Nutrition and Metabolism Practice Questions

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

8 gm. **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.

Q: Which of the following statements is FALSE regarding Keshan's disease?

It is caused by selenium excess.. **Explanation:** **1. Why Option A is the Correct Answer (The False Statement):** Keshan’s disease is caused by a **deficiency** of Selenium, not an excess. Selenium is a vital trace element that serves as a cofactor for the enzyme **Glutathione Peroxidase**, which protects cells from oxidative damage. In the absence of selenium, oxidative stress leads to myocardial necrosis. Selenium excess, on the other hand, leads to **Selenosis**, characterized by garlic breath, hair loss, and nail changes. **2. Analysis of Other Options:** * **Option B:** It is indeed an **endemic cardiomyopathy** first identified in the Keshan province of **China**, where the soil is severely depleted of selenium. * **Option C:** It is associated with an increased intake of **maize** (corn) grown in selenium-poor soil. Maize-based diets often lack diverse micronutrients, exacerbating the deficiency in these specific geographic regions. * **Option D:** The disease predominantly affects vulnerable populations, specifically **children and women of childbearing age**, likely due to higher physiological demands for trace elements. **3. High-Yield Clinical Pearls for NEET-PG:** * **Enzyme Link:** Selenium is essential for **Glutathione Peroxidase** (antioxidant) and **5'-deiodinase** (converts T4 to T3). * **Kashin-Beck Disease:** Another selenium deficiency disorder characterized by osteoarthropathy (cartilage degeneration). * **Viral Link:** Co-infection with the **Coxsackievirus B** is often implicated as a trigger that converts subclinical selenium deficiency into overt Keshan’s disease. * **Antidote:** Sodium selenite supplementation is used for prevention in endemic areas.

Q: What is the normal nitrogen content in 200 gm of protein?

32 g. **Explanation:** The correct answer is **32 g**. **1. Underlying Concept:** In biochemistry and nutrition, it is a standard physiological principle that proteins contain an average of **16% nitrogen** by weight. This relationship is fundamental for calculating the Nitrogen Balance of a patient. To find the nitrogen content, we use the following formula: * **Nitrogen (g) = Protein (g) × 0.16** (or Protein ÷ 6.25) * Calculation: 200 g (Protein) × 0.16 = **32 g of Nitrogen**. **2. Analysis of Incorrect Options:** * **Option A (8 g):** This represents only 4% nitrogen content, which is incorrect for standard dietary proteins. * **Option B (16 g):** This is the nitrogen content of 100 g of protein (100 × 0.16). It is a common distractor for students who confuse the percentage (16%) with the absolute mass. * **Option D (64 g):** This represents 32% nitrogen content, which is double the physiological average. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **The 6.25 Factor:** The inverse of 16% (100/16) is **6.25**. In clinical practice, to estimate protein intake from urinary urea nitrogen, we multiply the nitrogen value by 6.25. * **Nitrogen Balance Formula:** $B = I - (U + F + S)$, where $I$ is nitrogen intake, $U$ is urinary loss, $F$ is fecal loss, and $S$ is skin loss. * **Positive Nitrogen Balance:** Seen during growth, pregnancy, and convalescence (recovery from illness). * **Negative Nitrogen Balance:** Seen in starvation, severe burns, high-grade fever, and uncontrolled diabetes mellitus. * **Kjeldahl Method:** This is the classic laboratory technique used to estimate the nitrogen content of biological samples.

Q: Which of the following minerals possesses antioxidant properties?

Zinc. ### Explanation **Correct Option: C (Zinc)** Zinc is a vital trace element that functions as an essential cofactor for over 300 enzymes. Its antioxidant properties are primarily attributed to its role as a structural component of **Copper-Zinc Superoxide Dismutase (Cu-Zn SOD)**, an enzyme that neutralizes superoxide radicals into hydrogen peroxide. Furthermore, Zinc induces the synthesis of **metallothioneins**, which are cysteine-rich proteins that scavenge hydroxyl radicals. It also protects protein sulfhydryl groups from oxidation and competes with pro-oxidant metals like iron and copper to prevent the formation of highly reactive free radicals via the Fenton reaction. **Why other options are incorrect:** * **A. Calcium:** Primarily functions in bone mineralization, muscle contraction, nerve impulse transmission, and as a secondary messenger (e.g., in the Calmodulin pathway). It does not possess intrinsic antioxidant activity. * **B. Magnesium:** Acts as a cofactor for enzymes involving ATP (kinases). While it is essential for metabolic stability, it is not classified as a primary antioxidant mineral. * **D. Iron:** Iron is actually a **pro-oxidant**. In its free form, it catalyzes the **Fenton reaction**, leading to the production of the highly damaging hydroxyl radical ($\cdot OH$). **High-Yield Clinical Pearls for NEET-PG:** * **Key Antioxidant Minerals:** Zinc, Selenium (cofactor for Glutathione Peroxidase), Copper, and Manganese. * **Zinc Deficiency:** Characterized by **Acrodermatitis enteropathica**, poor wound healing, hypogeusia (decreased taste), and growth retardation. * **Superoxide Dismutase (SOD) Isoforms:** * Cytosolic: Cu-Zn SOD * Mitochondrial: Mn-SOD (Manganese)

Q: How is protein best assessed?

Per gram of calories given. **Explanation:** The assessment of protein utilization and adequacy is intrinsically linked to total energy intake. This concept is known as the **Protein-Sparing Action of Carbohydrates**. **Why the correct answer is right:** Protein is best assessed **per gram of calories given** because the body’s ability to utilize protein for tissue synthesis (anabolism) depends on meeting total caloric requirements. If energy intake is insufficient, the body oxidizes dietary protein to produce energy instead of using it for growth and repair. Therefore, the "Protein:Calorie ratio" (typically expressed as grams of protein per 100 kcal) is the most accurate clinical measure to ensure that protein is being used efficiently for its intended structural purposes. **Analysis of Incorrect Options:** * **Protein energy ratio (A):** While related, this is a general term. The specific measurement of protein relative to the total caloric density (Option C) is the standard for nutritional assessment. * **BUN (Blood Urea Nitrogen) (B):** This is a marker of protein catabolism and renal function, not a primary tool for assessing the adequacy of dietary protein intake. * **Amino acid score (D):** This measures the **quality** of a specific protein (based on its limiting amino acid) relative to a reference protein, but it does not assess the overall nutritional status or the adequacy of protein in a patient's total diet. **Clinical Pearls for NEET-PG:** * **Protein-Sparing Action:** Carbohydrates and fats "spare" proteins from being used as fuel. * **Nitrogen Balance:** The clinical gold standard for assessing net protein change in the body (Positive in growth/pregnancy; Negative in trauma/starvation). * **Reference Protein:** Egg protein (Biological Value = 100) is the standard against which others are compared. * **Limiting Amino Acids:** Pulses are deficient in Methionine; Cereals are deficient in Lysine.

Q: Which of the following are caused by zinc deficiency?

Reduced growth and gonadal atrophy. **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 protein synthesis, cell division, and nucleic acid metabolism, which are vital for growth and reproductive health. **Why Option D is correct:** * **Reduced Growth:** Zinc is indispensable for the synthesis of growth-related proteins and DNA. Deficiency leads to growth retardation and skeletal abnormalities. * **Gonadal Atrophy:** Zinc is essential for the maturation of the reproductive system and spermatogenesis. Deficiency results in hypogonadism, delayed puberty, and gonadal atrophy. **Analysis of Incorrect Options:** * **Option A (Mental Retardation):** While zinc deficiency can cause irritability or emotional lability, "Mental Retardation" is more characteristically associated with **Iodine deficiency** (Cretinism) or metabolic disorders like Phenylketonuria. * **Option B (Gonadal Atrophy):** While correct, it is an incomplete answer compared to Option D. * **Option C (Cardiomyopathy):** Cardiomyopathy is a classic hallmark of **Selenium deficiency** (Keshan disease), not zinc deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder causing impaired zinc absorption, characterized by the triad of **alopecia, diarrhea, and vesiculobullous dermatitis** (periorificial and acral). * **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:** A common symptom where the patient experiences a distorted sense of taste.

Q: Which of the following grains can be used safely in patients with celiac sprue?

Rice. **Explanation:** Celiac sprue (Gluten-sensitive enteropathy) is an autoimmune-mediated inflammatory condition of the small intestine triggered by the ingestion of **prolamins** (gluten proteins) in genetically susceptible individuals (HLA-DQ2/DQ8). The primary management is a lifelong strict gluten-free diet. **Why Rice is the Correct Answer:** Rice (along with maize/corn) is naturally gluten-free. It does not contain the specific toxic peptide sequences (like the 33-mer α-gliadin) that trigger the T-cell mediated immune response and subsequent villous atrophy seen in celiac patients. Therefore, rice is a safe carbohydrate source. **Why Other Options are Incorrect:** The mnemonic **"BROW"** (Barley, Rye, Oats, Wheat) is commonly used to remember grains containing gluten that should be avoided: * **Wheat:** Contains **Gliadin**, the most potent trigger for celiac disease. * **Rye:** Contains **Secalin**, which is toxic to these patients. * **Barley:** Contains **Hordein**, which also triggers the inflammatory cascade. *(Note: Pure oats are often tolerated, but are frequently avoided due to cross-contamination during processing).* **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Small intestinal biopsy showing **villous atrophy**, crypt hyperplasia, and increased intraepithelial lymphocytes. * **Serology:** Anti-tissue Transglutaminase (**anti-tTG**) IgA is the screening drug of choice; Anti-endomysial antibody (EMA) is highly specific. * **Dermatologic Association:** **Dermatitis herpetiformis** (itchy, vesicular skin lesions) is the pathognomonic cutaneous manifestation. * **Complications:** Increased risk of **Enteropathy-associated T-cell lymphoma (EATL)** if the diet is not strictly followed.

Q: Selenium deficiency causes which of the following conditions?

Keshan disease. ### Explanation **Correct Answer: C. Keshan disease** Selenium is an essential trace element that functions primarily as a cofactor for the enzyme **Glutathione Peroxidase**, which protects cells against oxidative damage. * **Keshan disease** is a juvenile cardiomyopathy associated with selenium deficiency. It was first identified in the Keshan province of China, where the soil is selenium-poor. The deficiency leads to myocardial necrosis and heart failure, often triggered by a secondary viral infection (e.g., Coxsackievirus). **Analysis of Incorrect Options:** * **A. Menke’s disease:** This is an X-linked recessive disorder of **Copper absorption** and transport (ATP7A mutation). It is characterized by "kinky" or steely hair, growth failure, and neurological degeneration. * **B. Wilson’s disease:** This is an autosomal recessive disorder of **Copper excretion** (ATP7B mutation). It leads to toxic copper accumulation in the liver (cirrhosis), brain (basal ganglia), and eyes (Kayser-Fleischer rings). * **D. Kashin-Beck disease:** While also associated with selenium deficiency, it is primarily an **osteoarthropathy** (degeneration of joint cartilage) rather than a cardiomyopathy. In the context of NEET-PG, Keshan disease is the classic, most frequently tested association for selenium deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Enzyme Link:** Selenium is a component of **Selenocysteine**, found in Glutathione Peroxidase, Thioredoxin reductase, and Deiodinase (converts T4 to T3). * **Toxicity:** Excess selenium (Selenosis) causes garlic breath, hair loss (alopecia), and nail dystrophy. * **Antioxidant Trio:** Selenium works synergistically with **Vitamin E** to prevent lipid peroxidation.

Q: Zinc is not required for:

Coagulation pathway. **Explanation:** Zinc is an essential trace element that acts as a structural component or cofactor for over 300 enzymes, including DNA polymerases, RNA polymerases, and Zinc-finger proteins (transcription factors). **1. Why Coagulation Pathway is the correct answer:** The coagulation cascade is primarily dependent on **Calcium (Factor IV)** and Vitamin K-dependent γ-carboxylation. Zinc does not play a direct catalytic or structural role in the activation of clotting factors or the formation of a fibrin clot. Therefore, it is not required for the coagulation pathway. **2. Why the other options are incorrect:** * **DNA Synthesis:** Zinc is a vital cofactor for **DNA polymerase** and **Thymidine kinase**. It is essential for cell division and the maintenance of genetic stability. * **Embryonic Development:** Due to its role in DNA synthesis and gene expression (Zinc-finger motifs), Zinc is critical for rapid cell proliferation during embryogenesis. Deficiency leads to congenital malformations and growth retardation. * **Spermatogenesis:** Zinc is found in high concentrations in the testes and prostate. It is required for the maturation of spermatozoa, maintenance of the germinal epithelium, and sperm motility. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder of zinc absorption characterized by periorificial/acral dermatitis, alopecia, and diarrhea. * **Wound Healing:** Zinc is essential for collagen synthesis and fibroblast proliferation; deficiency leads to poor wound healing. * **Gustin:** A zinc-containing protein in saliva required for the development of taste buds (deficiency causes **hypogeusia**). * **Insulin Storage:** Zinc is required for the crystallization and storage of insulin in the β-cells of the pancreas.

Q: Manganese deficiency leads to which of the following conditions?

Impaired skeletal growth. **Explanation:** **Manganese (Mn)** is an essential trace element that acts as a cofactor for several critical enzymes, including **glycosyltransferases**, pyruvate carboxylase, and superoxide dismutase (Mn-SOD). 1. **Why "Impaired skeletal growth" is correct:** Glycosyltransferases are essential for the synthesis of **proteoglycans and chondroitin sulfate**, which are the structural building blocks of bone and cartilage matrix. Manganese deficiency leads to defective cartilage formation, resulting in skeletal abnormalities, retarded bone growth, and conditions like "perosis" (slipped tendon) in animals. In humans, it manifests as impaired skeletal development and reduced bone mineral density. 2. **Why the other options are incorrect:** * **Parkinsonism:** While Manganese *toxicity* (Manganism) causes a Parkinson-like syndrome due to accumulation in the basal ganglia, its *deficiency* does not. * **Impaired glucose tolerance:** Although Manganese is a cofactor for pyruvate carboxylase (gluconeogenesis), impaired glucose tolerance is more classically associated with **Chromium deficiency** (Glucose Tolerance Factor). * **Anaemia:** This is typically associated with deficiencies in **Iron, Copper** (due to ceruloplasmin/ferroxidase activity), Vitamin B12, or Folate. **High-Yield Clinical Pearls for NEET-PG:** * **Mn-SOD:** Manganese is the specific cofactor for the mitochondrial version of Superoxide Dismutase (SOD), which protects mitochondria from oxidative stress. * **Toxicity:** Chronic inhalation of Mn (seen in miners) leads to **"Psychosis" followed by Parkinsonian symptoms** (refractory to L-Dopa). * **MRI Sign:** In Mn toxicity or chronic liver disease, Mn deposits in the **globus pallidus**, showing hyperintensity on T1-weighted MRI images.

Question 1

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

Accepted Answer

8 gm

Answer

5 gm

Answer

10 gm

Answer

16 gm

Question 2

Which of the following statements is FALSE regarding Keshan's disease?

Accepted Answer

It is caused by selenium excess.

Answer

It is an endemic cardiomyopathy found in China.

Answer

It is associated with an increased intake of maize.

Answer

It is most commonly observed in children and women of childbearing age.

Question 3

What is the normal nitrogen content in 200 gm of protein?

Accepted Answer

32 g

Answer

8 g

Answer

16 g

Answer

64 g

Question 4

Which of the following minerals possesses antioxidant properties?

Accepted Answer

Zinc

Answer

Calcium

Answer

Magnesium

Answer

Iron

Question 5

How is protein best assessed?

Accepted Answer

Per gram of calories given

Answer

Protein energy ratio

Answer

BUN

Answer

Amino acid score

Question 6

Which of the following are caused by zinc deficiency?

Accepted Answer

Reduced growth and gonadal atrophy

Answer

Mental retardation

Answer

Gonadal atrophy

Answer

Cardiomyopathy and reduced growth

Question 7

Which of the following grains can be used safely in patients with celiac sprue?

Accepted Answer

Rice

Answer

Wheat

Answer

Rye

Answer

Barley

Question 8

Selenium deficiency causes which of the following conditions?

Accepted Answer

Keshan disease

Answer

Menke's disease

Answer

Wilson's disease

Answer

Kashinbeck disease

Question 9

Zinc is not required for:

Accepted Answer

Coagulation pathway

Answer

Embryonic development

Answer

DNA synthesis

Answer

Spermatogenesis

Question 10

Manganese deficiency leads to which of the following conditions?

Accepted Answer

Impaired skeletal growth

Answer

Parkinsonism

Answer

Impaired glucose tolerance

Answer

Anaemia

Nutrition and Metabolism — MCQs

Nutrition and Metabolism — MCQs

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