GATE- PRACTICE QUESTION

172. Based on the data, which of the following statements best describes the uptake of sucrose by these cells?
(A) Sucrose crosses the membrane by simple
diffusion.
(B) Sucrose is transported by a carrier-mediated
system.
(C) Sucrose transport is not dependent on Na+.
(D) Sucrose transport occurs by only one
mechanism.
(E) Sucrose is not transported into the cell under
most conditions.

173. The primary reason for testing the effects of CCCP is to determine whether
(A) the effect of Li+ is dependent on Na+
(B) a proton gradient is required for sucrose
transport
(C) Na+ transport occurs alone
(D) nonsaturable transport occurs
(E) K+ can substitute for Na+ in sucrose
transport

174. Which of the following is the best explanation for the effects of Li+ and K+ on the uptake of sucrose?
(A) These ions bind to sucrose and block its entry
into the cell.
(B) These ions decrease the net Na+ available in
the cells for cotransport.
(C) These ions uncouple the respiratory process
that generates energy for the uptake of
sucrose.
(D) These ions are not transported rapidly by the
Na+/sucrose cotransporter system.
(E) These ions are allosteric effectors of the
sucrose transporter system.

Questions 182-185 refer to the following model as an example of adaptive radiation and species diversification.

One of the classical examples of evolution occurs on the Galápagos Islands with Darwin's finches. The islands have always been separate from the South American mainland and vary in size and elevation. The lowlands are covered with thorn scrub, while higher elevations (found only on the larger islands) are covered with moist, dense forests. All the organisms living on these islands are descendants of species that have emigrated there, primarily from South America. In studying the finch populations, researchers have identified fourteen species, none of which are found on the mainland.

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Mahantesh.I.B
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www.sitbiotech.blogspot.com
+91 9611558989
+91 9037652343

NET JRF Paper 2 Questions

1．Describe the similarities and differences in the cycling of G_s
   and Ras between the active and inactive forms.

 2. Some integral membrane enzymes depend upon the lipids in their microenvironment not only for scaffolding, but for enzymatic activity. The Na+-K+ ATPase is one example. Please design an experiment to test the influence of membrane fluidity on the velocity of the Na+-K+ ATPase.

3. a. The average molecular weight of proteins in the cell is about 30,000  daltons. A few proteins, however, are very much larger. The largest known polypeptide chain made by any cell is a protein called titin (made by muscle cells), and it has a molecular weight of 3,000,000 daltons.  Estimate how long it will take a muscle cell to translate an mRNA coding  for titin (assume the average molecular weight of an amino acidto be 120, and a translation rate of two amino acids per second for eucaryotic cells). 
b. Transcription occurs at a rate of about 30 nucleotides per second. Is it possible to calculate the time required to synthesize a titin mRNA from the information given here?

 4. What is the advantage of having an extracellular signal transmitted by a cascade of sequential events?

5. Heating of calf type I collagen fibers to 45⁰C denatures the triple helices and separates the three chains from each other. Collagen that has been treated in this way does not renature to form a normal collagen triple helix. Why?

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Thanks&Regards
Mahantesh.I.B
www.biotrack.yolasite.com
www.sitbiotech.blogspot.com
+91 9611558989
+91 9037652343