Nutrition and Metabolism Practice Questions

Q: Soya bean contains protein to the tune of:

40%. **Explanation:** Soybean (*Glycine max*) is uniquely classified as both a pulse and an oilseed. It is recognized as the richest plant-based source of complete protein, containing all essential amino acids. **Why 40% is correct:** The average protein content of soybean ranges between **38% to 42%**. This high concentration is nearly double that of other common pulses (like grams or lentils) and significantly higher than animal sources like meat (20%) or eggs (13%). In addition to its 40% protein content, it contains approximately 20% fat (oil) and 30% carbohydrates. **Analysis of Incorrect Options:** * **A (20%):** This is the typical protein content of most other pulses (e.g., Bengal gram, Green gram) and meat. Soybean is significantly more concentrated. * **C & D (60% & 80%):** These values are physiologically impossible for a raw agricultural seed. Such high concentrations are only found in processed supplements like **Soy Protein Isolate**, which is manufactured to contain >90% protein. **High-Yield NEET-PG Pearls:** 1. **Limiting Amino Acid:** Like most legumes, soybean is deficient in **Methionine** (sulfur-containing amino acid) but rich in **Lysine**. It is often used to "supplement" cereal proteins (which are rich in Methionine but deficient in Lysine). 2. **Biological Value:** It has the highest biological value among plant proteins, often compared to casein (milk protein). 3. **Antinutritional Factors:** Raw soybean contains **Trypsin inhibitors**, which interfere with protein digestion. These are heat-labile and destroyed by proper cooking. 4. **Isoflavones:** Soy contains Genistein and Daidzein (phytoestrogens), which are studied for their role in reducing menopausal symptoms and lowering LDL cholesterol.

Q: Which amino acid is deficient in pulses?

Methionine. **Explanation:** In nutritional biochemistry, proteins are classified as "complete" or "incomplete" based on their essential amino acid profile. Most plant-based proteins are incomplete as they lack one or more essential amino acids, known as the **limiting amino acid**. **1. Why Methionine is the correct answer:** Pulses (legumes) are rich in lysine but are characteristically deficient in **sulfur-containing amino acids**, primarily **Methionine** and Cysteine. This is why a diet based solely on pulses cannot meet the body's total protein requirements for growth and repair. **2. Analysis of Incorrect Options:** * **Tryptophan (A):** This is the limiting amino acid in **Maize (Corn)**. A deficiency of tryptophan leads to Pellagra because tryptophan is a precursor for Niacin (Vitamin B3) synthesis. * **Lysine (B):** This is the limiting amino acid in **Cereals** (wheat, rice, maize). Interestingly, pulses are an excellent source of lysine, which is why the "cereal-pulse combination" (e.g., rice and dal) provides a complete amino acid profile. * **Leucine (D):** This is found in high amounts in **Sorghum (Jowar)**. An excess of leucine can interfere with tryptophan metabolism, potentially precipitating Pellagra. **High-Yield Clinical Pearls for NEET-PG:** * **Mutual Supplementation:** Combining cereals (deficient in lysine, rich in methionine) with pulses (deficient in methionine, rich in lysine) creates a **Complementary Protein** effect. * **Limiting Amino Acid Summary:** * **Pulses:** Methionine * **Cereals:** Lysine * **Maize:** Tryptophan and Lysine * **Reference Protein:** Egg protein is considered the "standard" or "complete" protein (Biological Value = 100) against which others are compared.

Q: Selenium deficiency causes which of the following conditions?

Cardiomyopathy. **Explanation:** **Correct Answer: A. Cardiomyopathy** Selenium is an essential trace element that functions as a cofactor for the enzyme **Glutathione Peroxidase**, which protects cells from oxidative damage by neutralizing hydrogen peroxide. A deficiency in Selenium leads to increased oxidative stress, particularly in cardiac myocytes. This manifests clinically as **Keshan Disease**, an endemic juvenile cardiomyopathy characterized by cardiac enlargement and heart failure. It is also associated with **Kashin-Beck disease**, a type of osteoarthropathy. **Analysis of Incorrect Options:** * **B. Neuropathy:** While Vitamin B1 (Thiamine), B6 (Pyridoxine), and B12 (Cobalamin) deficiencies are classic causes of peripheral neuropathy, Selenium deficiency does not typically present with neurological deficits. * **C. Growth retardation:** This is primarily associated with **Zinc deficiency** (along with acrodermatitis enteropathica and hypogonadism) or severe protein-energy malnutrition (Kwashiorkor). * **D. Rhabdomyolysis:** This is a clinical syndrome of muscle breakdown often caused by trauma, extreme exertion, or statin use. While Selenium deficiency can cause generalized muscle weakness (myopathy), it is not a primary cause of acute rhabdomyolysis. **High-Yield Facts for NEET-PG:** * **Enzyme Link:** Selenium is a vital component of **Selenocysteine**, found in Glutathione Peroxidase and **Thioredoxin reductase**. * **Thyroid Metabolism:** Selenium is also a cofactor for **Type 1 deiodinase**, which converts T4 to the active T3. * **Toxicity (Selenosis):** Excess selenium intake leads to garlic breath, hair loss (alopecia), and brittle nails. * **Key Association:** Always link Selenium deficiency to **Keshan Disease** (Cardiomyopathy) and **Kashin-Beck Disease** (Chondrodystrophy).

Q: What is the best index for calculating the nutritional value of protein?

Net protein utilization. ### Explanation The nutritional value of a protein depends on two factors: its amino acid composition and its digestibility. **Why Net Protein Utilization (NPU) is the best index:** NPU is considered the most comprehensive index because it accounts for both the **quality** (amino acid profile) and the **digestibility** of the protein. It is calculated as the percentage of ingested nitrogen that is retained in the body. * **Formula:** $NPU = \text{Biological Value (BV)} \times \text{Digestibility Coefficient}$. By incorporating digestibility, NPU provides a more accurate reflection of how much protein is actually available for metabolic use compared to Biological Value alone. **Analysis of Incorrect Options:** * **A. Biological Value (BV):** This measures the percentage of *absorbed* nitrogen retained by the body. While it assesses protein quality, it ignores the fraction of protein lost during digestion (fecal loss). * **C. Protein Digestibility:** This only measures how much of the ingested protein is absorbed into the bloodstream. It does not account for the essential amino acid balance or how well the body utilizes the absorbed protein. * **D. Protein Efficiency Ratio (PER):** This is the gain in body weight per gram of protein ingested (usually measured in rats). It is flawed because it assumes all weight gain is muscle/protein and does not account for maintenance needs. **High-Yield Clinical Pearls for NEET-PG:** * **Reference Protein:** Egg protein (Albumin) is the gold standard with a BV and NPU of approximately 100. * **Limiting Amino Acids:** Pulses are deficient in Methionine; Cereals are deficient in Lysine. * **PDCAAS (Protein Digestibility Corrected Amino Acid Score):** Currently the internationally "preferred" method for evaluating protein quality in human nutrition, though NPU remains the best traditional biological index.

Q: Which of the following micronutrients plays a role in the regulation of protein binding to DNA?

Zinc. **Explanation:** The correct answer is **Zinc**. Zinc plays a critical structural and functional role in the regulation of gene expression through the formation of **Zinc Finger Motifs**. These are the most common DNA-binding motifs found in eukaryotic transcription factors (e.g., steroid hormone receptors). In these motifs, a zinc ion is coordinated by cysteine and histidine residues, stabilizing a "finger-like" protein fold that fits precisely into the major groove of the DNA helix, allowing the protein to regulate transcription. **Why other options are incorrect:** * **Copper:** Primarily acts as a redox cofactor for enzymes like Cytochrome c oxidase, Superoxide Dismutase (SOD), and Lysyl oxidase. It is not involved in direct DNA-binding structural motifs. * **Selenium:** Essential for the antioxidant enzyme **Glutathione Peroxidase** and the conversion of T4 to T3 (Deiodinase). It does not regulate protein-DNA binding. * **Nickel:** While a trace element, its biological role in humans is minimal and primarily related to urease in certain bacteria; it has no established role in human DNA regulation. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder causing zinc malabsorption, characterized by periorificial/acral dermatitis, alopecia, and diarrhea. * **Zinc & Wound Healing:** Zinc is a cofactor for **collagenase** (Matrix Metalloproteinases), making it vital for tissue repair. * **Dysgeusia:** Zinc deficiency is a classic cause of distorted sense of taste. * **DNA/RNA Polymerase:** Zinc is also a required cofactor for these enzymes, further emphasizing its role in nucleic acid metabolism.

Q: Metabolism of 100 grams of fat yields approximately how many kilocalories?

900. **Explanation:** The correct answer is **D (900)**. This is based on the physiological fuel values of macronutrients, which represent the amount of energy available to the body after digestion and absorption. 1. **Why 900 is correct:** Fat is the most energy-dense macronutrient. The standard physiological fuel value for fat is **9 kcal/gram**. Therefore, the metabolism of 100 grams of fat yields: * $100 \text{ g} \times 9 \text{ kcal/g} = \mathbf{900 \text{ kcal}}$. Fats provide more than double the energy of carbohydrates or proteins because they are more reduced (contain more carbon-hydrogen bonds), requiring more oxidation to produce $CO_2$ and $H_2O$. 2. **Why other options are incorrect:** * **Option B (400):** This represents the energy yield of 100 grams of **Carbohydrates** or **Proteins**. Both yield approximately **4 kcal/gram** ($100 \times 4 = 400$). * **Options A and C (200 and 600):** These values do not correspond to the standard metabolism of any single primary macronutrient in these quantities. **High-Yield Clinical Pearls for NEET-PG:** * **Respiratory Quotient (RQ):** Fat has an RQ of **0.7**, which is lower than carbohydrates (1.0) because fat requires more oxygen for its oxidation. * **Specific Dynamic Action (SDA):** Also known as the Thermic Effect of Food. Protein has the highest SDA (~30%), followed by carbohydrates (5–10%) and fats (0–3%). * **Energy Storage:** Fat is stored in anhydrous form in adipose tissue, making it the most efficient long-term energy reservoir in the human body. * **Alcohol:** Yields **7 kcal/gram**, placing its energy density between carbohydrates and fats.

Q: Rice is deficient in which essential amino acid?

Threonine. **Explanation:** In nutritional biochemistry, cereals and pulses are characterized by their "limiting amino acids"—the essential amino acids present in the shortest supply relative to human requirements. **Why Threonine is correct:** While most medical textbooks traditionally emphasize **Lysine** as the primary limiting amino acid in all cereals (including rice, wheat, and maize), **Threonine** is recognized as the **second limiting amino acid** in rice. In many competitive exams like NEET-PG, when Lysine is not provided in the options, Threonine is the established correct answer for rice deficiency. **Analysis of Incorrect Options:** * **Serine:** This is a non-essential amino acid synthesized from 3-phosphoglycerate; it is not a limiting factor in dietary proteins. * **Methionine & Cysteine:** These are sulfur-containing amino acids. While they are the limiting amino acids in **pulses/legumes**, they are generally present in adequate amounts in cereals like rice. **High-Yield Clinical Pearls for NEET-PG:** * **Cereals (Rice/Wheat):** Deficient in Lysine (1st) and Threonine (2nd). * **Pulses (Legumes):** Deficient in Methionine and Cysteine. * **Maize (Corn):** Deficient in Lysine and **Tryptophan**. (Note: Tryptophan deficiency in maize leads to Pellagra because it is a precursor for Niacin/Vitamin B3). * **Mutual Supplementation:** This is the nutritional strategy of combining cereals and pulses (e.g., Rice and Dal) to provide a complete amino acid profile, as the deficiency of one is compensated by the other.

Q: Which of the following trace elements has a Vitamin E sparing effect?

Selenium. **Explanation:** The correct answer is **Selenium (D)**. This relationship is a classic example of nutrient synergy in the body's antioxidant defense system. **Why Selenium is correct:** Selenium and Vitamin E function together to protect cells from oxidative damage caused by free radicals. * **Vitamin E (Tocopherol)** is a lipid-soluble antioxidant that acts within cell membranes to prevent the peroxidation of polyunsaturated fatty acids (PUFAs) by neutralizing free radicals. * **Selenium** is an essential component of the enzyme **Glutathione Peroxidase (GPx)**. This enzyme converts harmful hydrogen peroxide and lipid hydroperoxides into harmless water and alcohols. By reducing the overall load of peroxides in the cell, Selenium decreases the "workload" of Vitamin E. Consequently, adequate Selenium levels reduce the requirement for Vitamin E, a phenomenon known as the **"Vitamin E sparing effect."** **Why other options are incorrect:** * **Copper (A) and Iron (B):** Both are transition metals that can actually promote oxidative stress via the **Fenton reaction**, which generates highly reactive hydroxyl radicals. They do not spare Vitamin E; in excess, they may increase the demand for antioxidants. * **Magnesium (C):** While essential for over 300 enzymatic reactions (mostly involving ATP), Magnesium does not have a direct synergistic antioxidant relationship with Vitamin E. **High-Yield Clinical Pearls for NEET-PG:** * **Glutathione Peroxidase:** Contains Selenium in the form of **Selenocysteine** (the 21st amino acid). * **Keshan Disease:** A cardiomyopathy caused by Selenium deficiency. * **Synergy:** Both Vitamin E and Selenium are required to prevent conditions like hepatic necrosis and muscular dystrophy in animal models. * **Antioxidant Trio:** Remember that Vitamin E (membranes), Vitamin C (cytosol), and Selenium (enzyme cofactor) form the primary defense against lipid peroxidation.

Question 1

Soya bean contains protein to the tune of:

Accepted Answer

40%

Answer

20%

Answer

60%

Answer

80%

Question 2

Which amino acid is deficient in pulses?

Accepted Answer

Methionine

Answer

Tryptophan

Answer

Lysine

Answer

Leucine

Question 3

Selenium deficiency causes which of the following conditions?

Accepted Answer

Cardiomyopathy

Answer

Neuropathy

Answer

Growth retardation

Answer

Rhabdomyolysis

Question 4

What is the best index for calculating the nutritional value of protein?

Accepted Answer

Net protein utilization

Answer

Biological Value

Answer

Protein digestibility

Answer

Protein efficiency ratio

Question 5

Which of the following micronutrients plays a role in the regulation of protein binding to DNA?

Accepted Answer

Zinc

Answer

Copper

Answer

Selenium

Answer

Nickel

Question 6

A 52-year-old man presents with chronic diarrhea of several years' duration, now complicated by difficulty with night driving due to vision impairment. He is found to have microcytic anemia, a slight elevation in INR, low ionized calcium, and low albumin levels. What is the most likely underlying cause of his diarrhea?

Accepted Answer

Malabsorption

Answer

Osmotic diarrhea

Answer

Secretory diarrhea

Answer

Inflammatory bowel disease

Question 7

Metabolism of 100 grams of fat yields approximately how many kilocalories?

Accepted Answer

900

Answer

200

Answer

400

Answer

600

Question 8

Rice is deficient in which essential amino acid?

Accepted Answer

Threonine

Answer

Serine

Answer

Methionine

Answer

Cysteine

Question 9

Which of the following trace elements has a Vitamin E sparing effect?

Accepted Answer

Selenium

Answer

Copper

Answer

Iron

Answer

Magnesium

Question 10

Which of the following correlates well to overcoming of limiting amino acids in the diet?

Accepted Answer

Complementary action of proteins

Answer

Rancidity

Answer

Tertiary structure of proteins

Answer

Biological value

Nutrition and Metabolism — MCQs

Nutrition and Metabolism — MCQs

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