Nutrition and Metabolism Practice Questions

Q: Calorie restriction increases longevity through which mechanism?

Sirtuins. **Explanation:** **Mechanism of Longevity (Sirtuins):** Calorie restriction (CR) is the most robust non-genetic intervention known to increase lifespan. The primary mediators of this effect are **Sirtuins (SIRT1-7)**, a family of NAD+-dependent deacetylases. When caloric intake is reduced, the **NAD+/NADH ratio increases**, which activates Sirtuins. * **Action:** Sirtuins deacetylate key transcription factors (like PGC-1α and FOXO), leading to enhanced DNA repair, increased mitochondrial biogenesis, reduced apoptosis, and improved insulin sensitivity. * **Result:** This metabolic shift mimics a "survival mode" that protects cells from oxidative stress and age-related decline. **Analysis of Incorrect Options:** * **Albumin:** This is the primary plasma protein responsible for maintaining oncotic pressure and transporting bilirubin/drugs. While it reflects nutritional status, it has no direct signaling role in the genetic regulation of longevity. * **Amyloid:** These are misfolded protein aggregates associated with pathology (e.g., Alzheimer’s disease, Systemic Amyloidosis). Amyloid accumulation is a feature of aging and disease, rather than a mechanism for extending life. * **Carotene:** A precursor to Vitamin A with antioxidant properties. While antioxidants help reduce free radical damage, they do not regulate the genetic pathways of longevity in the same systemic way that Sirtuins do. **High-Yield Clinical Pearls for NEET-PG:** * **Resveratrol:** A polyphenol found in red wine that is a potent activator of **SIRT1**, often cited as a "calorie restriction mimetic." * **AMPK:** Another key enzyme activated during calorie restriction; it works in tandem with Sirtuins to sense low energy states. * **mTOR Pathyway:** Calorie restriction **inhibits** mTOR (Mammalian Target of Rapamycin). Inhibition of mTOR is associated with increased autophagy and lifespan.

Q: Which of the following cannot be degraded by colonic microorganisms and gastrointestinal enzymes?

Lignin. ### Explanation The question tests the understanding of **Dietary Fiber** and its digestibility within the human gastrointestinal tract. **1. Why Lignin is the Correct Answer:** Dietary fiber is broadly classified into soluble and insoluble types. **Lignin** is a complex polymer of aromatic alcohols (phenylpropane units) found in the woody parts of plants. Unlike other dietary fibers, it is **not a carbohydrate**. It is uniquely resistant to both human digestive enzymes (in the small intestine) and **bacterial fermentation** (by colonic microflora). Therefore, it passes through the entire GI tract completely unchanged, providing bulk to the stool. **2. Analysis of Incorrect Options:** * **Pectin (Option A):** A soluble fiber found in fruits. While indigestible by human enzymes, it is **almost completely fermented** by colonic bacteria into short-chain fatty acids (SCFAs). * **Cellulose (Option B):** An insoluble fiber (β-1,4-linked glucose polymer). Humans lack cellulase, but colonic microorganisms can **partially degrade** it through fermentation. * **Glucose (Option D):** A simple monosaccharide that is rapidly and completely absorbed in the small intestine via SGLT-1 and GLUT-2 transporters. It never reaches the colon under normal physiological conditions. **3. Clinical Pearls for NEET-PG:** * **Short-Chain Fatty Acids (SCFAs):** Products of bacterial fermentation (e.g., Butyrate, Propionate, Acetate). **Butyrate** is the primary energy source for colonocytes and has anti-inflammatory properties. * **Classification:** * *Non-polysaccharide Fiber:* Lignin (only one). * *Polysaccharide Fibers:* Cellulose, Hemicellulose, Pectins, Gums, and Mucilages. * **Health Benefits:** Dietary fiber increases stool bulk, decreases transit time, and lowers glycemic index and cholesterol absorption. High-fiber diets are protective against diverticulosis and colorectal cancer.

Q: Zinc deficiency may lead to all the following except?

Muscular weakness. **Explanation:** Zinc is an essential trace element that acts as a cofactor for over 300 enzymes (e.g., Carbonic anhydrase, Alkaline phosphatase, RNA polymerase). It plays a crucial role in growth, immune function, and protein synthesis. **Why "Muscular Weakness" is the correct answer:** Muscular weakness is not a characteristic feature of zinc deficiency. It is more typically associated with deficiencies of minerals like **Potassium** (hypokalemia), **Magnesium**, or Vitamin D (osteomalacia), and disorders of the neuromuscular junction. **Analysis of Incorrect Options:** * **Sexual infantilism:** Zinc is vital for the development of primary and secondary sexual characteristics. Deficiency leads to hypogonadism, delayed puberty, and oligospermia because zinc is required for testosterone synthesis and the function of "Zinc fingers" in steroid hormone receptors. * **Decreased insulin synthesis:** Zinc is required for the structural integrity of insulin. It is involved in the **storage and crystallization of insulin** within the beta cells of the pancreas (forming zinc-insulin hexamers). Deficiency impairs insulin secretion and glucose tolerance. * **Aguesia (Loss of taste):** Zinc is a component of **gustin**, a salivary protein necessary for the development and maintenance of taste buds. Deficiency leads to aguesia (loss of taste) and anosmia (loss of smell). **High-Yield Clinical Pearls for NEET-PG:** 1. **Acrodermatitis Enteropathica:** An autosomal recessive disorder causing impaired zinc absorption, characterized by periorificial/acral dermatitis, alopecia, and diarrhea. 2. **Wound Healing:** Zinc is essential for collagen synthesis and cell division; deficiency leads to poor wound healing. 3. **Immunity:** Zinc deficiency causes thymic atrophy and impaired T-cell function. 4. **Zinc Fingers:** These are the most common DNA-binding motifs in transcription factors, highlighting zinc's role in gene expression.

Q: Which of the following vitamin deficiencies is most commonly seen in short bowel syndrome?

Vitamin B12. **Explanation:** **Short Bowel Syndrome (SBS)** occurs due to extensive surgical resection of the small intestine, leading to malabsorption. The correct answer is **Vitamin B12** because its absorption is highly site-specific. 1. **Why Vitamin B12 is correct:** Vitamin B12 (cobalamin) absorption requires a complex process: it binds to Intrinsic Factor (IF) in the stomach, and the IF-B12 complex is exclusively absorbed in the **terminal ileum**. In SBS, the terminal ileum is the most common site of resection. Without this specific segment, B12 cannot be absorbed, leading to megaloblastic anemia and subacute combined degeneration of the spinal cord. 2. **Why other options are incorrect:** * **Biotin (B7) and Vitamin B1 (Thiamine):** These are water-soluble vitamins primarily absorbed in the proximal small intestine (jejunum). While their absorption can be reduced, the body’s requirement is often met by the remaining proximal segment or, in the case of Biotin, synthesis by gut flora. * **Vitamin K:** This is a fat-soluble vitamin. While fat-soluble vitamins (A, D, E, K) are malabsorbed in SBS due to bile acid depletion, Vitamin B12 deficiency is more "classically" associated with SBS because its absorption site is so anatomically restricted compared to the broader absorption area of Vitamin K. **Clinical Pearls for NEET-PG:** * **The "Rule of Terminal Ileum":** Resection of >100 cm of the terminal ileum inevitably leads to B12 deficiency and bile acid malabsorption (causing steatorrhea). * **Bile Acid Diarrhea:** If the ileum is missing, bile salts enter the colon, causing secretory diarrhea. * **Management:** Patients with SBS and ileal resection require lifelong **parenteral (IM) Vitamin B12** supplementation.

Q: Which of the following dietary components determines the glycemic index of food?

Fibre. ### Explanation **1. Why Fibre is the Correct Answer:** The **Glycemic Index (GI)** is a ranking of carbohydrates (0–100) based on how quickly they raise blood glucose levels after consumption. Dietary **fibre**, particularly soluble fibre (e.g., pectin, gums), is the primary determinant that lowers the GI of a food. It functions by increasing the viscosity of the intestinal contents, which slows down gastric emptying and delays the enzymatic digestion of starch. This results in a slower, more gradual absorption of glucose into the bloodstream, preventing rapid postprandial "spikes." **2. Why Other Options are Incorrect:** * **Protein (A) and Fat (B):** While protein and fat can influence the overall glycemic *load* of a meal by slowing digestion, they are not the primary dietary components used to define or determine the GI of a specific carbohydrate-rich food. GI is specifically a property of the carbohydrates present in the food. * **None of the above (D):** Incorrect, as fibre is a well-established physiological modulator of the glycemic response. **3. NEET-PG High-Yield Pearls:** * **Glycemic Load (GL):** Unlike GI, GL accounts for the **quantity** of carbohydrates in a typical serving (GL = GI × grams of carbohydrate / 100). * **Clinical Significance:** Low-GI diets (rich in fibre) are crucial in managing **Diabetes Mellitus**, metabolic syndrome, and PCOS, as they improve insulin sensitivity. * **Processing Factor:** Highly processed or overcooked foods generally have a higher GI because the physical barriers to digestion are removed, allowing for rapid glucose release.

Q: In Kwashiorkor, which immunoglobulin is most affected?

IgA. **Explanation:** In **Kwashiorkor** (protein-energy malnutrition characterized by edema), the immune system is significantly compromised. While total serum protein levels are low, the impact on specific immunoglobulins varies. **IgA** is the most affected because its production and secretion are highly dependent on the integrity of mucosal surfaces and the availability of specific amino acids. In malnutrition, there is marked atrophy of the mucosal-associated lymphoid tissue (MALT) and a decrease in secretory component synthesis, leading to a significant reduction in **Secretory IgA (sIgA)**. This explains why children with Kwashiorkor are highly susceptible to mucosal infections, such as gastroenteritis and respiratory tract infections. **Analysis of Options:** * **IgA (Correct):** It is the primary immunoglobulin of the mucosal immune system. Malnutrition leads to thymic atrophy and impaired mucosal immunity, specifically lowering IgA levels. * **IgD:** This is primarily a B-cell surface receptor. Its levels are generally very low in serum and are not a clinical marker for nutritional status. * **IgE:** Levels are often **elevated** rather than decreased in Kwashiorkor, primarily due to the high prevalence of concomitant parasitic (helminthic) infections in malnourished populations. * **IgM:** Serum levels of IgM (and often IgG) are usually maintained within normal limits or may even be elevated due to chronic underlying infections, despite the overall protein deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Edema in Kwashiorkor:** Primarily due to hypoalbuminemia (decreased oncotic pressure). * **Immune Status:** Kwashiorkor is often described as "nutritional AIDS" due to profound T-cell dysfunction and thymic atrophy. * **Fatty Liver:** Occurs due to decreased synthesis of **Apolipoprotein B-100**, preventing the export of triglycerides from the liver (VLDL formation).

Q: Which micronutrient is associated with rash and diarrhea?

Zinc. **Explanation:** **Zinc deficiency** is the classic cause of the clinical triad: **Dermatitis (rash), Diarrhea, and Alopecia.** The characteristic rash is known as **Acrodermatitis Enteropathica**, which presents as erythematous, vesiculobullous, and eczematous lesions typically located periorificially (around the mouth, anus) and on the extremities (acral distribution). Zinc is a vital cofactor for over 300 enzymes, including Carbonic Anhydrase and Alkaline Phosphatase, and is essential for cell division and mucosal integrity, explaining why its deficiency manifests in rapidly turnover tissues like the skin and gut. **Analysis of Incorrect Options:** * **Manganese:** Deficiency is extremely rare in humans but may lead to impaired growth, skeletal abnormalities, and defects in lipid/carbohydrate metabolism. Toxicity (Manganism) presents with Parkinsonian-like neurological symptoms. * **Copper:** Deficiency typically presents with **Microcytic Hypochromic Anemia** (refractory to iron), neutropenia, and skeletal demineralization. It does not typically cause the specific rash/diarrhea triad. * **Iron:** Deficiency primarily leads to **Microcytic Hypochromic Anemia**, pica, and koilonychia (spoon-shaped nails). While it can cause glossitis, it is not associated with acral dermatitis or chronic diarrhea. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder involving a mutation in the **SLC39A4** gene, leading to impaired zinc absorption. * **Zinc & Wound Healing:** Zinc is crucial for collagen synthesis; deficiency leads to poor wound healing. * **Hypogonadism:** Chronic zinc deficiency is a known cause of delayed puberty and stunted growth. * **Taste Sensation:** Zinc is a component of **Gustin**; deficiency leads to decreased taste acuity (**Hypogeusia**).

Q: All of the following are reasons for impaired absorption of calcium except:

Decreased iron intake. **Explanation:** Calcium absorption occurs primarily in the duodenum and jejunum via active transport (regulated by Vitamin D) and passive diffusion. The absorption is highly sensitive to the chemical environment of the intestinal lumen. **Why "Decreased iron intake" is the correct answer:** Iron and calcium are both divalent cations that compete for similar transport mechanisms (though iron primarily uses DMT-1). **High intake** of iron can interfere with calcium absorption, and conversely, high calcium can inhibit iron absorption. Therefore, **decreased iron intake** would theoretically **increase** or have a neutral effect on calcium bioavailability, rather than impairing it. **Analysis of Incorrect Options (Factors that impair absorption):** * **Inositol hexaphosphate (Phytic acid):** Found in cereals and grains, phytates form insoluble calcium-phytate complexes that cannot be absorbed by the intestine. * **High intake of oxalate:** Present in leafy greens (like spinach) and chocolate, oxalates bind to calcium to form insoluble **calcium oxalate** crystals, significantly reducing bioavailability. * **High concentrations of fatty acids:** In malabsorption syndromes (steatorrhea), unabsorbed fatty acids react with calcium to form insoluble **"calcium soaps."** This not only impairs calcium absorption but also increases free oxalate absorption (leading to enteric hyperoxaluria and renal stones). **High-Yield Clinical Pearls for NEET-PG:** * **Promoters of Calcium Absorption:** Vitamin D (Calcitriol), PTH, acidic pH (Gastrin/HCl), and certain amino acids (Lysine, Arginine). * **Inhibitors of Calcium Absorption:** Phytates, oxalates, high dietary fiber, phosphates, and malabsorption of fats. * **The "Soap" Connection:** In Crohn’s disease or Celiac disease, fat malabsorption leads to hypocalcemia and a high risk of calcium oxalate kidney stones.

Question 1

Calorie restriction increases longevity through which mechanism?

Accepted Answer

Sirtuins

Answer

Albumin

Answer

Amyloid

Answer

Carotene

Question 2

Copper deficiency can manifest as which of the following conditions?

Accepted Answer

Hepatomegaly

Answer

Anemia

Answer

Cardiomyopathy

Answer

Growth retardation

Question 3

Which of the following cannot be degraded by colonic microorganisms and gastrointestinal enzymes?

Accepted Answer

Lignin

Answer

Pectin

Answer

Cellulose

Answer

Glucose

Question 4

Zinc deficiency may lead to all the following except?

Accepted Answer

Muscular weakness

Answer

Sexual infantilism

Answer

Decreased insulin synthesis

Answer

Aguesia

Question 5

Which of the following vitamin deficiencies is most commonly seen in short bowel syndrome?

Accepted Answer

Vitamin B12

Answer

Biotin

Answer

Vitamin B1

Answer

Vitamin K

Question 6

Which of the following dietary components determines the glycemic index of food?

Accepted Answer

Fibre

Answer

Protein

Answer

Fat

Answer

None of the above

Question 7

In Kwashiorkor, which immunoglobulin is most affected?

Accepted Answer

IgA

Answer

IgD

Answer

IgE

Answer

IgM

Question 8

Which of the following is NOT an antioxidant?

Accepted Answer

Elastase

Answer

Ceruloplasmin

Answer

Transferrin

Answer

Catalase

Question 9

Which micronutrient is associated with rash and diarrhea?

Accepted Answer

Zinc

Answer

Manganese

Answer

Copper

Answer

Iron

Question 10

All of the following are reasons for impaired absorption of calcium except:

Accepted Answer

Decreased iron intake

Answer

Inositol hexaphosphate in cereals

Answer

High intake of oxalate

Answer

High concentrations of fatty acids in the intestinal lumen

Nutrition and Metabolism — MCQs

Nutrition and Metabolism — MCQs

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