Which of the following is required for proper effects of Insulin?
Which of the following acids is MOST commonly used as a reagent in medical laboratory analytical procedures?
Shadow casting is used in -
What is the molecular mass of Immunoglobulin G (IgG) in kilodaltons (kDa)?
What is the Net Protein Utilization (NPU) for eggs?
Which of the following is a metabolic disorder inherited in an X-linked manner?
Which of these is not a part of extracellular matrix:
Dermatitis may be a clinical manifestation of deficiency states of all of the following nutrients except -
Dietary deficiency of which vitamin is considered extremely rare?
Which of the following is NOT a manifestation of vitamin E deficiency?
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 101: 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 102: Which of the following acids is MOST commonly used as a reagent in medical laboratory analytical procedures?
- A. Nitric acid is used in chemical analysis.
- B. Carbolic acid is used as a disinfectant.
- C. Oxalic acid is used in various laboratory applications.
- D. Sulphuric acid is used in various laboratory processes. (Correct Answer)
Explanation: ***Sulphuric acid*** is the most commonly used acid in medical laboratory analytical procedures. - **Sulfuric acid (H₂SO₄)** is a strong mineral acid with the **widest range of applications** in clinical and research laboratories - Used extensively as a **catalyst and reagent** in numerous analytical procedures including **protein digestion**, **Kjeldahl nitrogen estimation**, and **enzymatic assays** - Essential in **sample preparation** for heavy metal analysis and trace element detection - Utilized in **deproteinization** procedures and various **colorimetric assays** - Its strong **dehydrating properties** make it valuable in multiple biochemical protocols *Nitric acid* - **Nitric acid (HNO₃)** is primarily used for **acid digestion** of samples in trace element analysis - Strong **oxidizing agent** but has more **specialized applications** compared to sulfuric acid - More commonly used in **environmental and toxicology testing** than routine clinical biochemistry - Its highly **corrosive and oxidizing nature** limits its use in routine procedures *Carbolic acid* - **Carbolic acid (phenol/C₆H₅OH)** is technically not a mineral acid but a weak organic acid - Historically used as an **antiseptic and disinfectant** (Lister's antiseptic) - Modern laboratory use is **limited** to specific applications like **phenol-chloroform extraction** in molecular biology - Due to **toxicity concerns**, largely replaced by safer alternatives in routine disinfection *Oxalic acid* - **Oxalic acid (C₂H₂O₄)** is an organic dicarboxylic acid with **specialized applications** - Used in **decalcification of bone samples** for histopathology - Functions as a **reducing agent** in specific analytical procedures - Not a routine reagent in general medical laboratory practice compared to sulfuric acid
Question 103: Shadow casting is used in -
- A. Light microscopy
- B. Electron microscopy (Correct Answer)
- C. Fluorescence microscopy
- D. Phase contrast microscopy
Explanation: ***Electron microscopy*** - **Shadow casting** is a technique used in **electron microscopy** to enhance contrast and reveal the three-dimensional topography of small structures and molecules by depositing a thin film of heavy metal at an angle. - This process creates areas with more metal (which appears darker) and areas shielded from the metal deposition (appearing lighter, like a shadow), thereby outlining the specimen. *Light microscopy* - **Light microscopy** uses visible light to illuminate specimens and a system of lenses to magnify images, and it does not typically employ shadow casting techniques for contrast enhancement. - While various techniques like staining are used for contrast, the principle of creating shadows by metal deposition is not applicable to light interactions with the sample. *Fluorescence microscopy* - **Fluorescence microscopy** utilizes the property of some substances to emit light of a longer wavelength when excited by light of a shorter wavelength (fluorescence), and it relies on fluorochromes for visualization, not shadow casting. - This technique creates contrast based on specific labels or autofluorescence, highlighting particular structures without direct shadowing. *Phase contrast microscopy* - **Phase contrast microscopy** converts phase shifts in light passing through a transparent specimen into changes in amplitude (brightness), which are then visible as differences in image contrast, and it does not involve metal deposition or shadow casting. - This method is particularly useful for observing live, unstained biological samples by detecting optical path differences.
Question 104: 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 105: 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 106: 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 107: 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 108: 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.
Question 109: 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 110: 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.