Vitamin A and Its Importance

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Questions and Answers

Which type of vitamin K has a 30C side chain?

Vitamin K4

Vitamin K2 (correct)

Vitamin K1

Vitamin K3

Which of the following is NOT a clinical manifestation of vitamin K deficiency?

Increased tendency to bleed

Hemorrhagic disease of the newborn

Reduced bone density

Weight gain in adults (correct)

What role does vitamin K play in the body?

Bone mineralization and coagulation (correct)

Hormone synthesis

Energy production

Cellular respiration

Under what condition is vitamin K deficiency most likely to occur?

Prolonged antibiotic therapy Signup and view all the answers

Which form of vitamin K is synthetic and water-soluble?

Vitamin K3 Signup and view all the answers

What is a primary function of Vitamin E?

Acting as a powerful natural antioxidant Signup and view all the answers

Which condition is NOT directly linked to Vitamin E deficiency?

Calcium deficiencies Signup and view all the answers

What causes Vitamin E deficiency in premature infants?

Poor dietary absorption Signup and view all the answers

Which of the following statements is true regarding Vitamin E's protective role?

It protects red blood cells from hemolysis by preventing peroxidation. Signup and view all the answers

Which of the following best describes the sources of Vitamin E?

Found in vegetable and seed oils, as well as fish liver oils Signup and view all the answers

What is the active form of vitamin A that is present only in animal tissues?

Retinol Signup and view all the answers

Which enzyme plays a crucial role in transporting vitamin A from the liver to peripheral tissues?

Retinol binding protein (RBP) Signup and view all the answers

What is a consequence of vitamin A deficiency that affects vision?

Xerophthalmia Signup and view all the answers

Which of the following is NOT a function of retinol?

Muscle repair Signup and view all the answers

Which compounds are categorized as having vitamin A activity?

Retinol, retinal, and retinoic acid Signup and view all the answers

What is the primary function of rod cells in the human retina?

Vision in low light Signup and view all the answers

Which of the following conditions can lead to a deficiency of Vitamin A due to its impact on retinol binding protein (RBP) synthesis?

Cirrhosis of the liver Signup and view all the answers

Which symptom is associated with Vitamin A deficiency related to the eyes?

Night blindness Signup and view all the answers

What role do retinoids and carotenoids play in the body?

Act as antioxidants Signup and view all the answers

In severe malnutrition, what is a key factor impacting Vitamin A availability?

Lack of amino acids for RBP synthesis Signup and view all the answers

What is the result of cooking vegetables high in Vitamin C?

70% of Vitamin C is lost Signup and view all the answers

Which of the following acids has antiscorbutic activity?

Both B and C Signup and view all the answers

Which function of Vitamin C involves hydroxylation of proline and lysine?

Formation of collagen protein Signup and view all the answers

What is a consequence of Vitamin C deficiency?

Scurvy, characterized by decreased collagen formation Signup and view all the answers

How does Vitamin C facilitate iron mobilization in the body?

By acting as a reducing agent to keep it in ferrous state Signup and view all the answers

What is the primary dietary source of vitamin B12?

Meat, eggs, and milk Signup and view all the answers

Which component is NOT involved in the absorption of vitamin B12?

Vitamins D and K Signup and view all the answers

What is the color of vitamin B12 attributed to?

Cobalt ion Signup and view all the answers

Which statement regarding vegetarians and vitamin B12 is true?

They are at risk for vitamin B12 deficiency. Signup and view all the answers

Which of the following correctly describes the structure of vitamin B12?

Includes a nucleotide side chain and a cyano group Signup and view all the answers

Which of the following statements about vitamin B complex is true?

They are all water-soluble. Signup and view all the answers

What is a primary manifestation of vitamin B complex deficiency?

Delayed wound healing. Signup and view all the answers

How are B vitamins predominantly absorbed in the body?

From the intestines via portal circulation. Signup and view all the answers

Which of the following is a key role of folic acid and vitamin B12?

Acting as coenzymes in red blood cell formation. Signup and view all the answers

What component is crucial for the absorption of vitamin B12?

Intrinsic factor. Signup and view all the answers

Which of the following is NOT a correct source of vitamin B vitamins?

Fruit juices. Signup and view all the answers

Which of the following vitamins is specifically associated with the formation of red blood cells?

Cobalamin (Vitamin B12). Signup and view all the answers

What is a common effect of a deficiency in B vitamins?

Defective bone and tooth formation. Signup and view all the answers

Which condition is a cause of folate deficiency due to defective absorption?

Celiac disease Signup and view all the answers

What is one of the main manifestations of folate deficiency?

Megaloblastic anemia Signup and view all the answers

How does the 'folate trap' contribute to folate deficiency?

It prevents the formation of free THFA when B12 is deficient Signup and view all the answers

Which factor is least likely to contribute to folate deficiency?

Excess folate intake Signup and view all the answers

Which of the following describes a consequence of folate deficiency in fetuses?

Neural tube defects Signup and view all the answers

Which condition is associated with a deficiency of vitamin B12 that results from a lack of intrinsic factor?

Pernicious anemia Signup and view all the answers

What is the primary manifestation of folate deficiency caused by vitamin B12 deficiency?

Megaloblastic anemia Signup and view all the answers

Which of the following sources is rich in folic acid?

Leafy vegetables Signup and view all the answers

What is one of the key functions of tetrahydrofolic acid (H4 folate) in the body?

Synthesis of glycine Signup and view all the answers

What neurological condition can arise from vitamin B12 deficiency impacting both motor and sensory tracts?

Subacute combined degeneration of the spinal cord Signup and view all the answers

What form of vitamin B12 is involved in the synthesis of methionine?

Methylcobalamin Signup and view all the answers

Which physiological function is NOT associated with vitamin B12?

Production of erythropoietin Signup and view all the answers

Which of the following statements about vitamin B12 storage is true?

It is stored in the liver and requires regular intake. Signup and view all the answers

What is the result of the reaction catalyzed by methionine synthase?

Homocysteine is converted into methionine. Signup and view all the answers

Which condition can lead to a deficiency in vitamin B12?

Gastrectomy Signup and view all the answers

Study Notes

Vitamin A

Vitamin A is fat-soluble and essential for vision, reproduction, growth, and maintaining epithelial cells.
The active form of vitamin A is found in animal tissues, while the pro-vitamin, beta-carotene, is found in plant tissues.
Different forms of vitamin A include retinol, retinal, and retinoic acid.
Retinol is transported to peripheral tissues by retinol binding protein (RBP).

Vitamin A and Vision

Retinal is essential for vision and is a component of rhodopsin, a visual pigment found in rod cells responsible for light vision.
Cone cells are responsible for color vision.

Vitamin A Deficiency

Causes include decreased intake, liver cirrhosis, severe malnutrition, and chronic nephrosis.
Manifestations include night blindness, xerophthalmia, keratomalacia, blindness, and growth retardation.

Vitamin A's Antioxidant Role

Retinoids and carotenoids act as antioxidants, protecting tissues from the toxic effects of oxidants.

Vitamin C

Guava is a rich source of vitamin C.
Vitamin C is water-soluble and easily destroyed by heat, alkali, and storage.
Only L-ascorbic acid and dehydroascorbic acid have antiscorbutic activity.

Functions of Vitamin C

Essential for converting procollagen into collagen, which is vital for connective tissue, bone, and cartilage formation.
Involved in the absorption and mobilization of iron by keeping it in its ferrous state.
Acts as a co-enzyme for various hydroxylase enzymes involved in bile acid, osteocalcin, carnitine, and epinephrine synthesis.
Acts as an antioxidant, protecting tissues from toxic effects of oxidants.

Vitamin C Deficiency (Scurvy)

Characterized by manifestations due to decreased collagen formation.

Vitamin K

Exists in three forms: K1, K2, and K3.
Vitamin K1 has a 20C side chain, while K2 has a 30C side chain.
Vitamin K3 is synthetic, water-soluble, and more potent than K1 and K2.

Sources of Vitamin K

Green leafy vegetables are good sources.
Intestinal bacteria synthesis can meet daily requirements as long as absorption is normal.

Biochemical Role of Vitamin K

Necessary for blood coagulation by activating factors II, VII, IX, and X.
Essential for the functional activity of osteocalcin, a calcium-binding protein in bones.

Vitamin K Deficiency

Seldom occurs in normal adults due to sufficient intestinal bacterial synthesis.
Deficiency can occur due to malabsorption of lipids, prolonged antibiotic therapy, and chronic intestinal infections.

Clinical Manifestations of Vitamin K Deficiency

Hemorrhagic disease of the newborn, especially in premature infants.

Vitamin E (Tocopherols)

Sources include vegetables, seed oils, and fish liver oils.

Functions of Vitamin E

Powerful natural antioxidant preventing enzymatic oxidation of cell components.
Removes peroxide formation in polyunsaturated fatty acids.
Protects red blood cells from hemolysis by preventing peroxidation.
Protects against heart disease by acting as an antioxidant and preventing oxidation of LDL.

Vitamin E Deficiency

No major disease states are directly linked to vitamin E deficiency due to typical dietary sufficiency.
Deficiency can occur in cases with impaired dietary absorption, premature infants, abetalipoproteinemia, and mutations in the tocopherol transfer protein gene.

Causes of Vitamin E Deficiency

Neurological problems due to poor nerve conduction including neuromuscular problems.
Hemolysis of red blood cells and anemia due to lack of protection against peroxidation.

Vitamin B Complex

A group of water-soluble vitamins found in similar sources like whole grains, liver, and yeast.

Vitamin B Complex Deficiencies

Deficiencies often occur simultaneously due to their presence in similar foods.
Manifestations include bleeding, defective bone formation, delayed wound healing, anemia, behavioral changes, weakened neurological functions, and decreased carnitine and fatty acid oxidation.

Functions of Vitamin B Complex

Act as coenzymes in enzymatic reactions.
Folic acid and vitamin B12 are coenzymes in hematopoiesis (red blood cell formation).

Absorption of Vitamin B Complex

Absorbed from the intestines and transported via the portal circulation.
The body has minimal tissue stores of most B vitamins, leading to rapid depletion with dietary restriction or increased need.

Sources of B Vitamins

Meat, eggs, milk, and milk products.
Intestinal microorganisms synthesize some B vitamins.

Important Vitamin B Members

Thiamine (vitamin B1)
Riboflavin (vitamin B2)
Niacin (nicotinic acid, B3)
Pyridoxine (vitamin B6)
Pantothenic acid
Biotin
Folic acid
Vitamin B12

Vitamin B12 (Cobalamin)

Contains a corrin ring with a cobalt ion at its center.
Essential for red blood cell production.
Water-soluble vitamin.
Absorption involves intrinsic factor, a glycoprotein.
Transport and storage mechanisms exist.

Sources of Vitamin B12

Meat, eggs, milk, and milk products.
Absent in plant sources, posing a risk for strict vegetarians.
Intestinal microorganisms synthesize vitamin B12 but it's not absorbed through the mucosa in this region.

Chemistry of Vitamin B12

Consists of a corrin ring, a cobalt ion, a nucleotide side chain, and a cyano group attached to the cobalt ion.
Water-soluble and heat-stable.

Absorption of Vitamin B12

Requires intrinsic factor (IF) secreted by gastric parietal cells and cobalophilin, secreted in saliva.

Vitamin B12 Deficiency

Causes include decreased intake, drug-induced deficiency, alcohol abuse, and atrophy of gastric mucosa leading to lack of intrinsic factor.

Manifestations of Vitamin B12 Deficiency

Megaloblastic anemia due to abnormal DNA replication in hematopoietic tissue.
Neurological manifestations due to lack of myelin sheath formation and disturbance in odd-numbered fatty acid metabolism.
Folate trap, which is a simultaneous folate deficiency caused by vitamin B12 deficiency.

Folic Acid (Folate)

Sources include leafy vegetables, liver, beans, and whole grain cereals.
Readily absorbed by the upper part of the jejunum.
Not stored in tissues.

Functions of Folic Acid

Forms tetrahydrofolic acid (H4 folate), which is a carrier for one-carbon groups.
Used in DNA and RNA synthesis, non-essential amino acid synthesis, and the conversion of homocysteine to methionine.

Vitamin B12 and Its Functions

Transcobalamin, a glycoprotein, is the specific carrier for vitamin B12 in the blood.
Stored in the liver, with sufficient stores for 2-3 years.

Physiological Functions of Vitamin B12

Essential for the synthesis of methionine, tetrahydrofolate, and myelin sheath.

Methionine Synthesis

Vitamin B12, as methylcobalamin, acts as a coenzyme for methionine synthase enzyme.
Catalyzes the conversion of homocysteine into methionine.

Tetrahydrofolate Synthesis

Methyl-tetrahydrofolate is converted to tetrahydrofolate by transferring a methyl group to cobalamin.
Methylcobalamin transfers the methyl group to homocysteine.