Nutrition and Metabolism Practice Questions

Q: What is the predominant type of whey protein in cow milk?

Lactoglobulin. **Explanation:** Milk proteins are broadly classified into two categories: **Casein** (80%) and **Whey** (20%). Whey protein is the liquid byproduct of cheese production and contains several globular proteins. **1. Why Lactoglobulin is Correct:** The predominant whey protein in cow’s milk is **Beta-lactoglobulin** (approximately 50–55% of total whey). It is a major source of essential and branched-chain amino acids (BCAAs). Notably, Beta-lactoglobulin is absent in human breast milk, which makes it a common allergen in infants (Cow’s Milk Protein Allergy). **2. Analysis of Incorrect Options:** * **Lactalbumin (Alpha-lactalbumin):** This is the second most abundant whey protein in cow’s milk (approx. 20–25%). However, it is the **predominant** whey protein in **human milk**. It plays a crucial role in lactose synthesis. * **Lactoferrin:** This is a minor whey protein known for its iron-binding properties and antimicrobial effects. While highly significant in colostrum and human milk for infant immunity, its concentration in cow’s milk is very low. **3. High-Yield Clinical Pearls for NEET-PG:** * **Casein vs. Whey Ratio:** Cow’s milk is Casein-dominant (80:20), whereas Human milk is Whey-dominant (40:60). * **The "Absent" Protein:** Beta-lactoglobulin is present in cow's milk but **absent in human milk**. This is a frequent MCQ point regarding infant formula sensitivity. * **Lactose Synthesis:** Alpha-lactalbumin acts as a regulatory subunit for the enzyme *lactose synthase*. * **Biological Value:** Whey protein has a higher biological value (BV) than casein due to its rapid digestion and high leucine content.

Q: Which of the following foods can a patient with gluten hypersensitivity consume?

Rice. **Explanation:** Gluten hypersensitivity, most notably **Celiac Disease**, is an autoimmune-mediated enteropathy triggered by the ingestion of **prolamins** (gluten proteins) in genetically susceptible individuals. The management revolves around a strict lifelong gluten-free diet. **Why Rice is the Correct Answer:** Rice is naturally gluten-free. The storage proteins in rice (oryzenin) do not contain the specific amino acid sequences (rich in proline and glutamine) that trigger the inflammatory T-cell response seen in Celiac disease. Therefore, rice, along with maize (corn), sorghum, and millets, are safe staples for these patients. **Analysis of Other Options:** * **Barley (Option B):** Contains the prolamin **Hordein**, which is highly toxic to patients with gluten hypersensitivity. * **Oats (Option C):** Contain **Avenin**. While some patients tolerate pure oats, most commercial oats are cross-contaminated with wheat during processing. In the context of standard medical exams, oats are generally excluded from a gluten-free diet unless specified as "certified gluten-free." * **Corn (Option D):** While corn is technically gluten-free, **Rice** is the most classically cited "safe" grain in biochemistry and pediatrics modules for this condition. *Note: In many clinical scenarios, both Rice and Corn are safe; however, if forced to choose the "most" standard answer in a single-choice format, Rice is the gold standard.* **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic (BROW):** Avoid **B**arley, **R**ye, **O**ats, and **W**heat. * **Toxic Prolamins:** Wheat (**Gliadin**), Barley (**Hordein**), Rye (**Secalin**). * **Diagnosis:** Gold standard is a **Duodenal Biopsy** showing villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes. * **Serology:** Anti-tissue Transglutaminase (**anti-tTG**) IgA is the screening drug of choice. * **HLA Association:** Strongly linked with **HLA-DQ2** and **HLA-DQ8**.

Q: Zinc deficiency leads to all of the following except:

Excessive appetite. **Explanation:** Zinc is an essential trace element required for the function of over 300 enzymes, playing a critical role in protein synthesis, cell division, and nucleic acid metabolism. **Why "Excessive Appetite" is the correct answer:** Zinc deficiency is classically associated with **hypogeusia** (loss of taste) and **anorexia** (loss of appetite), rather than an excessive appetite. Zinc is vital for the function of gustin, a salivary protein necessary for the development of taste buds. Therefore, a deficiency leads to a marked reduction in food intake. **Analysis of Incorrect Options:** * **Delayed skeletal maturation:** Zinc is essential for osteoblast activity and collagen synthesis. Deficiency leads to growth retardation and delayed bone age, a hallmark finding in pediatric zinc deficiency. * **Impaired immune system:** Zinc is crucial for T-lymphocyte function and cell-mediated immunity. Deficiency leads to thymic atrophy and increased susceptibility to infections (especially diarrhea and pneumonia). * **Skeletal abnormalities:** Chronic deficiency interferes with normal bone mineralization and longitudinal growth, leading to stunting and various structural skeletal defects. **NEET-PG High-Yield Pearls:** 1. **Acrodermatitis Enteropathica:** An autosomal recessive disorder of zinc absorption characterized by the triad of **alopecia, diarrhea, and vesiculobullous dermatitis** (periorificial and acral). 2. **Hypogonadism:** Zinc deficiency is a known cause of delayed sexual maturation and oligospermia. 3. **Wound Healing:** Zinc is a cofactor for RNA and DNA polymerase; deficiency leads to poor wound healing. 4. **Diarrhea Management:** WHO recommends 20 mg of Zinc daily for 10–14 days (10 mg for infants <6 months) during acute diarrhea to reduce severity and recurrence.

Q: Dietary fibre is rich in which of the following substances?

Pectin. ### Explanation **Correct Option: B (Pectin)** Dietary fibre consists of the remnants of edible plant cells that are resistant to digestion by human alimentary enzymes. It is primarily composed of **non-starch polysaccharides** (NSPs) and lignin. **Pectin** is a structural heteropolysaccharide found in the primary cell walls and middle lamella of terrestrial plants (especially fruits like apples and citrus). It is a soluble fibre that forms a gel-like substance in the gut, slowing gastric emptying and lowering serum cholesterol by binding to bile acids. **Analysis of Incorrect Options:** * **A. Starch:** This is a homopolymer of glucose ($\alpha$-1,4 and $\alpha$-1,6 linkages) and is the primary **digestible** carbohydrate in the human diet. It is broken down by salivary and pancreatic amylase, unlike dietary fibre. * **C. Collagen:** This is the most abundant **animal protein** found in connective tissues (skin, bone, cartilage). It is not found in plants and therefore cannot be a component of dietary fibre. * **D. Proteoglycan:** These are molecules consisting of a core protein with attached glycosaminoglycan (GAG) chains (e.g., chondroitin sulfate). They are essential components of the **animal extracellular matrix**, not plant cell walls. **High-Yield Clinical Pearls for NEET-PG:** * **Components of Dietary Fibre:** Include Cellulose, Hemicellulose, Pectin, Gums, Mucilages (all polysaccharides), and **Lignin** (the only non-polysaccharide component). * **Metabolic Benefits:** Fibre increases stool bulk (prevents constipation), reduces the glycemic index of meals (improves diabetes control), and is fermented by colonic bacteria into **Short-Chain Fatty Acids (SCFAs)** like butyrate, which are trophic to colonocytes. * **Recommended Intake:** Approximately 25–40 g/day. High fibre intake is associated with a decreased risk of colorectal cancer and diverticulosis.

Q: What is the limiting amino acid in maize?

Tryptophan. **Explanation:** The correct answer is **Tryptophan**. In nutritional biochemistry, a "limiting amino acid" is an essential amino acid found in the smallest quantity in a specific food source, thereby limiting the body's ability to synthesize proteins. **Why Tryptophan is correct:** Maize (corn) is characteristically deficient in two essential amino acids: **Lysine** and **Tryptophan**. Tryptophan is a precursor for the synthesis of **Niacin (Vitamin B3)**. Because maize is low in Tryptophan and the Niacin present in maize is in a bound, unabsorbable form (niacytin), populations dependent on maize as a staple diet are at high risk for developing Niacin deficiency. **Analysis of Incorrect Options:** * **A. Niacin:** This is a vitamin, not an amino acid. While maize is deficient in bioavailable Niacin, it cannot be a "limiting amino acid." * **B. Tyrosine:** This is a non-essential amino acid synthesized from Phenylalanine. It is not a limiting factor in cereal proteins. * **C. Methionine:** This is the limiting amino acid in **pulses/legumes**. Cereals like maize are generally rich in sulfur-containing amino acids like Methionine but lack Lysine. **High-Yield Clinical Pearls for NEET-PG:** * **Pellagra Connection:** Maize-eating populations often present with Pellagra (Dermatitis, Diarrhea, Dementia, Death) due to the lack of Tryptophan. * **Limiting Amino Acid Summary:** * **Pulses:** Methionine * **Cereals (Wheat/Rice):** Lysine * **Maize:** Lysine and Tryptophan * **Quality Protein Maize (QPM):** Biofortified varieties like *Shakti, Protina,* and *Rattan* are genetically developed to be rich in Lysine and Tryptophan.

Q: Which one of the following is a trace element?

Copper. ### Explanation In human nutrition, minerals are classified based on the daily requirement and their concentration in the body. **Trace elements** (or microminerals) are those required in amounts less than **100 mg/day**. **1. Why Copper is the Correct Answer:** Copper is a classic trace element. It serves as an essential cofactor for several "cuproenzymes" critical for metabolism, including **Cytochrome c oxidase** (electron transport chain), **Superoxide dismutase** (antioxidant defense), and **Lysyl oxidase** (collagen cross-linking). Its deficiency leads to Menkes disease, while its toxicity (impaired excretion) causes Wilson’s disease. **2. Analysis of Incorrect Options:** * **Sodium (B) & Calcium (C):** These are **Macro-elements** (principal minerals). They are required in amounts greater than 100 mg/day (often >1000 mg/day). They play structural roles (Calcium in bone) or maintain osmotic balance and nerve impulse conduction (Sodium). * **Fats (D):** These are **Macronutrients**, not minerals. They provide energy (9 kcal/g) and are required in large quantities (grams) as part of a balanced diet. **3. NEET-PG High-Yield Pearls:** * **Essential Trace Elements:** Iron, Zinc, Copper, Manganese, Iodine, Selenium, Molybdenum, and Cobalt. * **Ultra-trace elements:** Required in <1 mg/day (e.g., Chromium, Fluoride). * **Zinc:** Essential for carbonic anhydrase and DNA polymerase; deficiency causes *Acrodermatitis enteropathica*. * **Selenium:** Component of **Glutathione peroxidase**, protecting cells from oxidative damage. * **Chromium:** Part of the Glucose Tolerance Factor (GTF), enhancing insulin action.

Q: A patient on total parenteral nutrition develops delayed wound healing, loss of taste, deficient immunity, and diarrhea. Most probably, this could be due to deficiency of:

Zinc. **Explanation:** The clinical presentation of delayed wound healing, **dysgeusia** (loss of taste), impaired immunity, and diarrhea in a patient on Total Parenteral Nutrition (TPN) is a classic manifestation of **Zinc deficiency**. **Why Zinc is the Correct Answer:** Zinc is a vital trace element that acts as a cofactor for over 300 enzymes, including **RNA and DNA polymerases** and **alkaline phosphatase**. It plays a critical role in: * **Cell Division & Protein Synthesis:** Essential for collagen synthesis and epithelialization, explaining why deficiency leads to **delayed wound healing**. * **Immune Function:** Necessary for T-cell proliferation and cytokine production. * **Taste Perception:** Zinc is a component of **gustin**, a protein involved in taste bud development. * **Clinical Sign:** In TPN patients, zinc is often lost through increased gastrointestinal secretions or inadequate supplementation. **Why Other Options are Incorrect:** * **Selenium:** Deficiency typically leads to **Keshan disease** (cardiomyopathy) or muscle weakness, not wound healing issues. * **Copper:** Deficiency manifests as **microcytic anemia** (refractory to iron), neutropenia, and skeletal abnormalities (Menkes-like symptoms). * **Iron:** Primarily leads to **microcytic hypochromic anemia**, fatigue, and pica, but is not the primary cause of acute loss of taste or diarrhea in TPN. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder of zinc absorption characterized by periorificial and acral dermatitis, alopecia, and diarrhea. * **Zinc & Vitamin A:** Zinc is required for the synthesis of Retinol Binding Protein (RBP); thus, zinc deficiency can lead to secondary Vitamin A deficiency (night blindness). * **TPN Monitoring:** Chromium deficiency in TPN patients can lead to **glucose intolerance** (insulin resistance).

Question 1

What is the predominant type of whey protein in cow milk?

Accepted Answer

Lactoglobulin

Answer

Lactalbumin

Answer

Lactoferrin

Answer

None of the above

Question 2

Which of the following statements is true about Net Protein Utilization (NPU)?

Accepted Answer

It is the ratio of total nitrogen retained to total nitrogen intake, multiplied by 100.

Answer

It is the ratio of energy from protein to total energy in diet.

Answer

It is the amount of one amino acid per gram of a protein divided by the amount of the same amino acid per gram of egg protein.

Answer

A high NPU indicates a need for increased protein intake.

Question 3

Which of the following foods can a patient with gluten hypersensitivity consume?

Accepted Answer

Rice

Answer

Barley

Answer

Oats

Answer

Corn

Question 4

Zinc deficiency leads to all of the following except:

Accepted Answer

Excessive appetite

Answer

Delayed skeletal maturation

Answer

Impaired immune system

Answer

Skeletal abnormalities

Question 5

All of the following changes are seen in chronic starvation except?

Accepted Answer

Level of serum proteins less than 2.8 g/dL

Answer

All fat stores have been used up

Answer

Severe fat and muscle wasting

Answer

Brain uses ketoacids as fuel

Question 6

Dietary fibre is rich in which of the following substances?

Accepted Answer

Pectin

Answer

Starch

Answer

Collagen

Answer

Proteoglycan

Question 7

What is the limiting amino acid in maize?

Accepted Answer

Tryptophan

Answer

Niacin

Answer

Tyrosine

Answer

Methionine

Question 8

Which one of the following is a trace element?

Accepted Answer

Copper

Answer

Sodium

Answer

Calcium

Answer

Fats

Question 9

Which of the following is NOT a reported clinical manifestation of L-asparaginase deficiency in children?

Accepted Answer

Macrocytic anaemia

Answer

Dwarfism and hypogonadism

Answer

Liver and spleen enlargement

Answer

Impaired cell-mediated immunity

Question 10

A patient on total parenteral nutrition develops delayed wound healing, loss of taste, deficient immunity, and diarrhea. Most probably, this could be due to deficiency of:

Accepted Answer

Zinc

Answer

Selenium

Answer

Copper

Answer

Iron

Nutrition and Metabolism — MCQs

Nutrition and Metabolism — MCQs

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