MUSCLE PHYSIOLOGY

Detailed explanation-1: -RuBP combines with CO2 and forms an unstable compound that splits into two molecules of 3-PGA. So, two molecules of 3-PGA (3-phosphoglycerate) are synthesized for every CO2 fixed in the Calvin cycle. For the synthesis of one molecule of glucose, 6 carbon dioxide molecules are required and hence six Calvin cycles occur.

Detailed explanation-2: -In stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue. Only one carbon dioxide molecule is incorporated at a time, so the cycle must be completed three times to produce a single three-carbon GA3P molecule, and six times to produce a six-carbon glucose molecule.

Detailed explanation-3: -For each CO2 molecule that reacts with one RuBP, two molecules of 3-phosphoglyceric acid (3-PGA) form. 3-PGA has three carbons and one phosphate. Each turn of the cycle involves only one RuBP and one carbon dioxide and forms two molecules of 3-PGA.

Detailed explanation-4: -RuBisCO catalyzes a reaction between CO2 and RuBP, which forms a six-carbon compound that is immediately converted into two three-carbon compounds. This process is called carbon fixation, because CO2 is “fixed” from its inorganic form into organic molecules.