Nutrition and Metabolism — MCQs

Nutrition and Metabolism Indian Medical PG Practice Questions and MCQs

Question 221: What is the daily protein requirement for an individual?

A. 1 gm/kg (Correct Answer)
B. 2 gm/kg
C. 3 gm/kg
D. 4 gm/kg

Explanation: **Explanation:** The daily protein requirement for a healthy adult is approximately **0.8 to 1.0 gm/kg body weight/day**. This value is based on the Recommended Dietary Allowance (RDA) to maintain a positive nitrogen balance and support the physiological turnover of body proteins. **Why Option A is Correct:** In a balanced diet, protein should contribute about 10–15% of the total caloric intake. For an average adult weighing 60–70 kg, this translates to roughly 60–70 grams of protein daily. This amount is sufficient to replace the obligatory nitrogen losses (via urine, feces, and skin) and maintain structural and enzymatic functions in a sedentary to moderately active individual. **Why Other Options are Incorrect:** * **Option B (2 gm/kg):** This is excessive for a normal adult. However, such high intake may be indicated in specific hypermetabolic states like severe burns, multiple trauma, or for elite bodybuilders during heavy resistance training. * **Options C & D (3–4 gm/kg):** These levels are physiologically unnecessary and can place an undue load on the kidneys (increased glomerular filtration rate) and may lead to dehydration due to the osmotic effect of urea excretion. **High-Yield Clinical Pearls for NEET-PG:** * **Biological Value (BV):** Egg protein has the highest BV (100) and is considered the "Reference Protein." * **Specific Dynamic Action (SDA):** Protein has the highest SDA (~30%), meaning it requires more energy for digestion and metabolism compared to fats and carbohydrates. * **Kwashiorkor vs. Marasmus:** Kwashiorkor is a **pure protein deficiency** (edema present), whereas Marasmus is a **total calorie deficiency** (generalized wasting). * **Nitrogen Balance:** 1 gram of Nitrogen is equivalent to **6.25 grams** of protein. This conversion factor is frequently tested.

Question 222: Hypogonadism, reduced immunity, and alopecia may be a deficiency manifestation of which of the following?

A. Iron
B. Copper
C. Zinc (Correct Answer)
D. Magnesium

Explanation: **Explanation:** **Zinc deficiency** is the correct answer because Zinc is a vital trace element required for the structural integrity of over 300 enzymes (e.g., Carbonic anhydrase, Alcohol dehydrogenase, and DNA polymerase). It plays a crucial role in protein synthesis, cell division, and nucleic acid metabolism. * **Hypogonadism:** Zinc is essential for the synthesis of testosterone and the maturation of sperm. Deficiency leads to primary hypogonadism and delayed puberty. * **Reduced Immunity:** Zinc is critical for T-lymphocyte maturation and function. Deficiency causes thymic atrophy and impaired cell-mediated immunity. * **Alopecia and Skin Changes:** Zinc is required for keratinocyte proliferation. Deficiency leads to hair loss and characteristic periorificial/acral dermatitis. **Analysis of Incorrect Options:** * **Iron:** Deficiency typically presents with microcytic hypochromic anemia, pica, and koilonychia (spoon-shaped nails), not primary hypogonadism. * **Copper:** Deficiency leads to Menkes Kinky Hair Syndrome (presents with brittle "steely" hair), microcytic anemia, and neurological degradation. * **Magnesium:** Deficiency (hypomagnesemia) is characterized by neuromuscular irritability, tetany, and cardiac arrhythmias. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder causing impaired zinc absorption, presenting with the triad of **alopecia, diarrhea, and vesiculobullous dermatitis** (periorificial and acral). * **Zinc Finger Motifs:** Zinc is a structural component of DNA-binding proteins (transcription factors), making it essential for gene expression. * **Wound Healing:** Zinc is a cofactor for collagenase; deficiency leads to poor wound healing.

Question 223: Which of the following immuno-nutrients are required more in conditions of stress?

A. 1 and 3 only
B. 2 and 4 only
C. 1, 2 and 3 only
D. 1, 2, 3 and 4 only (Correct Answer)

Explanation: ### Explanation In conditions of metabolic stress (such as sepsis, major surgery, or severe trauma), the body’s nutritional requirements shift from basic maintenance to supporting immune function and tissue repair. **Immuno-nutrients** are specific nutrients that modulate the immune system and improve clinical outcomes in critically ill patients. The four primary immuno-nutrients required in increased amounts during stress are: 1. **Arginine:** Becomes a "conditionally essential" amino acid during stress. It serves as a precursor for **Nitric Oxide (NO)**, which enhances microcirculation and T-cell function, and promotes wound healing via collagen synthesis. 2. **Glutamine:** The most abundant amino acid in the body, but stores are rapidly depleted during catabolic stress. It is the primary fuel for rapidly dividing cells, specifically **enterocytes** (maintaining gut barrier integrity) and **lymphocytes**. 3. **Omega-3 Fatty Acids (EPA/DHA):** These compete with arachidonic acid to produce less inflammatory eicosanoids (3-series prostaglandins and 5-series leukotrienes), thereby modulating the systemic inflammatory response syndrome (SIRS). 4. **Nucleotides:** Essential for the rapid proliferation of immune cells (T-lymphocytes) and maintaining the gut-associated lymphoid tissue (GALT). **Why Option D is Correct:** All four substances listed are recognized as critical components of "immunonutrition" formulas. They work synergistically to reduce infectious complications and shorten hospital stays. **Why Other Options are Incorrect:** Options A, B, and C are incomplete because they omit one or more of these essential components. In the context of NEET-PG, "stress" implies a state where the demand for all these specific substrates exceeds endogenous production. ### High-Yield Clinical Pearls * **Glutamine** is the "fuel of the immune system" and prevents bacterial translocation from the gut. * **Arginine** should be used cautiously in patients with severe septic shock due to its role in Nitric Oxide production (potential vasodilation). * **Immunonutrition** is most effective when started **pre-operatively** (5–7 days) in patients undergoing major GI surgery.

Question 224: Why are cereals and pulses typically combined in dietary planning?

A. Cereals contain 10% protein, while pulses contain 40% protein.
B. Cereals are deficient in methionine, and lysine is deficient in pulses.
C. Cereals are deficient in lysine, and methionine is deficient in pulses. (Correct Answer)
D. Cereals are rich in essential amino acids.

Explanation: ### Explanation **1. The Concept of Mutual Supplementation** The core principle behind combining cereals and pulses is **Mutual Supplementation**. Most plant-based proteins are "incomplete proteins" because they lack one or more essential amino acids (limiting amino acids). * **Cereals** (e.g., rice, wheat, maize) are deficient in **Lysine** but relatively rich in **Methionine** and Cysteine. * **Pulses/Legumes** (e.g., lentils, beans, peas) are deficient in **Methionine** but rich in **Lysine**. By consuming them together (e.g., Dal-Chawal or Khichdi), the amino acid deficit of one is compensated by the other, resulting in a "complete protein" profile with a high **Biological Value (BV)** comparable to animal protein. **2. Analysis of Incorrect Options** * **Option A:** While pulses have more protein than cereals, the percentages are incorrect. Cereals typically contain 6–12% protein, while pulses contain 20–25% (not 40%, except for Soybeans). More importantly, the *quality* (amino acid profile) is the reason for the combination, not just the *quantity*. * **Option B:** This is a factual reversal. Lysine is the limiting amino acid in cereals, not pulses. * **Option D:** Cereals are not rich in all essential amino acids; they are specifically poor in Lysine and Tryptophan (especially Maize). **3. NEET-PG High-Yield Pearls** * **Limiting Amino Acid in Maize:** Tryptophan (leads to Pellagra as Tryptophan is a precursor for Niacin). * **Limiting Amino Acid in Pulses:** Methionine (Sulfur-containing amino acid). * **Reference Protein:** Egg protein (Albumin) is considered the "standard" with a Biological Value of 100. * **Net Protein Utilization (NPU):** This is the best indicator of dietary protein quality as it accounts for both digestibility and the amino acid profile.

Question 225: Which of the following are characteristic features of copper deficiency?

A. Anemia, Osteopenia, Growth retardation (Correct Answer)
B. Cardiomyopathy, Osteopenia, Growth retardation
C. Cardiomyopathy, Osteopenia
D. Anemia, Osteopenia

Explanation: Copper is an essential trace element required for the function of several key enzymes (metalloenzymes). Its deficiency manifests through multi-system involvement: **1. Why Option A is Correct:** * **Anemia:** Copper is a component of **Hephaestin** and **Ceruloplasmin** (ferroxidases). These enzymes convert ferrous iron ($Fe^{2+}$) to ferric iron ($Fe^{3+}$), allowing iron to bind to transferrin for transport. Deficiency leads to "iron-block anemia," typically presenting as **microcytic hypochromic anemia** that is unresponsive to iron therapy. * **Osteopenia:** Copper is a cofactor for **Lysyl Oxidase**, which is essential for the cross-linking of collagen and elastin. Defective cross-linking leads to a weak bone matrix and skeletal abnormalities (osteopenia/osteoporosis). * **Growth Retardation:** Impaired collagen synthesis and reduced activity of cytochrome c oxidase (limiting ATP production) result in failure to thrive and stunted growth. **2. Why Other Options are Incorrect:** * **Options B & C (Cardiomyopathy):** While copper deficiency can affect the heart in animal models, **Cardiomyopathy** is the hallmark clinical feature of **Selenium deficiency** (Keshan Disease). * **Option D:** While correct, it is incomplete. NEET-PG questions often require the most comprehensive clinical triad. **Clinical Pearls for NEET-PG:** * **Menkes Disease:** An X-linked recessive disorder caused by a mutation in the **ATP7A** gene, leading to systemic copper deficiency. Look for "Kinky/Steely hair" and seizures. * **Pancytopenia:** Severe copper deficiency can also cause neutropenia. * **Wilson Disease:** Caused by a mutation in **ATP7B**, leading to copper *toxicity* (Kayser-Fleischer rings). * **Key Enzyme:** Remember **Lysyl Oxidase**—it is the most high-yield link between copper and connective tissue/bone defects.

Question 226: Which of the following is the richest source of essential fatty acids?

A. Safflower oil (Correct Answer)
B. Corn oil
C. Sunflower oil
D. Soyabean oil

Explanation: **Explanation:** Essential Fatty Acids (EFAs), primarily **Linoleic acid (Omega-6)** and **Alpha-linolenic acid (Omega-3)**, cannot be synthesized by the human body and must be obtained through diet. The richness of an oil in EFAs is generally determined by its Linoleic acid content. **1. Why Safflower Oil is Correct:** Safflower oil contains the highest concentration of Linoleic acid among common vegetable oils, typically ranging from **70% to 75%**. This makes it the "richest" source of EFAs. In medical biochemistry, it is often cited as the gold standard for treating EFA deficiency. **2. Analysis of Incorrect Options:** * **Sunflower oil:** While a very good source, it contains approximately **60-65%** Linoleic acid, which is lower than Safflower oil. * **Corn oil:** Contains roughly **55-60%** Linoleic acid. * **Soyabean oil:** Contains about **50-55%** Linoleic acid. While it is unique for having a decent amount of Alpha-linolenic acid (~7%), its total EFA percentage remains lower than Safflower oil. **3. Clinical Pearls for NEET-PG:** * **EFA Deficiency:** Leads to **Phrynoderma** (follicular hyperkeratosis/toad skin), poor wound healing, and hair loss. * **Omega-6 vs. Omega-3:** Linoleic acid (18:2; Δ9,12) is the precursor for Arachidonic acid. Alpha-linolenic acid (18:3; Δ9,12,15) is the precursor for EPA and DHA. * **P/S Ratio:** Safflower oil has a high Polyunsaturated to Saturated fatty acid (P/S) ratio, which is beneficial for lowering serum cholesterol. * **Coconut Oil:** Note that coconut oil is a rich source of Medium Chain Triglycerides (MCTs) but is very poor in EFAs.

Question 227: What is the primary purpose of carbohydrate loading practiced by endurance athletes?

A. To form glycogen with fewer branch points than normal (Correct Answer)
B. To form glycogen with more branch points than normal
C. To convert glucose to proteins
D. To maintain optimal blood glucose concentration

Explanation: **Explanation:** **1. Why Option A is Correct:** Carbohydrate loading (glycogen supercompensation) involves depleting glycogen stores through intense exercise followed by a high-carbohydrate diet. During the rapid resynthesis phase, the activity of **Glycogen Synthase** (responsible for linear α-1,4 linkages) increases significantly more than the activity of the **Branching Enzyme** (amylo-1,4→1,6-transglucosidase). This results in the formation of glycogen molecules that are larger and have **fewer branch points** than normal. These "less branched" molecules are more compact, allowing the muscle to store a higher total mass of glucose per unit volume, providing a larger energy reservoir for endurance activities. **2. Why Other Options are Incorrect:** * **Option B:** More branch points would increase the solubility and rate of degradation (glycogenolysis) but would occupy more space, preventing the "packing" of extra glucose required for endurance. * **Option C:** Carbohydrate loading is specifically designed to maximize polysaccharide storage, not to facilitate gluconeogenesis or protein synthesis. * **Option D:** While blood glucose maintenance is a general physiological function of *liver* glycogen, the primary goal of carb-loading is to maximize *muscle* glycogen for local energy use during prolonged exertion. **3. High-Yield Clinical Pearls for NEET-PG:** * **Rate-limiting enzyme of Glycogenesis:** Glycogen Synthase (activated by Insulin/Glucose-6-P). * **Branching Enzyme:** Also known as *Glucosyl 4:6 transferase*. Deficiency leads to **Andersen’s Disease (GSD Type IV)**, characterized by long, unbranched glucose chains (amylopectin-like) that trigger an immune response. * **Muscle vs. Liver:** Muscle glycogen lacks **Glucose-6-Phosphatase**; therefore, it cannot contribute to blood glucose and is used exclusively for muscle contraction.

Question 228: Which one of the following pulses has the highest content of iron?

A. Bengal gram
B. Black gram
C. Red gram
D. Soyabean (Correct Answer)

Explanation: **Explanation:** In the context of nutritional biochemistry, pulses and legumes are significant plant-based sources of non-heme iron. Among the common pulses consumed in India, **Soyabean (Glycine max)** stands out as the richest source of both protein and iron. **Why Soyabean is Correct:** Soyabean contains approximately **10.4 mg of iron per 100g**. This high concentration makes it superior to other pulses. Beyond iron, it is also a "complete" plant protein source, containing all essential amino acids, which is a high-yield fact for metabolic biochemistry. **Analysis of Incorrect Options:** * **Bengal gram (Chickpea):** Contains approximately **4.6 to 5.3 mg** of iron per 100g. While a good source, it is roughly half the concentration found in soyabean. * **Black gram (Urad dal):** Contains approximately **3.8 to 6.0 mg** of iron per 100g. It is often highlighted for its high phosphoric acid content but falls short of soyabean in iron density. * **Red gram (Arhar/Pigeon pea):** Contains approximately **2.7 to 3.0 mg** of iron per 100g, making it the lowest iron provider among the given options. **Clinical Pearls for NEET-PG:** 1. **Bioavailability:** Although pulses are high in iron, the presence of **phytates and oxalates** acts as an anti-nutrient, inhibiting iron absorption. 2. **Enhancement:** Vitamin C (Ascorbic acid) should be co-ingested to convert ferric iron ($Fe^{3+}$) to ferrous iron ($Fe^{2+}$) for better absorption in the duodenum. 3. **Comparison:** While Soyabean is the highest among pulses, the overall highest plant-based source of iron often cited in exams is **Green Leafy Vegetables (specifically Amaranth or Phalse)**. 4. **Reference Values:** Always remember that the RDA for iron in an adult male is ~17 mg/day and for a menstruating female is ~21 mg/day.

Question 229: Which of the following characterizes the Atkins diet?

A. Severely reduced fat content
B. Severely reduced carbohydrate content (Correct Answer)
C. Severely reduced protein content
D. Reduced mineral content

Explanation: The **Atkins diet** is a classic example of a **Low-Carbohydrate, High-Fat, High-Protein diet**. It is designed to induce a metabolic state known as **ketosis**, where the body shifts from using glucose as its primary fuel source to burning stored fats and dietary fats, producing ketone bodies (acetoacetate and β-hydroxybutyrate). ### **Explanation of Options:** * **Option B (Correct):** The hallmark of the Atkins diet is the severe restriction of carbohydrates (typically <20g/day in the induction phase). By limiting glucose availability, insulin levels drop, and glucagon levels rise, stimulating lipolysis and ketogenesis. * **Option A:** Incorrect. Unlike traditional low-calorie diets, the Atkins diet encourages high fat intake to provide satiety and energy. * **Option C:** Incorrect. Protein intake is usually moderate to high in this diet to maintain muscle mass and promote thermogenesis. * **Option D:** Incorrect. While the diet doesn't focus on minerals, it does not intentionally reduce them; in fact, supplementation is often recommended to prevent electrolyte imbalances (the "keto flu"). ### **High-Yield Clinical Pearls for NEET-PG:** * **Metabolic Shift:** The diet mimics the biochemical state of **starvation** (increased Acetyl-CoA leading to Ketogenesis). * **Therapeutic Use:** Ketogenic diets are clinically indicated for **refractory epilepsy** in children. * **Adverse Effects:** Potential risks include hyperuricemia (gout), nephrolithiasis (kidney stones), and "Ketoacidosis" (rare in non-diabetics, but metabolic acidosis can occur). * **Biochemical Marker:** The presence of **ketonuria** is a sign of adherence to the restrictive phase of the diet.

Question 230: Which of the following is the mechanism of action of dietary fiber in reducing atherosclerosis?

A. Binding to cholesterol (Correct Answer)
B. Decreases VLDL
C. Increasing fluid retention
D. Forming antioxidants

Explanation: **Explanation:** The correct answer is **A. Binding to cholesterol.** **Mechanism of Action:** Dietary fiber, particularly **soluble fiber** (e.g., pectin, gums, and mucilages), reduces the risk of atherosclerosis primarily through its interaction with bile acids and cholesterol in the intestinal lumen. Soluble fiber forms a viscous gel that **binds to bile acids**, preventing their enterohepatic circulation. This forces the liver to utilize endogenous cholesterol to synthesize new bile acids, thereby upregulating LDL receptors and lowering circulating serum LDL-cholesterol levels. Additionally, fiber can directly bind to dietary cholesterol, inhibiting its absorption. **Analysis of Incorrect Options:** * **B. Decreases VLDL:** While fiber significantly lowers LDL, its effect on VLDL (triglycerides) is inconsistent and not the primary mechanism for reducing atherosclerotic plaque formation. * **C. Increasing fluid retention:** Fiber actually increases fecal water content and bulk, aiding in laxation, but fluid retention has no protective role against atherosclerosis; in fact, systemic fluid retention is associated with hypertension and heart failure. * **D. Forming antioxidants:** While many high-fiber foods (fruits/vegetables) contain antioxidants, the fiber molecule itself does not "form" antioxidants. Its cardiovascular benefit is mechanical and metabolic rather than chemical neutralization of free radicals. **High-Yield Clinical Pearls for NEET-PG:** * **Types of Fiber:** *Soluble* (Pectin, Gums) lowers cholesterol; *Insoluble* (Cellulose, Lignin) mainly increases stool bulk and prevents constipation. * **Glycemic Index:** High fiber intake slows glucose absorption, leading to a lower glycemic index, which is beneficial for Diabetes Mellitus. * **Caloric Value:** Dietary fiber provides approximately **2 kcal/g** due to partial fermentation by colonic bacteria into short-chain fatty acids (SCFAs). * **Recommended Intake:** 25–40 g/day is generally advised for adults.

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free