Cell Biology Questions and Answers – Cytoplasmic Membrane Systems – Endocytosis

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This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cytoplasmic Membrane Systems – Endocytosis”.

1. Endocytosis and phagocytosis refer to the same process.
a) True
b) False
View Answer

Answer: b
Explanation: Endocytosis is the process where the cell engulfs cell surface receptors bound with ligands; whereas phagocytosis is the process where the cell uptakes particulate matter.
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2. Which of the following is a type of endocytosis?
a) Pinocytosis
b) Phagocytosis
c) Hemolysis
d) Cytogenesis
View Answer

Answer: a
Explanation: Pinocytosis, also called bulkphase endocytosis is the nonspecific uptake of extracellular material. This process also removes portions of the plasma membrane and function in membrane recycling.

3. The process in which cell uptakes extracellular material bound to cell surface receptors is known as __________________
a) phagocytosis
b) pinocytosis
c) receptormediated endocytosis
d) bulkphase endocytosis
View Answer

Answer: c
Explanation: The specific uptake of extracellular materials in which they are bound to external surface of the plasma membrane, is known as receptormediated endocytosis.

4. Receptormediated endocytosis (RME) leads to the formation of ___________ coated pits.
a) clathrin
b) lipid
c) lysosome
d) mannose
View Answer

Answer: a
Explanation: Substances bound to receptors enter a cell by receptormediated endocytosis and collect in specialized domains of the plasma membrane called the ‘coated pits’. Clathrin is present on the electrondense coat of these pits.

5. A molecule of clathrin has a ______________ structure.
a) triskelion
b) spherical
c) cylindrical
d) polygonal
View Answer

Answer: a
Explanation: A molecule of clathrin has three heavy and three light chains joined at the center, forming a threelegged structure called triskelion.
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6. Which adaptor molecule operate in clathrinmediated endocytosis?
a) GGA
b) AP1
c) AP2
d) Sar1
View Answer

Answer: c
Explanation: AP2 adaptor molecules are associated with clathrin coated pits formed in the plasma membranes as a result of receptormediated endocytosis.

7. Dynamin is a _____________________
a) adaptor molecule
b) accessory protein
c) integral membrane protein
d) phospholipids
View Answer

Answer: b
Explanation: Dynamin is a large GTPbinding accessory protein that aids in the release of clathrincoated vesicle from the membrane on which it is formed.

8. Receptor down regulation leads to a decrease in the sensitivity of the cell towards further stimulation.
a) True
b) False
View Answer

Answer: a
Explanation: There are two different types of receptors involved in the endocytosis. The endocytosis mediated by the second group of receptors leads to their destruction, called the receptor down regulation. This decreases the sensitivity of the cell towards further stimulation.

9. Following internalization, vesiclebound materials are transported to _________________
a) nucleus
b) peroxisomes
c) lysosomes
d) endosomes
View Answer

Answer: d
Explanation: Following the internalization of materials from the extracellular environment to the intracellular environment, the vesicle bound materials are transported to endosomes.
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10. Late endosomes are located near the _____________
a) membrane
b) nucleus
c) mitochondria
d) peroxisomes
View Answer

Answer: b
Explanation: The complex network of tubules and vesicles is collectively known as endosomes. There are two classes of endosomes: early endosomes, located near the cell periphery, and late endosomes, located near the nucleus.

11. Transformation from an early to a late endosome is characterized by a decrease in ______________
a) mobility
b) lipid content
c) pH
d) protein content
View Answer

Answer: c
Explanation: Transformation from an early endosome to a late endosome is characterized by a decrease in the pH and a major change in the internal morphology of the structure.

12. Receptors dissociate from their bound ligands as a result of ________________
a) high H+ concentration
b) low H+ concentration
c) high Cl concentration
d) low Cl concentration
View Answer

Answer: a
Explanation: The receptors dissociate from their bound ligands as a result of high H+ concentration in the early endosomes. Following which they are concentrated into specialized tubular compartments representing the recycling centers of endosomes.

13. Where do the materials ingested by endocytosis, reach after travelling through the late endosome?
a) nucleus
b) lysosome
c) mitochondria
d) early endosome
View Answer

Answer: b
Explanation: After endocytosis materials reach the late endosome, where the bound ligands are concentrated. After late endosome the materials reach lysosome for further processing.
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14. ‘NiemannPick type C disease’ is caused due to deficiency of a specific ________________
a) protein
b) receptor
c) ligand
d) gene
View Answer

Answer: a
Explanation: ‘NiemannPick type C disease’ is an inherited disorder in which a protein required to transfer cholesterol out of the lysosomes is lacking. Consequently, cholesterol is accumulated in these organelles leading to nerve degeneration.

15. Mycobacterium tuberculosis inhibits the fusion of its phagosome with _________________ following phagocytosis.
a) membrane
b) lysosome
c) endosome
d) chromosome
View Answer

Answer: b
Explanation: Mycobacterium tuberculosis is the agent responsible for tuberculosis. Following its phagocytosis, the bacterium inhibits the fusion of phagosome with the lysosome, preventing its deactivation in the cell.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn