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Questions and Answers
What is the maximum amount of Vitamin B12 that is needed per day?
What is the maximum amount of Vitamin B12 that is needed per day?
- 10 mg
- 10 μg
- 50kDa
- 0.0002 mg (correct)
What is the role of Intrinsic Factor (IF) in Vitamin B12 absorption?
What is the role of Intrinsic Factor (IF) in Vitamin B12 absorption?
- IF competes with other nutrients for absorption in the ileum.
- IF directly transports Vitamin B12 into the bloodstream.
- IF binds to Vitamin B12 and facilitates its absorption in the ileum. (correct)
- IF breaks down Vitamin B12 into smaller, absorbable molecules.
What is the primary source of Vitamin B12 in the diet?
What is the primary source of Vitamin B12 in the diet?
- Plant-based foods such as legumes and leafy greens.
- Dietary supplements.
- Fortified foods such as cereals and bread.
- Animal products such as meat, poultry, and dairy. (correct)
What is the mechanism of action (MOA) of Vitamin B12 deficiency in terms of folate metabolism?
What is the mechanism of action (MOA) of Vitamin B12 deficiency in terms of folate metabolism?
What is the relationship between Vitamin B12 and homocysteine?
What is the relationship between Vitamin B12 and homocysteine?
Which of the following statements about the function of Vitamin D is NOT true?
Which of the following statements about the function of Vitamin D is NOT true?
What is the primary function of osteoclasts in the skeletal system?
What is the primary function of osteoclasts in the skeletal system?
Which of the following is a consequence of prolonged vitamin D deficiency?
Which of the following is a consequence of prolonged vitamin D deficiency?
Why is adequate exposure to sunlight essential for maintaining bone health?
Why is adequate exposure to sunlight essential for maintaining bone health?
Which of the following statements about Vitamin E is TRUE?
Which of the following statements about Vitamin E is TRUE?
Which of the following conditions can be caused by a deficiency in magnesium?
Which of the following conditions can be caused by a deficiency in magnesium?
What is the most common nutritional deficiency disease?
What is the most common nutritional deficiency disease?
What is the primary function of iron in the body?
What is the primary function of iron in the body?
Which of the following is NOT a symptom of zinc deficiency?
Which of the following is NOT a symptom of zinc deficiency?
Which of the following is a consequence of hypercalcemia?
Which of the following is a consequence of hypercalcemia?
What is the primary function of calcium in the body?
What is the primary function of calcium in the body?
In which of the following groups is iron deficiency most common?
In which of the following groups is iron deficiency most common?
What is the main reason for the high requirement of iron in pregnant teenagers?
What is the main reason for the high requirement of iron in pregnant teenagers?
What is the primary function of SAM (S-adenosyl methionine) in the context of the provided text?
What is the primary function of SAM (S-adenosyl methionine) in the context of the provided text?
What is the direct consequence of a lack of Vitamin B12 in the context of the text?
What is the direct consequence of a lack of Vitamin B12 in the context of the text?
Which of the following is a consequence of a deficiency in Vitamin C?
Which of the following is a consequence of a deficiency in Vitamin C?
What is the primary role of carnitine in the body, as mentioned in the text?
What is the primary role of carnitine in the body, as mentioned in the text?
What is the primary role of bile salts in the body, as described in the text?
What is the primary role of bile salts in the body, as described in the text?
What is the primary difference between the role of Vitamin B12 and Vitamin C as described in the text?
What is the primary difference between the role of Vitamin B12 and Vitamin C as described in the text?
What is the primary function of Vitamin C as an antioxidant, according to the provided information?
What is the primary function of Vitamin C as an antioxidant, according to the provided information?
What is the significance of the hydroxylation reaction in the context of collagen synthesis as mentioned in the text?
What is the significance of the hydroxylation reaction in the context of collagen synthesis as mentioned in the text?
What is the primary role of norepinephrine in the body, as described in the text?
What is the primary role of norepinephrine in the body, as described in the text?
In the context of the provided text, what is the primary reason why a deficiency in Vitamin C can lead to fatigue and lassitude?
In the context of the provided text, what is the primary reason why a deficiency in Vitamin C can lead to fatigue and lassitude?
What is the effect of a THF deficiency on DNA synthesis?
What is the effect of a THF deficiency on DNA synthesis?
Which of the following is a key source of folate?
Which of the following is a key source of folate?
How does methotrexate affect folate metabolism?
How does methotrexate affect folate metabolism?
What characteristic distinguishes megaloblastic anemia from other types of anemia?
What characteristic distinguishes megaloblastic anemia from other types of anemia?
What is the relationship between folate deficiency and megaloblastic changes in red blood cells?
What is the relationship between folate deficiency and megaloblastic changes in red blood cells?
Which of the following is NOT a characteristic of megaloblastic anemia?
Which of the following is NOT a characteristic of megaloblastic anemia?
What is the primary function of vitamin C in the context of the provided information?
What is the primary function of vitamin C in the context of the provided information?
What is the main reason why fat-soluble vitamins should be taken with a fatty meal?
What is the main reason why fat-soluble vitamins should be taken with a fatty meal?
Which of the following is NOT a form of vitamin A listed in the text?
Which of the following is NOT a form of vitamin A listed in the text?
What is the primary role of retinol phosphate in the context of vitamin A function?
What is the primary role of retinol phosphate in the context of vitamin A function?
Which of the following is a direct consequence of a vitamin A deficiency, as described in the text?
Which of the following is a direct consequence of a vitamin A deficiency, as described in the text?
How does vitamin A contribute to the maintenance of epithelial tissues?
How does vitamin A contribute to the maintenance of epithelial tissues?
What is the primary function of β-carotene in the context of vitamin A?
What is the primary function of β-carotene in the context of vitamin A?
Which TWO options accurately describe the characteristics of micelles?
Which TWO options accurately describe the characteristics of micelles?
Flashcards
Cobalt ion function
Cobalt ion function
Cobalt ion is central to Vitamin B12 structure and function.
Dietary B12 sources
Dietary B12 sources
Animal products are the only dietary source of Vitamin B12.
Intrinsic Factor (IF)
Intrinsic Factor (IF)
A glycoprotein secreted by parietal cells that binds B12 for absorption.
B12 deficiency symptoms
B12 deficiency symptoms
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Methyl folate trap
Methyl folate trap
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Folic Acid
Folic Acid
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Tetrahydrofolate (THF)
Tetrahydrofolate (THF)
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One-carbon units
One-carbon units
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Methotrexate
Methotrexate
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Megaloblastic anemia
Megaloblastic anemia
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Thymidine nucleotides
Thymidine nucleotides
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Folic Acid during Pregnancy
Folic Acid during Pregnancy
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Vitamin B12 (Cobalamin)
Vitamin B12 (Cobalamin)
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Radicals
Radicals
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ROS
ROS
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Vitamin C
Vitamin C
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Micelles
Micelles
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Fat-soluble vitamins
Fat-soluble vitamins
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Vitamin A
Vitamin A
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Xerophthalmia
Xerophthalmia
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Retinol
Retinol
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Coenzymes
Coenzymes
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Methyl-THF
Methyl-THF
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Hydroxylation
Hydroxylation
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Scurvy
Scurvy
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Carnitine
Carnitine
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Norepinephrine
Norepinephrine
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Bile Salts
Bile Salts
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Oxidation of Vitamin C
Oxidation of Vitamin C
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Reactive Oxygen Species (ROS)
Reactive Oxygen Species (ROS)
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Calcium distribution
Calcium distribution
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Hypocalcemia effects
Hypocalcemia effects
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Hypercalcemia symptoms
Hypercalcemia symptoms
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Magnesium functions
Magnesium functions
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Iron's role
Iron's role
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Iron deficiency anemia
Iron deficiency anemia
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Zinc importance
Zinc importance
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Zinc deficiency symptoms
Zinc deficiency symptoms
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Function of osteoblasts
Function of osteoblasts
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Function of osteoclasts
Function of osteoclasts
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Vitamin D synthesis
Vitamin D synthesis
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Osteomalacia
Osteomalacia
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Rickets
Rickets
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Study Notes
Folic Acid
- Latin name: "folium" = leaf
- Best sources: Green leafy vegetables, uncooked fruits
- In intestinal mucosa: Folate reductase converts to dihydrofolate reductase, then to THF (tetrahydrofolate) using 2 NADPH2 to 2 NADP
- Anticancer drug Methotrexate prevents THF formation
Function of THF
- Carrier of one-carbon units
- Used in biosynthetic reactions
- Required for purine and thymidine nucleotide synthesis (DNA building blocks)
- Lack of THF results in lack of DNA reduplication and mitosis
THF Deficiency
- Clinical expression: Megaloblastic changes (large cytoplasm)
- Reason: DNA synthesis is inhibited; DNA replication and nuclear maturation are impaired; cytoplasmic maturation is unaffected
- Hematological Changes: Megaloblastic anemia (macrocytic anemia)
- Large, but not enough erythrocytes
- Folic acid requirements increase during pregnancy
- THF deficiency during pregnancy can lead to birth defects
Vitamin B12 (Cobalamin)
- Source: Synthesized only by microorganisms (no cobalamin in plants)
- Animal products are the only dietary source
- Strict vegetarians are at risk for deficiency
- Liver stores up to 10 mg
- Only 0.0002 mg needed daily
- Stored amount lasts 136 years; if intestinal absorption is normal
- Clinical symptoms within 2 years if intestinal absorption is impaired
Vitamin B12 Absorption
- B12 alone is not absorbed
- Daily intake up to 10 ug B12 via bile from liver to duodenum and ileum, then excretion
- Dietary B12 travels from stomach towards excretion
- Parietal cells secrete intrinsic factor (50kDa glycoprotein)
- Intrinsic factor creates a tight complex with B12, which is absorbed in the ileum
- In blood, it is replaced by transcobalamin (transport protein)
- Transcobalamin prevents renal excretion & mediates uptake of B12 into tissues
Vitamin B12 Deficiency
- Megaloblastic anemia, indistinguishable from THF deficiency
- MOA: "Methyl folate trap"
Vitamin C (Ascorbic Acid)
- Structure identified in 1932, isolated from lemon juice
- MOA: Oxidation of vitamin C (-2H+ - 2e-)
- Large doses plus large amounts of calcium in daily diet can lead to kidney stones
- Degradation: hydrolysis of inner ester(lactone) to dehydroascorbic acid and further degradation to oxalate.
- Physiological function: Hydroxylation
- One oxygen atom is inserted between carbon and hydrogen to form a hydroxyl group
- 2nd oxygen reacts with 2H from Vit C to produce water
- Several physiological hydroxylation reactions affected by Vit C deficiency
- Physiological Vitamin C dependent hydroxylation reactions: -Hydroxylation of prolyl and lysyl residues in procollagen (essential for collagen synthesis; deficiency leads to scurvy) -Synthesis of carnitine (carrier for transport of fatty acids into mitochondrial matrix; deficiency leads to decrease in ATP energy level)
Vitamin D
- Minimal exposure to sunlight leads to sufficient endogenous synthesis
- MOA: Induces synthesis of Ca-binding proteins, interacting with DNA (regulation of transcription) via 7-Dehydrocholesterol (Cholesterol) and conversion of Cholecalciferol (Vitamin D3) to 1,25-Dihydroxycholecalciferol (Calcitriol)
- Physiological Functions:
-Release of Ca from bone
- Intestinal calcium absorption
- Prevent renal calcium excretion
- Long-term deficiency:
- Ca in blood stays constant, but bone tissue is depleted of calcium
- Bone tissue poorly mineralized resulting in softening
- Rickets (children), osteomalacia (adults)
- Hypervitaminosis D:
- Chronic elevation of blood calcium levels leads to cardiovascular and renal damage
Vitamin E (Tocopherol)
- More than 8 derivatives in plants, differing in ring substitutions and side chains
- α-Tocopherol is most abundant
- Deficiency is rare; mild hemolytic anemia in premature infants due to poor intestinal absorption
- Non-toxic at 50x RDA
- Epidemiological studies suggest inverse relationship between Vitamin E intake and coronary heart disease
Vitamin K
-
Coagulation
-
Phylloquinone (in vegetables)
-
Menaquinone (synthesized by bacteria)
-
Menadione (synthetic previtamine); alkylated in the human body
-
Absorbed easily, even without bile salts
-
Not significantly stored. First fat-soluble vitamin to be deficient in fat malabsorption.
-
Deficiency results in bleeding disorders
-
Hemorrhagic diseases of newborns happen due to low tissue stores at birth, insufficient Vitamin K in breast milk, and immature intestinal flora/inadequate bacterial production
-
Essential co-enzyme for the carboxylation of glutamate residues in prothrombin
Micronutrients (Minerals)
- Minerals comprise about 4-5% of total body weight
- 50% = calcium (Ca); 25% = phosphorus (P) in bones and teeth
- Remaining 25% is other essential macro/micro minerals & trace elements.
- Essential Macrominerals ( >100 mg/day): Mg, Na, K, Cl, S, etc.
- Essential Microminerals (<15 mg/day): Fe, Zn, I, Se, Mn, F, Mo, Cr, Co, B, etc.
- Ultratrace Elements (micrograms): As, Al, Sn, Ni, V, Si, etc
- "Problem Minerals" (in the U.S. diet): Low intake of calcium, iron, zinc, and magnesium. Food fortification with iron and zinc is common, but not calcium.
- Calcium and Phosphate: 99% of total body calcium in bones, and 2.5 mM in blood (tightly regulated). Intracellular Ca: 100-1000 nM, but essential for majority of physiologic processes.
- Hypocalcemia: low blood calcium, causes muscle spasms, tetany, cardiac dysfunction.
- Hypercalcemia: high blood calcium, causes diffuse precipitation of (Ca)3(PO4)2
- Magnesium (Mg): Key component for >300 metabolic enzymes and is essential component of ATP. No cAMP formation without Mg
Vitamin A
- Source #1: Beta-carotene = orange pigment, carrots, and other vegetables
- Beta-carotene dioxygenase in intestinal mucosa oxidizes carotene to 2 molecules of retinal
- Retinal is a prosthetic group in rhodopsins
- Deficiency: Night blindness
- Other Forms:
- Retinol (alcoholic group) = storage form in animal tissues
- Retinal (aldehyde group) = in rhodopsin
- Retinoic acid (carboxylic group) = involved in gene expression.
- Retinophosphoate (ester of retinol and phosporic acid) = crucial for carbohydrate transfer reactions onto proteins; important for synthesis of glycoproteins
- Deficiencies:
- Maintenance of epithelial tissues via synthesis of glycoproteins; deficiency leads to slowed down mucus producing cells and low glycoprotein content of tears, "dry eyes" (xerophthalmia), bacterial infections, and corneal perforation
- Function of osteoblasts and osteoclasts; deficiency leads to impaired balance between these, and retinoic acid activates osteoclasts, enhancing bone resorption.
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