Assume that you have an illuminated suspension of Chlorella cells carrying out p

Question

Assume that you have an illuminated suspension of Chlorella cells carrying out photosynthesis in the presence of 0.1% carbon dioxide and 20% oxygen. What will be the short-term effects of the following changes in conditions on the levels of 3-phosphoglycerate (PGA) and ribulose-1, 5-bisphosphate (RuBP)? An inhibitor of photosystem II is added. PGA down, RuBP up PGA up, RuBP down PGA up, RuBP unchanged PGA unchanged, RuBP up Oxygen concentration is reduced from 20% to 1%. PGA down, RuBP up PGA up, RuBP down PGA up, RuBP unchanged PGA unchanged, RuBP up

Explanation / Answer

1. B PGA - UP and RuBP - Down

In Photosystem II inhibitor added means there is no production of ATP and NAPDH. No light reaction happen.

In calvin cycle the co2 and RuBP join together and form PGA. After PGA to 1,3 biPGA ATP required. Due to no light reaction no ATP form so, PGA will started increase and meanwhile RuBP decrease.

2. A - PGA - DOWN and RuBP - UP

When the 02 concentration was changed from 21 to 1%, PGA composition was depressed by 35 to 40% and RuBP was increased by 40 to 45%

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