Nutrition and Metabolism — MCQs

Nutrition and Metabolism Indian Medical PG Practice Questions and MCQs

Question 91: What is the daily requirement of protein for adults?

A. 6 grams
B. 60 grams (Correct Answer)
C. 120 grams
D. 250 grams

Explanation: **Explanation:** The daily protein requirement for a healthy adult is approximately **0.8 to 1.0 gram per kilogram of body weight**. For an average adult weighing 60–70 kg, this translates to roughly **60 grams per day**. This amount is necessary to maintain a positive nitrogen balance, ensuring that the rate of protein synthesis equals or exceeds the rate of protein degradation. * **Option A (6 grams):** This is significantly below the physiological requirement. Such a low intake would lead to a negative nitrogen balance and muscle wasting. * **Option C (120 grams):** This represents a high-protein diet (approx. 2g/kg). While common in athletes or bodybuilders, it is double the standard RDA for a sedentary adult. * **Option D (250 grams):** This is an excessive intake that can strain renal function and is not sustainable or required for normal metabolism. **High-Yield Clinical Pearls for NEET-PG:** * **Nitrogen Balance:** 1 gram of Nitrogen is equivalent to **6.25 grams of protein**. This is a frequent calculation-based question. * **Biological Value (BV):** Egg protein has the highest biological value (100) and is considered the "Reference Protein." * **Specific Dynamic Action (SDA):** Protein has the highest SDA (approx. 30%), meaning it requires more energy for digestion and processing compared to fats or carbohydrates. * **Increased Requirements:** Protein needs increase during pregnancy (+0.5g/kg), lactation (+1g/kg), and pathological states like burns, sepsis, or post-surgery recovery to facilitate tissue repair.

Question 92: Parenteral nutrition causes all of the following complications EXCEPT?

A. Diarrhea (Correct Answer)
B. Hepatic steatosis
C. Hyperglycemia
D. Electrolyte imbalance

Explanation: **Explanation:** The correct answer is **A. Diarrhea**. **1. Why Diarrhea is the correct answer:** Parenteral nutrition (PN) involves the intravenous administration of nutrients, bypassing the gastrointestinal (GI) tract entirely. Diarrhea is a complication typically associated with **Enteral Nutrition** (tube feeding), often due to high osmolarity of the formula, malabsorption, or bacterial contamination. In contrast, the lack of enteral stimulation in PN patients often leads to **villous atrophy** of the gut mucosa and **constipation** (due to bowel disuse), rather than diarrhea. **2. Why the other options are incorrect:** * **Hepatic steatosis (B):** This is a common metabolic complication of PN, especially with excessive calorie intake (overfeeding) or high carbohydrate loads. It occurs due to increased de novo lipogenesis and impaired lipid export from the liver. * **Hyperglycemia (C):** This is the most frequent metabolic complication of PN. It results from the continuous infusion of high-concentration dextrose, often exceeding the body’s oxidative capacity or insulin response, especially in stressed or septic patients. * **Electrolyte imbalance (D):** PN requires precise formulation. Common imbalances include hypophosphatemia, hypokalemia, and hypomagnesemia (often seen in **Refeeding Syndrome**), as well as abnormalities in sodium and calcium levels. **Clinical Pearls for NEET-PG:** * **Refeeding Syndrome:** Characterized by severe **hypophosphatemia** upon restarting nutrition in malnourished patients. * **Long-term PN complication:** Cholelithiasis and biliary sludge due to lack of CCK-mediated gallbladder contraction. * **Most common infection:** Catheter-related bloodstream infections (CRBSI), often caused by *Staphylococcus aureus* or *Candida*.

Question 93: Zinc deficiency causes which of the following?

A. Cardiomyopathy
B. Reduced growth (Correct Answer)
C. Anemia
D. Hypothyroidism

Explanation: **Explanation:** **Zinc (Zn)** is an essential trace element that acts as a cofactor for over 300 enzymes, including **DNA and RNA polymerases**. It plays a critical role in protein synthesis, cell division, and nucleic acid metabolism. 1. **Why "Reduced Growth" is Correct:** Zinc is indispensable for the function of the **Growth Hormone (GH) - Insulin-like Growth Factor 1 (IGF-1) axis**. Deficiency leads to impaired cell proliferation and protein synthesis, manifesting clinically as **growth retardation**, delayed skeletal maturation, and hypogonadism (delayed puberty). It is a hallmark feature of zinc deficiency in children. 2. **Analysis of Incorrect Options:** * **Cardiomyopathy:** This is primarily associated with **Selenium deficiency** (Keshan disease) or Thiamine (Vitamin B1) deficiency (Wet Beriberi). * **Anemia:** While zinc is involved in heme synthesis, anemia is the classic presentation of **Iron, Vitamin B12, or Folate** deficiencies. Excess zinc can actually *cause* anemia by interfering with Copper absorption. * **Hypothyroidism:** This is classically caused by **Iodine deficiency**. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder of zinc absorption characterized by the triad of **dermatitis** (periorificial and acral), **alopecia**, and **diarrhea**. * **Wound Healing:** Zinc is vital for collagen synthesis; deficiency leads to poor wound healing. * **Immunity:** Zinc deficiency causes thymic atrophy and impaired T-cell function. * **Dysgeusia:** Loss of taste sensation is a common early sign of zinc deficiency. * **Antidote:** Zinc supplementation is used to treat **Wilson’s Disease** as it induces metallothionein in the gut, which sequesters copper.

Question 94: Which of the following oils contains the highest percentage of polyunsaturated fatty acids?

A. Groundnut oil
B. Soyabean oil (Correct Answer)
C. Margarine
D. Palm oil

Explanation: **Explanation:** The correct answer is **Soyabean oil**. This question tests the knowledge of fatty acid composition in common dietary fats, a high-yield topic in nutrition biochemistry. **1. Why Soyabean oil is correct:** Polyunsaturated fatty acids (PUFAs) are fatty acids containing two or more double bonds. Soyabean oil is exceptionally rich in PUFAs, containing approximately **60-62%** (primarily Linoleic acid, an omega-6 fatty acid, and some Alpha-linolenic acid, an omega-3). Among the given options, it has the highest concentration of these essential fatty acids. **2. Analysis of Incorrect Options:** * **Groundnut oil:** While it is considered a healthy oil, it is primarily rich in **Monounsaturated Fatty Acids (MUFA)**, specifically Oleic acid (~50%), with PUFA content being lower (around 30%). * **Margarine:** This is a processed fat produced by the partial hydrogenation of vegetable oils. This process converts liquid unsaturated fats into solid fats, significantly increasing the content of **Trans-fatty acids** and saturated fats while reducing the PUFA percentage. * **Palm oil:** This is one of the few vegetable oils high in **Saturated Fatty Acids** (~50%, mainly Palmitic acid). It contains much less PUFA compared to soyabean or groundnut oil. **Clinical Pearls for NEET-PG:** * **P/S Ratio:** The Polyunsaturated/Saturated (P/S) ratio is a measure of the cholesterol-lowering potential of an oil. A ratio of **>1.0** is considered heart-healthy. * **Essential Fatty Acids (EFA):** Linoleic acid (ω-6) and Linolenic acid (ω-3) are EFAs because the human body lacks the enzymes ($\Delta^{12}$ and $\Delta^{15}$ desaturases) to synthesize them. * **Safflower oil and Sunflower oil** generally have even higher PUFA content than Soyabean oil, but among the provided choices, Soyabean is the highest. * **Coconut oil** has the highest saturated fat content (~90%) among vegetable oils.

Question 95: Which food item has the highest concentration of calcium?

A. Dates (Correct Answer)
B. Guava
C. Amla
D. Halibut liver oil

Explanation: **Explanation:** The correct answer is **Dates**. In the context of the provided options, dates are a significant plant-based source of calcium, containing approximately **120 mg of calcium per 100g**. **Why Dates are correct:** While dairy products are the primary source of calcium in a standard diet, among fruits and dry fruits, dates (especially dried ones) stand out for their high mineral density. They are frequently highlighted in biochemistry and nutrition textbooks as a rich source of non-heme iron and calcium, making them an important dietary recommendation for preventing bone demineralization and anemia. **Analysis of Incorrect Options:** * **Guava:** While extremely rich in Vitamin C (Ascorbic acid), its calcium content is relatively low (approx. 18-20 mg/100g) compared to dates. * **Amla (Indian Gooseberry):** Amla is the richest natural source of Vitamin C. While it contains some minerals, its primary nutritional value lies in its antioxidant properties, not calcium. * **Halibut liver oil:** This is a potent source of **Vitamin A and Vitamin D**. While Vitamin D is essential for calcium *absorption* in the gut, the oil itself does not contain significant concentrations of calcium. **High-Yield NEET-PG Pearls:** * **Richest overall source:** Among all foods, **Ragi (Finger millet)** is the richest source of calcium (344 mg/100g). * **Animal source:** Milk and milk products are the most bioavailable sources. * **Absorption:** Calcium absorption is enhanced by Vitamin D, lactose, and acidic pH, while it is inhibited by phytates (found in cereals), oxalates (found in spinach), and high dietary fiber. * **Clinical Correlation:** Calcium deficiency leads to Rickets (children) and Osteomalacia (adults). The daily requirement for a normal adult is roughly 600-1000 mg/day.

Question 96: Ceruloplasmin contains which of the following metal ions?

A. Zinc (Zn)
B. Copper (Cu) (Correct Answer)
C. Selenium (Se)
D. Iron (Fe)

Explanation: **Explanation:** **Ceruloplasmin** is an alpha-2 globulin synthesized in the liver. It is the primary transport protein for **Copper (Cu)** in the blood, carrying approximately 95% of the body's circulating copper. Each molecule of ceruloplasmin binds 6 to 8 atoms of copper. Beyond transport, ceruloplasmin functions as a **ferroxidase enzyme**. It oxidizes toxic ferrous iron ($Fe^{2+}$) to ferric iron ($Fe^{3+}$), allowing iron to bind to transferrin for safe transport. This link between copper and iron metabolism explains why copper deficiency can lead to microcytic anemia. **Analysis of Incorrect Options:** * **Zinc (Zn):** Zinc is primarily associated with enzymes like Carbonic Anhydrase, Alcohol Dehydrogenase, and DNA polymerase. It is transported by albumin and alpha-2 macroglobulin. * **Selenium (Se):** This is a key component of **Glutathione Peroxidase**, an essential antioxidant enzyme that protects cells from oxidative damage. * **Iron (Fe):** While ceruloplasmin acts *on* iron, it does not contain iron as a structural metal ion. Iron is found in hemoglobin, myoglobin, and cytochromes. **High-Yield Clinical Pearls for NEET-PG:** * **Wilson’s Disease:** Characterized by a **decrease** in serum ceruloplasmin levels due to defective biliary copper excretion and failed incorporation of copper into apoceruloplasmin. * **Menkes Disease:** An X-linked recessive disorder of copper absorption leading to low copper and ceruloplasmin levels ("kinky hair" syndrome). * **Acute Phase Reactant:** Ceruloplasmin levels **increase** during inflammation, infection, or pregnancy. * **Aceruloplasminemia:** A rare genetic disorder leading to iron overload in the brain and viscera because iron cannot be mobilized without ferroxidase activity.

Question 97: Which one among the following is not an antioxidant?

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

Explanation: ### Explanation The correct answer is **Iron (D)**. While many minerals act as essential components of the body’s antioxidant defense system, Iron is primarily considered a **pro-oxidant** in its free form. **Why Iron is the Correct Answer:** Free iron ($Fe^{2+}$) participates in the **Fenton Reaction**, where it reacts with hydrogen peroxide ($H_2O_2$) to generate the **hydroxyl radical (•OH)**. The hydroxyl radical is the most reactive and damaging reactive oxygen species (ROS), causing lipid peroxidation and DNA damage. Therefore, rather than preventing oxidative stress, excess free iron promotes it. **Why the other options are incorrect:** * **Selenium (B):** A vital antioxidant mineral. It is a mandatory cofactor for **Glutathione Peroxidase**, the enzyme responsible for neutralizing hydrogen peroxide into water. * **Zinc (A) and Copper (C):** Both are essential structural and catalytic components of **Cytosolic Superoxide Dismutase (Cu-Zn SOD)**. This enzyme dismutates the superoxide radical ($O_2^{•-}$) into less harmful hydrogen peroxide. Zinc also protects protein sulfhydryl groups from oxidation. **High-Yield Clinical Pearls for NEET-PG:** * **Manganese (Mn):** Acts as a cofactor for **Mitochondrial SOD**. * **Haber-Weiss Reaction:** Another pathway where iron (or copper) facilitates the formation of hydroxyl radicals from superoxide and hydrogen peroxide. * **Clinical Correlation:** In conditions like **Hemochromatosis** (iron overload), the massive production of free radicals via the Fenton reaction leads to tissue damage (cirrhosis, bronze diabetes). * **Antioxidant Vitamins:** Remember the mnemonic **"ACE"** (Vitamins A, C, and E). Vitamin E is the most potent chain-breaking antioxidant in lipid membranes.

Question 98: The nitrogen content in 50 gm of a typical dietary protein is most likely to be?

A. 5 gm
B. 8 gm (Correct Answer)
C. 10 gm
D. 16 gm

Explanation: **Explanation:** The nitrogen content of a typical dietary protein is a fundamental concept in nutritional biochemistry, specifically in the calculation of **Nitrogen Balance**. **1. Why Option B (8 gm) is Correct:** On average, dietary proteins contain approximately **16% nitrogen** by weight. This is a standard biological constant used in clinical medicine. To find the nitrogen content in 50 gm of protein, the calculation is: * $50 \text{ gm (Protein)} \times 0.16 \text{ (16\%)} = \mathbf{8 \text{ gm of Nitrogen}}$ Conversely, if the nitrogen content is known, the protein amount can be calculated using the **protein factor of 6.25** ($100/16 = 6.25$). For example, $8 \text{ gm Nitrogen} \times 6.25 = 50 \text{ gm Protein}$. **2. Why Other Options are Incorrect:** * **Option A (5 gm):** This represents only 10% nitrogen content, which is too low for standard dietary proteins. * **Option C (10 gm):** This represents 20% nitrogen content. While some specific amino acids (like Arginine) are nitrogen-rich, the average for mixed dietary protein remains 16%. * **Option D (16 gm):** This is a common "distractor" value because 16 is the percentage used in the calculation ($16\%$), not the absolute weight in grams for a 50 gm sample. **Clinical Pearls & High-Yield Facts:** * **Nitrogen Balance Equation:** $\text{Nitrogen Balance} = \text{Nitrogen Intake} - (\text{Urinary Urea Nitrogen} + 4)$. (The '+4' accounts for insensible losses via skin and feces). * **Positive Nitrogen Balance:** Seen during growth, pregnancy, and recovery from illness (anabolic states). * **Negative Nitrogen Balance:** Seen in starvation, severe burns, sepsis, and high-fever (catabolic states). * **Kjeldahl Method:** The standard laboratory technique used to determine the nitrogen content of organic substances.

Question 99: Which of the following has the highest biological value of protein?

A. Eggs (Correct Answer)
B. Fish
C. Soyabean
D. Gram

Explanation: **Explanation:** The **Biological Value (BV)** of a protein is a measure of the proportion of absorbed protein from food which becomes incorporated into the proteins of the organism's body. It specifically assesses how efficiently the body utilizes the nitrogen absorbed from the diet. **1. Why Eggs are the Correct Answer:** Whole eggs are considered the "Gold Standard" for protein quality in nutrition. They have a **Biological Value of approximately 94–100%**, the highest among all natural whole foods. This is because eggs contain all the essential amino acids in the exact proportions required by the human body for growth and maintenance. In many biochemical indices, egg protein is used as the reference unit (score of 100) against which other proteins are compared. **2. Analysis of Incorrect Options:** * **Fish (Option B):** While fish is a high-quality animal protein with a high BV (approx. 76–80), it is lower than that of eggs. * **Soyabean (Option C):** Soy is the best plant-based protein source (BV approx. 74), but like most legumes, it is relatively limiting in sulfur-containing amino acids (Methionine) compared to animal sources. * **Gram (Option D):** Pulses and legumes generally have a lower BV (approx. 50–60) because they are deficient in Methionine, though they are rich in Lysine. **3. High-Yield Clinical Pearls for NEET-PG:** * **Net Protein Utilization (NPU):** While BV measures absorbed nitrogen, NPU measures retained nitrogen relative to *ingested* nitrogen. For eggs, NPU is also the highest (~94). * **Limiting Amino Acids:** * Pulses/Grains: Limited in **Methionine**. * Cereals (Wheat/Rice): Limited in **Lysine**. * Corn (Maize): Limited in **Tryptophan** (leads to Pellagra). * **Reference Protein:** Egg protein is termed a "complete protein" because it contains all essential amino acids.

Question 100: Which of the following are clinical features of Zinc deficiency?

A. Acrodermatitis enteropathica
B. Poor wound healing
C. Hypogonadism
D. All of the above (Correct Answer)

Explanation: **Explanation:** Zinc is an essential trace element that acts as a cofactor for over 300 enzymes, including **Carbonic anhydrase**, **Alkaline phosphatase**, and **RNA/DNA polymerases**. Its deficiency manifests across multiple organ systems due to its role in cell division, protein synthesis, and immune function. 1. **Acrodermatitis enteropathica:** This is the classic clinical hallmark of zinc deficiency. It can be hereditary (autosomal recessive mutation in the *ZIP4* transporter) or acquired. It presents with a triad of **periorificial and acral dermatitis**, alopecia, and diarrhea. 2. **Poor wound healing:** Zinc is vital for collagen synthesis and cell proliferation. Deficiency impairs the inflammatory phase and remodeling phase of healing, leading to delayed recovery. 3. **Hypogonadism:** Zinc is crucial for the function of the hypothalamic-pituitary-gonadal axis and spermatogenesis. Deficiency in adolescent males often leads to growth retardation and delayed sexual maturation (hypogonadism). **Why "All of the above" is correct:** Since zinc is integral to integumentary integrity (skin/wounds) and endocrine health (gonads), all three features are characteristic clinical presentations of a deficient state. **High-Yield Clinical Pearls for NEET-PG:** * **Immune Function:** Zinc deficiency causes **thymic atrophy** and impaired T-cell function, leading to increased susceptibility to infections. * **Dysgeusia:** A common early sign is a distorted sense of taste. * **Night Blindness:** Zinc is required for the enzyme *Retinol dehydrogenase*, which converts Retinol to Retinal; thus, deficiency can potentiate Vitamin A-related vision issues. * **Diagnosis:** Low serum zinc levels (though clinical response to supplementation is often used for confirmation).

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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