Nutrition and Metabolism Practice Questions

Q: Glutathione peroxidase contains which of the following trace elements?

Selenium. **Explanation:** The correct answer is **Selenium (D)**. **Why Selenium is Correct:** Glutathione peroxidase (GPx) is a vital antioxidant enzyme that protects cells from oxidative damage by reducing lipid hydroperoxides and free hydrogen peroxide ($H_2O_2$) into water. It requires **Selenium** as an essential cofactor. Specifically, Selenium is incorporated into the enzyme's active site in the form of **Selenocysteine**, often referred to as the "21st amino acid." This trace element is crucial for the enzyme's catalytic activity in neutralizing reactive oxygen species (ROS). **Why Other Options are Incorrect:** * **Chromium (A):** Primarily functions as a component of the **Glucose Tolerance Factor (GTF)**, which enhances the action of insulin. * **Manganese (B):** Acts as a cofactor for enzymes like **Superoxide Dismutase (Mn-SOD)** found in mitochondria, Arginase, and Pyruvate carboxylase. * **Zinc (C):** A cofactor for over 300 enzymes, including **Cytoplasmic SOD (Cu-Zn SOD)**, Carbonic anhydrase, Alcohol dehydrogenase, and DNA/RNA polymerases. **High-Yield Clinical Pearls for NEET-PG:** * **Keshan Disease:** A cardiomyopathy resulting from Selenium deficiency, often seen in regions with selenium-poor soil. * **Kashin-Beck Disease:** An osteoarthropathy associated with Selenium deficiency. * **Antioxidant Defense:** While Glutathione Peroxidase requires Selenium, remember that **Superoxide Dismutase (SOD)** requires Copper, Zinc, or Manganese, and **Catalase** requires Iron (Heme). * **Selenocysteine** is encoded by the stop codon **UGA**, requiring a specific insertion sequence (SECIS) in the mRNA.

Q: Which of the following has the maximum medium-chain fatty acid content?

Coconut oil. **Explanation:** The correct answer is **Coconut oil**. **1. Why Coconut Oil is Correct:** Medium-chain fatty acids (MCFAs) are fatty acids with a carbon chain length of 6 to 12 carbons (e.g., Caprylic and Lauric acid). **Coconut oil** is the richest natural source of MCFAs, containing approximately **60-65%** medium-chain triglycerides (MCTs). Unlike long-chain fatty acids, MCTs are unique because they are absorbed directly into the portal circulation without requiring bile salts or chylomicron formation, making them a vital energy source for patients with malabsorption syndromes. **2. Why the Other Options are Incorrect:** * **Sunflower oil:** Primarily composed of Long-Chain Fatty Acids (LCFAs), specifically Omega-6 polyunsaturated fatty acids (PUFA) like Linoleic acid. * **Flaxseed oil:** A major source of Alpha-linolenic acid (ALA), which is an essential Omega-3 polyunsaturated **long-chain** fatty acid. * **Fish oil:** Renowned for its high content of Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA). These are **very-long-chain** Omega-3 fatty acids (20-22 carbons). **3. High-Yield Clinical Pearls for NEET-PG:** * **Therapeutic Use:** MCTs are used in the dietary management of **Chyluria**, **Short Bowel Syndrome**, and **Pancreatic insufficiency** because they bypass the lymphatic system. * **Essential Fatty Acids:** Remember that Linoleic (ω-6) and Linolenic (ω-3) acids are "essential" because humans lack the enzymes (Δ12 and Δ15 desaturases) to introduce double bonds beyond carbon 9. * **Rancidity:** Oils with high PUFA content (like Sunflower) are more prone to oxidative rancidity compared to saturated-rich Coconut oil.

Q: Which of the following food items has the highest Glycemic Index?

Corn flakes. **Explanation:** The **Glycemic Index (GI)** is a ranking of carbohydrates on a scale of 0 to 100 based on how quickly they raise blood glucose levels after consumption. Foods with a high GI (>70) are rapidly digested and absorbed, causing a sharp spike in blood sugar. **Why Corn Flakes is the correct answer:** Corn flakes undergo extensive industrial processing (extrusion and high-heat treatment), which gelatinizes the starch. This makes the starch highly accessible to digestive enzymes like alpha-amylase. Consequently, corn flakes have a very high GI (approximately **81–93**), leading to a rapid postprandial glucose surge. **Analysis of Incorrect Options:** * **Brown rice (GI ~50–55):** It is a whole grain that retains the bran and germ layer. The high fiber content slows down the enzymatic breakdown of starch, resulting in a low-to-medium GI. * **Ice-cream (GI ~50–60):** Despite the high sugar content, ice cream contains significant amounts of fat and sometimes protein. Fat delays gastric emptying, which slows the absorption of glucose into the bloodstream, resulting in a lower GI than many processed cereals. * **Whole wheat bread (GI ~71–75):** While considered "high" GI, it is generally lower than corn flakes. The presence of intact fiber and complex structures in whole wheat slightly moderates the glycemic response compared to highly processed corn grits. **High-Yield Clinical Pearls for NEET-PG:** * **Reference Standard:** The GI is usually measured against **Glucose or White Bread** (both assigned a value of 100). * **Glycemic Load (GL):** This is a more practical clinical measure as it accounts for both the GI and the actual portion size (GL = GI × Carbohydrate amount / 100). * **Clinical Utility:** Low GI diets are recommended in the management of **Diabetes Mellitus, PCOS, and Metabolic Syndrome** to improve insulin sensitivity and weight loss.

Q: Which of the following is not a trace element?

Calcium. **Explanation:** In medical biochemistry, minerals are classified based on their daily dietary requirement and their concentration in the body into two categories: **Macro-elements (Major minerals)** and **Trace elements (Micro-minerals).** **Why Calcium is the correct answer:** Calcium is a **Macro-element**. Macro-elements are required in the diet in amounts greater than **100 mg/day**. Calcium is the most abundant mineral in the human body (approx. 1–1.5 kg in an adult), essential for bone mineralization, blood coagulation, and neuromuscular signaling. Other macro-elements include Magnesium, Phosphorus, Sodium, Potassium, and Chloride. **Why the other options are incorrect:** * **Zinc (A), Copper (B), and Selenium (C)** are all classified as **Trace elements**. These are required in the diet in amounts less than **100 mg/day** (often <20 mg/day). * **Zinc** is a cofactor for over 300 enzymes (e.g., Carbonic anhydrase, Alcohol dehydrogenase). * **Copper** is essential for iron metabolism (Ceruloplasmin) and collagen cross-linking (Lysyl oxidase). * **Selenium** is a vital component of the antioxidant enzyme **Glutathione peroxidase**. **High-Yield Clinical Pearls for NEET-PG:** * **Ultra-trace elements:** Required in microgram quantities (e.g., Chromium, Manganese, Molybdenum, Iodine). * **Zinc Deficiency:** Characterized by Acrodermatitis enteropathica, poor wound healing, and hypogonadism. * **Copper Deficiency:** Seen in **Menkes Kinky Hair Syndrome** (ATP7A mutation); excess is seen in **Wilson’s Disease** (ATP7B mutation). * **Selenium Deficiency:** Associated with **Keshan disease** (cardiomyopathy).

Q: Which of the following minerals potentiates the action of insulin?

Chromium. **Explanation:** **Chromium (Cr³⁺)** is the correct answer because it is an essential trace element that plays a vital role in carbohydrate and lipid metabolism. It functions as a component of **Chromodulin** (also known as Glucose Tolerance Factor or GTF). **Mechanism:** Chromium potentiates insulin action by facilitating the binding of insulin to its cell surface receptors and increasing the number of insulin receptors. It enhances the tyrosine kinase activity of the insulin receptor, thereby increasing insulin sensitivity and improving glucose uptake by peripheral tissues. **Analysis of Incorrect Options:** * **Molybdenum:** Acts as a cofactor for metalloenzymes such as Xanthine oxidase (involved in purine catabolism), Sulfite oxidase, and Aldehyde oxidase. * **Manganese:** A cofactor for enzymes like Pyruvate carboxylase (gluconeogenesis), Arginase (urea cycle), and Superoxide dismutase (mitochondrial antioxidant). * **Selenium:** A vital component of the enzyme **Glutathione peroxidase**, which protects cells against oxidative damage by neutralizing hydrogen peroxide. **High-Yield Clinical Pearls for NEET-PG:** * **Chromium Deficiency:** Leads to impaired glucose tolerance (IGT), glycosuria, and a syndrome mimicking Type 2 Diabetes Mellitus. * **Chromium Supplementation:** Often discussed in the management of PCOS and metabolic syndrome to reduce insulin resistance. * **Key Association:** Remember **Chromium = Chromodulin = Insulin Potentiation.**

Q: Which of the following statements about nutrition is FALSE?

Zinc deficiency is associated with pulmonary fibrosis.. **Explanation:** **Why Option B is the Correct (False) Statement:** Zinc deficiency is not associated with pulmonary fibrosis. Instead, its classic clinical presentation includes **acrodermatitis enteropathica** (periorificial and acral dermatitis), alopecia, diarrhea, impaired wound healing, hypogonadism, and growth retardation. Zinc is a critical cofactor for over 300 enzymes, including carbonic anhydrase and alkaline phosphatase. While zinc toxicity (via inhalation) can cause lung irritation, deficiency has no established link to pulmonary fibrosis. **Analysis of Incorrect (True) Options:** * **Option A:** Vitamin A is a fat-soluble vitamin stored extensively in the **Ito cells** of the liver. These reserves are sufficient to last for 1–2 years in a well-nourished individual, meaning clinical symptoms like night blindness take a long time to manifest after intake stops. * **Option C:** Selenium is a component of **glutathione peroxidase**. Its deficiency leads to **Keshan disease**, an endemic cardiomyopathy characterized by cardiac enlargement and heart failure (originally described in China). * **Option D:** Calcium and iron compete for the same transport mechanisms in the intestinal mucosa (specifically the DMT1 transporter). High calcium intake, particularly from dairy or supplements, significantly inhibits the absorption of non-heme iron. **High-Yield NEET-PG Pearls:** 1. **Zinc:** Essential for "Zinc Finger" motifs in DNA-binding proteins. Deficiency causes **dysgeusia** (distorted taste). 2. **Selenium:** Deficiency is also linked to **Kashin-Beck disease** (an osteoarthropathy). 3. **Iron Absorption:** Enhanced by Vitamin C (reduces $Fe^{3+}$ to $Fe^{2+}$) and inhibited by phytates, oxalates, and calcium. 4. **Vitamin A:** The earliest clinical sign of deficiency is **Nyctalopia** (night blindness); the earliest conjunctival sign is **Conjunctival Xerosis**.

Q: Vitamin K dependent clotting factors of hepatic origin are all of the following except?

VIII. **Explanation:** The correct answer is **C (Factor VIII)**. The synthesis of certain coagulation factors requires **Vitamin K** as a cofactor for the enzyme **gamma-glutamyl carboxylase**. This enzyme catalyzes the carboxylation of glutamic acid residues on pro-clotting proteins, allowing them to bind calcium and adhere to phospholipid surfaces. **Why Factor VIII is the correct answer:** While most clotting factors are synthesized in the liver, **Factor VIII** is unique. It is primarily produced in the **sinusoidal endothelial cells** of the liver and extrahepatic endothelial cells, rather than the hepatocytes. More importantly, Factor VIII is **not Vitamin K-dependent**. Its deficiency leads to Hemophilia A. **Analysis of incorrect options:** * **Option A (Factor II - Prothrombin):** This is a Vitamin K-dependent serine protease synthesized in the liver hepatocytes. * **Option B (Factor VII):** This factor has the shortest half-life of all clotting factors and is the first to decrease during Vitamin K deficiency or Warfarin therapy. * **Option D (Factor X):** This is a key component of the common pathway and is Vitamin K-dependent. **High-Yield Clinical Pearls for NEET-PG:** * **Vitamin K-dependent factors:** Remember the mnemonic **"1972"** (Factors **II, VII, IX, and X**). * **Anticoagulant proteins:** Proteins **C and S** are also Vitamin K-dependent and act as natural anticoagulants. * **Warfarin Mechanism:** It inhibits **Vitamin K Epoxide Reductase (VKOR)**, preventing the recycling of Vitamin K, thereby inhibiting the synthesis of these factors. * **PT vs. aPTT:** Vitamin K deficiency or Warfarin therapy primarily prolongs the **Prothrombin Time (PT)** initially due to the short half-life of Factor VII.

Q: An obese individual is brought to the emergency room by a concerned friend. The patient has been on a self-imposed "starvation diet" for four months, and has lost 60 pounds while consuming only water and vitamin pills. If extensive blood studies were performed, which of the following would be expected to be elevated?

Acetoacetic acid. ### Explanation **Correct Option: A. Acetoacetic acid** During prolonged starvation (4 months), the body undergoes metabolic adaptation to preserve glucose for the brain and switch to fat utilization. As glycogen stores are depleted within 24 hours, the liver begins **ketogenesis**. Fatty acids are mobilized from adipose tissue and converted into ketone bodies—**acetoacetic acid**, $\beta$-hydroxybutyrate, and acetone—in the liver mitochondria. After several weeks of starvation, the brain adapts to use these ketone bodies as its primary energy source, significantly reducing the need for gluconeogenesis and sparing muscle protein. **Why Incorrect Options are Wrong:** * **B. Alanine:** During early starvation, alanine is the primary glucogenic amino acid released from muscle. However, in prolonged starvation, muscle proteolysis decreases to conserve body protein, leading to **decreased** plasma alanine levels. * **C. Bicarbonate:** The accumulation of ketone bodies (which are organic acids) leads to a state of **metabolic acidosis**. To buffer the excess $H^+$ ions, serum bicarbonate levels will be **decreased**, not elevated. * **D. Chylomicrons:** Chylomicrons are lipoproteins synthesized in the intestine to transport **dietary (exogenous) lipids**. Since the patient is consuming only water and vitamins, no dietary fats are being ingested, making chylomicron levels negligible. **NEET-PG High-Yield Pearls:** * **Ketogenesis Rate-Limiting Step:** HMG-CoA Synthase (Mitochondrial). * **Organ that cannot use Ketones:** The **Liver** (lacks thiophorase/$\beta$-ketoacyl-CoA transferase) and **RBCs** (lack mitochondria). * **Starvation Fuel Shift:** * *Early (1-3 days):* Gluconeogenesis (Protein breakdown). * *Late (>3 days):* Ketolysis (Fat/Protein sparing). * **Major Ketone Body:** $\beta$-hydroxybutyrate is typically the most abundant ketone in the blood during ketoacidosis.

Question 1

Glutathione peroxidase contains which of the following trace elements?

Accepted Answer

Selenium

Answer

Chromium

Answer

Manganese

Answer

Zinc

Question 2

Which of the following has the maximum medium-chain fatty acid content?

Accepted Answer

Coconut oil

Answer

Sunflower oil

Answer

Flaxseed oil

Answer

Fish oil

Question 3

Which of the following food items has the highest Glycemic Index?

Accepted Answer

Corn flakes

Answer

Brown rice

Answer

Ice-cream

Answer

Whole wheat bread

Question 4

Which of the following is not a trace element?

Accepted Answer

Calcium

Answer

Zinc

Answer

Copper

Answer

Selenium

Question 5

Which of the following statements is true regarding the Recommended Dietary Allowance (RDA)?

Accepted Answer

RDA is statistically defined as two standard deviations above the estimated average requirement (EAR).

Answer

RDA is statistically defined as equal to the estimated average requirement.

Answer

RDA is statistically defined as equal to the adequate intake.

Answer

RDA is defined as the recommended minimum requirement.

Question 6

Which of the following minerals potentiates the action of insulin?

Accepted Answer

Chromium

Answer

Molybdenum

Answer

Manganese

Answer

Selenium

Question 7

Which of the following statements about nutrition is FALSE?

Accepted Answer

Zinc deficiency is associated with pulmonary fibrosis.

Answer

Vitamin A deficiency does not typically manifest for a year or more after cessation of intake.

Answer

Selenium deficiency can lead to cardiomyopathy.

Answer

A diet high in calcium can reduce iron absorption.

Question 8

Vitamin K dependent clotting factors of hepatic origin are all of the following except?

Accepted Answer

VIII

Answer

II

Answer

VI

Answer

X

Question 9

Net Protein Utilization is maximum (100%) for:

Accepted Answer

Egg

Answer

Ragi

Answer

Soyabean

Answer

Pulses

Question 10

An obese individual is brought to the emergency room by a concerned friend. The patient has been on a self-imposed "starvation diet" for four months, and has lost 60 pounds while consuming only water and vitamin pills. If extensive blood studies were performed, which of the following would be expected to be elevated?

Accepted Answer

Acetoacetic acid

Answer

Alanine

Answer

Bicarbonate

Answer

Chylomicrons

Nutrition and Metabolism — MCQs

Nutrition and Metabolism — MCQs

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