Nutrition and Metabolism — MCQs

Nutrition and Metabolism Indian Medical PG Practice Questions and MCQs

Question 311: Which of the following is not a dietary fiber?

A. Cellulose
B. Starch (Correct Answer)
C. Pectin
D. Inulin

Explanation: ***Starch*** - **Starch** is a **complex carbohydrate** that serves as a major energy source for humans and can be digested into glucose. - Unlike dietary fiber, starch is broken down by enzymes (like **amylase**) in the digestive tract, absorbed, and used for energy. *Cellulose* - **Cellulose** is a **polysaccharide** found in the cell walls of plants and is a major component of dietary fiber. - Humans lack the enzymes to digest cellulose, so it passes through the digestive system largely intact, adding **bulk to stool**. *Pectin* - **Pectin** is a **soluble dietary fiber** found in fruits, particularly apples and citrus. - It forms a gel-like substance when mixed with water and is known for its ability to lower cholesterol and regulate blood sugar. *Inulin* - **Inulin** is a **soluble dietary fiber** and a type of fructan, found in many plants like chicory root, onions, and garlic. - It acts as a **prebiotic**, promoting the growth of beneficial gut bacteria in the colon.

Question 312: Which nutrient is essential for collagen synthesis?

A. Vitamin D
B. Vitamin C (Correct Answer)
C. Folic acid
D. Vitamin A

Explanation: ***Vitamin C*** - **Vitamin C (ascorbic acid)** is absolutely essential as a cofactor for **prolyl hydroxylase and lysyl hydroxylase** enzymes - These enzymes hydroxylate proline and lysine residues in procollagen, which is critical for **stable collagen triple helix formation** - Deficiency causes **scurvy** with defective collagen leading to bleeding gums, poor wound healing, and perifollicular hemorrhages - **Copper** (as a cofactor for lysyl oxidase) is also important for collagen cross-linking but Vitamin C is the primary essential nutrient for synthesis *Vitamin D* - Primarily involved in **calcium and phosphate metabolism** and bone mineralization - Deficiency leads to **rickets** (children) and **osteomalacia** (adults), not defective collagen - No direct role in collagen synthesis pathways *Folic acid* - Essential for **DNA synthesis, cell division**, and red blood cell formation - Plays no direct role in the **enzymatic mechanisms of collagen formation** - Deficiency causes megaloblastic anemia *Vitamin A* - Important for **vision, immune function**, epithelial integrity, and cell differentiation - While it influences tissue health, it is not a direct cofactor for **collagen synthesis enzymes**

Question 313: Which of the following minerals is needed for fertility?

A. Copper
B. Iron
C. Zinc (Correct Answer)
D. Selenium

Explanation: ***Zinc*** - Zinc is crucial for **reproductive health** in both men and women, impacting **testosterone synthesis**, **spermatogenesis**, egg quality, and **hormone regulation**. - Essential for **gonadal development** and function in both sexes. - Deficiency leads to **hypogonadism**, reduced fertility, impaired sperm production, and increased risk of **miscarriage**. - Most commonly deficient mineral affecting fertility globally. *Selenium* - Selenium is also **essential for male fertility**, being a critical component of **glutathione peroxidase** in sperm mitochondria. - Required for **sperm motility**, morphology, and structural integrity of the sperm midpiece. - Deficiency can cause male infertility due to impaired sperm function. - However, zinc deficiency is more prevalent and has broader effects across both male and female reproductive systems. *Iron* - Iron is vital for **red blood cell formation** and preventing **anemia**. - Severe iron deficiency anemia can **impair ovulation** and indirectly affect fertility in women. - Not directly involved in reproductive processes at the cellular level like zinc. *Copper* - Essential for various enzymatic functions but not primarily associated with fertility. - **Excessive copper** can negatively impact fertility and cause hormonal imbalances. - Deficiency is rare and not a primary cause of infertility.

Question 314: A 70 kg farmer is consuming 56 grams of protein, 275 grams of carbohydrates, and 60 grams of lipids. How does his caloric intake compare to the estimated daily needs for a moderately active male?

A. More than the recommended intake
B. Adequate for his needs
C. Cannot be determined
D. Less than the recommended intake (Correct Answer)

Explanation: ***Less than the recommended intake*** - The farmer's total caloric intake is approximately 1864 kcal (Protein: 56g x 4 kcal/g = 224 kcal; Carbs: 275g x 4 kcal/g = 1100 kcal; Lipids: 60g x 9 kcal/g = 540 kcal), which is **lower than the estimated needs** for a moderately active male. - A moderately active male typically requires about **2400-2800 kcal/day** depending on age and specific activity levels. *More than the recommended intake* - His calculated intake of 1864 kcal is on the **lower end** and does not exceed the general recommendations for moderately active adult males. - This option would be correct if the calculated intake was significantly higher than the average daily caloric requirements. *Adequate for his needs* - While 1864 kcal might be adequate for a very sedentary lifestyle, a farmer (implied to be **moderately active**) would generally require a **higher caloric intake** to meet energy demands and maintain body weight. - A caloric intake closer to 2400-2800 kcal/day would be considered more appropriate for a moderately active individual. *Cannot be determined* - The caloric content of macronutrients is standard (4 kcal/g for protein and carbohydrates, 9 kcal/g for lipids), allowing for a **direct calculation** of total caloric intake. - While exact individual needs can vary, general dietary guidelines provide a sufficient basis to assess if this intake is likely low, adequate, or high for a moderately active individual.

Question 315: What is the recommended daily protein intake for a healthy adult male?

A. 0.5 gm/kg/day
B. 1 gm/kg/day (Correct Answer)
C. 1.5 gm/kg/day
D. 2 gm/kg/day

Explanation: ***1 gm/kg/day*** - The recommended daily protein intake for healthy adults is generally around **0.8 to 1.0 gram per kilogram of body weight** to maintain nitrogen balance and prevent deficiency. - This intake supports normal bodily functions, tissue repair, and muscle maintenance in non-athletic individuals. *0.5 gm/kg/day* - This amount is generally considered **below the optimal daily protein intake** for most healthy adults and may be insufficient to maintain proper nitrogen balance. - While it may prevent overt deficiency in some sedentary individuals, it does not support optimal muscle protein synthesis or recovery for active or moderately active adults. *1.5 gm/kg/day* - This level of protein intake is often recommended for individuals who are **highly active, engaged in resistance training**, or aiming for muscle gain. - While not harmful for most healthy individuals, it generally **exceeds the basic requirements** for a typical healthy adult male not involved in intense physical activity. *2 gm/kg/day* - This is a very high protein intake, often utilized by **competitive athletes, bodybuilders**, or individuals on specific weight loss programs. - While generally safe for healthy kidneys, it is **significantly higher than the recommended daily allowance** for the average healthy adult and not necessary for general health maintenance.

Question 316: Which of the following statements about phosphorus is true?

A. Parathormone acts on NaPiIIc receptors
B. Most of it (85%) is found in the bones
C. Comprises about 1% of the total body weight (Correct Answer)
D. Dietary phosphorus deficiency is common in healthy individuals

Explanation: ***Correct: Comprises about 1% of the total body weight*** - Phosphorus is an **abundant mineral** in the body, accounting for approximately **1% of total body weight** (about 700g in a 70kg adult). - This fundamental fact highlights its crucial roles in **bone structure, energy metabolism (ATP), nucleic acids (DNA/RNA), and cell membrane structure (phospholipids)**. - This is the most **comprehensive and primary characteristic** of phosphorus in the body. *Most of it (85%) is found in the bones* - This statement is **factually correct** – approximately **85% of total body phosphorus** is found in bones as **hydroxyapatite crystals** (Ca₁₀(PO₄)₆(OH)₂). - However, this describes the **distribution** of phosphorus rather than its fundamental quantitative presence in the body. - The remaining **15%** is distributed in soft tissues, extracellular fluid, and plays vital roles in cellular metabolism. - Both this and the correct answer are true, but the 1% body weight statement is the more **fundamental and primary fact**. *Parathormone acts on NaPiIIc receptors* - **Parathyroid hormone (PTH)** regulates phosphorus homeostasis by acting primarily on **NaPiIIa (NaPi2a) and NaPiIIb (NaPi2b)** sodium-phosphate co-transporters in the **proximal renal tubules**. - PTH **inhibits** these transporters, leading to **decreased phosphate reabsorption** and increased urinary phosphate excretion. - **NaPiIIc (NaPi2c)** is another sodium-phosphate cotransporter subtype found mainly in the **intestine and kidney**, but it is **not the primary target** of PTH regulation. *Dietary phosphorus deficiency is common in healthy individuals* - **Dietary phosphorus deficiency is rare** in healthy individuals because phosphorus is **abundantly available** in the diet (dairy products, meat, fish, poultry, nuts, legumes, and grains). - The typical Western diet often contains **excess phosphorus**, particularly from food additives in processed foods. - Hypophosphatemia is usually seen in specific clinical conditions: **refeeding syndrome, malabsorption syndromes, alcoholism, vitamin D deficiency**, or with medications like **phosphate binders** or **antacids**.

Question 317: Which of the following factors in diet increases iron absorption?

A. Vitamin C (Correct Answer)
B. Iron-fortified foods
C. Vitamin A
D. Fibre diet

Explanation: ***Vitamin C*** - **Vitamin C** (ascorbic acid) enhances **non-heme iron absorption** by reducing ferric iron (Fe3+) to ferrous iron (Fe2+), which is more soluble and readily absorbed in the gut. - It also counteracts the inhibitory effects of certain dietary components like **phytates and tannins** on iron absorption. *Iron-fortified foods* - While iron-fortified foods *provide* iron, they don't inherently increase the *efficiency* of absorption of all forms of iron present in the meal. - The absorption of iron from these foods still depends on the **form of iron used** for fortification and the presence of **absorption enhancers** or inhibitors. *Vitamin A* - **Vitamin A** plays a role in iron metabolism by influencing red blood cell development and mobilization of iron from stores, but it does **not directly enhance iron absorption** from the gut. - Deficiency in Vitamin A can *exacerbate* iron deficiency anemia, but its supplementation doesn't primarily serve to increase absorption. *Fibre diet* - A **high-fibre diet** can *decrease* iron absorption because certain components of fibre, particularly **phytates** (found in whole grains and legumes), bind to iron and hinder its uptake. - While fibre is important for digestive health, it is generally considered an **inhibitor** of iron absorption, especially of non-heme iron.

Question 318: All of the following are examples of Dietary fibre except for which of the following?

A. Starch (Correct Answer)
B. Pectin
C. Lignin
D. Cellulose

Explanation: ***Correct: Starch*** - **Starch** is a **polysaccharide** that serves as a **storage carbohydrate** in plants and is readily digestible by human enzymes, breaking down into glucose. - While it's a carbohydrate found in plant foods, it does not fit the definition of dietary fibre which is generally resistant to human digestive enzymes. *Incorrect: Pectin* - **Pectin** is a type of **soluble dietary fibre** found in fruits, particularly apples and citrus. - It forms a gel in water, contributing to satiety and helping to **lower cholesterol** and **regulate blood sugar**. *Incorrect: Lignin* - **Lignin** is a **non-carbohydrate dietary fibre** that provides structural support in plants. - It is an **insoluble fibre** and is resistant to breakdown by digestive enzymes, aiding in bulk formation in stool. *Incorrect: Cellulose* - **Cellulose** is a major component of **plant cell walls** and is a type of **insoluble dietary fibre**. - It adds bulk to stool, promoting regularity and preventing constipation.

Question 319: What is the Net Protein Utilization (NPU) for eggs?

A. 70
B. 80
C. 94 (Correct Answer)
D. 100

Explanation: ***94*** - **Eggs** are considered a **high-quality protein source** with a Net Protein Utilization (NPU) of approximately **94**, indicating very efficient protein absorption and utilization by the body. - This high NPU reflects the excellent balance of **essential amino acids** in eggs, making them a benchmark for protein quality. *70* - An NPU of 70 is generally considered good but is lower than that of **eggs**, which are among the most efficiently utilized proteins. - This value might be typical for some **plant-based proteins** or mixtures of proteins with slightly less optimal essential amino acid profiles. *80* - An NPU of 80 indicates good protein quality but is still significantly lower than the **NPU of eggs**. - This value is often seen in high-quality **meat proteins** or well-balanced **dairy products**. *100* - An NPU of 100 would mean that all ingested protein is perfectly absorbed and utilized by the body without any loss, which is **theoretically impossible** for biological systems. - While some protein quality metrics might approach 100, **NPU is a measure of actual utilization** and never reaches 100 due to metabolic losses.

Question 320: Which food item contains the highest protein content among the following options?

A. Egg
B. Soyabean (Correct Answer)
C. Rice
D. Wheat

Explanation: ***Soyabean*** - **Soybeans** are considered a complete protein, containing all **nine essential amino acids** required for human health. - They typically contain about **36-40 grams of protein per 100 grams** (dried/raw), making them one of the richest plant-based protein sources. - This is **significantly higher** than any of the other options listed. *Egg* - A **large egg** contains approximately **6 grams of high-quality protein**, including all essential amino acids. - Per 100 grams, eggs provide about **12-13 grams of protein** - excellent quality but much lower quantity than soybeans. *Rice* - **Rice**, particularly white rice, is primarily a source of **carbohydrates** and contains relatively low protein content. - Raw white rice provides about **7 grams of protein per 100 grams** (uncooked), making it the lowest protein source among these options. *Wheat* - **Wheat** is a grain rich in carbohydrates and also contains a moderate amount of protein, primarily **gluten**. - Whole wheat grain contains approximately **13-14 grams of protein per 100 grams**, which is comparable to eggs but significantly less than soybeans.

Practice by Chapter

Macronutrients and Energy Requirements

Practice Questions

Protein Quality and Nitrogen Balance

Practice Questions

Essential Amino Acids and Proteins

Practice Questions

Essential Fatty Acids and Lipids

Practice Questions

Dietary Fiber and Complex Carbohydrates

Practice Questions

Glycemic Index and Glycemic Load

Practice Questions

Micronutrients: Vitamins and Minerals

Practice Questions

Trace Elements and Metabolism

Practice Questions

Malnutrition: Biochemical Consequences

Practice Questions

Dietary Antioxidants

Practice Questions

Functional Foods and Nutraceuticals

Practice Questions

Dietary Guidelines and Recommendations

Practice Questions

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