Previous Year Question Papers of CSIR – UGC /JRF/NET: Life Science Examination, December 2015 (II)
COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH (CSIR) & UGC
(Original Question Paper with Answer Key, Explanations and References)
PART: B (Questions 21 – 40)
(21). The ionic strength of a 0.2 M Na2HPO4 solution will be:
a. 0.2 M
b. 0.3 M
c. 0.6 M
d. 0.8 M
Ionic strength of a solution is the function of all ions present in a solution.
(22). A cell line deficient in salvage pathway for nucleotide biosynthesis was fed with medium containing 15N labelled amino acids. Purines were then extracted. Treatment with which one of the following amino acids is likely to produce 15N labelled purines?
a. Aspartic acid
(23). Enzymes accelerate a reaction by which one of the following strategies?
a. Decreasing energy required to form the transition state.
b. Increasing kinetic energy of the substrate.
c. Increasing the free energy difference between substrate and the product.
d. Increasing the turn over number of enzymes.
Transition state is the state of substrate with highest energy; they are least stable than products and other substrate molecules. They have the highest energy along the reaction coordinate and they have the highest free energy. Enzymes accelerate the chemical reactions by lowering the energy required to reach the transition state of a substrate.