This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cell Signaling and Signal Transduction – Apoptosis”.
1. Which of the following type of cells recognize and kill the abnormal pathogen infected cells?
a) Mast cells
Explanation: The T-lymphocytes are immune cells that recognize and kill the pathogen infected target cells in an orderly manner (apoptosis). These cells accomplish the feat by binding to the cell surface receptors of infected/ abnormal cell.
2. When was the term apoptosis coined?
Explanation: The term apoptosis was coined in the year 1972 by John Kerr, Andrew Wyllie, and A. R. Currie of the University of Aberdeen, Scotland. Molecular basis of apoptosis were revealed by studies conducted on C.elegans.
3. Apoptosis is programmed cell death.
Explanation: Apoptosis is the programmed cell death in which a cascade of events leads to the death of the cell. Apoptosis usually occurs in response to an external stimulus or an abnormal change in the cell’s environment.
4. The CED3 gene product in nematodes has homologous _______________ in mammals.
Explanation: The CED3 gene plays a crucial role in the nematodes during apoptosis. The homologous family of proteins – caspases in mammals are cysteine proteases (having a cysteine residue in the catalytic site).
5. Inactivation of which of the following leads to detachment of the apoptotic cell?
Explanation: The focal adhesion kinase (FAK) is inactivated by the cleaving action of caspases during apoptosis. Cleavage of FAK leads to detachment of the apoptotic cell from its neighboring cells.
6. Inactivation of which of the following leads to shrinkage of the nucleus?
Explanation: Inactivation of lamins by the caspases leads to disassembly of nuclear lamina and shrinkage of the nucleus. Lamins are a special class of proteins that make up the inner lining of the nuclear envelope.
7. Cytokines serve as _____________________ for apoptosis.
a) internal stimuli
b) external stimuli
Explanation: Cytokines are substances including interleukin, interferon, secreted by certain immune cells that act as external stimulus whereas abnormalities in the DNA act as internal stimulus for apoptosis.
8. Which of the following is an extracellular messenger of apoptosis?
b) tumor necrosis factor
d) translation inhibitor
Explanation: Tumor necrosis factor (TNF) is an extracellular messenger for the extrinsic pathway of apoptosis. It has the ability to ablate tumor cells and is secreted by the cells of immune system in response to adverse conditions.
9. Which of the following is also termed as a death receptor?
Explanation: The tumor necrosis factor receptor (TNFR1) is also termed as the death receptor because it turns on the apoptotic process. The tumor necrosis factor (TNF) evokes its response by binding to the transmembrane receptor TNFR1.
10. The TNFR1 is a trimeric receptor.
Explanation: The TNFR1 is a trimeric receptor that contains a domain of 70 amino acids to which the tumor necrosis factor binds and brings about a change in the shape of the receptor. After there is a conformational change, proteins are recruited.
11. The last proteins to involve in the apoptotic pathway induced by TNF are ______________________
Explanation: The last proteins that get involved in the apoptotic pathway triggered by the tumor necrosis factor are procaspases-8 – the precursors of caspase proteins. Procaspases contain an extra portion that must be removed by catalytic action.
12. Which family of proteins regulates the intrinsic pathway of apoptosis?
Explanation: B-cell lymphoma 2 (Bcl2) is the family of proteins that regulate the intrinsic pathway of apoptosis. The family consists of three protein groups – proapoptotic, antiapoptotic and BH3-only proteins.
13. Which of the following is involved in the intrinsic pathway of apoptosis?
a) cytochrome a
b) cytochrome b
c) cytochrome c
d) cytochrome d
Explanation: Cytochrome c is the compound involved in intrinsic pathway of apoptosis. It is also a component of electron transport chain and mitochondrion. As the process of apoptosis initiates, the cells lose contact with the environment.
14. Apoptotic bodies can be recognized by the presence of _____________________ on the surface.
Explanation: The apoptotic bodies can be recognized by the presence of phosphatidylserine on their surface. Phosphatidylserine is a compound usually present on the inner surface of the plasma membrane.
Sanfoundry Global Education & Learning Series – Cell Biology.
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