Signal Transduction — MCQs
On this page
Which type of interferon is predominantly produced by fibroblasts in tissue culture?
Which of the following induces apoptosis in a cell?
cGMP is a second messenger for which hormone(s)?
In apoptosis, cytochrome C acts through:
During angiogenesis, what factors are responsible for the recruitment of pericytes and periendothelial cells?
Serpentine receptor is a:
Which one of the following substances increases the release of Ca2+ from the endoplasmic reticulum?
Signal Transduction Indian Medical PG Practice Questions and MCQs
Question 141: Which type of interferon is predominantly produced by fibroblasts in tissue culture?
- A. Alpha
- B. Beta (Correct Answer)
- C. Gamma
- D. None of the options
Explanation: ***Beta*** - **Interferon-beta** (IFN-β) is predominantly produced by **fibroblasts** in response to viral infections. - It is a **Type I interferon** playing a crucial role in the initial innate immune response. *Alpha* - **Interferon-alpha** (IFN-α) is primarily produced by **leukocytes**, particularly **plasmacytoid dendritic cells**. - While also a **Type I interferon**, its cellular origin differs from fibroblasts. *Gamma* - **Interferon-gamma** (IFN-γ) is a **Type II interferon** typically produced by **T lymphocytes** and **natural killer (NK) cells**. - It is involved in adaptive immunity and immune regulation, distinct from the antiviral response of fibroblasts. *None of the options* - This option is incorrect as one of the interferons listed is indeed produced by fibroblasts. - **Interferon-beta** is specifically known for its production by fibroblasts.
Question 142: Which of the following induces apoptosis in a cell?
- A. Glucocorticoids (Correct Answer)
- B. Isoprenoids
- C. Myristic acid
- D. Oleic acid
Explanation: ***Glucocorticoids*** - **Glucocorticoids** are known to induce apoptosis in various cell types, particularly lymphocytes, making them useful in **lymphoid malignancies**. - They activate a complex signaling pathway that leads to the activation of pro-apoptotic proteins and the suppression of anti-apoptotic proteins, ultimately resulting in **programmed cell death**. *Isoprenoids* - **Isoprenoids** are a large class of organic compounds derived from isoprene, involved in various metabolic processes like cholesterol synthesis and protein prenylation, but do not directly induce apoptosis. - While some isoprenoid precursors or inhibitors of isoprenoid synthesis can affect cell proliferation or survival, isoprenoids themselves are not primary apoptosis inducers. *Myristic acid* - **Myristic acid** is a saturated fatty acid primarily involved in protein myristoylation, a post-translational modification essential for various cellular functions. - It is not known to be a direct inducer of apoptosis but can influence signaling pathways that may indirectly impact cell survival or death. *Oleic acid* - **Oleic acid** is a monounsaturated fatty acid that is a major component of cell membranes and is involved in energy storage and signaling. - It is generally considered cytoprotective and can even inhibit apoptosis in some contexts, rather than inducing it.
Question 143: cGMP is a second messenger for which hormone(s)?
- A. Atrial natriuretic factor (Correct Answer)
- B. Antidiuretic hormone (ADH)
- C. Angiotensin II
- D. Somatostatin
Explanation: ***Atrial natriuretic factor*** - **Atrial natriuretic peptide (ANP)** binds to a **particulate guanylyl cyclase receptor**, activating it to convert **GTP to cGMP**. - **cGMP** then mediates the downstream effects of ANP, such as **vasodilation** and increased **sodium excretion**. *Somatostatin (inhibits growth hormone and insulin secretion)* - Somatostatin acts primarily through **G-protein coupled receptors** that inhibit **adenylyl cyclase**, leading to a decrease in **cAMP** levels. - It does not directly utilize **cGMP** as a second messenger. *Angiotensin II (increases blood pressure via other pathways).* - Angiotensin II primarily acts through **Gq-protein coupled receptors**, leading to activation of **phospholipase C** and generation of **IP3** and **DAG**. - Its effects are mediated by **calcium** and **protein kinase C**, not **cGMP**. *Antidiuretic hormone (ADH)* - **ADH** acts through two main receptor types: **V1 receptors** (via **IP3/DAG** pathway) and **V2 receptors** (via **cAMP** pathway). - Neither of these pathways involves **cGMP** as a primary second messenger.
Question 144: In apoptosis, cytochrome C acts through:
- A. FADD
- B. TNF
- C. Apaf1 (Correct Answer)
- D. Bcl-2
Explanation: ***Apaf1*** - Cytochrome C released from the mitochondria binds to **Apaf1**, which leads to the formation of the **apoptosome** [1][2]. - This complex activates **caspase-9**, initiating the caspase cascade that leads to apoptosis [2]. *TNF* - Tumor Necrosis Factor (TNF) is involved in **necrosis** and **inflammatory processes**, not directly in the intrinsic pathway of apoptosis. - It activates **caspase-8**, which is part of the **extrinsic pathway**, differing from the role of cytochrome C [1]. *FADD* - FADD (Fas-associated protein with death domain) is part of the **death receptor pathway**, linking to caspase-8, not associated with cytochrome C [1]. - It does not play a role in the assembly of the apoptosome like Apaf1 does. *Bcl_2* - Bcl-2 is an **anti-apoptotic protein** that inhibits apoptosis rather than inducing it or acting through cytochrome C [1]. - It functions by preventing the release of cytochrome C from mitochondria, thereby opposing the apoptotic process [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 310. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 64-67.
Question 145: During angiogenesis, what factors are responsible for the recruitment of pericytes and periendothelial cells?
- A. VEGF & PDGF
- B. Angiopoietins, TGF & PDGF (Correct Answer)
- C. VEGF, IL-2, IL-6
- D. TGF, VEGF & PDGF
Explanation: ***Angiopoietins, TGF & PDGF*** - **Angiopoietins** are crucial for the stabilization of blood vessels and recruitment of **pericytes**, enhancing vessel maturation [1]. - **TGF (Transforming Growth Factor)** and **PDGF (Platelet-Derived Growth Factor)** also play significant roles in the recruitment and proliferation of **pericytes** and periendothelial cells during angiogenesis [1]. *VEGF & PDGF* - While **VEGF (Vascular Endothelial Growth Factor)** is important for endothelial cell migration and proliferation, it does not directly recruit **pericytes** alone. - This combination lacks **angiopoietins**, which are key for the stabilization of newly formed blood vessels [1]. *VEGF, IL-2, IL-6* - **IL-2** and **IL-6** are primarily associated with immune responses and do not directly contribute to pericyte recruitment during angiogenesis. - **VEGF** alone supports endothelial cells but does not effectively recruit **pericytes** without the cooperation of other factors. *TGF, VEGF & PDGF* - Although both **TGF** and **PDGF** are involved in pericyte recruitment [1], the absence of **angiopoietins** limits the effectiveness of this combination for the recruitment process. - **VEGF** alone does not facilitate direct recruitment of **pericytes**, as it mainly focuses on endothelial cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 115-116.
Question 146: Serpentine receptor is a:
- A. Five-pass transmembrane protein
- B. Seven-pass transmembrane protein (Correct Answer)
- C. Nine-pass transmembrane protein
- D. Three-pass transmembrane protein
Explanation: ***Seven-pass transmembrane protein*** - Serpentine receptors, also known as **G protein-coupled receptors (GPCRs)**, are characterized by their structure, which threads through the cell membrane **seven times**. - This characteristic "serpentine" structure forms **three extracellular and three intracellular loops**, along with an extracellular N-terminus and an intracellular C-terminus, crucial for ligand binding and G protein activation, respectively. *Five-pass transmembrane protein* - This structural configuration is **not characteristic** of serpentine receptors or GPCRs, which consistently pass through the membrane seven times. - Receptors with five transmembrane domains would have a **different folding pattern** and functional mechanism compared to GPCRs. *Nine-pass transmembrane protein* - This is an **incorrect description** for serpentine receptors; GPCRs are specifically defined by their seven transmembrane helices. - While some transmembrane proteins can have more passes, nine passes are **not typical** for this class of receptors. *Three-pass transmembrane protein* - This describes a protein with **fewer transmembrane segments** than a serpentine receptor. - Receptors with only three transmembrane domains would be structurally and functionally **distinct** from GPCRs, which require seven passes to mediate their characteristic signaling.
Question 147: Which one of the following substances increases the release of Ca2+ from the endoplasmic reticulum?
- A. Inositol triphosphate (Correct Answer)
- B. 1,25 - dihydroxy cholecalciferol
- C. Diacylglycerol
- D. Parathyroid hormone
Explanation: ***Inositol triphosphate*** - **Inositol triphosphate (IP3)** is a secondary messenger that binds to specific receptors on the **endoplasmic reticulum (ER)**, triggering the release of stored **Ca2+** into the cytoplasm. - This calcium release plays a crucial role in various cellular processes, including **muscle contraction**, **neurotransmission**, and **hormone secretion**. *1,25 - dihydroxycholecalciferol* - This is the active form of **vitamin D**, primarily involved in **calcium absorption** from the gut and **calcium reabsorption** in the kidneys. - It does not directly increase Ca2+ release from the endoplasmic reticulum. *Diacylglycerol* - **Diacylglycerol (DAG)** is another secondary messenger, also produced from the cleavage of **PIP2** along with IP3. - DAG primarily activates **protein kinase C (PKC)**, which is involved in signal transduction pathways, but it does not directly trigger Ca2+ release from the ER. *Parathyroid hormone* - **Parathyroid hormone (PTH)** is a hormone that primarily regulates **extracellular calcium levels** by promoting bone resorption, increasing renal calcium reabsorption, and stimulating the synthesis of 1,25-dihydroxycholecalciferol. - While it ultimately increases blood calcium, it does not directly cause Ca2+ release from the endoplasmic reticulum.
Practice by Chapter
Cell Surface Receptors: Types and Functions
Practice Questions
G-Protein Coupled Receptors
Practice Questions
Enzyme-Linked Receptors
Practice Questions
Second Messengers in Signal Transduction
Practice Questions
cAMP and cGMP Signaling
Practice Questions
Calcium as Second Messenger
Practice Questions
Inositol Phosphate Pathway
Practice Questions
MAP Kinase Cascades
Practice Questions
JAK-STAT Signaling Pathway
Practice Questions
Insulin Signaling Pathway
Practice Questions
Nuclear Receptors and Gene Regulation
Practice Questions
Defects in Signal Transduction and Disease
Practice Questions
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free