how is glucose produced during dark reaction
Answers
Answer:
Photosynthesis consists of two parts. The first requires sunlight and the second does not.
The Calvin cycle is also called the dark reactions or light-independent reactions because it's the part that doesn't need energy from the sun to happen.
The Calvin cycle takes place within the stroma of the chloroplast. This is where plants make sugar molecules that they can use to make other essential components, and that all other organisms can use for energy.
The cycle uses ATP and NADPH synthesized in the light-dependent reactions to drive its reactions forward. So although the cycle itself doesn't use light energy, it does depend on the light reactions to provide it with the ATP and NADPH.
Reactions in the Cycle
The cycle begins when carbon dioxide (
C
O
2
) from the atmosphere enters plant cells. An enzyme called rubisco catalyzes the first reaction, where
C
O
2
binds to a specific 5-carbon molecule called ribulose-1,5-bisphosphate (RuBP). This reaction creates a 6-carbon molecule which then splits into two 3-carbon molecules. This part of the cycle is called carbon fixation. This just means that inorganic carbon is converted to organic molecules, like sugar.
The high-energy products from the light reactions are used in the next reaction. ATP and NADH donate electrons to the 3-carbon molecules, which are converted into a 3-carbon sugar called glyceraldehyde-3-phosphate (G3P).
Some of these G3P molecules leave the cycle to form glucose molecules. These will be used by the plant during cellular respiration. Three turns of the cycle are needed for one G3P molecule to exit the cycle. Glucose is made of six carbons, so two G3P molecules are needed to make one glucose molecule.
After three turns of the cycle, this leaves five more G3P molecules which are recycled. This allows the cycle to continue. ATP is used to convert the leftover G3P into the molecules that can bind incoming carbon dioxide and restart the cycle.