Could you run through the stages in the light-independent reaction (Calvin Cycle) of photosynthesis?

Okay, so here we have what seems like a very daunting​ list of chemical reactions to remember that don't seem to make any sense! But don't worry​, with practice you will soon grasp the concept quickly.

Location

The first​ thing you need to remember is where this reaction takes place. This reaction takes place within a fluid known as the​ stroma​ in a structure called a ​chloroplast​ inside a leaf.

Stages of Reaction

1) All plants need ​CO2​ for photosynthesis.​ This is our first step. CO2 enters the leaf through the stomata and diffuses into our liquid stroma.

2) Next, this CO2 is combined with a 5-carbon compound called ribulose biphosphate (RUBP) forming an unstable 6 carbon compound. ​This is catalysed by an enzyme called rubsico.

​3) Since it is unstable, this 6 carbon compound quickly breaks down into two molecules of a 3-carbon compound called ​glycerate-3-phosphate.

​4) ​ATP and reduced NADP (from the light-dependent reaction) ​then reduce our glycerate-3-phosphate into a different 3-carbon compound called triose phosphate. (TP)

​5) This is the product we've been after. Two things can then happen once we have ​TP:​ it can either be used to produce hexose​ (six carbon) sugars such as ​glucose, ​or go back into the cycle to ​regenerate RUBP ​so that more CO2 can combine with it and the cycle can begin anew.

So in summary:

1) CO​2 ​enters stomata and diffuses into stroma.

2) CO2​ + RUBP = unstable 6-C compound

3) 6-C breaks into x2 of G-3-P

4) ATP + Reduced NADP then reduce G-3-P into TP

5) TP either makes useful substances such as glucose or regenerates RUBP.

Any more questions, feel free to drop a message.

 

Answered by Shane C. Biology tutor

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