12

C. contain about the same amount of vitamin B-12 as is found in animal foods, such as liver

D. can make vitamin B-12 in the presence of folate

3.With excessive intakes of vitamin C, increased urinary excretion of ______ (a by-product of vitamin C metabolism) may cause kidney stone formation in susceptible individuals.

A.oxalate

B. pyruvate

C. phosphate

D. uric acid

4.Which have vitamin-like compounds that have antioxidant functions in the body?(select those that apply)

A.Taurine

B.Choline

C.Carnitine

D. Lipoic

E. Inositol

5. Why are older adults at increased risk for vitamin B-12 deficiency compared to younger people?

A. As you age, your macula begins to turn yellow—a sign of excessive folate absorption, which masks vitamin B-12 deficiency.

B. As you age, your metabolism slows and a rapid metabolism is required for optimal vitamin B-12 absorption.

C. As you age, your bones become more porous; porous bones do not absorb vitamin B-12 as well as dense bones do.

D. As you age, your stomach produces less acid, which limits cleavage of vitamin B-12 from food. In addition, decreased production of intrinsic factor by the stomach limits vitamin B-12 absorption.

Answer 1

1. Option a

Myelin which is a fatty substance is essential for the formation of myelin sheaths. An adequate level of vitamin B12 is necessary for the growth and development. Vit B12 plays an important role in the maintenance of the myelin nerve sheaths.Transfer of methyl groups during DNA synthesis is a common function of folate and Vit B12.   

2.Option b

Plants generally do not produce Vit B12, it is obtained from animal products. Spirulina is the plant food that is claimed to contain vitamin B12. However, it is reported to offer pseudovitamin B12, which is biologically unavailable.

3. Option a

The excess of Vitamin C is usually excreted from the body as oxalate. Oxalate is a waste product that binds to minerals and sticks together to form crystals that result in the formation of a solid mass or kidney stones. Dehydration, digestive diseases and obesity can cause excretion of oxalate from urine.

4. Options a,c d and e

Taurine is a sulfur-containing amino acid is reported to have antioxidant activity. But it does not have classical free radical scavenger activity.

Carnitine is a mitochondria-specific antioxidant. It helps in maintenance of the integrity of mitochondria. It also regulates ROS signaling.

Inositol have antioxidant properties it helps to fight the harmful effects of free radicals in the circulatory system, and brain.

Lipoic acid also has antioxidant property. The properties include metal chelating capacity, reactive oxygen species (ROS) scavenging activity and repair of oxidative damage.

5. Option d

As we age our body produces low levels of stomach acid, this can be due to the weakening of the lining of the stomach. Use of certain medicines are also reported to cause reduction in stomach acid. The intrinsic factor is a glycoprotein that binds the vitamin B12 that is ingested and helps in absorption of Vit B12 from the ileum.This intrinsic factor (IF) is reported to be produced by the parietal cells of the stomach.If the stomach lining is weak then IF will not be produced and thus the ingested Vit B12 will not be protected and will not be absorbed properly.