What is the dark reaction of photosynthesis?

Answer 1

There are three main phases of the light-independent reactions: fixation, reduction, regeneration of RuBP.

1. During fixation, RuBisCO (ribulose 1,5-bisphosphate carboxylase/oxidase) fixates a carbon to RuBP (ribulose 1,5-bisphosphate) to make 3-phosphoglycerate. There are three RuBP's and each one makes two 3-phosphoglycerates. Ergo, there are six 3-phosphoglycerates.
2. During the reduction phase, 6 ATP and 6 NADPH are used to reduce the 3-phosphoglycerate to glyceraldehyde 3-phosphate (G3P). The ATP goes first and converts the 3-phosphoglycerate into 3-bisphosphoglycerate. Next, the NADPH reduces the 3-bisphosphoglycerate and converts it into G3P. An inorganic phosphate comes off and NADP+ and ADP are released back to the light reactions. There are 6 G3P molecules and one will be used to make the six carbon sugar, glucose.
3. During regeneration, 3 ATP are used to convert the G3P back into 3 RuBP's through a series of reactions. This will restart the cycle.

Two turns of the cycle will produce the six-carbon sugar product.

Answer 2

The dark reaction (preferably called the light-independent reaction) is called the Calvin cycle. This process of carbon fixation takes place in the stroma of the chloroplasts. It's a long and complicated process but these are the basic steps in it:

1) CO2 that is taken in by the plant combines with a 5-carbon compound called ribulose-1,5-bisphosphate (RuBP) to form a 6-carbon compound. This conversion is catalysed by ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCo).

2) The 6-carbon compound is unstable, and cleaves itself to form two 3-carbon compounds called 3-phosphoglycerate (3PG).

3) The 3PG molecules then undergo a reduction reaction to form phosphoglyceraldehyde (PGAL) molecules. These are also known as G3P or TP. In this redox process, NADPH is oxidised to form NADP+. This requires energy from ATP.

4) Some PGAL molecules leave the Calvin cycle here, to form more complex carbohydrates. However, most PGAL molecules are converted back to RuBP (see Step 1), a process which requires energy from ATP.

5) The cycle continues with the re-formation of RuBP and the continuing intake of CO2.

One more thing, this process is preferentially referred to as the light-independent reaction and not the dark reaction because it simply can take place without the presence of light, and not necessarily in the dark. In fact, it takes place in the presence of light most of the time as the NADPH that is required in Step 3 is produced by the light-dependent reaction of photosynthesis.

I hope this helps!

Answer 3

to use CO2, energy, and H+ ions from ATP and NADPH to make sugar

Answer 4

The dark reactions of photosynthesis doesn't require the presence of light to photosynthesize.

Answer 5

dark reaction is a reaction in which carbon dioxide is converted into glucose by using the end products of light reaction.

Answer 6

The function of dark reactions include the use of ATP to make glyceraldehyde 3 phosphate. Another function is for other sugars are produced to undergo glycoses.

Answer 7

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Answer 8

The role of the dark (light independent) reactions of photosynthesis are to fix the carbon from carbon dioxide into the sugar molecule glucose.