What vitamin is significantly absent in breast milk?
Effect of environment on genes is called?
Which amino acid in Jowar is responsible for its pellagragenic effect?
What is the amount of protein (in grams) in human milk per 100 milliliters?
Which oil has the highest concentration of linolenic acid?
What is the daily requirement of vitamin K?
What is the recommended daily calcium intake for adult non-pregnant females?
Mechanism of cyanide poisoning is by inhibiting: NEET 2013
Selenium deficiency is seen in -
Which vitamin deficiency is most commonly associated with chronic alcohol consumption and may require supplementation in alcohol use disorders?
NEET-PG 2012 - Biochemistry NEET-PG Practice Questions and MCQs
Question 171: What vitamin is significantly absent in breast milk?
- A. Vitamin D
- B. Vitamin K (Correct Answer)
- C. Vitamin C
- D. Vitamin A
Explanation: ***Vitamin K*** - Breast milk contains **critically low amounts** of **vitamin K** (approximately 2-5 μg/L), making it the **most significantly absent** vitamin in breast milk. - Newborns are at high risk for **Vitamin K deficiency bleeding (VKDB)**, which can be life-threatening. - This deficiency is so critical that **prophylactic vitamin K injection** is routinely administered to **all newborns** at birth to prevent hemorrhagic disease. - Vitamin K is essential for the synthesis of **clotting factors II, VII, IX, and X** in the liver. *Vitamin D* - While breast milk does contain **some vitamin D**, the levels are often **insufficient** to meet the infant's daily requirements (contains ~25-78 IU/L; infant needs 400 IU/day). - However, it is **present in measurable amounts**, unlike vitamin K which is nearly absent. - Infants are recommended to receive **vitamin D supplementation** starting soon after birth, especially if the mother has low vitamin D levels or limited **sun exposure**. *Vitamin C* - **Breast milk** contains adequate amounts of **vitamin C** (40-50 mg/L), which is sufficient for the infant's needs. - Maternal diet typically provides enough vitamin C to ensure its presence in breast milk. *Vitamin A* - Breast milk is a **good source** of **vitamin A**, particularly in the form of **beta-carotene** and retinol. - Vitamin A levels in breast milk are adequate for infant **vision development** and **immune function**.
Question 172: Effect of environment on genes is called?
- A. Euthenics
- B. Positive Eugenics
- C. Negative Eugenics
- D. Epigenetics (Correct Answer)
Explanation: ***Epigenetics*** - **Epigenetics** refers to heritable changes in **gene expression** that do not involve alterations to the underlying **DNA sequence**. - These changes are often influenced by **environmental factors**, such as diet, stress, and exposure to toxins, which can affect how genes are turned on or off. *Positive Eugenics* - **Positive eugenics** aims to improve the human population by encouraging the reproduction of individuals deemed to have "desirable" traits. - This concept is ethically controversial and focuses on directed breeding rather than environmental gene influence. *Negative Eugenics* - **Negative eugenics** aims to reduce the prevalence of "undesirable" traits in the human population by discouraging or preventing the reproduction of individuals deemed to possess them. - Like positive eugenics, this is a highly controversial concept focused on limiting reproduction based on perceived genetic quality. *Euthenics* - **Euthenics** is a movement focused on improving human well-being and development by improving living conditions and the environment. - While it acknowledges the impact of the environment, it focuses on societal and lifestyle improvements rather than the direct molecular changes in gene expression.
Question 173: Which amino acid in Jowar is responsible for its pellagragenic effect?
- A. Leucine (Correct Answer)
- B. Lysine
- C. Tryptophan
- D. Methionine
Explanation: ***Leucine*** - A high intake of **leucine**, an essential amino acid, interferes with the metabolism of **tryptophan** and niacin, leading to **pellagra**. - Jowar (sorghum) contains high levels of leucine, which, when it forms a major part of the diet, can induce **niacin deficiency**. *Lysine* - Lysine is an essential amino acid and is generally considered to be in **limited supply** in many cereal grains, making it a desirable amino acid to increase in diets. - It does not directly contribute to the pellagragenic effect; rather, a deficiency in lysine can be a nutritional concern. *Tryptophan* - Tryptophan is a **precursor to niacin (Vitamin B3)** in the body; a deficiency in tryptophan can lead to pellagra. - The high leucine content in jowar interferes with the conversion of tryptophan to niacin, thus exacerbating niacin deficiency. *Methionine* - Methionine is an **essential sulfur-containing amino acid** important for various metabolic functions and protein synthesis. - It is not directly implicated in the pellagragenic effect associated with high jowar consumption.
Question 174: What is the amount of protein (in grams) in human milk per 100 milliliters?
- A. 1.1 (Correct Answer)
- B. 2.2
- C. 3.3
- D. 4.4
Explanation: ***1.1*** - Human milk contains approximately **1.1 grams of protein per 100 milliliters**, which is appropriate for the growth and development of infants. - The protein composition of human milk is lower than that of cow's milk, but it is highly bioavailable and easily digestible due to the presence of **whey protein** and **casein**. *2.2* - This value is significantly higher than the typical protein content found in human milk. Such a high concentration could potentially strain an infant's immature kidneys. - The **protein content of cow's milk** (around 3.3-3.5 g/100ml) is much higher than human milk and is not suitable for routine infant feeding without modification. *3.3* - This protein concentration is also substantially higher than what is naturally found in human milk, possibly exceeding an infant's metabolic needs and kidney function. - This value is closer to the protein content of **unmodified cow's milk**, which is why it is often diluted or altered for infant formula. *4.4* - This protein amount is exceptionally high and not representative of natural human milk. - Excessive protein intake in infants could increase the risk of **obesity later in life** and place an undue burden on the **renal system**.
Question 175: Which oil has the highest concentration of linolenic acid?
- A. Safflower oil
- B. Coconut oil
- C. Groundnut oil
- D. Soyabean oil (Correct Answer)
Explanation: ***Soyabean oil*** - **Soyabean oil** contains approximately **7-10% linolenic acid (C18:3)**, an omega-3 fatty acid. - Among the given options, it has the **highest concentration** of this essential fatty acid. - **Linolenic acid** is crucial for **heart health** and **reducing inflammation**. *Coconut oil* - **Coconut oil** is primarily composed of **saturated fatty acids**, notably **lauric acid (C12:0)**. - It contains **negligible amounts** of **linolenic acid** (<0.5%). *Groundnut oil* - **Groundnut oil** (peanut oil) is rich in **oleic acid (C18:1)** and **linoleic acid (C18:2)**. - Its concentration of **linolenic acid** is very low (**~0.5-1%**), much lower than soyabean oil. *Safflower oil* - **Safflower oil** is known for its high content of **linoleic acid (C18:2)**, an omega-6 fatty acid. - It contains **minimal amounts** of **linolenic acid** (<1%).
Question 176: What is the daily requirement of vitamin K?
- A. 5-10 mg/kg
- B. 0.5-1 mg/kg
- C. 1-2 mcg/kg (Correct Answer)
- D. 10-15 mcg/kg
Explanation: ***1-2 mcg/kg*** - The daily requirement of **vitamin K** for adults is approximately **1-2 mcg/kg body weight** (or about 90-120 mcg/day for average adults). - This amount is sufficient for **γ-carboxylation** of clotting factors II, VII, IX, and X, as well as proteins C and S. - The **Adequate Intake (AI)** set by dietary guidelines supports normal coagulation and bone health at these levels. *0.5-1 mg/kg* - This represents a **500-1000 fold excess** over the actual requirement (mg instead of mcg). - This is a **unit error** - the requirement is in **micrograms (mcg)**, not milligrams (mg). - Such high doses would be **pharmacological** rather than physiological, though vitamin K has relatively low toxicity. *10-15 mcg/kg* - This is approximately **10 times higher** than the actual daily requirement. - While not toxic, this amount is **unnecessarily high** for maintaining normal hemostasis. - Typical dietary intake and physiological needs are much lower. *5-10 mg/kg* - This represents an extremely **excessive amount** (5000-10000 times the requirement). - Another example of a **unit confusion** (mg vs mcg). - Such doses have no physiological benefit and are not used clinically except in specific therapeutic situations (e.g., warfarin reversal).
Question 177: What is the recommended daily calcium intake for adult non-pregnant females?
- A. 1000 mg (Correct Answer)
- B. 1200 mg
- C. 600 mg
- D. 800 mg
Explanation: ***1000 mg*** - The recommended daily calcium intake for adult non-pregnant females (ages 19-50) is **1000 mg** according to **WHO and international guidelines** (US RDA/NIH) to maintain bone health and prevent osteoporosis. - This is the **standard recommendation** used in most medical textbooks and international nutritional guidelines. - Adequate calcium intake supports various bodily functions, including **nerve transmission**, **muscle contraction**, and **hormone secretion**. *1200 mg* - While 1200 mg is the recommended intake for **older women (above 50-70 years)** or during **pregnancy/lactation** per some guidelines, it is generally higher than necessary for non-pregnant adult females aged 19-50. - While not harmful, this higher dose is not specifically indicated for the general non-pregnant adult female population. *600 mg* - This amount of calcium is **lower than the internationally recommended daily allowance** for adult women (though it aligns with some regional guidelines like ICMR for sedentary women). - For optimal bone health and prevention of osteoporosis, **1000 mg is the widely accepted standard** in medical education. *800 mg* - This value is **below the internationally recommended daily intake** for adult non-pregnant females, which could lead to long-term calcium deficiency. - Insufficient calcium intake can increase the risk of conditions like **osteopenia** and **osteoporosis**.
Question 178: Mechanism of cyanide poisoning is by inhibiting: NEET 2013
- A. DNA synthesis
- B. Cytochrome oxidase (Correct Answer)
- C. Protein breakdown
- D. Protein synthesis
Explanation: ***Cytochrome oxidase*** - **Cyanide** is a potent poison because it binds to the **ferric iron (Fe3+)** in the active site of **cytochrome c oxidase**. - This binding completely inhibits the enzyme, halting **cellular respiration** and **ATP production**, leading to rapid cell death. *DNA synthesis* - **Cyanide** does not directly inhibit **DNA polymerase** or other enzymes involved in DNA replication. - While overall cellular processes are disrupted, its primary toxic effect is not on DNA synthesis. *Protein breakdown* - **Cyanide** does not directly interfere with proteasomes or lysosomal enzymes responsible for **protein degradation**. - Its mechanism of action is upstream, affecting energy production necessary for all cellular processes, including protein turnover. *Protein synthesis* - **Cyanide** does not directly inhibit **ribosomes** or the enzymatic machinery for **protein synthesis**. - The lack of **ATP** caused by cyanide poisoning would eventually shut down protein synthesis, but this is a secondary effect, not the primary mechanism of action.
Question 179: Selenium deficiency is seen in -
- A. Keshan disease (Correct Answer)
- B. Wilson disease
- C. Acrodermatitis enteropathica
- D. None of the options
Explanation: ***Keshan disease*** - **Keshan disease** is a form of **cardiomyopathy** caused by **selenium deficiency**, particularly prevalent in regions with selenium-poor soil. - It presents with **heart failure**, arrhythmias, and cardiac enlargement. *Wilson disease* - **Wilson disease** is a disorder of **copper metabolism**, leading to excessive copper accumulation in organs, primarily the liver and brain. - It is not related to selenium deficiency. *Acrodermatitis enteropathica* - **Acrodermatitis enteropathica** is a genetic disorder of **zinc deficiency**, characterized by dermatitis, diarrhea, and alopecia. - It does not involve selenium deficiency. *None of the options* - This option is incorrect because Keshan disease is directly linked to selenium deficiency.
Question 180: Which vitamin deficiency is most commonly associated with chronic alcohol consumption and may require supplementation in alcohol use disorders?
- A. Pyridoxine
- B. Thiamine (Correct Answer)
- C. Riboflavin
- D. Niacin
Explanation: ***Thiamine*** - **Thiamine** (Vitamin B1) deficiency is extremely common in chronic alcoholics due to **poor dietary intake**, impaired absorption, and increased excretion. - Deficiency can lead to serious neurological complications like **Wernicke-Korsakoff syndrome**, characterized by confusion, ataxia, and ophthalmoplegia. *Pyridoxine* - **Pyridoxine** (Vitamin B6) deficiency can occur in alcoholics, but it is less common and less clinically significant than thiamine deficiency. - While it can manifest as peripheral neuropathy or **sideroblastic anemia**, it is not the most common or critical deficiency in this population. *Riboflavin* - **Riboflavin** (Vitamin B2) deficiency can also be seen in chronic alcoholics due to poor nutrition. - Symptoms like **cheilosis** and **angular stomatitis** are mild compared to the severe neurological consequences of thiamine deficiency. *Niacin* - **Niacin** (Vitamin B3) deficiency, known as **pellagra**, is rare in developed countries but can occur in severe malnutrition, including in some alcoholics. - Pellagra presents with the "3 Ds": **dermatitis**, **diarrhea**, and **dementia**, but it is generally less prevalent than thiamine deficiency in alcohol use disorders.