A classic biochemical experiment nicely illustrated the point that the ribosome recognizes tRNA and not the amino acid that it is carrying. In that following observation were made. Which of them can be correct.

A. The cysteine attached to cysteine-tRNACys can be converted to an alanine by chemical reduction to give alanine-tRNACys.

B. Alanine-tRNACys introduces alanines at codons that specify insertion of cysteine.

C. Different mechanism is used to incorporate selenocyteine on tRNA as selenocysteine is incorporated into proteins by chemical modification after translation

D. Selenocysteine is generated enzymatically from serine carried on a special tRNA that is charged by serine-tRNA synthetase

E. Above examples can conclude that the translation machinery relies on the high fidelity of the aminoacyl-tRNA synthetases to ensure the accurate decoding of each mRNA

#Question id: 10129

#Unit 6. System Physiology – Plant

Oxidation of water to form molecular oxygen is very difficult: The photosynthetic oxygen-evolving complex is the only known biochemical system that carries out this reaction which essential cofactor are involved in the water-oxidizing process?

#Question id: 10130

#Unit 6. System Physiology – Plant

manganese (Mn) is an essential cofactor in the water-oxidizing process, and a classic hypothesis in photosynthesis research postulates that Mn ions undergo a series of oxidations—known as S states, This hypothesis has received strong support from a variety of experiments, which of the following techniques detect the manganese ions directly and Analytical experiments indicate that how much Mn ions are associated with each oxygen-evolving complex?

#Question id: 10131

#Unit 6. System Physiology – Plant

The detailed chemical mechanism of the oxidation of water to O2 is not yet well understood, but with structural information shows_one electron carrier, generally identified as Yz, functions between the oxygen-evolving complex and P680 to function in this region, Yz needs to have a very strong tendency to retain its electrons, this species has been identified as;

#Question id: 10132

#Unit 6. System Physiology – Plant

Which of the following statements would be correct for photophosphorylation ?

#Question id: 10133

#Unit 6. System Physiology – Plant

The PSI reaction center complex is a large multi-subunit complex in which the antenna chlorophylls are associated with the reaction center Components of the PSI reaction center are organized around as follows choose the incorrect one;

#Question id: 10134

#Unit 6. System Physiology – Plant

Some herbicides such as dichlorophenyldimethylurea (DCMU, also known as diuron) and paraquat, block photosynthetic electron flow from where ?

a.) DCMU blocks electron flow at the quinone acceptors of PSII, by competing for the binding site of plastoquinone that is normally occupied by PQB

b.) Paraquat accepts electrons from the early acceptors of PSI and then reacts with oxygen to form superoxide, O2 – , a species that is very damaging to chloroplast components

c.) DCMU blocks electron flow at the pheophytin acceptors of PSII, by competing for the binding site of pheophytin

d.) Paraquat accepts electrons from the Iron-sulfur system of PSI and then reacts with oxygen to form superoxide, O2 – , a species that is very damaging to chloroplast components

Which of the following combination is true?