This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cytoplasmic Membrane Systems – Studying Endomembrane System”.
1. Which technique was used to study the secretory pathway in acinar cells of the pancreas for the first time?
a) Gel electrophoresis
b) Chromatography
c) Autoradiography
d) ELISA
View Answer
Explanation: The acinar cells of the pancreas secrete digestive enzyme that reach the small intestine and aid in digestion of food. The steps involved in the synthesis of these proteins, migration to cell surface and the subsequent discharge was studied using autoradiography by James Jamieson and George Palade of Rockefeller University.
2. Which type of molecules are used for labeling the cellular entities in the autoradiography technique?
a) Glycoproteins
b) Radioisotopes
c) Stereoisomers
d) Enantiomers
View Answer
Explanation: In Autoradiography, cells labeled with radioisotopes are overlaid with a photographic emulsion that contains silver grains. The labeled entities can then be viewed under the microscope by the silver grain.
3. “Pulse-chase” is an experiment related to radioactivity.
a) True
b) False
View Answer
Explanation: “Pulse-chase” is an experiment that led to elucidation of biosynthetic pathway of the secretory proteins. Pulse was the brief period in which acinar cells were incubated in a solution mixture containing radioactively labeled amino acids and chase is the period when incubation in solution containing unlabeled amino acids is done.
4. Green fluorescent protein (GFP) is observed from which of the following organism?
a) Octopus
b) Jellyfish
c) Drosophila
d) Mouse
View Answer
Explanation: The green fluorescent protein is a protein synthesized by the jellyfish which is used to tag biological entities; for instance the gene synthesizing GFP can be combined with the gene of test protein and the whole biosynthetic pathway of the protein can be traced.
5. GFP joined at the end of a protein can interfere in its synthesis.
a) True
b) False
View Answer
Explanation: GFP is a fluorescent protein used to tag the protein whose biosynthetic pathway has to be determined. A chimeric of GFP synthesizing and test protein synthesizing gene is incorporated in the cell. GFP joined at the end the protein has absolutely no effect on the protein’s activity or pathway.
6. After the synthesis of proteins in endoplasmic reticulum, where do they reach before being secreted from the cell?
a) Lysosomes
b) Golgi complex
c) Lysozymes
d) Nucleus
View Answer
Explanation: After being synthesized in the endoplasmic reticulum, proteins travel through and reach the Golgi complex where they are modified finally reaching the plasma membrane and being discharged from the cell.
7. Which of the following can be used as a temperature-sensitive mutant to study the endomembrane system?
a) Vesicular Stomatitis Virus
b) Human Immunodeficiency Virus
c) Tobacco Mosaic Virus
d) Retrovirus
View Answer
Explanation: VSVG is a viral gene of the Vesicular Stomatitis Virus, which is fused with the green fluorescent protein (GFP) to study the pathway of VSVG protein. In this case, a VSV with mutant VSVG protein can be used that can only grow at lower temperatures than normal; called the temperature-sensitive mutant.
8. Subcellular fragmentation is a technique to study the endomembrane system, based on _____________ of the cells.
a) homogenization
b) degradation
c) labeling
d) freezing
View Answer
Explanation: Subcellular fragmentation is a technique that elucidates the molecular composition of an organelle. The cells are first ruptured by homogenization and as a result their membranes and internal structures get fragmented and form vesicles. Since the vesicles derived from different organelles (like ribosome, endoplasmic reticulum etc.) have different properties, they get separated from one another.
9. The microsomal content of a ruptured cell represents how many organelles?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The heterogeneous similar sized membranous vesicles derived from the endomembrane system of a homogenized cell, primarily represented by the endoplasmic reticulum and Golgi complex, are referred to as microsomes.
10. Which of the following technique was used to study the function of ribosomes and contrast it with the function of ER membrane?
a) Cell-free systems
b) Autoradiography
c) Spectroscopy
d) Microscopy
View Answer
Explanation: Cell-free systems refer to the isolated organelles of the homogenized cells. These were first used to comprehend the protein synthesizing role of ribosomes and the protein sequestering role of endoplasmic reticulum membrane.
11. A mutant organism or cell encodes normal proteins that can be used for studying the endomembrane system.
a) True
b) False
View Answer
Explanation: A mutant organism or cultured cell contains chromosomes with on more genes that encode for an abnormal protein. As a result a characteristic deficiency is exhibited by the cell which can be used to study the usual function of the protein.
12. RNAi phenomenon inhibits the synthesis of which biomolecules?
a) RNA
b) DNA
c) Proteins
d) Carbohydrates
View Answer
Explanation: RNA interference phenomenon wherein cells produce small RNAs called the siRNAs that bind to mRNAs and inhibit the synthesis of proteins. RNAi is a strategy used by the researchers to investigate the function of a missing protein.
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