Nutrition and Metabolism — MCQs

Nutrition and Metabolism Indian Medical PG Practice Questions and MCQs

Question 251: Features like hypogonadism, dwarfism, loss of hair, pigmentation and ulcers of skin and decreased immunity are associated with deficiency of?

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

Explanation: **Explanation:** The correct answer is **Zinc (Option B)**. Zinc is an essential trace element required for the function of over 300 enzymes, including DNA and RNA polymerases, which are vital for rapid cell turnover. **Why Zinc is correct:** Zinc deficiency manifests primarily in tissues with high turnover rates (skin, immune system, and gonads). * **Hypogonadism and Dwarfism:** Zinc is crucial for the function of the growth hormone-IGF-1 axis and steroid hormone receptors. Deficiency leads to growth retardation and delayed sexual maturation. * **Skin and Hair:** It is essential for collagen synthesis and keratinization. Deficiency causes **acrodermatitis enteropathica** (periorificial and acral dermatitis), alopecia (hair loss), and poor wound healing (ulcers). * **Immunity:** Zinc is vital for T-lymphocyte function; its absence leads to lymphopenia and increased susceptibility to infections. **Why other options are incorrect:** * **Iron:** Deficiency typically presents with microcytic hypochromic anemia, pica, and koilonychia (spoon-shaped nails), not primary hypogonadism. * **Iodine:** Deficiency leads to goiter and hypothyroidism (cretinism in children), characterized by mental retardation rather than specific skin ulcers and alopecia. * **Copper:** Deficiency causes Menkes Kinky Hair Syndrome (steely hair), microcytic anemia, and skeletal abnormalities, but is not the primary cause of the triad of hypogonadism, dwarfism, and skin ulcers. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder of zinc absorption. * **Zinc & Taste:** Deficiency causes **Hypogeusia** (loss of taste sensation). * **Enzyme Marker:** Alkaline Phosphatase (ALP) is a zinc-dependent enzyme; low ALP levels can be a biochemical marker for zinc deficiency.

Question 252: Which of the following elements is NOT deficient in patients receiving hyperalimentation?

A. Calcium
B. Phosphates
C. Zinc
D. None of the above (Correct Answer)

Explanation: ### Explanation **Concept Overview:** Hyperalimentation, commonly known as **Total Parenteral Nutrition (TPN)**, involves the intravenous administration of all necessary nutrients. While TPN is life-saving, it frequently leads to metabolic and electrolyte imbalances if not meticulously monitored. The question asks which element is *not* deficient; since all listed elements (Calcium, Phosphate, and Zinc) are commonly found to be deficient in TPN patients, the correct answer is "None of the above." **Why the Options are Incorrect (Common Deficiencies):** * **Phosphates (Option B):** This is the most classic deficiency seen in TPN, often manifesting as **Refeeding Syndrome**. When glucose is infused, insulin release shifts phosphate into cells for glycolysis and ATP production, leading to severe hypophosphatemia. * **Calcium (Option A):** Hypocalcemia is common due to inadequate supplementation, vitamin D deficiency, or complexing with the high phosphate levels sometimes found in TPN formulations. Long-term TPN can also lead to metabolic bone disease. * **Zinc (Option C):** Zinc is the most common trace element deficiency in TPN. It typically presents as **Acrodermatitis enteropathica-like skin lesions** (perioral and perianal rashes), alopecia, and impaired wound healing. **Clinical Pearls for NEET-PG:** * **Refeeding Syndrome:** Characterized by the triad of **Hypophosphatemia, Hypomagnesemia, and Hypokalemia** upon initiating TPN in malnourished patients. * **Copper Deficiency:** Can occur in long-term TPN, leading to microcytic anemia and neutropenia. * **Chromium Deficiency:** May manifest as sudden-onset glucose intolerance (insulin resistance). * **Essential Fatty Acid Deficiency (EFAD):** Presents with "scaly dermatitis" if lipids are not included in the TPN regimen.

Question 253: Which of the following fatty acids is found exclusively in breast milk?

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

Explanation: ### Explanation **Correct Answer: D. Docosahexaenoic acid (DHA)** **Why it is correct:** Docosahexaenoic acid (DHA) is a long-chain polyunsaturated fatty acid (LC-PUFA) of the **Omega-3 series** (22:6 n-3). While the body can synthesize small amounts of DHA from alpha-linolenic acid, the conversion rate is extremely low in infants. Breast milk is uniquely rich in preformed DHA, which is critical for the **structural development of the retina and the cerebral cortex**. It is considered "exclusive" in the context of natural infant nutrition because, unlike standard bovine milk (cow's milk), breast milk provides these long-chain derivatives essential for optimal cognitive and visual outcomes. **Why the other options are incorrect:** * **A & B (Linoleic and Linolenic acid):** These are 18-carbon essential fatty acids. While present in breast milk, they are also widely available in vegetable oils and are found in standard infant formulas and cow's milk. They are precursors, not the specialized long-chain products like DHA. * **C (Palmitic acid):** This is a common 16-carbon saturated fatty acid. It is the most abundant saturated fat in both human milk and bovine milk, as well as many animal fats; therefore, it is not unique or exclusive to the functional profile of breast milk. **NEET-PG High-Yield Pearls:** * **Composition:** Breast milk contains roughly 3.5% to 4.5% fat, providing about 50% of the infant's total energy. * **DHA vs. ARA:** Breast milk contains both DHA (Omega-3) and Arachidonic acid (ARA, Omega-6). Both are vital for neural myelination. * **Cow’s Milk vs. Human Milk:** Cow’s milk is higher in protein (mostly casein) and minerals but lacks the LC-PUFAs (DHA/ARA) and IgA found in human milk. * **Mnemonic:** Remember **DHA** for **D**evelopment of **H**ead (Brain) and **A**cuity (Vision).

Question 254: How is the protein quantity assessed?

A. Amino acid score
B. Net protein utilization (NPU)
C. Protein efficiency (PE) ratio (Correct Answer)
D. None of the above

Explanation: ### Explanation The assessment of protein quality and quantity is a high-yield topic in biochemistry and nutrition. While several indices evaluate protein, they differ in whether they measure biological quality or the efficiency of utilization for growth. **1. Why Protein Efficiency Ratio (PER) is the Correct Answer:** The **Protein Efficiency Ratio (PER)** is the standard measure used to assess the **quantity** of protein in terms of its ability to support growth. It is defined as the gain in body weight (in grams) per gram of protein consumed. Since it directly correlates weight gain to the amount of protein ingested, it is the most practical measure for assessing how the quantity of a specific protein translates into physical mass. **2. Analysis of Incorrect Options:** * **Amino Acid Score (Chemical Score):** This measures the **quality** of a protein by comparing its essential amino acid content to a reference protein (usually egg albumin). it does not account for digestibility or quantity-based growth. * **Net Protein Utilization (NPU):** This measures the **biological value** and digestibility. It represents the proportion of dietary protein that is actually retained by the body. While it is a superior indicator of protein *quality*, it is not the primary measure for assessing growth-related *quantity*. **3. NEET-PG High-Yield Clinical Pearls:** * **Reference Protein:** Egg protein is considered the "Gold Standard" (Biological Value = 100) because it contains all essential amino acids in ideal proportions. * **Limiting Amino Acids:** Pulses are deficient in **Methionine**, while Cereals are deficient in **Lysine**. * **Biological Value (BV):** Measures nitrogen retained divided by nitrogen absorbed. * **PDCAAS:** The "Protein Digestibility Corrected Amino Acid Score" is currently the preferred international standard for evaluating protein quality in human nutrition.

Question 255: All of the following changes are seen in chronic starvation except?

A. All fat stores have been used up
B. Severe fat and muscle wasting
C. Brain uses ketoacids as fuel
D. Level of serum proteins less than 2.8 g/dL (Correct Answer)

Explanation: This question tests the ability to differentiate between the metabolic profiles of **Marasmus (Chronic Starvation)** and **Kwashiorkor (Protein-Energy Malnutrition)**. ### **Explanation of the Correct Answer** **Option D** is the correct "except" choice because a significant drop in serum proteins (hypoalbuminemia < 2.8 g/dL) is the hallmark of **Kwashiorkor**, not chronic starvation (Marasmus). In chronic starvation, the body undergoes an adaptive response where muscle protein is broken down slowly for gluconeogenesis, but the liver continues to synthesize essential proteins like albumin effectively. Therefore, **serum albumin levels remain normal or only slightly decreased** in Marasmus, and edema is absent. ### **Analysis of Incorrect Options** * **Option A & B:** In chronic starvation, the body exhausts its glycogen stores within 24 hours and transitions to lipolysis and proteolysis. Over a prolonged period, this leads to the **depletion of almost all subcutaneous fat stores** and **severe muscle wasting**, giving the patient a "skin and bones" appearance. * **Option C:** This is a key metabolic adaptation. To preserve muscle mass (by reducing the need for gluconeogenesis from amino acids), the brain adapts to using **ketone bodies (acetoacetate and β-hydroxybutyrate)** as its primary energy source after about 2–3 weeks of starvation. ### **NEET-PG High-Yield Pearls** * **Marasmus:** "Energy deficiency." Characterized by growth retardation, loss of subcutaneous fat, and muscle wasting. Serum albumin is **Normal**. * **Kwashiorkor:** "Protein deficiency." Characterized by **Edema** (due to hypoalbuminemia), "flag sign" hair, and fatty liver (due to decreased Apo-B100 synthesis). * **Metabolic Fuel Switch:** * *Early Starvation:* Liver glycogenolysis and muscle proteolysis. * *Chronic Starvation:* Lipolysis (Fatty acids) and Ketogenesis (Brain uses ketones). * **Death in Starvation:** Usually occurs when ~40% of body weight is lost, often due to secondary infections or heart failure.

Question 256: Biological value of protein is related to which of the following?

A. Amino acid content
B. Essential amino acid content
C. Nitrogen content
D. Protein quality (Correct Answer)

Explanation: ### Explanation **Biological Value (BV)** is a measure of **protein quality** that assesses how efficiently the body utilizes dietary protein for growth and maintenance. It is defined as the percentage of absorbed nitrogen that is retained by the body. #### Why "Protein Quality" is Correct Protein quality refers to the ability of a dietary protein to provide the specific amino acids required for human tissue synthesis. BV specifically measures the "usability" of a protein. A high BV (e.g., Egg protein = 100) indicates that the amino acid profile of the food closely matches the body's requirements, resulting in minimal nitrogen excretion in the urine. #### Analysis of Incorrect Options * **A & B. Amino acid content / Essential amino acid (EAA) content:** While BV depends on the presence of EAAs, these options describe the *composition* rather than the *biological effectiveness*. A protein might contain all EAAs but in disproportionate amounts (limiting amino acids), lowering its overall quality. * **C. Nitrogen content:** All proteins contain approximately 16% nitrogen. Nitrogen content alone does not determine how well the protein is utilized by the body; rather, it is the *retention* of that nitrogen that determines BV. #### NEET-PG High-Yield Pearls * **Formula:** $BV = \frac{\text{Nitrogen Retained}}{\text{Nitrogen Absorbed}} \times 100$. * **Reference Standard:** **Egg albumin** is considered the "Gold Standard" with a BV of 100. * **Limiting Amino Acids:** Pulses are deficient in **Methionine**, while Cereals are deficient in **Lysine**. This is why a cereal-pulse combination improves overall protein quality (Mutual Supplementation). * **Net Protein Utilization (NPU):** Unlike BV, NPU takes **digestibility** into account ($NPU = BV \times \text{Digestibility coefficient}$). * **Kwashiorkor:** A clinical state of protein-energy malnutrition where the *quality* and quantity of protein are insufficient, despite adequate caloric intake.

Question 257: Which of the following oils has a high quantity of saturated fatty acids?

A. Coconut oil (Correct Answer)
B. Sunflower oil
C. Safflower oil
D. Soyabeen oil

Explanation: **Explanation:** The correct answer is **Coconut oil**. In biochemistry and nutrition, fats are classified based on the saturation of their fatty acid chains. **Saturated Fatty Acids (SFAs)** contain no double bonds between carbon atoms and are typically solid at room temperature. **Why Coconut Oil is correct:** Coconut oil is unique among plant oils because it is exceptionally high in saturated fats (approximately **90-92%**). It primarily consists of medium-chain triglycerides (MCTs), such as **Lauric acid** (C12), Myristic acid, and Palmitic acid. Despite being a plant source, its high SFA content makes it highly stable but also a subject of cardiovascular debate. **Why the other options are incorrect:** * **Sunflower, Safflower, and Soybean oils** are all classified as **Polyunsaturated Fatty Acids (PUFAs)**. * **Safflower oil** has the highest concentration of **Linoleic acid** (an omega-6 PUFA), making it excellent for lowering LDL cholesterol but prone to oxidation. * **Sunflower and Soybean oils** are also rich in PUFAs and contain significant amounts of Vitamin E, serving as common heart-healthy alternatives to animal fats. **High-Yield Clinical Pearls for NEET-PG:** * **Highest SFA content:** Coconut oil (~92%) > Palm kernel oil (~80%) > Butter (~60%). * **Highest PUFA content:** Safflower oil (~75%) > Sunflower oil (~65%). * **Highest MUFA (Monounsaturated) content:** Olive oil (rich in Oleic acid). * **Essential Fatty Acids:** Remember that Linoleic (ω-6) and Linolenic (ω-3) acids cannot be synthesized by the body and must be obtained from oils like soybean or safflower. * **P/S Ratio:** The Polyunsaturated to Saturated fat ratio is a key indicator of dietary quality; a higher ratio is generally considered cardioprotective.

Question 258: Alopecia, hyperpigmentation, and hypogonadism are characteristic of a deficiency of which micronutrient?

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

Explanation: **Explanation:** **Zinc deficiency** is the correct answer because Zinc is a critical cofactor for over 300 enzymes involved in DNA synthesis, cell division, and protein metabolism. It is highly concentrated in the skin, hair, and reproductive organs. * **Alopecia:** Zinc is essential for hair follicle proliferation; deficiency leads to telogen effluvium and thinning. * **Hyperpigmentation/Dermatitis:** Classically presents as **Acrodermatitis Enteropathica** (periorificial and acral dermatitis). * **Hypogonadism:** Zinc is vital for testosterone synthesis and spermatogenesis; deficiency results in delayed puberty and stunted growth. **Why other options are incorrect:** * **Magnesium:** Deficiency typically presents with neuromuscular irritability (tetany, seizures) and arrhythmias, not primary skin or hair loss. * **Selenium:** Deficiency is associated with **Keshan disease** (cardiomyopathy) and **Kashin-Beck disease** (osteoarthritis), or muscle weakness. * **Copper:** Deficiency leads to **Menkes Kinky Hair Syndrome** (steely/brittle hair), microcytic anemia (refractory to iron), and neutropenia, but not typically hypogonadism. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder causing impaired zinc absorption. * **Triad of Zinc Deficiency:** Dermatitis (periorificial), Alopecia, and Diarrhea. * **Other signs:** Poor wound healing, **dysgeusia** (distorted taste), and impaired night vision (Zinc is required for Retinol Binding Protein synthesis). * **Risk Factors:** Chronic alcoholism, TPN without supplementation, and malabsorption syndromes.

Question 259: Which of the following are manifestations of zinc deficiency?

A. Hypogonadism and diarrhea (Correct Answer)
B. Hypogonadism and pigmentation
C. Hypogonadism and psychosis
D. Diarrhea and pigmentation

Explanation: **Explanation:** Zinc is an essential trace element that acts as a cofactor for over 300 enzymes, including Carbonic Anhydrase, Alcohol Dehydrogenase, and DNA/RNA Polymerases. It plays a critical role in cell division, protein synthesis, and immune function. **Why Option A is Correct:** Zinc deficiency classically presents with a triad of **dermatitis (acrodermatitis enteropathica), alopecia, and diarrhea**. * **Hypogonadism:** Zinc is vital for the synthesis of testosterone and spermatogenesis; its deficiency leads to delayed puberty and primary hypogonadism. * **Diarrhea:** Zinc is necessary for intestinal mucosal integrity and water/electrolyte transport. This is why zinc supplementation is a standard WHO protocol for managing pediatric diarrhea. **Analysis of Incorrect Options:** * **Pigmentation (Options B & D):** While zinc deficiency causes skin lesions (vesiculobullous and pustular lesions), diffuse hyperpigmentation is more characteristic of Vitamin B12 deficiency or Addison’s disease. Zinc deficiency is more associated with poor wound healing and periorificial dermatitis. * **Psychosis (Option C):** While zinc deficiency can cause neuropsychiatric symptoms like irritability, emotional lability, or depression, frank **psychosis** is not a hallmark. Psychosis is more commonly associated with Vitamin B12 (megaloblastic madness) or Niacin (Pellagra) deficiencies. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder causing impaired intestinal zinc absorption. * **Immune Function:** Zinc deficiency leads to **thymic atrophy** and impaired T-cell function, increasing susceptibility to infections. * **Dysgeusia:** Loss of taste sensation is a classic early sign of zinc deficiency. * **Growth:** It is a common cause of **growth retardation** and stunted height in children.

Question 260: Which of the following can result from zinc deficiency?

A. Loss of libido
B. Poor weight gain
C. Sexual infantilism
D. All of the above (Correct Answer)

Explanation: **Explanation:** Zinc is a vital trace element that acts as a cofactor for over 300 enzymes, including Carbonic Anhydrase, Alcohol Dehydrogenase, and DNA/RNA polymerases. It plays a critical role in protein synthesis, cell division, and immune function. **Why "All of the above" is correct:** Zinc deficiency manifests through a multisystemic clinical spectrum because it is essential for the growth and maintenance of various tissues: * **Poor weight gain:** Zinc is crucial for DNA synthesis and cell proliferation. Deficiency leads to growth retardation and failure to thrive in children. * **Sexual infantilism and Loss of libido:** Zinc is mandatory for the development of primary and secondary sexual characteristics. It is involved in the synthesis of testosterone and the maturation of the hypothalamic-pituitary-gonadal axis. Deficiency results in hypogonadism, delayed puberty (sexual infantilism), and decreased sperm count (oligospermia), which clinically presents as a loss of libido. **Analysis of Options:** Since zinc is fundamental to both somatic growth (Option B) and reproductive health (Options A and C), all three manifestations are classic clinical features of its deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder causing impaired zinc absorption, characterized by the triad of **dermatitis** (periorificial and acral), **diarrhea**, and **alopecia**. * **Wound Healing:** Zinc is essential for collagen synthesis; deficiency leads to delayed wound healing. * **Taste and Smell:** Zinc is a component of **Gustin**; deficiency causes **Hypogeusia** (loss of taste) and **Hyposmia** (loss of smell). * **Immunity:** It is vital for T-cell function; deficiency leads to increased susceptibility to infections.

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

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Malnutrition: Biochemical Consequences

Practice Questions

Dietary Antioxidants

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Functional Foods and Nutraceuticals

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Dietary Guidelines and Recommendations

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