What is the limiting amino acid in cereals?
Protein quality assessment is best done by?
Which nutrient is lost maximally in polished rice?
In which type of hemoglobin are zeta 2 and gamma 2 chains present?
Which of the following is required for proper effects of Insulin?
Which of these is not a part of extracellular matrix:
Which of the following is a metabolic disorder inherited in an X-linked manner?
Dietary deficiency of which vitamin is considered extremely rare?
Which of the following is NOT a manifestation of vitamin E deficiency?
Dermatitis may be a clinical manifestation of deficiency states of all of the following nutrients except -
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 101: What is the limiting amino acid in cereals?
- A. Methionine
- B. Tryptophan
- C. Lysine (Correct Answer)
- D. Cysteine
Explanation: ***Lysine*** - **Lysine** is the **first limiting amino acid in cereals** (wheat, rice, corn), meaning it is present in the lowest proportion relative to the body's needs. - This deficiency can impact **protein synthesis** if cereals are the sole or primary protein source without supplementation. - Complementing cereals with **legumes** (rich in lysine but low in methionine) provides complete protein nutrition. *Methionine* - **Methionine** is typically the limiting amino acid in **legumes**, not cereals. - It works with cysteine to provide **sulfur-containing amino acids** essential for various metabolic processes. - This is why cereal-legume combinations (rice and lentils, corn and beans) are nutritionally complementary. *Tryptophan* - **Tryptophan** is an essential amino acid, but it is generally **not the primary limiting amino acid in cereals**. - While corn can be relatively low in tryptophan, **lysine deficiency is more significant** across cereal grains. - It is a precursor to **serotonin** and **niacin**. *Cysteine* - **Cysteine** is a non-essential amino acid, meaning the body can synthesize it from methionine. - While important for protein structure and function, it is **not considered a limiting amino acid** since it can be produced endogenously.
Question 102: Protein quality assessment is best done by?
- A. NPU (Correct Answer)
- B. Biological value
- C. Amino acid score
- D. Digestibility coefficient
Explanation: ***NPU*** - **Net Protein Utilization (NPU)** is considered the best method for assessing protein quality because it measures the percentage of ingested protein that is actually retained and utilized by the body. - It accounts for both the **digestibility** of the protein and the **biological value** of the absorbed amino acids, providing a comprehensive assessment. *Biological value* - **Biological Value (BV)** measures the proportion of absorbed protein from food that becomes incorporated into proteins in the organism's body. - While important, BV does not account for the **digestibility** of the protein, meaning some protein may not be absorbed even if its amino acid profile is excellent. *Digestibility coefficient* - The **digestibility coefficient** measures the proportion of food protein that is absorbed from the gastrointestinal tract. - It only reflects the extent of **absorption** and does not provide information about how efficiently the absorbed amino acids are utilized once inside the body for protein synthesis. *Amino acid score* - The **amino acid score** compares the amino acid profile of a test protein with the amino acid requirements of humans. - This score identifies the **limiting amino acid** but does not factor in the protein's digestibility or how effectively the absorbed amino acids are used by the body.
Question 103: Which nutrient is lost maximally in polished rice?
- A. Proteins
- B. Thiamine (Correct Answer)
- C. Ascorbic acid
- D. Calcitriol
Explanation: ***Thiamine*** - **Polishing rice** removes the outer layers (bran and germ), which are rich in **thiamine (vitamin B1)**. - Significant loss of thiamine can lead to **beriberi**, characterized by neurological and cardiovascular symptoms. *Proteins* - While some protein is lost during milling, the primary nutritional loss in polished rice is not protein. - The germ and aleurone layer contain some protein, but the main carbohydrate-rich endosperm remains. *Ascorbic acid* - **Ascorbic acid (Vitamin C)** is not a significant nutrient in rice, so its loss during polishing is negligible. - Rice is not a primary dietary source of vitamin C. *Calcitriol* - **Calcitriol** is the active form of **vitamin D**, and rice does not naturally contain vitamin D. - Therefore, it cannot be lost during the polishing process.
Question 104: In which type of hemoglobin are zeta 2 and gamma 2 chains present?
- A. Gower I
- B. Gower II
- C. Portland (Correct Answer)
- D. Fetal hemoglobin
Explanation: ***Portland*** - **Portland hemoglobin** is a primitive embryonic hemoglobin composed of **zeta (ζ) 2 and gamma (γ) 2 chains** (ζ2γ2). - It plays a role in early fetal oxygen transport, particularly in the yolk sac stage. *Gower I* - **Gower I hemoglobin** is another embryonic hemoglobin, but it consists of **zeta (ζ) 2 and epsilon (ε) 2 chains** (ζ2ε2). - This composition is crucial for oxygen delivery during the very initial stages of embryonic development. *Gower II* - **Gower II hemoglobin** is an embryonic hemoglobin made up of **alpha (α) 2 and epsilon (ε) 2 chains** (α2ε2). - It represents a transitional form as the embryo develops and starts producing alpha globin chains. *Fetal hemoglobin* - **Fetal hemoglobin (HbF)** consists of **alpha (α) 2 and gamma (γ) 2 chains** (α2γ2). - It is the predominant hemoglobin during the second and third trimesters of pregnancy and has a higher affinity for oxygen than adult hemoglobin.
Question 105: Which of the following is required for proper effects of Insulin?
- A. Chromium (Correct Answer)
- B. Selenium
- C. Copper
- D. Iron
Explanation: ***Chromium*** - **Chromium** is an essential trace mineral that plays a crucial role in enhancing the action of **insulin** by promoting its binding to cell receptors. - It is a key component of **glucose tolerance factor (GTF)**, which helps cells absorb glucose more efficiently. *Selenium* - **Selenium** is an antioxidant and is involved in thyroid hormone metabolism and immune function, but it does not directly facilitate insulin action. - While important for overall health, it has no known direct requirement for the proper effects of insulin. *Copper* - **Copper** is involved in various enzymatic reactions, iron metabolism, and connective tissue formation, but it is not directly required for insulin's proper function. - High levels of **copper** can even negatively impact glucose metabolism in some contexts. *Iron* - **Iron** is essential for oxygen transport in hemoglobin and myoglobin, as well as for many enzymatic processes, but it does not directly enhance insulin sensitivity or action [1]. - Both **iron deficiency** and **iron overload** can indirectly affect metabolic health but do not directly influence insulin's effects in the same way chromium does [2].
Question 106: Which of these is not a part of extracellular matrix:
- A. Collagen
- B. Laminin
- C. Fibronectin
- D. Integrins (Correct Answer)
Explanation: ***Integrins*** - Integrins are **transmembrane receptors** on the cell surface that facilitate cell-extracellular matrix (ECM) adhesion and cell-cell adhesion. - They are part of the cell membrane, **not** an extracellular component. *Laminin* - **Laminin** is a major protein component of the **basal lamina**, a specialized extracellular matrix that underlies epithelial cells. - It plays a crucial role in cell adhesion, differentiation, and migration within the ECM. *Fibronectin* - **Fibronectin** is a large glycoprotein present in the **extracellular matrix** and in soluble form in blood plasma. - It mediates cell adhesion to the ECM by binding to integrins and various ECM components like collagen and proteoglycans. *Collagen* - **Collagen** is the most abundant protein in the human body and a primary structural component of the **extracellular matrix**. - It provides tensile strength and structural integrity to tissues like skin, bone, tendons, and cartilage.
Question 107: Which of the following is a metabolic disorder inherited in an X-linked manner?
- A. Duchenne muscular dystrophy
- B. Adrenoleukodystrophy (Correct Answer)
- C. Phenylketonuria
- D. Marfan syndrome
Explanation: ***Adrenoleukodystrophy*** - **Adrenoleukodystrophy (ALD)** is an **X-linked recessive disorder** that affects the metabolism of very long-chain fatty acids (VLCFAs). - It leads to the demyelination of nerve cells in the brain and spinal cord, as well as adrenal gland insufficiency. *Phenylketonuria* - **Phenylketonuria (PKU)** is an **autosomal recessive metabolic disorder** caused by a defect in the enzyme phenylalanine hydroxylase. - It results in the accumulation of phenylalanine, leading to intellectual disability if not treated with a specialized diet. *Duchenne muscular dystrophy* - While **Duchenne muscular dystrophy (DMD)** is indeed an **X-linked recessive disorder**, it is primarily a muscle disorder, not a metabolic disorder in the classic sense. - It involves a mutation in the **dystrophin gene**, leading to progressive muscle degeneration and weakness. *Marfan syndrome* - **Marfan syndrome** is an **autosomal dominant disorder** affecting connective tissue. - It is caused by a mutation in the **FBN1 gene**, which codes for fibrillin-1, and primarily affects the skeletal, ocular, and cardiovascular systems.
Question 108: Dietary deficiency of which vitamin is considered extremely rare?
- A. Thiamine
- B. Vitamin B6
- C. Vitamin E (Correct Answer)
- D. Vitamin D
Explanation: ***Vitamin E*** - **Vitamin E deficiency** is exceptionally rare because it is a **fat-soluble vitamin** stored in the body and is widely available in many common foods. - Symptoms of deficiency, when they do occur, are usually seen in individuals with severe **malabsorption syndromes** or genetic abnormalities affecting its metabolism. *Vitamin B6* - **Vitamin B6 deficiency** can occur, especially in individuals with **alcoholism**, those taking certain medications, or with certain chronic diseases. - It can manifest with neurological symptoms, such as **neuropathy** and **seizures**, as well as dermatological issues. *Thiamine* - **Thiamine (Vitamin B1) deficiency** is a known problem in regions with poor nutrition and in chronic alcoholics. - It leads to conditions like **beriberi** (wet and dry) and **Wernicke-Korsakoff syndrome**, affecting the cardiovascular and nervous systems. *Vitamin D* - **Vitamin D deficiency** is common globally, particularly in populations with limited sun exposure or inadequate dietary intake. - It can cause **rickets** in children and **osteomalacia** in adults, impacting bone health.
Question 109: Which of the following is NOT a manifestation of vitamin E deficiency?
- A. Posterior column abnormalities
- B. Cerebellar ataxia
- C. Hemolytic anemia
- D. Autonomic dysfunction (Correct Answer)
Explanation: ***Autonomic dysfunction*** - **Autonomic dysfunction** is not typically associated with vitamin E deficiency. Instead, it is commonly seen in conditions like **diabetes mellitus**, Parkinson's disease, or certain inherited neuropathies. - Vitamin E primarily acts as an **antioxidant** and is crucial for neurological and red blood cell health. *Hemolytic anemia* - Vitamin E is an **antioxidant** that protects red blood cell membranes from **oxidative damage**. - Its deficiency can lead to increased fragility and **hemolysis** of red blood cells, resulting in hemolytic anemia, particularly in premature infants. *Posterior column abnormalities* - Vitamin E deficiency can cause **neurological dysfunction** due to oxidative damage to neuronal membranes. - This often manifests as degeneration of the **posterior columns** of the spinal cord, leading to impaired proprioception and vibratory sensation. *Cerebellar ataxia* - The **cerebellum** is highly susceptible to oxidative stress, and vitamin E deficiency can lead to damage in this area. - This damage results in **ataxia**, characterized by impaired coordination, balance, and gait disturbances.
Question 110: Dermatitis may be a clinical manifestation of deficiency states of all of the following nutrients except -
- A. Biotin
- B. Niacin
- C. Pyridoxine
- D. Thiamine (Correct Answer)
Explanation: ***Thiamine*** - A deficiency in **thiamine (vitamin B1)** primarily affects the nervous and cardiovascular systems, leading to conditions like **beriberi**, characterized by neuropathy, heart failure, and Wernicke-Korsakoff syndrome. - Dermatitis is **not a typical or direct clinical manifestation** of thiamine deficiency. *Biotin* - **Biotin (vitamin B7)** deficiency can cause **dermatitis**, often described as a scaly, erythematous rash around the eyes, nose, and mouth. - Hair loss (**alopecia**) and **neurological symptoms** are also associated with biotin deficiency. *Niacin* - **Niacin (vitamin B3)** deficiency leads to **pellagra**, classically presenting with the "3 Ds": **dermatitis**, **diarrhea**, and **dementia**. - The dermatitis in pellagra is typically symmetrical and photosensitive, affecting sun-exposed areas. *Pyridoxine* - **Pyridoxine (vitamin B6)** deficiency can result in **seborrheic dermatitis-like rash**, especially around the eyes, nose, and mouth. - Other symptoms include **glossitis**, **cheilosis**, and **neurological disturbances** like peripheral neuropathy.