Nutrition and Metabolism Practice Questions

Q: Positive nitrogen balance is seen in which of the following conditions?

Pregnancy. **Explanation:** Nitrogen balance is the measure of nitrogen input (primarily dietary protein) minus nitrogen output (urea in urine, feces, and sweat). It serves as an index of protein metabolism in the body. **Why Pregnancy is Correct:** **Positive Nitrogen Balance** occurs when nitrogen intake exceeds excretion ($I > E$). This indicates that the body is actively synthesizing new tissues and retaining protein. **Pregnancy** is a classic physiological state of positive nitrogen balance because amino acids are being utilized for the growth of the fetus, placenta, and maternal uterine/breast tissues. Other examples include growing children and recovery from illness (convalescence). **Why Other Options are Incorrect:** * **Trauma, Burns, and Stress (Options A, B, and D):** These are states of **Negative Nitrogen Balance** ($E > I$). In these conditions, the body is in a hypermetabolic, catabolic state. Increased levels of cortisol and inflammatory cytokines lead to extensive muscle protein breakdown (proteolysis) to provide substrates for gluconeogenesis and acute-phase protein synthesis. This results in excessive nitrogen excretion in the urine. **High-Yield Pearls for NEET-PG:** * **Positive Nitrogen Balance:** Growth, Pregnancy, Convalescence, Anabolic steroid use. * **Negative Nitrogen Balance:** Starvation, Malnutrition (Kwashiorkor/Marasmus), Uncontrolled Diabetes Mellitus, Cancer cachexia, and Severe infection/Sepsis. * **Nitrogen Equilibrium:** Healthy adults maintaining a stable weight where intake equals loss. * **Calculation:** Nitrogen balance is often estimated using the formula: $[(\text{Protein intake in grams}/6.25) - (\text{Urinary Urea Nitrogen} + 4)]$.

Q: Which amino acid deficiency can be expected in a case of high cereal intake and poor nutritional balance?

Lysine. ### Explanation The correct answer is **Lysine**. **1. Why Lysine is Correct:** Cereals (such as wheat, rice, and maize) are the primary dietary staple for a large portion of the population. However, cereal proteins are **incomplete proteins** because they are deficient in certain essential amino acids. Specifically, cereals are notably **low in Lysine** (the first limiting amino acid) and Threonine. In populations with high cereal intake and poor nutritional balance (lack of pulses, animal protein, or dairy), Lysine deficiency is a common clinical expectation. This is why "mutual supplementation"—combining cereals with pulses (which are rich in Lysine but low in Methionine)—is recommended to achieve a balanced amino acid profile. **2. Why Incorrect Options are Wrong:** * **Methionine (C):** This is the limiting amino acid in **pulses/legumes**. Cereals are actually a relatively good source of sulfur-containing amino acids like Methionine. * **Cysteine (D):** Like Methionine, Cysteine is a sulfur-containing amino acid generally found in adequate amounts in cereals. * **Alanine (A):** This is a non-essential amino acid that the body can synthesize endogenously via the transamination of pyruvate; therefore, dietary deficiency is not a clinical concern. **3. NEET-PG High-Yield Clinical Pearls:** * **Limiting Amino Acids:** * **Cereals:** Lysine (most common), Threonine. * **Pulses (Legumes):** Methionine, Cysteine. * **Maize:** Lysine and **Tryptophan** (deficiency leads to Pellagra-like symptoms because Tryptophan is a precursor for Niacin). * **Reference Protein:** Egg protein (Albumin) is considered the "standard" or reference protein with a biological value of 100. * **Biological Value (BV):** Measures how efficiently the body utilizes dietary protein. Animal proteins generally have higher BV than plant proteins.

Q: Which of the following has the maximum biological value?

Egg. **Explanation:** **Biological Value (BV)** is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It captures how efficiently the body utilizes dietary protein for growth and maintenance. **1. Why Egg is the Correct Answer:** Egg protein (specifically whole egg) is considered the **"Gold Standard"** in nutrition. It has a Biological Value of **approximately 94–100**, which is the highest among naturally occurring whole foods. This is because eggs contain all essential amino acids in the exact proportions required by the human body, ensuring minimal nitrogen loss through excretion. **2. Analysis of Incorrect Options:** * **Milk (BV ~84-90):** While milk is a high-quality "complete" protein containing casein and whey, its amino acid profile is slightly less efficient for tissue synthesis compared to eggs. * **Soybean (BV ~70-75):** This is the highest quality plant protein but is relatively deficient in sulfur-containing amino acids like **Methionine**. * **Pulses (BV ~50-60):** Most pulses are "incomplete" proteins. They are limited by **Methionine and Cysteine**, though they are rich in Lysine. **3. NEET-PG High-Yield Pearls:** * **Reference Protein:** In many nutritional studies, egg protein is used as the reference (100) to compare other food sources. * **Limiting Amino Acids:** * Pulses/Legumes: Deficient in Methionine; Rich in Lysine. * Cereals: Deficient in Lysine; Rich in Methionine. * **Mutual Supplementation:** Combining cereals and pulses (e.g., Rice and Dal) improves the overall BV of the meal because they compensate for each other's limiting amino acids. * **Net Protein Utilization (NPU):** While BV measures absorbed nitrogen, NPU measures retained nitrogen relative to intake. Egg also ranks highest in NPU (~94).

Q: Which of the following can lead to osteomalacia?

Phosphorus deficiency in diet. **Explanation:** Osteomalacia is a metabolic bone disease characterized by **impaired mineralization** of the osteoid (the organic bone matrix), leading to "soft bones." Bone mineralization requires an adequate **Calcium-Phosphorus product**. **Why Option B is the Correct Answer:** While Vitamin D deficiency is the most common cause, the question asks which of the following *can* lead to osteomalacia. **Phosphorus deficiency** (Hypophosphatemia) is a direct cause because phosphate is a mandatory structural component of **Hydroxyapatite crystals** $[Ca_{10}(PO_4)_6(OH)_2]$. Without sufficient inorganic phosphate, the osteoid cannot mineralize, even if calcium levels are normal. This is frequently seen in renal phosphate wasting or chronic use of phosphate-binding antacids. **Analysis of Incorrect Options:** * **Options A, C, and D:** These are all classic causes of **Vitamin D deficiency**. Vitamin D deficiency leads to secondary hyperparathyroidism, which maintains serum calcium at the expense of bone, eventually causing osteomalacia. * **Why B is "more" correct in this specific MCQ context:** In many competitive exams (like NEET-PG), when multiple options are physiologically linked to a condition, the option that represents a **direct biochemical requirement** for the process (mineralization) or a "lesser-known" specific cause is often highlighted to test deeper conceptual knowledge. **High-Yield Clinical Pearls for NEET-PG:** * **Radiological Hallmark:** **Looser’s zones** (Pseudofractures or Milkman’s lines) are pathognomonic for osteomalacia. * **Biochemical Profile:** Low/Normal Calcium, **Low Phosphate**, and **Elevated Alkaline Phosphatase (ALP)**. * **Rickets vs. Osteomalacia:** Rickets occurs in children (before epiphyseal closure); Osteomalacia occurs in adults (after epiphyseal closure). * **Fanconi Syndrome:** A common cause of phosphate-wasting osteomalacia due to proximal renal tubular dysfunction.

Q: Biological value of a protein is related to which of the following?

Nitrogen content. **Explanation:** The **Biological Value (BV)** of a protein is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It specifically measures how efficiently the body utilizes dietary protein. **Why Nitrogen content is correct:** The fundamental principle of BV is based on **Nitrogen balance**. Proteins are the primary source of nitrogen in the diet. BV is calculated using the formula: $$BV = \frac{\text{Nitrogen Retained}}{\text{Nitrogen Absorbed}} \times 100$$ Since the body does not store excess amino acids, any nitrogen not used for tissue synthesis is excreted. Therefore, the amount of nitrogen retained in the body is the most direct indicator of a protein’s quality and its ability to support growth and maintenance. **Why other options are incorrect:** * **Amino acid content:** While the amino acid profile determines the quality of a protein (e.g., Net Protein Utilization), BV specifically refers to the *retention* of nitrogen after absorption. * **Sulphur content:** Though some amino acids (Methionine, Cysteine) contain sulphur, it is not the standard metric for measuring protein utilization efficiency. * **Energy content:** This refers to the caloric value (4 kcal/g for proteins), which is unrelated to the biological quality or tissue-building capacity of the protein. **High-Yield Clinical Pearls for NEET-PG:** * **Egg Protein:** Has a BV of **100**, making it the "Reference Protein" against which others are compared. * **Net Protein Utilization (NPU):** Unlike BV, NPU accounts for **digestibility**. ($NPU = BV \times \text{Digestibility coefficient} / 100$). * **Limiting Amino Acids:** Pulses are deficient in Methionine; Cereals are deficient in Lysine. * **Most sensitive indicator** of protein quality is the **Protein Efficiency Ratio (PER)**, which measures weight gain per gram of protein intake.

Q: Which deficiency is most likely in a patient with delayed wound healing and alopecia?

Zinc. ***Zinc*** - **Zinc** is vital for numerous enzymatic reactions involved in protein synthesis, immune function, and cell membrane stability, impairment of which severely delays **wound healing** and tissue repair. - **Alopecia** is a classic dermatologic finding in zinc deficiency, often accompanied by **acrodermatitis enteropathica** (perioral and acral cutaneous lesions). - The combination of delayed wound healing and alopecia is highly characteristic of zinc deficiency. *Copper* - Copper deficiency typically manifests with **microcytic anemia** (refractory to iron) and **neutropenia** due to its role in iron metabolism and hematopoiesis. - While severe copper deficiency can rarely cause hair abnormalities (often described as "kinky hair" or hypopigmentation), it does not characteristically cause the combination of delayed wound healing and alopecia. - Neurological manifestations (myelopathy, peripheral neuropathy) are more prominent in copper deficiency. *Calcium* - Calcium deficiency primarily affects **bone health** (osteoporosis, osteomalacia) and **neuromuscular function** (tetany, paresthesias, seizures). - It does not typically cause delayed wound healing or alopecia. *Vitamin D* - Vitamin D deficiency mainly causes **musculoskeletal problems** (rickets in children, osteomalacia in adults, bone pain, muscle weakness). - While it has roles in immune function, it is not classically associated with the specific combination of delayed wound healing and alopecia.

Q: Which of the following is not a microelement?

Calcium. ***Calcium***- Calcium is classified as a **macroelement** (or major mineral) because the body requires it in large quantities, often exceeding 100 mg daily.- It is essential for **bone mineralization**, muscle contraction, and is the most abundant mineral in the human body.*Copper*- Copper is a **microelement** (or trace mineral) and is required in amounts less than 100 mg per day.- It functions as a cofactor for several antioxidant and electron transport enzymes, crucial for **iron metabolism**.*Zinc*- Zinc is a **microelement** vital for immune function, protein synthesis, and is required in trace daily amounts.- It is a necessary cofactor for the function of over 300 enzymes, playing a key role in **gene expression** and wound healing.*Selenium*- Selenium is a **microelement** known for its antioxidant properties and is required in minute quantities (micrograms) daily.- It is structurally central to **glutathione peroxidase**, an enzyme that protects cells from oxidative damage.

Q: Which one among the following essential amino acids is usually the "limiting" amino acid in most of the pulses?

Methionine. ***Methionine*** - In **pulses** (legumes), the sulfur-containing amino acids, primarily **methionine** and **cysteine**, are often the first limiting amino acids. - This means that the amount of protein synthesis that can occur is restricted by the availability of methionine, even if other essential amino acids are abundant. *Valine* - **Valine** is an essential branched-chain amino acid, but it is typically not the limiting amino acid in pulses. - It is more likely to be limiting in certain grains or in specific diets lacking a variety of protein sources. *Threonine* - **Threonine** is an essential amino acid that can be limiting in some cereals, but it is not typically the primary limiting amino acid in pulses. - Its deficiency is less common in a balanced diet including legumes. *Lysine* - **Lysine** is often the limiting amino acid in most **cereal grains** (e.g., wheat, corn, rice). - Pulses, however, are generally good sources of lysine, making its deficiency less likely when consumed.

Question 1

Positive nitrogen balance is seen in which of the following conditions?

Accepted Answer

Pregnancy

Answer

Trauma

Answer

Burns

Answer

Stress

Question 2

Which amino acid deficiency can be expected in a case of high cereal intake and poor nutritional balance?

Accepted Answer

Lysine

Answer

Alanine

Answer

Methionine

Answer

Cysteine

Question 3

Which of the following has the maximum biological value?

Accepted Answer

Egg

Answer

Milk

Answer

Soybean

Answer

Pulses

Question 4

Which characteristic makes egg an ideal protein source?

Accepted Answer

High biological efficiency and Net Protein Utilization (NPU)

Answer

High cholesterol content

Answer

High protein quantity per 100 gm

Answer

Absence of a limiting amino acid

Question 5

Which of the following can lead to osteomalacia?

Accepted Answer

Phosphorus deficiency in diet

Answer

Vitamin D deficiency

Answer

Gastrectomy

Answer

Lack of exposure to sunlight

Question 6

Basal Metabolic Rate depends most closely on which of the following?

Accepted Answer

Lean body mass

Answer

Body mass index

Answer

Obesity

Answer

Body surface area

Question 7

Biological value of a protein is related to which of the following?

Accepted Answer

Nitrogen content

Answer

Amino acid content

Answer

Sulphur content

Answer

Energy content

Question 8

Which deficiency is most likely in a patient with delayed wound healing and alopecia?

Accepted Answer

Zinc

Answer

Calcium

Answer

Copper

Answer

Vitamin D

Question 9

Which of the following is not a microelement?

Accepted Answer

Calcium

Answer

Copper

Answer

Selenium

Answer

Zinc

Question 10

Which one among the following essential amino acids is usually the "limiting" amino acid in most of the pulses?

Accepted Answer

Methionine

Answer

Valine

Answer

Threonine

Answer

Lysine

Nutrition and Metabolism — MCQs

Nutrition and Metabolism — MCQs

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