Vitamin Discovery and Functions Quiz
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Questions and Answers

What significant discovery did C. Eijkman make in 1890?

  • The classification of vitamins into groups
  • The role of vitamins in energy production
  • A nutritional factor that cures beriberi (correct)
  • The first synthetic vitamin

Which statement accurately describes vitamins?

  • They are inorganic compounds essential for body function
  • They provide significant energy for the body
  • They are synthesized in large quantities by the human body
  • They are required in very small amounts for proper body function (correct)

Who coined the term 'vitamin' and what does it mean?

  • C. Eijkman; minor nutrient
  • C. Funk; vital amine (correct)
  • C. Funk; synthetic nutrient
  • C. Eijkman; vital amine

How are vitamins typically obtained by the human body?

<p>Primarily through a balanced diet (C)</p> Signup and view all the answers

What is the role of vitamins in the human body?

<p>They act as essential micronutrients for metabolic processes (B)</p> Signup and view all the answers

Which vitamin is synthesized in the skin's epidermis when stimulated by UVB rays?

<p>Vitamin D (D)</p> Signup and view all the answers

What is the final product of the synthesis of Vitamin B₁?

<p>Thiamine Triphosphate (TTP) (B)</p> Signup and view all the answers

Which of the following vitamins undergoes bacterial synthesis in the gut?

<p>Vitamin K₂ (A)</p> Signup and view all the answers

What is the provitamin for Vitamin A?

<p>β-Carotene (D)</p> Signup and view all the answers

Which water-soluble vitamin is involved in the synthesis of Coenzyme A?

<p>Vitamin B₅ (A)</p> Signup and view all the answers

What are the common causes of vitamin deficiencies?

<p>Insufficient intake, impaired absorption, and increased needs (D)</p> Signup and view all the answers

Which form of vitamin A is considered the most active biological form?

<p>Trans-retinol (D)</p> Signup and view all the answers

How are ester forms of retinol like retinyl acetate utilized in the body?

<p>They are hydrolyzed to produce retinol (D)</p> Signup and view all the answers

What distinguishes carotenoids from retinoids?

<p>Carotenoids can be converted into retinoids in the body (B)</p> Signup and view all the answers

Why is a varied diet important in preventing vitamin deficiencies?

<p>It helps maintain adequate intake with normal needs (B)</p> Signup and view all the answers

What is required for the absorption of vitamin A and carotenoids?

<p>Fatty acids and bile salts (C)</p> Signup and view all the answers

What percentage of vitamin A absorption is considered efficient?

<p>80-90% (C)</p> Signup and view all the answers

What form is excess vitamin A primarily stored in the liver?

<p>Retinyl palmitate (A)</p> Signup and view all the answers

Which cell type captures the RBP-retinol complex?

<p>Target cells using STRA6 receptor (A)</p> Signup and view all the answers

Which enzyme is involved in the irreversible oxidation of retinal to retinoic acid?

<p>Aldehyde dehydrogenases (C)</p> Signup and view all the answers

What is the process called that helps conserve vitamin A through reabsorption into the bloodstream?

<p>Enterohepatic cycle (D)</p> Signup and view all the answers

Which dietary source is NOT listed as a source of vitamin A?

<p>Rice (B)</p> Signup and view all the answers

Which vitamin A metabolic reaction is NOT mentioned as part of vitamin A metabolism?

<p>Decarboxylation (A)</p> Signup and view all the answers

Which function is NOT a role of vitamin A?

<p>Bone density maintenance (C)</p> Signup and view all the answers

What is a primary consequence of vitamin A deficiency?

<p>Night blindness (C)</p> Signup and view all the answers

Which food source contains the highest amount of vitamin A?

<p>Cod liver oil (B)</p> Signup and view all the answers

Which of the following statements regarding vitamin A is accurate?

<p>Vitamin A is essential for immune development. (D)</p> Signup and view all the answers

What are the symptoms of severe vitamin A deficiency?

<p>Retinal dysfunction and corneal damage (D)</p> Signup and view all the answers

Which vitamins are classified as fat-soluble?

<p>Vitamins A, D, E, K (B)</p> Signup and view all the answers

What is a primary function of water-soluble vitamins?

<p>Excretion of excess amounts (D)</p> Signup and view all the answers

Which vitamin plays a vital role in antioxidant function?

<p>Vitamin A (D)</p> Signup and view all the answers

What can result from a deficiency in water-soluble vitamins?

<p>Hypovitaminosis (B)</p> Signup and view all the answers

Which of the following vitamins is NOT involved in proton and electron transfer?

<p>Vitamin C (A)</p> Signup and view all the answers

What is the primary dietary source of cholecalciferol (D3)?

<p>Fish liver oil (C)</p> Signup and view all the answers

Which vitamin D metabolite is synthesized in the distal renal tubule?

<p>Calcitriol (A)</p> Signup and view all the answers

What stimulates the synthesis of calcitriol?

<p>Parathyroid hormone (PTH) (A)</p> Signup and view all the answers

Which process occurs when vitamin D is incorporated into mixed micelles?

<p>Absorption (C)</p> Signup and view all the answers

How is vitamin D synthesized in the body?

<p>By exposure to UV light (A)</p> Signup and view all the answers

Which of the following statements accurately describes the properties of Vitamin E?

<p>Vitamin E is stable to heat but sensitive to oxygen. (A)</p> Signup and view all the answers

What are the main metabolites involved in the absorption of Vitamin E?

<p>Bile salts and fats. (A)</p> Signup and view all the answers

Which of the following populations is at risk of osteomalacia due to Vitamin E deficiency?

<p>Adults with liver disease. (B)</p> Signup and view all the answers

What is the most biologically active form of Vitamin E?

<p>RRR-α-tocopherol. (D)</p> Signup and view all the answers

How does the structure of Vitamin E vary among its homologues?

<p>The differences are based on the number and position of methyl groups. (D)</p> Signup and view all the answers

What is the primary role of calcitriol in the body?

<p>To elevate calcium and phosphate levels in the blood (D)</p> Signup and view all the answers

How is calcidiol (25-hydroxyvitamin D₃) produced in the body?

<p>By the liver converting vitamin D₃ (B)</p> Signup and view all the answers

What condition can arise from vitamin D deficiency in children?

<p>Rickets (A)</p> Signup and view all the answers

What impact does 1,25(OH)₂D have on parathyroid hormone (PTH) synthesis?

<p>It inhibits PTH synthesis and secretion (C)</p> Signup and view all the answers

Which form of vitamin D is biologically active?

<p>Calcitriol (1,25(OH)₂D₃) (B)</p> Signup and view all the answers

What is one potential effect of excessive vitamin D intake?

<p>Increased intestinal calcium absorption (D)</p> Signup and view all the answers

Where are the major storage sites for vitamin D in the body?

<p>Adipose tissue and muscles (B)</p> Signup and view all the answers

Which population is at risk of vitamin D deficiency due to hereditary diseases?

<p>Those with lack of 1α-hydroxylase activity (B)</p> Signup and view all the answers

What is the primary transport protein for Vitamin D metabolites in the bloodstream?

<p>Vitamin D-binding protein (DBP) (D)</p> Signup and view all the answers

Which organs are primarily affected by calcitriol's mechanism of action?

<p>Kidney, Bone, and Intestine (B)</p> Signup and view all the answers

Where is Vitamin D stored in the body?

<p>Adipose tissue and muscles (A)</p> Signup and view all the answers

What distinguishes Vitamin D2 from Vitamin D3 at the molecular level?

<p>Absence of a methyl group at C24 (A)</p> Signup and view all the answers

How is Vitamin D and its derivatives eliminated from the body?

<p>Via the fecal route (B)</p> Signup and view all the answers

Flashcards

Vitamins Definition

Organic compounds (micronutrients) needed in small amounts for bodily functions, but not for energy or building materials.

Vitamins Source

Obtained from food, because the body cannot produce them sufficiently in the necessary quantities.

Vitamin Importance

Crucial for the body's proper functioning, although they don't provide energy or building blocks of the body.

Vitamin Discovery

Early work by Eijkman (1890s found a food factor in rice to cure a disease called beri-beri; Funk (1911) coined the term "vitamin" (vital amine).

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Vitamin Amount

Vitamins are needed in very small quantities (micrograms to milligrams).

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Fat-soluble vitamins

Vitamins that are absorbed and stored in fat tissue.

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Vitamin D synthesis

Vitamin D is produced in the body when sunlight activates a precursor molecule in the skin.

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Vitamin K2 synthesis

Vitamin K2 is produced by bacteria in the gut.

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Water-soluble vitamins

Vitamins absorbed directly into the bloodstream and not stored in large quantities.

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Vitamin B complex

A group of water-soluble vitamins, crucial for various metabolic processes.

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Vitamin A forms

Includes retinol, retinoids, retinal, and retinoic acid. Trans-retinol is a key active form.

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Vitamin function

Vitamins are needed in small amounts for proper body function.

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Vitamin A Ester forms

More stable forms of retinol (e.g., retinyl acetate, retinyl palmitate).

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Vitamin A Absorption

Ester forms of Vitamin A are broken down into retinol by enzymes in the body.

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Vitamin Deficiency Risk

Can arise from insufficient intake, poor absorption, or increased needs. Often part of multiple deficiencies.

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Vitamin absorption

Fat-soluble vitamins need fats to absorb properly, while water-soluble vitamins dissolve in water.

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Carotenoid Conversion

Carotenoids are changed into vitamin A in the intestines, cleaving into retinal molecules and then reducing them to retinol.

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Vitamin A Transport

Vitamin A travels through lymph in chylomicrons to the liver.

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Vitamin A Storage

The liver stores excess vitamin A as retinyl palmitate in hepatocytes & parenchymal cells.

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Vitamin A Mobilization

Liver releases retinol into the blood when other tissues need it, bonded to RBP and transthyretin, for targeted delivery.

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Vitamin A Target Cells

Target cells use a specific receptor (STRA6) to take in the RBP-retinol complex.

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Vitamin A Metabolism Reactions

Vitamin A is processed through esterification, oxidation, conjugation, isomerization, and chain cleavage.

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Vitamin A Excretion

Vitamin A is primarily excreted in bile as glucuronates, with some reabsorption and remaining eliminated in feces.

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Vitamin A and Vision

Vitamin A is crucial for vision. It's converted into retinal, which combines with opsin to form rhodopsin, a light-sensitive pigment that allows us to see in low light.

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Vitamin A Deficiency

Lack of vitamin A can lead to various eye problems, including night blindness (difficulty seeing in low light), xerophthalmia (dry eyes), keratitis (inflammation of the cornea), and keratomalacia (softening of the cornea).

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Vitamin A and Epithelial Integrity

Vitamin A is essential for maintaining the healthy structure of epithelial tissues, which line body surfaces like skin, mucous membranes, and digestive tract.

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Vitamin A and Immunity

Vitamin A is vital for a healthy immune system, functioning as an antioxidant and protecting against infections.

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What is Vitamin D?

Vitamin D is a steroid hormone that helps regulate calcium levels in the body.

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Vitamin D2 vs. D3

Vitamin D2 (ergocalciferol) has an unsaturated side chain and a methyl group at C24, while Vitamin D3 (cholecalciferol) has a saturated side chain.

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Calcitriol's Role

Calcitriol (1,25-dihydroxyvitamin D) is the active form of Vitamin D. It binds to a nuclear receptor, affecting gene expression in the intestine, kidney, and bone.

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Vitamin D Elimination

Vitamin D and its derivatives are eliminated through the feces.

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Vitamin D Metabolism: Key Metabolites

Vitamin D undergoes several transformations in the body. The most important are 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D).

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1,25-dihydroxyvitamin D (Calcitriol)

This active form of vitamin D is produced in the kidneys and regulates calcium levels in the body.

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Vitamin D Chemical Structure: D3 vs. D2

Vitamin D3 (cholecalciferol) has a saturated side chain, while Vitamin D2 (ergocalciferol) is unsaturated and methylated at carbon 24.

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Most Active Vitamin E

RRR-α-tocopherol is the most biologically active form of Vitamin E.

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Vitamin E Solubility

Vitamin E is insoluble in water, but dissolves in fats and organic solvents.

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Vitamin E Stability

Vitamin E is stable to heat and visible light, but sensitive to UV light and oxygen.

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Active Vitamin D

The biologically active form of vitamin D is 1,25-dihydroxyvitamin D₃ (calcitriol). It's produced in the kidneys and regulates calcium and phosphate levels.

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Parathyroid Hormone (PTH) and Vitamin D

Calcitriol inhibits PTH synthesis and secretion. Conversely, PTH stimulates the production of active vitamin D by activating 1-alpha-hydroxylase.

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Vitamin D Catabolism

Vitamin D and its derivatives are eliminated through the feces in bile. Various degradation pathways exist, including oxidation and formation of different derivatives.

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Excessive Vitamin D Intake

High doses of vitamin D can lead to hypercalcemia, where the kidneys fail to eliminate excess calcium, resulting in potential health issues.

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Study Notes

Vitamin Metabolism

  • Vitamins are organic micronutrients, not building materials, needed in small amounts for bodily functions
  • Humans cannot produce certain vitamins, and must obtain them through diet
  • They are categorized as either water-soluble or fat-soluble
  • Fat-soluble vitamins are absorbed by micelles with the presence of bile salts.
  • Water-soluble vitamins are absorbed passively through the intestines and excreted by the kidney
  • Vitamin A: retinol, retinal, retinoic acid, carotenoids. Fat-soluble vitamins are stored in the liver and adipose tissue.
  • Vitamin A metabolism involves conversion to different forms, storage, and transport to cells.
  • Excess vitamin A is stored in the liver, and in fat cells.
  • Excess vitamin A can be harmful.

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Description

Test your knowledge on the discovery of vitamins and their vital roles in human health. This quiz covers significant contributions like C. Eijkman's work, the synthesis of vitamins, and the consequences of vitamin deficiencies. Dive deep into the world of micronutrients and their importance in our diet.

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