Untitled Quiz

Questions and Answers

What is the classification of vitamins based on solubility?

Neither A nor B

Both A and B (correct)

Fat-soluble vitamins

Water-soluble vitamins

What are the food sources of Vitamin A?

Fat of animal foods, dark green leafy vegetables, deep orange fruits and vegetables.

Vitamin A is primarily stored in the ______.

liver

What happens to retinal in rhodopsin when it absorbs light?

It changes from cis to trans. Signup and view all the answers

Xerophthalmia is caused by excessive Vitamin A.

False Signup and view all the answers

What is keratinization?

Accumulation of keratin in tissues due to decreased mucous membrane integrity from Vitamin A deficiency. Signup and view all the answers

What is the chief function of Vitamin A?

All of the above Signup and view all the answers

Beta carotene is toxic and can cause teratogenic effects.

False Signup and view all the answers

What two methods can the body use to obtain Vitamin D?

Consumption of certain foods and synthesis via sunlight. Signup and view all the answers

Excessive vitamin A can lead to ______ and other birth defects.

teratogenic effects Signup and view all the answers

Match the following with their types:

Vitamin A = Fat-soluble vitamin Vitamin C = Water-soluble vitamin Beta-carotene = Precursor to Vitamin A Vitamin D = Can be synthesized by the body Signup and view all the answers

Study Notes

Vitamins Classification

Water-soluble vitamins include B vitamins (Thiamin, Niacin, B12, Biotin, Riboflavin, B6, Folate, Pantothenic acid) and Vitamin C.
Fat-soluble vitamins include Vitamins A, D, E, and K.

Vitamin A Food Sources

Vitamin A is primarily found in the fat of animal foods.
Beta-carotene, a precursor of Vitamin A, is abundant in dark green leafy vegetables and deep orange fruits (apricots, cantaloupe) and vegetables (squash, carrots, sweet potatoes, pumpkin).

Vitamin A Absorption, Storage, and Transport

Retinol is absorbed in the intestines and incorporated into micelles, then packed into chylomicrons for transport via the lymphatic system to the vascular system.
Approximately 70-80% of Vitamin A is stored in the liver, with the rest in adipocytes, kidneys, ovaries, intestines, and heart.
Retinol binding protein (RBP) transports retinol in the blood.

Vitamin A and Vision

Rhodopsin in retinal cells consists of opsin (protein) and cis-retinal (Vitamin A).
Light absorption by rhodopsin causes retinal to change from cis to trans, triggering nerve impulses for visual perception.

Xerophthalmia

Progressive blindness caused by Vitamin A deficiency, with symptoms including xerosis (drying of mucous membranes) and keratomalacia (softening of cornea leading to total blindness).
Vitamin A deficiency is the leading cause of blindness globally.

Vitamin A and Epithelial Tissue Integrity

Vitamin A supports the structure and function of mucous membranes and epithelial tissue.
Epithelial tissues cover body surfaces, including skin and linings of the GI tract and respiratory tract.

Keratinization

Keratin accumulation occurs due to reduced mucous membrane integrity from Vitamin A deficiency.
Effects on the GI tract include diminished goblet cells, limiting nutrient absorption, while skin integrity declines, increasing infection risk.

Vitamin A Specifics

Other names include Retinol, retinal, retinoic acid; precursor is beta-carotene.
Chief functions: vision, maintenance of the retina, cornea, epithelial cells, skin integrity, bone remodeling, reproduction, immunity, and antioxidant action of beta-carotene.
Food sources for Retinol: fortified milk/dairy, margarine, eggs, liver; for beta-carotene: leafy greens, orange fruits and vegetables.
Deficiency diseases include night blindness and xerothalmia with symptoms such as corneal drying and weakened immunity.
Toxicity can result in hypercarotenemia (orange skin) and hypervitaminosis A (acute symptoms like headache and blurred vision), mainly from supplements, not food.

Teratogenic Effects of Vitamin A Toxicity

Excess Vitamin A can cause birth defects, including cleft palate; therefore, Accutane is contraindicated during pregnancy.
Beta-carotene is not toxic or teratogenic.

Vitamin D

Available through dietary sources like fortified dairy, cereals, egg yolks, and fatty fish.
Can also be synthesized in the body through sunlight exposure, requiring 10-15 minutes of sunlight a few times a week for adequate production. Factors such as pollution and sunscreen can affect synthesis.