38 Questions
What is the primary reason why vitamins are essential for the human body?
Because they are essential for health and growth
What is a characteristic of vitamins in the human body?
They do not enter into the body's tissue structure
Why must vitamins be taken in through food?
Because the body cannot synthesize them in sufficient quantities
What is the process by which vitamin A is transported to the liver?
Through chylomicrons
What role do vitamins play in the body?
They act as catalysts to facilitate bodily functions
What is the function of rhodopsin in the retina?
To transmit light signals to the brain
What is a common characteristic of all vitamins?
They are organic substances needed in small amounts
What is the form of vitamin A that is essential for visual function?
Retinol
What is a consequence of not consuming enough vitamins?
Deficiency diseases may occur
What is the result of vitamin A deficiency in the retina?
Night blindness
What is a primary function of vitamins in the body?
To act as catalysts to facilitate bodily functions
What is the role of retinol-binding protein in vitamin A metabolism?
To transport vitamin A in the blood
What is the function of vitamin A in bone growth and development?
To facilitate bone calcification
Why are vitamins considered essential nutrients?
Because they are essential for health and growth
What is the precursor to vitamin A that is converted to retinol?
Carotene
What is the name of the pigment found in the rods of the retina?
Rhodopsin
What is the primary function of vitamin D in the small intestine?
Stimulation of calcium binding protein biosynthesis
What is the primary form of vitamin D that is transported to the kidney for further hydroxylation?
Calcifediol
What is the primary consequence of vitamin D deficiency in children?
Rickets
What is the primary mechanism by which vitamin D regulates calcium levels in the blood?
Stimulation of calcium binding protein biosynthesis
What is the primary form of vitamin D that is transported to the target organs, such as the intestine and bone?
Calcitriol
What is the primary consequence of vitamin D deficiency in adults?
Osteomalacia
What is the primary difference between fat soluble vitamins and water soluble vitamins in terms of their solubility?
Fat soluble vitamins are nonpolar and soluble in fat, while water soluble vitamins are polar and soluble in water.
Which of the following vitamins is NOT stored in the liver?
Vitamin E
What is the primary function of vitamin A in the body?
It is essential for vision and immune function
What is the provitamin of vitamin A?
Carotene
Which of the following sources is NOT a rich source of vitamin A?
Spinach
What is the percentage of vitamin A stored in the liver?
95%
What is the difference between vitamin A1 and vitamin A2 in terms of their activity?
Vitamin A2 has 40% of the activity of vitamin A1
Which of the following is a characteristic of water soluble vitamins?
They are not stored in the body except vitamin B12
What is the result of the increased keratinization of the skin due to vitamin A deficiency?
All of the above
What is the recommended daily intake of vitamin A?
750 ug/day
What is the source of vitamin D2?
Plants and yeast
What is the result of chronic toxicity of vitamin A?
Hair loss and skin fissuring
What is the precursor to vitamin D3?
7-dehydrocholesterol
What is the daily requirement of vitamin D for normal adults?
100 I.U
What is the effect of vitamin A deficiency on the conjunctiva?
Squamous metaplasia
What is the source of vitamin D3?
All of the above
Study Notes
Metabolism of Vitamin D
- Dietary vitamin D is absorbed from the small intestine and transported to the liver via chylomicrons.
- In the liver, vitamin D is activated and metabolized to 25-hydroxycholecalciferol (calcifediol).
- Calcifediol is transported to the kidney, where it undergoes further hydroxylation to form the hormone 1,25-dihydroxycholecalciferol (calcitriol).
- Calcitriol is transported to target organs (intestine and bone) via vitamin D-binding protein.
Functions of Vitamin D
- Increases and regulates calcium and phosphate absorption from the small intestine.
- Stimulates the biosynthesis of calcium-binding protein, which transports calcium to the blood.
- Essential for bone mineralization (calcification).
- Inhibits calcium and phosphate excretion in the urine.
Vitamin D Deficiency
- Occurs due to inadequate sun exposure, inadequate dietary intake, or defective renal tubular phosphate reabsorption.
- Leads to rickets (in children) and osteomalacia (in adults), causing softening and deformities of bones.
Vitamins
- Organic substances essential for health and growth, but not synthesized in the body in sufficient quantities.
- Needed in small amounts and must be obtained through diet.
- Do not enter body structure or tissue structure.
- Act as catalysts and are not oxidized to produce energy.
Types of Vitamins
- Fat-soluble vitamins (A, D, E, and K) and water-soluble vitamins (B and C).
- Fat-soluble vitamins are nonpolar, require fat and bile salts for absorption, and are stored in the body.
- Water-soluble vitamins are polar, easily absorbed, and not stored in the body (except for vitamin B12).
Vitamin A
- Present in animal products (fish, liver, oils, meats, eggs, cheese, and butter) and plant products (carotenes in carrots, tomatoes, and sweet potatoes).
- Converted to vitamin A in the intestine and liver.
- 95% is stored in the liver.
- Has two forms: vitamin A1 (in animal products, high activity) and vitamin A2 (in fish and liver, 40% activity of A1).
- Provitamin is carotene.
Metabolism of Vitamin A
- Absorbed from the intestine in the presence of fat and bile salts.
- Transported to the liver through chylomicrons and lipoproteins.
- Converted to retinol, which can be oxidized to retinal or retinoic acid, both having vitamin activity.
Functions of Vitamin A
- Required for visual function, particularly for rhodopsin in the retina.
- Essential for health and growth, reproduction, mucus secretion, and maintaining differentiated epithelia.
- Essential for bone formation and calcification.
Deficiency of Vitamin A
- Leads to night blindness, keratomalacia, xerophthalmia, and premalignant conditions.
- Causes keratinization of the skin, blocking sebaceous glands, and squamous metaplasia.
Toxicity of Vitamin A
- Excess intake can cause drowsiness, headache, abdominal pain, vomiting, and skin desquamation in children.
- Chronic toxicity leads to hair loss and skin fissuring.
Learn about the process of vitamin D metabolism, from absorption in the small intestine to activation in the liver and kidneys. Understand how it's transported and converted into its active form, calcitriol.
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