Question

Why does it take three turns of the calvin cycle to produce G3P, the initial product of photosynthesis?

Short answer

As a three-carbon molecule, three turns of the Calvin cycle are required to produce one molecule of G3P, and only one carbon is fixed per turn of the cycle.

Step-by-step solution

step-1: Definition

The Calvin cycle is a process by which plants and algae convert carbon dioxide from the atmosphere into sugar, which autotrophs require to grow.

step-2: Introduction

Only one carbon dioxide molecule is fixed in one cycle of the Calvin cycle. Glyceraldehyde-3phosphate is abbreviated as G3P. It is the product that is then used to make glucose. Glyceraldehyde-3-phosphate is a three-carbon molecule, whereas glucose is a six-carbon molecule. One carbon cycle is fixed. Three cycles of the cycle fix three carbons, resulting in one G3P molecule.

step-3: Explanation

The light-independent reactions involve the Calvin cycle. By removing carbon from the atmosphere, it aids in the production of glucose molecules. This process also makes use of the products of light reactions, namely ATP and NADPH. The enzyme Rubisco, which has a high affinity for carbon dioxide, catalyzes the fixation of carbon from carbon dioxide. In one cycle turn, one molecule of carbon dioxide is fixed with one molecule of ribulose-1, 5-bisphosphate. Through a series of reactions, it produces glyceraldehyde-3-phosphate. A three-carbon molecule is glyceraldehyde-3-phosphate. Because only one carbon is fixed in a single turn of the cycle, three turns would result in one molecule of glyceraldehyde-3-phosphate. The remaining carbon molecules are consumed during the regeneration process, which is required to keep the Calvin cycle running.