Question

In a classic experiment on photosynthesis, R. L. Hill demonstrated that an illuminated in vitro suspension of isolated chloroplasts could produce oxygen in the presence of a hydrogen acceptor such as methylene blue. In this case methylene blue is reduced. Which one of the following compounds replaces methylene blue in the intact photosynthesising plant?

• A. Adenosine triphosphate(ATP)
• B. Carbon dioxide
• C. Nicotinamide adenine dinucleotide phosphate(NADP)
• D. Phosphoglyceric acid(PGA)

Answer 1

The correct option is C Nicotinamide adenine dinucleotide phosphate(NADP)

The Hill reaction of photosynthesis was discovered by Robin Hill (1937). He found that isolated chloroplasts from plants can release oxygen when they are illuminated by sunlight in the presence of a suitable electron acceptor such as ferricyanide or methylene blue. To demonstrate the Hill reaction in the laboratory dichlorophenolindophenol (DCPIP) was used as the terminal electron acceptor, replacing NADP which was not available due to the extraction of the chloroplasts from the plant cellular environment. The ferrocyanide is reduced (just as NADP is when the chloroplast is in vivo) while water is oxidized into oxygen and hydrogen cations during the reaction.

So, the correct option is 'Nicotinamide adenine dinucleotide phosphate(NADP)'.