2/3. Vitamin A (Retinol)

Question 1

what is the name of vitamin A?

Answer 1

It is three biologically active molecules; retinol, retinal and retinoic acid.

Question 2

Structure of retinal

Answer 2

-

Question 3

Structure of retinol

Answer 3

-

Question 4

Structure of retinoic acid:

Answer 4

-

Question 5

What is the provitamin of vit A? (structure)

Answer 5

-B-carotene

Question 6

Metabolism of vit A?

Answer 6

-

Question 7

How can you destroy vitamin A?

Answer 7

When O2 is present is will be destroyed, because it is less resistant when it is removed from its natural environment, because of less antioxidants, such as tocoferol.

Question 8

what is special about vit A in fish?

Answer 8

3-hydroretinol is a special product in the fresh water fish, metabolism in the liver.

Question 9

Who has no carotenase?

Answer 9

The cattle has no carotenase in the intestinal mucosa, but they absorb the B-carotene, they have carotenase in the liver.

Question 10

What form of Vit A is absorbed?

Answer 10

Retinol, in the mucosa cells.

Question 11

How is it excreted?

Answer 11

In bile when metabolized as retinol,retinal and retinoic acid.

Question 12

Biochemical functions:

Answer 12

1. Maintenance of epithelial cells
2. Reproduction
3. Bone growth
4. Visual cycle

Question 13

Visual cycle:

Answer 13

-

Question 14

Deficiency:

Answer 14

- Almost all cellular growth are affected.
Affect growth (loose their appetites, keratinzation of taste buds),bone development (CNS gets damaged), reproduction (cattle) and vision (night blindness, nyctalopia), dyrness of conjuctiva and cornea, blindness and ulcers.

Question 15

Hypervitaminosis:

Answer 15

Only by large injection!
-Not B-carotene injection, this will only lead to decreased utilization.
-General signs:
Loss of appetite, poor growth, loss of weight.
-Specific signs:
Bone fragility, resorption of bones (vit A release of lysosomal enzymes.)