Lipid soluble vitamins (KADE)

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Questions and Answers

Which of the following describes a consequence of vitamin E deficiency?

Improved bone mineralization

Decreased vascular health

Increased necrosis in cells under oxidative stress (correct)

Enhanced reproductive system function

What is a primary role of vitamin K in the body?

Enhancing vitamin A storage

Facilitating blood clotting (correct)

Promoting bone mineralization

Increasing neuromuscular function

Which vitamin K form is synthesized by green plants?

Synthetic vitamin K

Menaquinones

Menadione

Phylloquinones (correct)

What occurs as a result of consuming very high doses of vitamin E?

Decreased utilization of other fat-soluble vitamins Signup and view all the answers

What distinguishes vitamin K3 from vitamin K1 and K2?

Absence of the 2-methyl-1,4-naphthoquinone ring structure Signup and view all the answers

Which statement accurately defines vitamins?

Vitamins are organic compounds required in minute amounts for physiological functions. Signup and view all the answers

What characterizes fat-soluble vitamins?

They are stored in the body and excreted with feces. Signup and view all the answers

What can lead to vitamin deficiency?

Inadequate absorption or metabolism of vitamins even when intake is proper. Signup and view all the answers

Which vitamin is NOT classified as fat-soluble?

Ascorbic acid Signup and view all the answers

Which of the following is described as a form of vitamin A?

Retinal Signup and view all the answers

What is the primary method of treating vitamin deficiency?

Administering large doses of the vitamin and increasing dietary intake. Signup and view all the answers

Which vitamin class includes compounds like thiamin and riboflavin?

Water-soluble vitamins Signup and view all the answers

What is a characteristic of water-soluble vitamins regarding storage?

They can be depleted quickly and need regular intake. Signup and view all the answers

What is the primary structural component of visual pigments in the rod and cone cells?

11-cis-retinal Signup and view all the answers

Which condition is caused by a deficiency of vitamin A that involves difficulty adapting to different light conditions?

Nyctalopia Signup and view all the answers

What is the consequence of large doses of vitamin A on liver function?

Hypervitaminosis A Signup and view all the answers

Which vitamin is directly converted into retinal in the body?

Carotenoids Signup and view all the answers

What symptom is NOT associated with hypervitaminosis A?

Corneal ulceration Signup and view all the answers

Which of the following describes a characteristic skin change due to vitamin A deficiency?

Follicular hyperkeratosis Signup and view all the answers

In which form does retinal return for subsequent binding to opsin during the vision cycle?

11-cis-retinal Signup and view all the answers

Which of the following symptoms indicates vitamin A deficiency?

Night blindness Signup and view all the answers

What process occurs when light hits 11-cis-retinal in the photoreceptor cells?

It undergoes isomerization to all-trans-retinal Signup and view all the answers

What is a key characteristic of osteomalacia?

Presence of pseudofractures Signup and view all the answers

How does osteoporosis usually manifest in post-menopausal women?

Diminished bone mass Signup and view all the answers

What condition may result from hypervitaminosis D?

Hypercalcemia Signup and view all the answers

What is one of the primary roles of vitamin E?

Acting as an antioxidant Signup and view all the answers

Which class of vitamin E is considered the most biologically active?

α-tocopherol Signup and view all the answers

What serious consequence can result from the calcification of soft tissues due to hypervitaminosis D?

Organ damage such as in the heart and kidneys Signup and view all the answers

Which vitamin has the ability to convert free radicals to harmless metabolites?

Vitamin E Signup and view all the answers

What type of bone condition is characterized by high porosity and brittleness?

Osteoporosis Signup and view all the answers

Which of the following symptoms can occur due to vitamin D toxicity?

Headache and nausea Signup and view all the answers

What mechanism allows vitamin E to protect cell membranes?

Scavenging free radicals Signup and view all the answers

What is the primary function of calcitriol in the body?

Regulating calcium and phosphorus homeostasis Signup and view all the answers

What are the precursors of vitamin D produced from exposure to ultraviolet light?

7-Dehydrocholesterol and ergosterol Signup and view all the answers

The condition rickets is primarily associated with deficiencies in which nutrients?

Calcium and phosphorus Signup and view all the answers

Which process does calcitriol NOT participate in to maintain normal blood levels of calcium and phosphorus?

Enhancing bone resorption from blood Signup and view all the answers

What is a common symptom of vitamin D deficiency in children?

Beaded ribs Signup and view all the answers

What is the active form of vitamin D in the body?

1,25-dihydroxyvitamin D3 Signup and view all the answers

Which vitamin is known as the sunshine vitamin due to the body's ability to synthesize it from sunlight?

Vitamin D Signup and view all the answers

What happens to 7-dehydrocholesterol when it is exposed to ultraviolet light?

It converts to cholecalciferol Signup and view all the answers

Which of the following does NOT enhance dietary calcium absorption according to vitamin D functions?

Intestinal flora activity Signup and view all the answers

Which symptom is NOT associated with rickets?

Increased energy levels Signup and view all the answers

Study Notes

Vitamins

Vitamins are essential micronutrients, organic compounds distinct from carbohydrates, proteins, and lipids.
They are present in small amounts in food, and the body doesn't synthesize them sufficiently.
Vitamins are crucial for various physiological functions, including maintenance, growth, development, and reproduction.
Deficiency in specific vitamins leads to specific syndromes.

Vitamin Classes

Classified by their solubility.
Fat-soluble vitamins: Vitamins A, D, E, and K are absorbed passively with dietary lipids, stored in cells and lipid droplets, and excreted in feces.
Water-soluble vitamins: Ascorbic acid and the vitamin B family (thiamin, riboflavin, niacin, pyridoxine, biotin, pantothenic acid, folate, and cobalamin) are absorbed via passive or active transport, not stored in the body, and excreted in urine.

Vitamin Deficiencies and Treatment

Deficiency can arise from inadequate intake or insufficient absorption/metabolism.
Treatment typically involves administering large doses of the vitamin and increasing dietary intake.

Fat-soluble Vitamins

Vitamin A (Retinoids)

Includes retinol (alcohol), retinal (aldehyde), and retinoic acid.
Plants contain carotenoids, with β-carotene being the most important.
In the body, retinol is esterified to palmitate (retinyl palmitate).
Vitamin A is primarily found in animal products; carotenoids are metabolized to retinoids in the body.

Vitamin A Functions

Essential for vision.
Retinal forms part of the visual pigments in rod and cone cells of the retina.
11-cis-retinal is essential for photoreception.
Light-induced isomerization of 11-cis-retinal to all-trans forms triggers photoreception.
Rhodopsin (opsin protein + retinal) undergoes reactions leading to dissociation into all-trans-retinal and opsin.
All-trans-retinal is converted back to 11-cis-retinal for subsequent binding to opsin.

Vitamin A Deficiency

Blindness due to insufficient visual pigment synthesis.
Night blindness (nyctalopia): impaired adaptation from bright to dark conditions.
Xerophthalmia (dry eyes): dryness of the conjunctiva and cornea; untreated, it can lead to corneal ulceration and blindness.
Follicular hyperkeratosis: skin texture changes with keratin plugging hair follicles, resulting in dry, scaly, and rough skin.

Vitamin A Toxicity

Large doses overwhelm the liver's storage capacity, leading to intoxication and liver disease.
Hypervitaminosis A symptoms: dry lips, nasal mucosa, and eyes; skin scaling and peeling; hair loss; nail fragility; headache; nausea; vomiting; increased hip fracture risk in women.
Carotenoid toxicity is low; β-carotene accumulation mainly causes skin yellowing (hypercarotenodermia).

Vitamin D (Sunshine Vitamin)

Produced in the skin using sunlight's ultraviolet light and sterols.
Precursors: 7-dehydrocholesterol (animals) and ergosterol (plants).
Ultraviolet light causes photolytic ring opening: 7-dehydrocholesterol → cholecalciferol (vitamin D3) and ergosterol → ergocalciferol (vitamin D2).
Cholecalciferol and ergocalciferol are metabolized to the active form, 1,25-dihydroxyvitamin D3 (calcitriol).

Vitamin D Functions (Calcitriol)

Maintains calcium and phosphorus homeostasis through:
- Enhancing dietary calcium and phosphorus absorption from the gut.
- Regulating calcium and phosphorus levels in blood and bones (bone resorption). This involves calcitriol, parathyroid hormone, and estrogen.
- Increasing renal tubular reabsorption of calcium and phosphate.

Vitamin D Deficiency

Rickets (calcium and phosphorus deficiency): structural bone abnormalities, bone pain, muscle tenderness, hypocalcemic tetany, and bone weakness leading to bowed legs, beaded ribs, pigeon breast, and skull deformities.
Osteomalacia: reduced bone density, pseudofractures, and muscle weakness.
Osteoporosis: diminished bone mass, porous and brittle bones, and normal histological appearance. Associated with age and low estrogen levels, particularly in post-menopausal women.

Vitamin D Toxicity (Hypervitaminosis D)

Excessive intake leads to high serum calcium and phosphorus levels.
This can cause calcification of soft tissues (calcinosis) in organs like the heart, lungs, kidneys, and ears (deafness).
Symptoms: headache, nausea.

Vitamin E

Protects the body from the effects of free radicals generated metabolically or environmentally.
Two classes: tocopherols and tocotrienols (less biologically active).
α-tocopherol is the most significant.

Vitamin E Functions

Located in the lipid portion of cell membranes.
Functions as an antioxidant, protecting unsaturated phospholipids from oxidative degradation by free radicals.
Converts radicals to harmless metabolites by donating hydrogens (free radical scavenging).
α-tocopherol is converted to α-tocopherol quinone.

Vitamin E Deficiency

Cells exposed to oxidative stress experience increased injury and necrosis.
Impacts neuromuscular, vascular, and reproductive systems.

Vitamin E Toxicity

Relatively non-toxic due to tolerance of high intakes.
Very high doses impair the body's use of other fat-soluble vitamins, leading to deficiency-related disorders.

Vitamin K

Essential for blood clotting.
Naturally occurring forms:
- Phylloquinones (vitamin K1 series, synthesized by plants).
- Menaquinones (vitamin K2 series, synthesized by bacteria).
Menadione (vitamin K3, synthetic supplement) is twice as potent as other forms and converted to menaquinones in the liver.

Vitamin K Structure

Vitamin K1 and K2 contain a 2-methyl-1,4-nephthoquinone ring and alkylated side chains.
Vitamin K3 has the ring structure but lacks a side chain.

Vitamin K Functions

Essential in the blood clotting process (vitamin K cycle).
Carboxylates glutamic acid residues in clotting plasma proteins (thrombin), forming carboxy-glutamate.
Carboxy-glutamate binds calcium, aiding in blood coagulation.
Vitamin K is oxidized to an epoxide and then reduced back to its hydroquinone form by epoxide reductase and quinone reductase.

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Description

This quiz covers essential vitamins, their classifications, and the impact of deficiencies on health. Explore the differences between fat-soluble and water-soluble vitamins, as well as their roles in physiological functions. Test your knowledge on various vitamin-related topics and their significance in daily nutrition.