Question 1

Scurvy is a disease caused by the deficiency of which vitamin?

Accepted Answer

Scurvy is caused by vitamin C (ascorbic acid) deficiency. Vitamin C is essential for collagen synthesis, and its deficiency leads to weakened connective tissues, bleeding gums, poor wound healing, and other symptoms characteristic of scurvy. Historically, it affected sailors on long voyages without access to fresh fruits and vegetables.

Question 2

Which of the following is a water-soluble vitamin that acts as a coenzyme in carbohydrate metabolism?

Accepted Answer

Vitamin B1 (thiamine) is a water-soluble vitamin that functions as a coenzyme in carbohydrate metabolism, particularly in the conversion of pyruvate to acetyl-CoA. Deficiency causes beriberi, a disease affecting the nervous and cardiovascular systems.

Question 3

Deficiency of which mineral causes the disease 'Goitre'?

Accepted Answer

Goitre is caused by iodine deficiency. Iodine is essential for the synthesis of thyroid hormones (T3 and T4). When iodine intake is insufficient, the thyroid gland enlarges (becomes swollen) in an attempt to produce adequate thyroid hormones, resulting in goitre.

Question 4

Which of the following vitamins is synthesized by the human body when skin is exposed to sunlight?

Accepted Answer

Vitamin D is synthesized in the skin when exposed to ultraviolet B (UVB) radiation from sunlight. This is why it is sometimes called the 'sunshine vitamin.' It plays a crucial role in calcium absorption and bone health.

Question 5

Which of the following vitamins is synthesized by the human body and does NOT need to be obtained from dietary sources?

Accepted Answer

Vitamin D is synthesized by the human body when skin is exposed to sunlight (UV-B radiation). The 7-dehydrocholesterol in the skin is converted to previtamin D3, which is then converted to active vitamin D (calcitriol) in the liver and kidneys. While small amounts may be obtained from food sources like fatty fish and fortified milk, the body can produce sufficient amounts endogenously, making it unique among essential vitamins.

Question 6

Which of the following diseases is caused by a protozoan parasite?

Accepted Answer

Malaria is caused by Plasmodium, a protozoan parasite transmitted by Anopheles mosquitoes. Other protozoal diseases include sleeping sickness (Trypanosoma), dysentery (Entamoeba), and kala-azar (Leishmania). Bacterial diseases include tuberculosis and cholera; viral diseases include measles and polio.

Question 7

Scurvy, a disease characterized by bleeding gums, poor wound healing, and weakened connective tissue, is caused by the deficiency of which vitamin?

Accepted Answer

Scurvy is caused by vitamin C (ascorbic acid) deficiency. Vitamin C is essential for collagen synthesis, which is a major structural protein in connective tissue, blood vessel walls, and skin. Without adequate vitamin C, collagen cannot be properly cross-linked, leading to weak blood vessels (causing bleeding), poor wound healing, and deteriorating gums. Historically, scurvy was common among sailors on long voyages lacking fresh fruits and vegetables.

Question 8

Kwashiorkor is a severe form of malnutrition primarily caused by deficiency of which nutrient?

Accepted Answer

Kwashiorkor is a protein-deficiency disease characterized by edema (swelling), fatty liver, skin lesions, and growth retardation. It occurs when caloric intake may be adequate but protein intake is severely insufficient. The name comes from the Akan language of Ghana, meaning 'the sickness the older child gets when the new child is born' — reflecting the condition's prevalence when children are weaned onto carbohydrate-heavy diets lacking protein.

Question 9

Which of the following diseases is caused by a deficiency of iodine in the diet?

Accepted Answer

Goiter (enlargement of the thyroid gland) is primarily caused by iodine deficiency. Iodine is essential for the synthesis of thyroid hormones (T3 and T4). When iodine intake is insufficient, the thyroid gland enlarges in an attempt to trap more iodine from the bloodstream, resulting in visible neck swelling. Iodized salt programs have significantly reduced goiter prevalence in many countries.

Question 10

Which of the following vitamins is synthesized by the human body and does NOT need to be obtained primarily from dietary sources?

Accepted Answer

Vitamin D is synthesized by the human body when skin is exposed to sunlight (UV-B radiation), converting 7-dehydrocholesterol in the skin to cholecvitamin D3. While dietary sources exist, the body's endogenous production is significant. Other vitamins (A, B12, C) must be obtained from food sources as the body cannot synthesize them.

Question 11

Which of the following is a water-soluble vitamin that acts as a coenzyme in energy metabolism and is deficient in the disease beriberi?

Accepted Answer

Thiamine (Vitamin B1) is a water-soluble vitamin that functions as a coenzyme in carbohydrate metabolism, specifically in the pyruvate dehydrogenase complex and transketolase enzymes. Beriberi is the disease caused by thiamine deficiency, characterized by peripheral neuropathy (wet beriberi affecting the cardiovascular system) or Wernicke-Korsakoff syndrome (dry beriberi affecting the nervous system). The disease was historically common in populations consuming polished white rice lacking the thiamine-rich bran.

Question 12

Which of the following vitamins is synthesized by the human body and does NOT require dietary intake for its primary production?

Accepted Answer

Vitamin D is synthesized in the skin upon exposure to ultraviolet B (UVB) radiation from sunlight. The 7-dehydrocholesterol in the skin is converted to previtamin D3, which is then converted to active vitamin D (calcitriol) in the liver and kidneys. While dietary sources exist, the body can produce sufficient vitamin D endogenously.

Question 13

Which of the following is the primary mode of transmission for dengue fever, and what is the vector organism responsible?

Accepted Answer

Dengue fever is transmitted primarily through the bite of infected female Aedes aegypti mosquitoes (and secondarily Aedes albopictus). The virus is an arbovirus (arthropod-borne virus) belonging to the Flavivirus genus. Aedes aegypti is a day-biting mosquito found in tropical and subtropical regions, particularly in urban areas. Vertical transmission (mother to fetus) and blood transfusion are rare routes but not the primary mode.

Question 14

A patient presents with bleeding gums, poor wound healing, and follicular hyperkeratosis. Which vitamin deficiency is most likely responsible, and what is the biochemical role of this vitamin?

Accepted Answer

These symptoms are classic for vitamin C (ascorbic acid) deficiency, which leads to scurvy. Vitamin C is a cofactor for prolyl and lysyl hydroxylase enzymes, which are essential for collagen cross-linking and stabilization. Without adequate vitamin C, collagen synthesis is impaired, leading to fragile blood vessels (bleeding gums), poor wound healing, and characteristic perifollicular hemorrhages with hyperkeratosis.

Question 15

Kwashiorkor is a severe form of protein-energy malnutrition characterized by which of the following clinical hallmarks?

Accepted Answer

Kwashiorkor is caused by severe protein deficiency while caloric intake may be relatively adequate (often from carbohydrate-rich foods like cassava or plantains). The hallmark signs include edema (fluid retention in tissues), hepatomegaly (enlarged liver), skin depigmentation, hair changes (reddish/blonde discoloration), and a characteristic 'moon face' appearance. Unlike marasmus, body weight loss is masked by edema.

Question 16

Beriberi is a disease caused by deficiency of which vitamin, and which enzyme system is primarily affected, leading to the characteristic neurological and cardiac manifestations?

Accepted Answer

Beriberi is caused by thiamine (vitamin B1) deficiency. Thiamine pyrophosphate (TPP) is the active coenzyme form of thiamine and is essential for three major enzyme complexes: pyruvate dehydrogenase (in carbohydrate metabolism), alpha-ketoglutarate dehydrogenase (in the citric acid cycle), and transketolase (in the pentose phosphate pathway). Deficiency leads to impaired energy metabolism, particularly affecting high-energy-demand tissues like the nervous system and heart, causing wet beriberi (cardiac) and dry beriberi (neurological) forms.

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