Nutrition and Metabolism — MCQs

Nutrition and Metabolism Indian Medical PG Practice Questions and MCQs

Question 211: Basal Metabolic Rate (BMR) depends on which of the following factors?

A. Body weight
B. Body surface area (Correct Answer)
C. Amount of adipose tissue
D. Amount of lean body mass

Explanation: **Explanation:** **Why Body Surface Area (BSA) is the correct answer:** The Basal Metabolic Rate (BMR) is the minimum energy expenditure required to maintain vital functions at rest. The primary driver of BMR is **heat loss**, which occurs predominantly through the skin. According to the "Surface Law," the rate of heat loss is directly proportional to the **Body Surface Area**. Therefore, individuals with a larger BSA (e.g., tall and thin individuals) have a higher BMR to compensate for greater heat dissipation compared to shorter, stockier individuals of the same weight. **Analysis of Incorrect Options:** * **Body Weight:** While BMR increases with weight, it is not a direct determinant because weight does not account for metabolic activity levels of different tissues. * **Amount of Adipose Tissue:** Adipose tissue is metabolically inactive. An increase in fat mass actually **decreases** the BMR relative to total body weight. * **Amount of Lean Body Mass (LBM):** While LBM is the most significant *internal* determinant of BMR (as muscle is metabolically active), BMR is traditionally expressed and calculated in terms of **BSA (kcal/sq.m/hr)** for clinical standardization. **High-Yield Clinical Pearls for NEET-PG:** * **Age:** BMR is highest in children (due to rapid growth) and declines with age (approx. 2% per decade). * **Gender:** Males have a higher BMR than females (due to higher LBM and lower fat percentage). * **Hormones:** **Thyroxine (T4)** is the most important hormone regulating BMR. BMR increases in hyperthyroidism and decreases in hypothyroidism. * **Environmental Temperature:** BMR increases in cold climates to maintain body core temperature (thermogenesis). * **Specific Dynamic Action (SDA):** Also known as the thermic effect of food; it is highest for proteins (30%).

Question 212: Keshan disease is due to deficiency of which element?

A. Selenium (Correct Answer)
B. Chromium
C. Copper
D. Manganese

Explanation: **Explanation:** **Keshan disease** is a juvenile cardiomyopathy characterized by cardiac enlargement and congestive heart failure. It is caused by a deficiency of **Selenium (Option A)**. Selenium is a vital trace element that functions as a cofactor for the enzyme **Glutathione Peroxidase**, which protects cells from oxidative damage. In the absence of Selenium, oxidative stress leads to myocardial necrosis. Interestingly, the disease often involves a synergistic interaction between Selenium deficiency and the Coxsackie B virus. **Why other options are incorrect:** * **Chromium (Option B):** Deficiency is associated with **impaired glucose tolerance** and insulin resistance, as Chromium is a component of the Glucose Tolerance Factor (GTF). * **Copper (Option C):** Deficiency leads to **Menkes Kinky Hair Syndrome**, microcytic anemia (refractory to iron), and neutropenia. It is a cofactor for Lysyl oxidase and Tyrosinase. * **Manganese (Option D):** Deficiency is rare in humans but can lead to impaired growth, skeletal abnormalities, and defects in lipid and carbohydrate metabolism. It is a cofactor for Pyruvate carboxylase and Superoxide dismutase (Mn-SOD). **High-Yield Clinical Pearls for NEET-PG:** * **Kashin-Beck Disease:** Another Selenium deficiency disorder characterized by osteoarthropathy (cartilage degeneration). * **Selenocysteine:** Known as the **21st amino acid**, it is the form in which selenium is incorporated into proteins (e.g., Deiodinase, which converts T4 to T3). * **Toxicity:** Excess selenium (Selenosis) causes garlic breath, hair loss (alopecia), and nail dystrophy.

Question 213: What is the Atkins diet?

A. Low calorie and low carbohydrate diet (Correct Answer)
B. High carbohydrate and low calorie diet
C. Low carbohydrate and high calorie diet
D. High carbohydrate and high calorie diet

Explanation: The **Atkins diet** is a popular nutritional strategy primarily used for weight loss. It is characterized as a **low-carbohydrate, high-protein, and high-fat diet**. ### **Explanation of the Correct Answer** **Option A (Low calorie and low carbohydrate)** is the correct choice because the fundamental mechanism of the Atkins diet is the drastic restriction of carbohydrates (usually <20g/day in the induction phase). This forces the body to shift its metabolism from glucose oxidation to **fatty acid oxidation and ketogenesis**. While the diet allows for high fat and protein intake, it is functionally **low calorie** because: 1. **Satiety:** High protein and fat intake increase satiety (via CCK and PYY), leading to a spontaneous reduction in total caloric intake. 2. **Thermic Effect:** Protein has a higher thermic effect of food (TEF) compared to carbohydrates. 3. **Metabolic Shift:** The body enters a state of "nutritional ketosis," where stored body fat is mobilized for energy. ### **Why Other Options are Incorrect** * **Options B & D:** These involve high carbohydrate intake. High carbs trigger insulin release, which inhibits lipolysis and promotes fat storage, the exact opposite of the Atkins philosophy. * **Option C:** While Atkins is low carbohydrate, it is not "high calorie" in practice. A high-calorie diet, even if low in carbs, would eventually lead to weight gain or maintenance rather than the weight loss for which the Atkins diet is indicated. ### **NEET-PG High-Yield Pearls** * **Ketogenic Mechanism:** The diet mimics the metabolic state of fasting. The brain shifts from using glucose to **ketone bodies** (acetoacetate and β-hydroxybutyrate) as its primary energy source. * **Clinical Use:** Beyond weight loss, ketogenic diets are a high-yield treatment for **refractory epilepsy** in children and **Pyruvate Dehydrogenase (PDH) deficiency**. * **Side Effects:** Watch for "Keto flu" (electrolyte imbalance), hyperuricemia (due to high protein), and potential increases in LDL cholesterol.

Question 214: In which part of the body is the highest concentration of zinc found?

A. Prostate (Correct Answer)
B. Skin
C. Hair
D. Bone

Explanation: **Explanation:** **Correct Option: A (Prostate)** Zinc is an essential trace element required for the catalytic activity of over 300 enzymes. While the majority of total body zinc is stored in skeletal muscle and bone (due to their large mass), the **highest concentration** (amount per gram of tissue) is found in the **prostate gland**, specifically in the prostatic fluid. Zinc plays a crucial role in the prostate by inhibiting the enzyme m-aconitase, which redirects citrate metabolism toward secretion into seminal plasma rather than oxidation in the TCA cycle. This high concentration also serves an antimicrobial function in the male reproductive tract. **Incorrect Options:** * **B. Skin:** While the skin contains about 5-6% of total body zinc (primarily in the epidermis) and is vital for wound healing, its concentration is significantly lower than that of the prostate. * **C. Hair:** Zinc is present in hair and is often used as a marker for long-term nutritional status, but it does not reach the physiological concentrations found in prostatic tissue. * **D. Bone:** Bone contains a large *reservoir* of zinc (approximately 30% of total body stores), but the *density* or concentration per unit of tissue is less than that of the prostate. **NEET-PG High-Yield Pearls:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder caused by a mutation in the **ZIP4 transporter**, leading to zinc malabsorption. Clinical triad: Dermatitis (periorificial/acral), Alopecia, and Diarrhea. * **Enzymes:** Zinc is a cofactor for Carbonic Anhydrase, Alcohol Dehydrogenase, Alkaline Phosphatase, and RNA Polymerase. * **Zinc Fingers:** These are structural motifs in proteins that allow for DNA binding, essential for steroid hormone receptor function. * **Wound Healing:** Zinc is critical for collagen synthesis and cell division; deficiency leads to poor wound healing and gustatory dysfunction (hypogeusia).

Question 215: What is the recommended daily protein intake for an adult male in grams per kilogram of body weight?

A. 0-5 gm/kg/day
B. 1 gm/kg/day (Correct Answer)
C. 1-5 gm/kg/day
D. 2 gm/kg/day

Explanation: ### Explanation **Correct Option: B (1 gm/kg/day)** The recommended dietary allowance (RDA) for protein in a healthy adult is approximately **0.8 to 1.0 gm/kg of body weight per day**. This value is calculated to maintain a **positive nitrogen balance**, ensuring that the intake of nitrogen (via amino acids) equals or exceeds the loss through urea, sweat, and feces. For an average Indian adult male, the ICMR (Indian Council of Medical Research) guidelines traditionally suggest 1 gm/kg/day as a safe and practical standard to meet the physiological demands of tissue repair and enzyme synthesis. **Analysis of Incorrect Options:** * **Option A (0-5 gm/kg/day):** This range is clinically irrelevant. An intake near zero would lead to rapid muscle wasting and protein-energy malnutrition (PEM). * **Option C (1-5 gm/kg/day):** While the lower limit is correct, the upper limit (5 gm/kg) is excessively high and can lead to metabolic stress on the kidneys and dehydration due to increased urea excretion. * **Option D (2 gm/kg/day):** This level is typically reserved for specific physiological states such as elite athletes, patients with severe burns, or those recovering from major trauma/surgery, but it is not the standard recommendation for a healthy adult. **Clinical Pearls for NEET-PG:** * **Nitrogen Balance:** 1 gram of Nitrogen is equivalent to **6.25 grams of protein**. * **Biological Value (BV):** Egg protein has a BV of 100 (Reference Protein), while gelatin lacks tryptophan and has a BV of 0. * **Specific Dynamic Action (SDA):** Protein has the highest SDA (~30%), meaning it requires more energy for digestion and metabolism compared to fats or carbohydrates. * **Kwashiorkor vs. Marasmus:** Kwashiorkor is a **pure protein deficiency** (edema present), whereas Marasmus is a **total calorie deficiency** (generalized wasting).

Question 216: Which of the following acts as a defence against E. coli?

A. Lactoglobulin
B. Lactalbumin
C. Lactoferrin (Correct Answer)
D. None of the above

Explanation: **Explanation:** The correct answer is **Lactoferrin**. **1. Why Lactoferrin is correct:** Lactoferrin is an iron-binding glycoprotein found in high concentrations in human colostrum and milk. It acts as a potent bacteriostatic agent against iron-dependent bacteria like *E. coli*. The underlying mechanism is **"Nutritional Immunity"**: Lactoferrin sequesters free ferric iron ($Fe^{3+}$) in the gut, depriving bacteria of the essential iron required for their growth and replication. Additionally, it can directly bind to the lipopolysaccharides (LPS) on the bacterial cell wall, increasing membrane permeability and causing lysis. **2. Why the other options are incorrect:** * **Lactoglobulin:** This is a major whey protein found in cow’s milk but is notably **absent in human milk**. While it serves as a source of amino acids, it does not possess specific antimicrobial properties against *E. coli*. * **Lactalbumin ($\alpha$-lactalbumin):** This is the principal sugar-binding protein in human milk. Its primary physiological role is to act as a regulatory subunit for **lactose synthase**, the enzyme responsible for lactose synthesis. It does not function as a defense protein. **3. High-Yield Clinical Pearls for NEET-PG:** * **Lysozyme:** Another key defense factor in breast milk that works synergistically with lactoferrin by cleaving the peptidoglycan layer of bacterial cell walls. * **Bifidus Factor:** A carbohydrate in human milk that promotes the growth of *Lactobacillus bifidus*, which produces lactic acid, lowering intestinal pH and inhibiting *E. coli* growth. * **Secretory IgA:** The most abundant immunoglobulin in colostrum, providing mucosal immunity against enteric pathogens.

Question 217: Which of the following is NOT a good dietary source of iron?

A. Liver
B. Jaggery
C. Fish
D. Milk (Correct Answer)

Explanation: **Explanation:** The correct answer is **Milk**. In biochemistry and nutrition, milk is famously described as a "near-complete food" but is notoriously **deficient in Iron and Vitamin C**. **1. Why Milk is the Correct Answer:** Milk contains very negligible amounts of iron (approx. 0.1 mg/100g). Furthermore, the high calcium and phosphate content in milk can actually inhibit the absorption of whatever trace amounts of iron are present. In clinical practice, excessive intake of cow's milk in toddlers is a leading cause of "Nutritional Iron Deficiency Anemia." **2. Analysis of Incorrect Options:** * **Liver (Option A):** This is one of the richest sources of **Heme iron**, which has high bioavailability. It also provides Vitamin B12 and Vitamin A. * **Jaggery (Option B):** Unlike refined sugar, jaggery is prepared in iron vessels and contains significant non-heme iron. It is often recommended in community health programs in India to combat anemia. * **Fish (Option C):** Animal tissues (meat, poultry, and fish) are excellent sources of Heme iron. They also contain the "MPF factor" (Meat, Poultry, Fish factor) which enhances the absorption of non-heme iron from other foods. **3. NEET-PG High-Yield Pearls:** * **Absorption Site:** Iron is primarily absorbed in the **Duodenum** (and upper jejunum). * **Enhancers vs. Inhibitors:** Vitamin C (Ascorbic acid) enhances iron absorption by keeping it in the ferrous ($Fe^{2+}$) state. Phytates (cereals), Oxalates (spinach), Tannins (tea), and Calcium inhibit absorption. * **Storage Form:** Iron is stored as **Ferritin** (labile) and **Hemosiderin** (stable). * **Transport Form:** Iron is transported in the blood bound to **Transferrin**.

Question 218: Which of the following is not a micronutrient?

A. Iodine
B. Iron
C. Glucose (Correct Answer)
D. Boron

Explanation: **Explanation:** Nutrients are broadly classified into two categories based on the quantity required by the human body: **Macronutrients** and **Micronutrients**. **1. Why Glucose is the correct answer:** Glucose is a carbohydrate, which is a **macronutrient**. Macronutrients (Carbohydrates, Proteins, and Fats) are required in large quantities (grams per day) because they serve as the primary substrates for energy production (ATP) and structural components of cells. Glucose specifically provides approximately 4 kcal/g and is the obligatory fuel source for the brain and RBCs. **2. Why the other options are incorrect:** Micronutrients are required in trace amounts (milligrams or micrograms) and do not provide energy directly but act as essential cofactors for enzymes. * **Iodine (A):** A trace element essential for the synthesis of thyroid hormones (T3 and T4). * **Iron (B):** A critical micro-mineral required for heme synthesis, oxygen transport (hemoglobin), and the electron transport chain (cytochromes). * **Boron (D):** An ultra-trace element involved in bone metabolism and the utilization of Vitamin D and Calcium. **Clinical Pearls for NEET-PG:** * **Proximate Principles of Food:** Refers to macronutrients (Carbohydrates, Fats, Proteins). * **Energy Density:** Fat (9 kcal/g) > Alcohol (7 kcal/g) > Proteins/Carbohydrates (4 kcal/g). * **Hidden Hunger:** Refers to micronutrient deficiencies (e.g., Vitamin A, Iron, Iodine) where the caloric intake may be sufficient, but the quality of diet is poor. * **Essential vs. Non-essential:** While glucose is a primary fuel, it is not an "essential" nutrient in the diet because the body can synthesize it via gluconeogenesis.

Question 219: A 52-year-old female patient complains of abdominal pain. General examination reveals a BMI of 30 kg/m2. X-ray examination reveals osteoporotic changes. The physician suspects impaired absorption of calcium in this patient. All of the following could be the reason for this, except:

A. Inositol hexaphosphate in cereals
B. High intake of oxalate
C. High concentrations of fatty acids in the intestinal lumen
D. Decreased iron intake (Correct Answer)

Explanation: **Explanation:** The absorption of calcium in the gastrointestinal tract is a complex process influenced by various dietary factors. The correct answer is **D (Decreased iron intake)** because iron and calcium actually compete for the same transport mechanisms; therefore, a *decrease* in iron intake would theoretically favor, rather than impair, calcium absorption. **Why the other options are incorrect (Factors that impair calcium absorption):** * **Inositol hexaphosphate (Phytates):** Found in cereals and grains, phytates form insoluble complexes with calcium, preventing its absorption. * **Oxalates:** Present in leafy greens (like spinach) and berries, oxalates bind to calcium to form insoluble calcium oxalate, which is excreted in feces. * **High concentrations of fatty acids:** In conditions of fat malabsorption (steatorrhea), unabsorbed fatty acids react with calcium to form insoluble "calcium soaps." This is particularly relevant in this patient’s profile (BMI 30), where underlying metabolic or biliary issues might be present. **Clinical Pearls for NEET-PG:** 1. **Vitamin D:** The most potent stimulator of calcium absorption (via synthesis of Calbindin in intestinal cells). 2. **pH Effect:** An **acidic medium** (e.g., Vitamin C, HCl) increases calcium solubility and absorption, while an **alkaline medium** (e.g., antacids) inhibits it. 3. **Calcium-Iron Interaction:** High doses of calcium can inhibit the absorption of both heme and non-heme iron. Clinically, patients are advised not to take iron supplements with milk or calcium tablets. 4. **Phosphate Ratio:** An ideal dietary Calcium:Phosphorus ratio for optimum absorption is **1:1 to 2:1**. Excess phosphorus inhibits calcium uptake.

Question 220: Which is the limiting amino acid in wheat?

A. Methionine
B. Tryptophan
C. Lysine (Correct Answer)
D. Alanine

Explanation: **Explanation:** The concept of a **limiting amino acid** refers to the essential amino acid present in the lowest quantity relative to the body's requirements in a specific food source. When this amino acid is exhausted, protein synthesis in the body stops, regardless of the availability of other amino acids. **Why Lysine is Correct:** Cereals, including **wheat**, rice, and maize, are characteristically deficient in **Lysine**. In wheat specifically, the proteins (gliadin and glutenin) lack sufficient lysine to meet human nutritional needs. Therefore, lysine is the primary limiting amino acid in wheat. Threonine is often considered the second limiting amino acid in wheat. **Analysis of Incorrect Options:** * **A. Methionine:** This is the limiting amino acid in **pulses/legumes** (like beans and lentils). Pulses are rich in lysine but poor in sulfur-containing amino acids like methionine and cysteine. * **B. Tryptophan:** This is the limiting amino acid in **Maize** (along with Lysine). A diet solely dependent on maize can lead to Pellagra because tryptophan is a precursor for Niacin (Vitamin B3) synthesis. * **D. Alanine:** This is a non-essential amino acid. Limiting amino acids must be "essential" because the body cannot synthesize them endogenously. **High-Yield NEET-PG Pearls:** * **Mutual Supplementation:** This is the nutritional principle of combining cereals (low lysine, high methionine) with pulses (high lysine, low methionine) to provide a complete amino acid profile (e.g., "Dal-Chawal"). * **Reference Protein:** Egg albumin is considered the "standard" or reference protein (Biological Value = 100) as it contains all essential amino acids in ideal proportions. * **Limiting Amino Acid Summary:** * Wheat/Rice: Lysine * Pulses: Methionine * Maize: Tryptophan and Lysine

Practice by Chapter

Macronutrients and Energy Requirements

Practice Questions

Protein Quality and Nitrogen Balance

Practice Questions

Essential Amino Acids and Proteins

Practice Questions

Essential Fatty Acids and Lipids

Practice Questions

Dietary Fiber and Complex Carbohydrates

Practice Questions

Glycemic Index and Glycemic Load

Practice Questions

Micronutrients: Vitamins and Minerals

Practice Questions

Trace Elements and Metabolism

Practice Questions

Malnutrition: Biochemical Consequences

Practice Questions

Dietary Antioxidants

Practice Questions

Functional Foods and Nutraceuticals

Practice Questions

Dietary Guidelines and Recommendations

Practice Questions

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