Which of the following is not a free radical?
Which of the following is an example of an antiapoptotic gene?
Unfolded protein metabolism is associated with
Which of the following is the most reactive free radical?
Which of the following is a positive acute phase protein that enhances the acute phase response?
Location of gene on chromosome is identified by
Which of the following is required for proper effects of Insulin?
Which nutrient is lost maximally in polished rice?
In which type of hemoglobin are zeta 2 and gamma 2 chains present?
What is the Net Protein Utilization (NPU) for eggs?
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 91: Which of the following is not a free radical?
- A. Superoxide anion
- B. Hydrogen peroxide (H2O2) (Correct Answer)
- C. Nitric oxide (NO·)
- D. Hydroxyl radical (.OH)
Explanation: ***Hydrogen peroxide (H₂O₂)*** - **Hydrogen peroxide** is a **reactive oxygen species (ROS)** but is not a free radical because it has **no unpaired electrons** in its outermost shell. - While it can be converted into the highly reactive hydroxyl radical via the **Fenton reaction**, it is stable enough to be transported across membranes. *Superoxide anion (O₂⁻)* - The **superoxide anion (O₂⁻)** is a free radical because it has an **unpaired electron** in its outer shell. - It is one of the primary **reactive oxygen species** formed during cellular metabolism and can damage cellular components. *Nitric oxide (NO·)* - **Nitric oxide** is an important **free radical** with a single **unpaired electron** in its molecular structure. - It functions as a vital signaling molecule in vascular biology, regulating blood pressure and neurotransmission, despite being a free radical. *Hydroxyl radical (·OH)* - The **hydroxyl radical (·OH)** is one of the most reactive and damaging **free radicals** in biological systems. - It has a single **unpaired electron**, making it highly unstable and able to react indiscriminately with virtually all types of biomolecules.
Question 92: Which of the following is an example of an antiapoptotic gene?
- A. FLIP (Correct Answer)
- B. P53
- C. BAX
- D. BIM
Explanation: ***FLIP*** - **FLIP** is an **antiapoptotic gene** that inhibits the activation of caspase-8, thereby blocking the extrinsic apoptotic pathway. - It acts as an **FLICE-inhibitory protein**, preventing the formation of the death-inducing signaling complex (DISC) or its downstream activation. *P53* - **P53** is a **tumor suppressor gene** that promotes apoptosis in response to DNA damage or cellular stress. - It is a **pro-apoptotic gene**, orchestrating cell cycle arrest and apoptosis to prevent the propagation of damaged cells. *BAX* - **BAX** is a **pro-apoptotic gene** belonging to the Bcl-2 family, which promotes the release of cytochrome c from mitochondria. - This release initiates the **intrinsic apoptotic pathway**, leading to caspase activation and cell death. *BIM* - **BIM** is a **pro-apoptotic gene** of the Bcl-2 family, acting as a sensitizer for apoptosis by binding to and inhibiting anti-apoptotic Bcl-2 family proteins. - Its activation leads to the **neutralization of survival factors**, thereby promoting mitochondrial outer membrane permeabilization and apoptosis.
Question 93: Unfolded protein metabolism is associated with
- A. Endoplasmic reticulum (Correct Answer)
- B. Golgi apparatus
- C. Mitochondria
Explanation: ***Endoplasmic reticulum*** - The **endoplasmic reticulum (ER)** is the primary site for protein folding, modification, and assembly, especially for secreted and transmembrane proteins. - When misfolded proteins accumulate, the ER triggers the **unfolded protein response (UPR)** to restore homeostasis or induce apoptosis. *Golgi apparatus* - The Golgi apparatus is primarily involved in **further processing**, sorting, and packaging of proteins and lipids synthesized in the ER. - It does not directly manage the initial folding of proteins or the response to widespread protein misfolding. *Mitochondria* - **Mitochondria** are known for their role in **energy production** (ATP synthesis) through cellular respiration. - While they possess their own protein synthesis machinery for some essential mitochondrial proteins, they are not involved in the overall cellular management of unfolded protein metabolism from the ER.
Question 94: Which of the following is the most reactive free radical?
- A. Alkyl radical
- B. Superoxide radical
- C. Peroxide radical
- D. Hydroxyl radical (Correct Answer)
Explanation: ***Hydroxyl radical*** - The **hydroxyl radical (•OH)** is the most reactive free radical in biological systems due to its extremely high oxidation potential and short half-life. - It readily reacts with virtually all cellular macromolecules, including **DNA, proteins, and lipids**, causing widespread damage. *Peroxide radical* - The **peroxide radical (ROO•)**, or more specifically the peroxyl radical, is less reactive than the hydroxyl radical, but still significant in lipid peroxidation. - It plays a role in propagating chain reactions of **lipid damage** in cell membranes. *Alkyl radical* - **Alkyl radicals (R•)** are generally formed as intermediates during the abstraction of hydrogen atoms from saturated compounds. - While reactive, they are typically less reactive and less frequently encountered in biological systems compared to oxygen-centered radicals like the hydroxyl radical. *Superoxide radical* - The **superoxide radical (O₂•−)** is a relatively less reactive free radical compared to the hydroxyl radical, but it is the precursor to many other reactive oxygen species (ROS). - It is primarily involved in **initiation of oxidative stress** and can lead to the formation of more damaging species through reactions like the Haber-Weiss reaction.
Question 95: Which of the following is a positive acute phase protein that enhances the acute phase response?
- A. Fibrinogen (Correct Answer)
- B. Transferrin
- C. Albumin
- D. Prealbumin
Explanation: ***Fibrinogen*** - **Fibrinogen** is a key **positive acute phase protein** whose concentration increases significantly during inflammation - Its elevation contributes to the acute phase response by promoting **blood clotting** and influencing **erythrocyte sedimentation rate (ESR)** - Along with C-reactive protein (CRP), haptoglobin, and serum amyloid A, fibrinogen is among the major positive acute phase reactants *Transferrin* - **Transferrin** is a **negative acute phase protein**, meaning its concentration decreases during inflammation - This reduction is part of the body's iron-sequestration strategy to limit iron availability for invading pathogens - The decrease in transferrin helps restrict bacterial growth by reducing available iron *Albumin* - **Albumin** is a prominent **negative acute phase protein**, with its concentration decreasing during acute inflammation due to redistribution and reduced synthesis - It plays a vital role in maintaining **oncotic pressure** and transporting various substances - Its decline reflects the severity of inflammation and is used as a marker of the acute phase response *Prealbumin* - **Prealbumin** (also known as transthyretin) is a **negative acute phase protein** and a sensitive marker of nutritional status - Its rapid decline during inflammation makes it a useful indicator, as its synthesis is quickly reduced - It has a short half-life (2-3 days), making it more sensitive to acute changes than albumin
Question 96: Location of gene on chromosome is identified by
- A. Karyotyping
- B. Genetic mapping (Correct Answer)
- C. Microarray
- D. Genomic imprinting
Explanation: ***Genetic mapping*** - **Genetic mapping** (also called chromosome mapping) uses various techniques to determine the **physical location (locus)** of genes on a chromosome. - Techniques include **linkage analysis**, **FISH (Fluorescence In Situ Hybridization)**, chromosomal banding, and analysis of **inheritance patterns** of traits and genetic markers. - This identifies both the **relative positions** between genes and their **absolute chromosomal addresses**. *Karyotyping* - **Karyotyping** is a technique that visualizes the entire set of chromosomes in an organism. - While it can identify **large chromosomal abnormalities** like aneuploidy or major deletions/insertions, it does not pinpoint the exact location of a specific gene. *Microarray* - **Microarray** technology is used to study the expression levels of thousands of genes simultaneously or to detect specific genetic variations. - It does not directly map the physical location of a gene on a chromosome. *Genomic imprinting* - **Genomic imprinting** is an epigenetic phenomenon where certain genes are expressed in a **parent-of-origin-specific manner**. - It describes a mechanism of gene regulation rather than a method for identifying the location of a gene on a chromosome.
Question 97: 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 98: 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 99: 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 100: 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.