What is the molecular mass of Immunoglobulin G (IgG) in kilodaltons (kDa)?
What is the Net Protein Utilization (NPU) for eggs?
What is the limiting amino acid in cereals?
Protein quality assessment is best done by?
Which nutrient is lost maximally in polished rice?
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 molecular mass of Immunoglobulin G (IgG) in kilodaltons (kDa)?
- A. 150 (Correct Answer)
- B. 400
- C. 1000
- D. 1500
Explanation: **\*Correct Option: 150 kDa\*** - **Immunoglobulin G (IgG)** is the most abundant antibody in human serum and has a characteristic molecular mass of approximately **150 kDa**. - This mass is attributed to its structure, comprising two identical **heavy chains** (~50 kDa each) and two identical **light chains** (~25 kDa each). - IgG represents about **75-80% of total serum immunoglobulins** and is the main antibody involved in secondary immune responses. *Incorrect Option: 400 kDa* - A molecular mass of **400 kDa** is significantly higher than that of a monomeric IgG molecule. - This mass is closer to **IgM pentamers** (~900 kDa) or large protein complexes, but still does not match any standard immunoglobulin structure. *Incorrect Option: 1000 kDa* - A molecular mass of **1000 kDa (1 MDa)** is far too large for a single IgG molecule. - This weight typically corresponds to very large macromolecular structures or aggregates, such as **ribosomes** or large enzyme complexes. *Incorrect Option: 1500 kDa* - A molecular mass of **1500 kDa (1.5 MDa)** is extremely large for an individual antibody. - Such a mass would be characteristic of very large protein assemblies, viral capsids, or cellular components, not a soluble antibody.
Question 102: 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 103: 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 104: 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 105: 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 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.