Some xanthophylls also participate in energy dissipation such as in light conversion of Violaxanthin to Zeaxanthin with antheraxanthin as the intermediate and vice-versa, which of the following statements is CORRECT?

a.) The conversion of Violaxanthin to Zeaxanthin a singlet oxygen is removed with the help of co-factor Ascorbate and violaxanthin de-epoxidase under high PPFD

b.) Zeaxanthin is oxidised into violaxanthin with the help of NADPH and oxygen under low PPFD

c.) Conversion of Violaxanthin to Zeaxanthin a singlet oxygen is removed with the help of NADPH and water under low PPFD

d.) Zeaxanthin is oxidised into violaxanthin in presence of enzyme known as violaxanthin de-epoxidase and co-factor Ascorbate under high PPFD

#Question id: 3976

#Unit 3. Fundamental Processes

After binding by E. coli RNA polymerase, the correct order of events for transcription initiation is:

#Question id: 3977

#Unit 3. Fundamental Processes

Which one of the following statements about eukaryotic RNA polymerases is correct?

#Question id: 3978

#Unit 3. Fundamental Processes

The 5'-terminal cap structure of eukaryotic mRNAs is a(n):

#Question id: 3979

#Unit 3. Fundamental Processes

“Housekeeping genes” in bacteria are commonly expressed constitutively, but not all of these genes are expressed at the same level (the same number of molecules per cell).  The primary mechanism responsible for variations in the level of constitutive enzymes from different genes is that:

#Question id: 3980

#Unit 3. Fundamental Processes

Which of the following statements correctly describes promoters in E. coli?

#Question id: 3981

#Unit 3. Fundamental Processes

The diagram below represents a hypothetical operon in the bacterium E. coli.  The operon consists of two structural genes (A and B), which code for the enzymes A-ase and B-ase, respectively, and also includes P (promoter) and O (operator) regions as shown.

 When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes A-ase and B-ase are both synthesized at a 50-fold higher rate than in the absence of X.  (X has a molecular weight of about 200.)  Which of the following statements is true of the operon decribed above?