Nutrition and Metabolism — MCQs

Nutrition and Metabolism Indian Medical PG Practice Questions and MCQs

Question 111: Which of the following grains can be used safely in patients with celiac sprue?

A. Rice (Correct Answer)
B. Wheat
C. Rye
D. Barley

Explanation: **Explanation:** Celiac sprue (Gluten-sensitive enteropathy) is an autoimmune-mediated inflammatory condition of the small intestine triggered by the ingestion of **prolamins** (gluten proteins) in genetically susceptible individuals (HLA-DQ2/DQ8). The primary management is a lifelong strict gluten-free diet. **Why Rice is the Correct Answer:** Rice (along with maize/corn) is naturally gluten-free. It does not contain the specific toxic peptide sequences (like the 33-mer α-gliadin) that trigger the T-cell mediated immune response and subsequent villous atrophy seen in celiac patients. Therefore, rice is a safe carbohydrate source. **Why Other Options are Incorrect:** The mnemonic **"BROW"** (Barley, Rye, Oats, Wheat) is commonly used to remember grains containing gluten that should be avoided: * **Wheat:** Contains **Gliadin**, the most potent trigger for celiac disease. * **Rye:** Contains **Secalin**, which is toxic to these patients. * **Barley:** Contains **Hordein**, which also triggers the inflammatory cascade. *(Note: Pure oats are often tolerated, but are frequently avoided due to cross-contamination during processing).* **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Small intestinal biopsy showing **villous atrophy**, crypt hyperplasia, and increased intraepithelial lymphocytes. * **Serology:** Anti-tissue Transglutaminase (**anti-tTG**) IgA is the screening drug of choice; Anti-endomysial antibody (EMA) is highly specific. * **Dermatologic Association:** **Dermatitis herpetiformis** (itchy, vesicular skin lesions) is the pathognomonic cutaneous manifestation. * **Complications:** Increased risk of **Enteropathy-associated T-cell lymphoma (EATL)** if the diet is not strictly followed.

Question 112: From where does a growing fetus derive its energy?

A. Amino acids
B. Carbohydrates (Correct Answer)
C. Lipids
D. Minerals

Explanation: **Explanation:** The primary and preferred source of energy for a growing fetus is **Carbohydrates**, specifically **Glucose**. Glucose is the only major nutrient that crosses the placenta via **facilitated diffusion** (through GLUT-1 and GLUT-3 transporters) in significant quantities to meet the high metabolic demands of the developing brain and tissues. While the fetus can synthesize its own glycogen and fat, it depends almost entirely on the maternal glucose supply for its immediate oxidative metabolism. **Why other options are incorrect:** * **Amino acids:** While amino acids are actively transported across the placenta, they are primarily used as building blocks for **protein synthesis** and tissue growth rather than as a primary energy source. * **Lipids:** Free fatty acids cross the placenta in limited amounts. While they are essential for brain development (DHA/EPA) and the formation of cell membranes, the fetus has a limited capacity for beta-oxidation, making lipids a secondary energy source compared to glucose. * **Minerals:** Minerals (like Calcium and Iron) are essential cofactors for enzymatic reactions and structural development (bone mineralization) but do not provide caloric energy. **NEET-PG High-Yield Pearls:** * **GLUT-1** is the primary glucose transporter in the human placenta. * **Fetal Insulin:** The fetus secretes its own insulin starting from the end of the first trimester; maternal insulin does **not** cross the placenta. * **Warburg-like Effect:** Fetal tissues often exhibit high rates of glycolysis even in the presence of oxygen to support rapid biosynthesis. * **Ketone Bodies:** These can cross the placenta and serve as an alternative fuel source only during periods of maternal starvation or prolonged fasting.

Question 113: Which of the following is NOT true about ω3 fatty acids?

A. Decrease the risk of Cardiovascular Disease
B. Increase the risk of various mental illnesses (Correct Answer)
C. They are anti-inflammatory
D. Decrease serum triglycerides

Explanation: **Explanation:** The correct answer is **B (Increase the risk of various mental illnesses)** because it is a false statement. In fact, $\omega$-3 fatty acids are essential for neurodevelopment and cognitive function. Clinical studies suggest they have a protective effect against depression, anxiety, and cognitive decline; deficiency is actually linked to an increased risk of mental health disorders. **Analysis of Options:** * **A & D (Cardiovascular Benefits):** $\omega$-3 fatty acids (specifically EPA and DHA) are cardioprotective. They significantly **decrease serum triglycerides** by inhibiting VLDL synthesis in the liver and increasing fatty acid oxidation. They also reduce the risk of arrhythmias and atherosclerosis. * **C (Anti-inflammatory):** $\omega$-3 fatty acids compete with Arachidonic acid (an $\omega$-6 FA) for the enzyme cyclooxygenase (COX). While $\omega$-6 metabolism produces pro-inflammatory series-2 prostaglandins, $\omega$-3 metabolism produces **series-3 prostaglandins and resolvins**, which are potent anti-inflammatory mediators. **High-Yield NEET-PG Pearls:** * **Key Examples:** $\alpha$-Linolenic acid (ALA), Eicosapentaenoic acid (EPA), and Docosahexaenoic acid (DHA). * **Source:** ALA is found in flaxseed/walnuts; EPA and DHA are abundant in fish oils. * **Clinical Use:** Used therapeutically in **Hypertriglyceridemia** (Type IV and V hyperlipoproteinemia). * **DHA Significance:** It is the most abundant fatty acid in the **retina and cerebral cortex**, making it vital for vision and brain health.

Question 114: Selenium deficiency causes which of the following conditions?

A. Menke's disease
B. Wilson's disease
C. Keshan disease (Correct Answer)
D. Kashinbeck disease

Explanation: ### Explanation **Correct Answer: C. Keshan disease** Selenium is an essential trace element that functions primarily as a cofactor for the enzyme **Glutathione Peroxidase**, which protects cells against oxidative damage. * **Keshan disease** is a juvenile cardiomyopathy associated with selenium deficiency. It was first identified in the Keshan province of China, where the soil is selenium-poor. The deficiency leads to myocardial necrosis and heart failure, often triggered by a secondary viral infection (e.g., Coxsackievirus). **Analysis of Incorrect Options:** * **A. Menke’s disease:** This is an X-linked recessive disorder of **Copper absorption** and transport (ATP7A mutation). It is characterized by "kinky" or steely hair, growth failure, and neurological degeneration. * **B. Wilson’s disease:** This is an autosomal recessive disorder of **Copper excretion** (ATP7B mutation). It leads to toxic copper accumulation in the liver (cirrhosis), brain (basal ganglia), and eyes (Kayser-Fleischer rings). * **D. Kashin-Beck disease:** While also associated with selenium deficiency, it is primarily an **osteoarthropathy** (degeneration of joint cartilage) rather than a cardiomyopathy. In the context of NEET-PG, Keshan disease is the classic, most frequently tested association for selenium deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Enzyme Link:** Selenium is a component of **Selenocysteine**, found in Glutathione Peroxidase, Thioredoxin reductase, and Deiodinase (converts T4 to T3). * **Toxicity:** Excess selenium (Selenosis) causes garlic breath, hair loss (alopecia), and nail dystrophy. * **Antioxidant Trio:** Selenium works synergistically with **Vitamin E** to prevent lipid peroxidation.

Question 115: Which of the following is NOT an essential fatty acid?

A. Arachidonic acid
B. Linoleic acid
C. Palmitic acid (Correct Answer)
D. Linolenic acid

Explanation: ### Explanation **Core Concept: Essential vs. Non-Essential Fatty Acids** Essential fatty acids (EFAs) are those that the human body cannot synthesize de novo because humans lack the enzymes (**$\Delta^{12}$ and $\Delta^{15}$ desaturases**) required to introduce double bonds beyond the $\Delta^9$ position. Therefore, they must be obtained through the diet. **Why Palmitic Acid is the Correct Answer:** * **Palmitic acid (C16:0)** is a **saturated fatty acid**. It is the primary product of the Fatty Acid Synthase (FAS) complex in the human body. Since the body can synthesize it from Acetyl-CoA (derived from excess carbohydrates or proteins), it is **non-essential**. **Analysis of Incorrect Options:** * **Linoleic acid (C18:2, $\omega$-6):** An essential fatty acid. It is the precursor for the synthesis of arachidonic acid. * **Linolenic acid (C18:3, $\omega$-3):** Specifically alpha-linolenic acid (ALA), this is an essential fatty acid required for the synthesis of EPA and DHA, which are vital for brain and retinal function. * **Arachidonic acid (C20:4, $\omega$-6):** While technically "semi-essential" (it can be synthesized from linoleic acid), it is traditionally classified as an EFA in many medical texts because it becomes strictly essential if linoleic acid is deficient in the diet. **NEET-PG High-Yield Pearls:** 1. **True Essentials:** Only Linoleic and $\alpha$-Linolenic acid are strictly essential. 2. **EFA Deficiency:** Characterized by **Phrynoderma** (follicular hyperkeratosis/toad skin), poor wound healing, and hair loss. 3. **Omega Nomenclature:** $\omega$-3 (Linolenic) and $\omega$-6 (Linoleic) refer to the position of the first double bond from the methyl (omega) end. 4. **Palmitic Acid:** It is the most common saturated fatty acid in the human body and serves as the precursor for longer-chain fatty acids via elongation.

Question 116: Zinc is not required for:

A. Embryonic development
B. Coagulation pathway (Correct Answer)
C. DNA synthesis
D. Spermatogenesis

Explanation: **Explanation:** Zinc is an essential trace element that acts as a structural component or cofactor for over 300 enzymes, including DNA polymerases, RNA polymerases, and Zinc-finger proteins (transcription factors). **1. Why Coagulation Pathway is the correct answer:** The coagulation cascade is primarily dependent on **Calcium (Factor IV)** and Vitamin K-dependent γ-carboxylation. Zinc does not play a direct catalytic or structural role in the activation of clotting factors or the formation of a fibrin clot. Therefore, it is not required for the coagulation pathway. **2. Why the other options are incorrect:** * **DNA Synthesis:** Zinc is a vital cofactor for **DNA polymerase** and **Thymidine kinase**. It is essential for cell division and the maintenance of genetic stability. * **Embryonic Development:** Due to its role in DNA synthesis and gene expression (Zinc-finger motifs), Zinc is critical for rapid cell proliferation during embryogenesis. Deficiency leads to congenital malformations and growth retardation. * **Spermatogenesis:** Zinc is found in high concentrations in the testes and prostate. It is required for the maturation of spermatozoa, maintenance of the germinal epithelium, and sperm motility. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder of zinc absorption characterized by periorificial/acral dermatitis, alopecia, and diarrhea. * **Wound Healing:** Zinc is essential for collagen synthesis and fibroblast proliferation; deficiency leads to poor wound healing. * **Gustin:** A zinc-containing protein in saliva required for the development of taste buds (deficiency causes **hypogeusia**). * **Insulin Storage:** Zinc is required for the crystallization and storage of insulin in the β-cells of the pancreas.

Question 117: Approximately how many calories are provided by a standard cup of tea with the usual amount of sugar?

A. 50 calories
B. 80 calories (Correct Answer)
C. 130 calories
D. 200 calories

Explanation: **Explanation:** The caloric content of a standard cup of tea (approx. 150–200 ml) is primarily determined by its additives—milk and sugar—rather than the tea leaves themselves, which are virtually calorie-free. **Why 80 calories is correct:** A standard cup of Indian milk tea typically contains: 1. **Milk:** Approximately 60–100 ml of toned milk. Since 100 ml of milk provides ~60–70 kcal, this contributes roughly **40–50 kcal**. 2. **Sugar:** Usually 2 teaspoons (10g). Since 1g of carbohydrate provides 4 kcal, this adds **40 kcal**. Total: 40 (milk) + 40 (sugar) = **~80 calories**. This is a standard reference value used in community medicine and dietetics for nutritional assessment. **Analysis of Incorrect Options:** * **A (50 calories):** This represents a cup of tea with very little milk and minimal sugar, or a small serving size. * **C (130 calories):** This would reflect a large mug of tea with high-fat buffalo milk and excessive sugar (3–4 teaspoons). * **D (200 calories):** This is equivalent to a full meal or a heavy snack (like two medium biscuits or a small samosa) and is far too high for a single cup of tea. **High-Yield NEET-PG Pearls:** * **Caloric Values:** Carbohydrates/Proteins = 4 kcal/g; Lipids = 9 kcal/g; Alcohol = 7 kcal/g. * **Specific Dynamic Action (SDA):** Protein has the highest SDA (30%), meaning it requires more energy for digestion compared to fats (4%) or carbs (5%). * **Empty Calories:** Sugar in tea provides "empty calories" as it lacks essential micronutrients. * **Reference Man/Woman:** In nutrition questions, always assume standard Indian portion sizes unless specified otherwise.

Question 118: In the body, metabolism of 10 g of protein would produce approximately how many Kcal?

A. 1 Kcal
B. 41 Kcal (Correct Answer)
C. 410 Kcal
D. 4100 Kcal

Explanation: **Explanation:** The energy content of food is measured in kilocalories (kcal). In nutritional biochemistry, the standard **Atwater factors** are used to calculate the metabolizable energy provided by macronutrients. 1. **Why Option B is correct:** The physiological fuel value of **protein is 4.1 kcal/g** (often rounded to 4 kcal/g in basic calculations). * Calculation: 10 g of protein × 4.1 kcal/g = **41 kcal**. While the physical energy value (measured in a bomb calorimeter) for protein is 5.65 kcal/g, the physiological value is lower because nitrogenous components (like urea) are excreted and not fully oxidized for energy. 2. **Why the other options are incorrect:** * **Option A (1 kcal):** This is significantly lower than the energy density of any macronutrient. * **Option C (410 kcal):** This would be the energy yield for 100 g of protein, not 10 g. * **Option D (4100 kcal):** This value is physiologically impossible for 10 g of any substance; even pure fat would only yield 93 kcal for 10 g. **High-Yield Clinical Pearls for NEET-PG:** * **Physiological Fuel Values:** * Carbohydrates: 4.1 kcal/g * Proteins: 4.1 kcal/g * Lipids (Fats): 9.3 kcal/g (The most energy-dense macronutrient) * Alcohol: 7.0 kcal/g * **Respiratory Quotient (RQ):** Remember that the RQ for protein is approximately **0.8**, carbohydrates is **1.0**, and lipids is **0.7**. * **Specific Dynamic Action (SDA):** Protein has the highest SDA (approx. 30%), meaning it requires the most energy for its own digestion and processing compared to fats and carbs.

Question 119: Manganese deficiency leads to which of the following conditions?

A. Parkinsonism
B. Impaired skeletal growth (Correct Answer)
C. Impaired glucose tolerance
D. Anaemia

Explanation: **Explanation:** **Manganese (Mn)** is an essential trace element that acts as a cofactor for several critical enzymes, including **glycosyltransferases**, pyruvate carboxylase, and superoxide dismutase (Mn-SOD). 1. **Why "Impaired skeletal growth" is correct:** Glycosyltransferases are essential for the synthesis of **proteoglycans and chondroitin sulfate**, which are the structural building blocks of bone and cartilage matrix. Manganese deficiency leads to defective cartilage formation, resulting in skeletal abnormalities, retarded bone growth, and conditions like "perosis" (slipped tendon) in animals. In humans, it manifests as impaired skeletal development and reduced bone mineral density. 2. **Why the other options are incorrect:** * **Parkinsonism:** While Manganese *toxicity* (Manganism) causes a Parkinson-like syndrome due to accumulation in the basal ganglia, its *deficiency* does not. * **Impaired glucose tolerance:** Although Manganese is a cofactor for pyruvate carboxylase (gluconeogenesis), impaired glucose tolerance is more classically associated with **Chromium deficiency** (Glucose Tolerance Factor). * **Anaemia:** This is typically associated with deficiencies in **Iron, Copper** (due to ceruloplasmin/ferroxidase activity), Vitamin B12, or Folate. **High-Yield Clinical Pearls for NEET-PG:** * **Mn-SOD:** Manganese is the specific cofactor for the mitochondrial version of Superoxide Dismutase (SOD), which protects mitochondria from oxidative stress. * **Toxicity:** Chronic inhalation of Mn (seen in miners) leads to **"Psychosis" followed by Parkinsonian symptoms** (refractory to L-Dopa). * **MRI Sign:** In Mn toxicity or chronic liver disease, Mn deposits in the **globus pallidus**, showing hyperintensity on T1-weighted MRI images.

Question 120: Which of the following is NOT a manifestation of copper deficiency?

A. Hepatic fibrosis (Correct Answer)
B. Hemolytic anemia
C. Mental retardation
D. Growth retardation

Explanation: **Explanation:** The correct answer is **A. Hepatic fibrosis**. Hepatic fibrosis and cirrhosis are characteristic features of **Wilson’s Disease**, which is caused by **copper toxicity** (excessive accumulation) due to a defect in the ATP7B protein, not copper deficiency. **Why the other options are manifestations of copper deficiency:** * **Hemolytic anemia:** Copper is a vital component of **ceruloplasmin** (ferroxidase), which converts ferrous iron (Fe2+) to ferric iron (Fe3+) for binding to transferrin. Deficiency leads to impaired iron transport, resulting in microcytic hypochromic anemia and sometimes hemolytic anemia. * **Mental retardation:** Copper is a cofactor for **dopamine β-hydroxylase** (converting dopamine to norepinephrine) and **cytochrome c oxidase**. Deficiency impairs neurotransmitter synthesis and energy production in neurons, leading to neurological decline. * **Growth retardation:** Copper is essential for **lysyl oxidase**, an enzyme that cross-links collagen and elastin. Defective cross-linking results in skeletal abnormalities, vascular fragility, and stunted growth (often seen in **Menkes Kinky Hair Syndrome**). **High-Yield Clinical Pearls for NEET-PG:** * **Menkes Disease:** An X-linked recessive disorder caused by a defect in **ATP7A** (impaired intestinal copper absorption), leading to "steely" or "kinky" hair, seizures, and subnormal body temperature. * **Wilson’s Disease:** Caused by a defect in **ATP7B** (impaired biliary copper excretion), leading to Kayser-Fleischer (KF) rings and basal ganglia degeneration. * **Key Copper Enzymes:** Cytochrome c oxidase (ETC), Superoxide dismutase (antioxidant), Tyrosinase (melanin synthesis), and Lysyl oxidase (collagen strength).

Practice by Chapter

Macronutrients and Energy Requirements

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Protein Quality and Nitrogen Balance

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Essential Amino Acids and Proteins

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Essential Fatty Acids and Lipids

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Dietary Fiber and Complex Carbohydrates

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Glycemic Index and Glycemic Load

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Micronutrients: Vitamins and Minerals

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Trace Elements and Metabolism

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Malnutrition: Biochemical Consequences

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Dietary Antioxidants

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Functional Foods and Nutraceuticals

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Dietary Guidelines and Recommendations

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