Nutrition and Metabolism Practice Questions

Q: A 45-year-old male, a known case of hypertension under treatment, presents for a routine checkup. Which of the following fatty acids is advisable for him to include in a balanced diet?

Omega-3 fatty acids. **Explanation:** **1. Why Omega-3 Fatty Acids are Correct:** Omega-3 fatty acids (α-linolenic acid, EPA, and DHA) are essential polyunsaturated fatty acids (PUFAs) with significant cardioprotective benefits. In a hypertensive patient, Omega-3s help reduce blood pressure by improving endothelial function, increasing nitric oxide bioavailability, and reducing systemic inflammation. They are precursors to **Series-3 Prostaglandins** and **Series-5 Leukotrienes**, which are less inflammatory and possess anti-thrombotic properties, thereby reducing the risk of cardiovascular events. **2. Analysis of Incorrect Options:** * **Omega-6 Fatty Acids (Option B):** While essential (e.g., Linoleic acid), an excess of Omega-6 relative to Omega-3 can be pro-inflammatory. They are precursors to **Series-2 Prostaglandins** and **Series-4 Leukotrienes**, which promote platelet aggregation and vasoconstriction. * **Omega-9 Fatty Acids (Option C):** These are monounsaturated fatty acids (e.g., Oleic acid). While healthy (found in olive oil), they are **non-essential** because the human body can synthesize them. They do not offer the same potent anti-inflammatory and anti-hypertensive benefits as Omega-3s. * **Fatty acids are not necessary (Option D):** This is physiologically incorrect. Essential fatty acids (EFAs) cannot be synthesized by the body due to the absence of desaturase enzymes ($\Delta$12 and $\Delta$15) and must be obtained from the diet for membrane integrity and eicosanoid synthesis. **Clinical Pearls for NEET-PG:** * **Essential Fatty Acids:** Linoleic acid ($\omega$-6) and $\alpha$-Linolenic acid ($\omega$-3). * **P/S Ratio:** A high Polyunsaturated to Saturated fatty acid ratio is recommended to lower serum cholesterol. * **Fish Oil:** Rich in EPA (Eicosapentaenoic acid) and DHA (Docosahexaenoic acid), which lower plasma triglycerides. * **Trans-fatty acids:** Most harmful; they increase LDL and decrease HDL.

Q: Which of the following are semi-essential amino acids?

Arginine and Histidine. **Explanation:** Amino acids are classified based on their nutritional requirement into essential, non-essential, and semi-essential categories. **Why Arginine and Histidine are correct:** Semi-essential amino acids (also known as conditionally essential) are those that can be synthesized by the body, but the rate of synthesis is **insufficient** to meet the demands during periods of rapid growth, such as childhood, pregnancy, or recovery from severe illness. * **Arginine and Histidine** are the two primary semi-essential amino acids. While adults can synthesize enough Arginine through the urea cycle to maintain nitrogen balance, infants and growing children require dietary supplementation to support tissue growth and development. **Analysis of Incorrect Options:** * **A & B (Lysine and Leucine):** These are **purely essential** amino acids. The human body lacks the biochemical pathways to synthesize their carbon skeletons; therefore, they must be obtained entirely from the diet. (Note: Leucine is also one of the two purely ketogenic amino acids). * **C (Arginine and Lysine):** While Arginine is semi-essential, Lysine is strictly essential, making this combination incorrect. **NEET-PG High-Yield Pearls:** 1. **Mnemonic for Essential Amino Acids:** "PVT TIM HALL" (Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, Lysine). 2. **Purely Ketogenic:** Leucine and Lysine (The "L"s). 3. **Both Glucogenic & Ketogenic:** Phenylalanine, Tyrosine, Tryptophan, Isoleucine (The "PIT" amino acids). 4. **Arginine** is a precursor for Nitric Oxide (NO), Urea, and Creatine. 5. **Histidine** is the precursor for Histamine (via decarboxylation).

Q: Acrodermatitis enteropathica is due to deficiency of which essential trace element?

Zinc. **Explanation:** **Acrodermatitis enteropathica (AE)** is a rare autosomal recessive disorder caused by a mutation in the **SLC39A4 gene**, which encodes the **ZIP4 transporter**. This protein is essential for the intestinal absorption of **Zinc**. 1. **Why Zinc is correct:** Zinc is a vital cofactor for over 300 enzymes (e.g., Alkaline Phosphatase, Carbonic Anhydrase). Its deficiency leads to the classic triad of AE: **periorificial and acral dermatitis** (skin rash around the mouth, anus, and limbs), **alopecia**, and **diarrhea**. It also causes impaired wound healing and immune dysfunction. 2. **Why other options are incorrect:** * **Manganese:** Deficiency is extremely rare but may lead to impaired growth and skeletal abnormalities. Toxicity (Manganism) presents with Parkinson-like neurological symptoms. * **Copper:** Deficiency causes **Menkes disease** (kinky hair, connective tissue defects) or microcytic anemia. It is a cofactor for Lysyl oxidase and Tyrosinase. * **Selenium:** Deficiency leads to **Keshan disease** (cardiomyopathy) or Kashin-Beck disease (osteoarthritis). It is a key component of the antioxidant enzyme **Glutathione peroxidase**. **High-Yield Clinical Pearls for NEET-PG:** * **Zinc & Vitamin A:** Zinc is required for the synthesis of Retinol-Binding Protein (RBP); thus, zinc deficiency can mimic Vitamin A deficiency (night blindness). * **Diagnosis:** Low serum zinc levels and low serum **Alkaline Phosphatase** (a zinc-dependent enzyme). * **Treatment:** Lifelong oral zinc supplementation (usually Zinc Sulfate). * **Acquired AE:** Can occur in infants during weaning from breast milk to formula or in adults with severe malabsorption/TPN.

Q: All of the following statements about Net Protein Utilization (NPU) are true EXCEPT:

One gram of protein is equivalent to one gram of Nitrogen.. ### Explanation **1. Why Option D is the Correct Answer (The False Statement)** In nutritional biochemistry, protein and nitrogen are not equivalent in weight. Proteins, on average, contain approximately **16% nitrogen**. Therefore, to calculate the amount of nitrogen in a protein sample, the weight of the protein is divided by **6.25** (since 100/16 = 6.25). * **Correct conversion:** 6.25 grams of protein = 1 gram of Nitrogen. **2. Analysis of Other Options** * **Option A:** This is the standard formula for NPU. It measures the percentage of dietary nitrogen that is actually retained by the body for growth and maintenance. * **Option B:** NPU is a superior index for estimating protein quality compared to Biological Value (BV) because it accounts for **digestibility**. (NPU = BV × Digestibility coefficient). * **Option C:** Egg protein (whole egg) is considered the "reference protein" or "gold standard" in nutrition. It has an NPU value of approximately **94–100**, the highest among natural food sources. **3. High-Yield Clinical Pearls for NEET-PG** * **Biological Value (BV):** Measures nitrogen retained vs. nitrogen *absorbed*. Unlike NPU, it does not account for digestive losses. * **Reference Protein:** Egg is used as the standard (BV = 100, NPU = 100). * **Limiting Amino Acids:** Pulses are deficient in Methionine; Cereals are deficient in Lysine. * **Nitrogen Balance:** * *Positive:* Growth, pregnancy, convalescence. * *Negative:* Starvation, severe burns, uncontrolled diabetes, wasting diseases.

Q: Which of the following is considered the reference protein?

Egg. **Explanation:** The concept of a **Reference Protein** refers to a protein source that contains all essential amino acids in the optimal proportions required by the human body for growth and maintenance. **Why Egg is the Correct Answer:** Egg protein (specifically egg white) is considered the "Gold Standard" or reference protein because it has a **Biological Value (BV) of 100** and a **Net Protein Utilization (NPU) of approximately 94-100%**. It contains the most complete and balanced profile of essential amino acids, making it the benchmark against which the quality of all other dietary proteins is compared. **Analysis of Incorrect Options:** * **A. Fish:** While fish is a high-quality "first-class" protein, its amino acid profile is slightly less balanced than that of an egg. * **C. Rice:** Rice is a plant-based protein and is considered an "incomplete" or "second-class" protein. It is specifically deficient in the essential amino acid **Lysine**. * **D. Lemon:** Lemon is a citrus fruit primarily valued for Vitamin C (Ascorbic acid) and contains negligible amounts of protein. **High-Yield NEET-PG Pearls:** * **Limiting Amino Acids:** Pulses are generally deficient in **Methionine**, while Cereals (like rice/wheat) are deficient in **Lysine**. * **Protein Efficiency Ratio (PER):** This measures weight gain per gram of protein intake. * **PDCAAS (Protein Digestibility Corrected Amino Acid Score):** This is the current international standard for measuring protein quality. Egg and Milk both have a PDCAAS score of **1.0** (the maximum). * **Gelatin:** A unique animal protein that is "incomplete" because it lacks **Tryptophan**.

Q: Technical, infectious, and metabolic complications can occur during total parenteral nutrition (TPN). Which of the following is NOT a complication of TPN?

Congestive cardiac failure. **Explanation:** Total Parenteral Nutrition (TPN) is the intravenous administration of all necessary nutrients, bypassing the gastrointestinal tract. While life-saving, it is associated with various complications categorized as technical, infectious, and metabolic. **Why Congestive Cardiac Failure (CCF) is the correct answer:** CCF is **not** a direct complication of TPN itself. While fluid overload (iatrogenic) can occur during any IV therapy leading to pulmonary edema, it is not a specific metabolic or technical complication inherent to the TPN formulation. In contrast, the other options are well-documented metabolic consequences of long-term or improperly balanced TPN. **Analysis of Incorrect Options:** * **Metabolic Bone Disease (A):** Long-term TPN is associated with osteomalacia and osteoporosis due to negative calcium balance, vitamin D issues, and aluminum toxicity from TPN solutions. * **Essential Fatty Acid Deficiency (EFAD) (B):** This occurs if TPN consists solely of glucose and amino acids without lipid emulsions. Clinical signs include scaly dermatitis and alopecia. * **Hypomagnesemia (D):** This is a common electrolyte abnormality in TPN, often seen as part of **Refeeding Syndrome**, where the shift from catabolism to anabolism causes intracellular uptake of magnesium, phosphate, and potassium. **High-Yield Clinical Pearls for NEET-PG:** * **Most common TPN complication:** Catheter-related bloodstream infection (Sepsis), often due to *Staphylococcus aureus* or *Candida*. * **Refeeding Syndrome:** Characterized by **Hypophosphatemia** (the hallmark), hypokalemia, and hypomagnesemia when starting TPN in malnourished patients. * **Hepatobiliary complications:** TPN-associated cholestasis and cholelithiasis (gallstones) occur due to lack of enteral stimulation and decreased CCK release. * **Hyperglycemia:** The most common metabolic complication during the initiation phase of TPN.

Q: A patient with type 2 diabetes mellitus is being managed. What type of dietary component is crucial for their management?

Dietary Fiber. **Explanation:** **Why Dietary Fiber is Correct:** Dietary fiber, particularly **soluble fiber** (e.g., pectin, gums), plays a pivotal role in the management of Type 2 Diabetes Mellitus (T2DM). It functions by increasing the viscosity of intestinal contents, which **slows the rate of gastric emptying** and delays the absorption of glucose. This results in a blunted postprandial glycemic peak and improved insulin sensitivity. Furthermore, fiber fermentation in the colon produces short-chain fatty acids (SCFAs), which may further enhance metabolic health. **Why Other Options are Incorrect:** * **Carbohydrates:** While essential for energy, high intake—especially of simple sugars—leads to rapid spikes in blood glucose and worsens glycemic control. * **Fats:** High-fat diets, particularly those rich in saturated fats, are associated with increased insulin resistance and cardiovascular risk, which is already elevated in diabetic patients. * **Proteins:** While necessary for muscle maintenance, excessive protein intake does not directly improve glycemic control and may be contraindicated in patients with diabetic nephropathy. **High-Yield Clinical Pearls for NEET-PG:** * **Glycemic Index (GI):** Foods high in fiber typically have a **low GI**, meaning they cause a slower rise in blood glucose levels. * **Lipid Profile:** Soluble fiber also helps lower LDL cholesterol by binding to bile acids in the gut, reducing the risk of macrovascular complications. * **Recommended Intake:** The WHO recommends approximately **25–40g of fiber per day** for optimal metabolic benefits. * **Key Source:** Psyllium husk (Isabgol) is a common clinical recommendation for increasing soluble fiber intake.

Q: Which of the following minerals cannot generate free radicals?

Selenium. **Explanation:** The generation of free radicals by minerals typically occurs via **redox cycling** (such as the Fenton and Haber-Weiss reactions). This process requires the metal to be a **transition element** capable of existing in multiple oxidation states and acting as a pro-oxidant. **Why Selenium is the Correct Answer:** Unlike the other options, **Selenium (Se)** is primarily an **antioxidant** mineral. It does not participate in redox cycling to generate free radicals; instead, it is a vital structural component of antioxidant enzymes like **Glutathione Peroxidase (GPx)** and **Thioredoxin Reductase**. These enzymes are responsible for neutralizing hydrogen peroxide and lipid hydroperoxides, thereby protecting the cell from oxidative stress. **Analysis of Incorrect Options:** * **Copper (A):** A potent pro-oxidant. It undergoes redox cycling ($Cu^+ \leftrightarrow Cu^{2+}$) to generate the highly reactive hydroxyl radical (•OH) via Fenton-like chemistry. * **Cobalt (C) & Nickel (D):** Both are transition metals that can catalyze the formation of Reactive Oxygen Species (ROS). They can deplete cellular glutathione and trigger lipid peroxidation, contributing to oxidative DNA damage. **Clinical Pearls for NEET-PG:** * **Fenton Reaction:** $Fe^{2+} + H_2O_2 \rightarrow Fe^{3+} + \cdot OH + OH^-$. (Copper can substitute for Iron). * **Selenium Deficiency:** Leads to **Keshan Disease** (cardiomyopathy) and **Kashin-Beck Disease** (osteoarthritis). * **Glutathione Peroxidase:** Requires **Selenocysteine** (the 21st amino acid) at its active site for its catalytic activity.

Q: Fatty liver in Kwashiorkor occurs due to what?

Lack of substrates for protein synthesis in the liver. ### Explanation **Correct Answer: C. Lack of substrates for protein synthesis in the liver** The hallmark of **Kwashiorkor** is a severe deficiency of dietary protein despite adequate caloric intake. The development of fatty liver (steatosis) in these patients is primarily due to the **impaired synthesis of Apolipoprotein B-100**. In a healthy state, the liver exports excess triglycerides into the systemic circulation in the form of **Very Low-Density Lipoproteins (VLDL)**. The assembly of VLDL requires both lipids and a protein component, specifically Apo B-100. In Kwashiorkor, the lack of essential amino acids (substrates) prevents the liver from synthesizing these apolipoproteins. Consequently, triglycerides cannot be packaged into VLDL and exported, leading to their accumulation within the hepatocytes, resulting in an enlarged, fatty liver. #### Analysis of Incorrect Options: * **A & B (High carbohydrate/fat content):** While Kwashiorkor diets are often high in carbohydrates (e.g., maize or rice), the fatty liver is not caused by the *excess* of these macronutrients, but rather by the *inability to transport* fat out of the liver due to protein deficiency. * **D (Lack of substrates for gluconeogenesis):** While gluconeogenesis may be affected in malnutrition, it is not the mechanism behind lipid accumulation. Fatty liver is a transport failure, not a glucose production failure. #### NEET-PG High-Yield Pearls: * **Kwashiorkor vs. Marasmus:** Kwashiorkor presents with **edema** (due to hypoalbuminemia) and fatty liver; Marasmus presents with "skin and bones" appearance and no edema. * **Key Clinical Signs:** "Flaky paint" dermatosis and "Flag sign" (alternating bands of hair color). * **VLDL Assembly:** Remember that **Apo B-100** is essential for VLDL (liver), while **Apo B-48** is essential for Chylomicrons (intestine). A defect in both leads to Abetalipoproteinemia.

Question 1

A 45-year-old male, a known case of hypertension under treatment, presents for a routine checkup. Which of the following fatty acids is advisable for him to include in a balanced diet?

Accepted Answer

Omega-3 fatty acids

Answer

Omega-6 fatty acids

Answer

Omega-9 fatty acids

Answer

Fatty acids are not necessary in the diet

Question 2

Which of the following are semi-essential amino acids?

Accepted Answer

Arginine and Histidine

Answer

Lysine

Answer

Leucine

Answer

Arginine and Lysine

Question 3

Acrodermatitis enteropathica is due to deficiency of which essential trace element?

Accepted Answer

Zinc

Answer

Manganese

Answer

Copper

Answer

Selenium

Question 4

All of the following statements about Net Protein Utilization (NPU) are true EXCEPT:

Accepted Answer

One gram of protein is equivalent to one gram of Nitrogen.

Answer

NPU is defined as (Nitrogen retained / Nitrogen consumed) x 100.

Answer

NPU is useful for estimating protein quality.

Answer

Egg protein has the highest NPU value.

Question 5

Which of the following is considered the reference protein?

Accepted Answer

Egg

Answer

Fish

Answer

Rice

Answer

Lemon

Question 6

Technical, infectious, and metabolic complications can occur during total parenteral nutrition (TPN). Which of the following is NOT a complication of TPN?

Accepted Answer

Congestive cardiac failure

Answer

Metabolic bone disease

Answer

Essential fatty acid deficiency

Answer

Hypomagnesemia

Question 7

A patient with type 2 diabetes mellitus is being managed. What type of dietary component is crucial for their management?

Accepted Answer

Dietary Fiber

Answer

Proteins

Answer

Carbohydrates

Answer

Fats

Question 8

Which of the following minerals cannot generate free radicals?

Accepted Answer

Selenium

Answer

Copper

Answer

Cobalt

Answer

Nickel

Question 9

Fatty liver in Kwashiorkor occurs due to what?

Accepted Answer

Lack of substrates for protein synthesis in the liver

Answer

High carbohydrate content in the diet

Answer

High fat content in the diet

Answer

Lack of substrates for gluconeogenesis in the liver

Question 10

Which of the following proteins is biologically complete?

Accepted Answer

Both egg and milk

Answer

Egg

Answer

Milk

Answer

None of the above

Nutrition and Metabolism — MCQs

Nutrition and Metabolism — MCQs

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