CSIR-UGC National Eligibility Test (NET) for Junior Research Fellowship and Lecturer-ship

Some Important Questions Collected from the Memory of Students and Probable Questions and Answers

Previous Year Questions & Answers –Part C. June 2017

1.Metachromatic leukodystrophy (MLD) is caused by a deficiency of arylsulfatase A and affects the CNS. MLD is
1. a lysosomal storage disorder
2. a disease due to dysfunctional mitochondria
3. caused by loss of the myelin sheath
4. caused by a defect in proteins of the nuclear envelope
Ans:- 1
Expln:- Metachromatic leukodystrophy (MLD) is caused by aryl sulfatase A deficiency. It is a lysosomal storage disorder; MLD may cause in two ways. It is most commonly caused by a mutation in a gene called arylsulfatase A (ASA). The protein produced by ASA is present in the lysosome. MLD can also caused by a defect in Saposin B, which is a protein required for ASA to work properly. ASA is required for the breakdown of sulfatides (glycolipidcerebroside) which are fats present in myelin. When ASA is deficient, the sulfatides build up in the myelin to high levels, disrupting the myelin structure and causing demyelination
2.Which one of the following statements is NOT true ?
acids ?

1. Beta-oxidation of long chain fatty acids occurs in mitochondria
2. Fatty acid biosynthesis occurs in peroxisomes
3. Peroxisomes utilize H2O2 to oxidize a variety of substrates
4. Peroxisomes import their repertoire of proteins using sorting signalsne
Ans:- 2 
Expln:- In fatty acid synthesis, pyruvic acid is converted into acetyl-CoA in the mitochondrion. However, this acetyl CoA needs to be transported into cytosol where the synthesis of fatty acids and cholesterol occurs.
3.Rotenone is an inhibitor of the electron transport chain. The addition of rotenone to cells results in which of the following ?
1. Generation of mitochondrial reactive oxygen species and block in ATP generation.
2. Block in ATP generation but no generation of reactive oxygen species.
3. Generation of reactive oxygen species but no block in ATP generation.
4. Permeabilization of the inner membrane to compounds which are usually not able to
traverse the membrane.
Ans:- 1
Expln:-  The rate of H2O2 production is remarkably higher under succinate oxidation. Because H2O2 production driven by succinate oxidation is strongly inhibited by the complex I (CI) inhibitor rotenone, succinate oxidation produces ROS via a ‘reverse electron flow’ from comple II(C II) to CI.
4.Which one of the following pairs is NOT matched correctly ?
1. Glycocalyx – adherence
2. Fimbriae – motility
3. Pili – conjugation
4. Peptidoglycan – cell wall
Ans:- 2
Expln:-Most prokaryotic cells, particularly the bacterial cells, have a chemically complex cell envelope. The cell envelope consists of a tightly bound three layered structure ie., the outermost glycocalyx followed by the cell wall and then the plasma membrane. Besides flagella, Pili and Fimbriae are also surface structures of the bacteria but do not play a role in motility. The pili are elongated tubular structures made of a special protein. The fimbriae are small bristle like fibres sprouting out of the cell which help attach the bacteria to rocks in streams and also to the host tissues. A specialized pilus, the sex pilus, allows the transfer of genetic material from one bacterial cell to another a process known as conjugation.

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