Dark reaction by sohail

dark reactions
C3 cycle

1. Dark reaction

2. Presented by: Muhammad Sohail Riaz Presented to: Dr Anum Sajid

3. Table of Content Introduction Calvin cycle Carbon fixation Reduction Regeneration Chemical equation for the Calvin cycle Summary

4. Introduction Photosynthesis consists of two parts The first requires sunlight and the second does not The  light-independent reactions  make-up the second part of  photosynthesis You should note that the name "light- independent  reactions" is a little misleading

5. Cont ….. These reactions do not directly require light, but they can't occur without the NADPH and  ATP  produced in the  light-dependent reactions

6. Calvin Cycle The Calvin cycle is also called dark reactions or light-independent reactions because it's the part that doesn't need sunlight to happen The  Calvin cycle  (also known as the Benson- Calvin cycle )  is  the set of chemical reactions that take place in chloroplasts during photosynthesis

7. Cont …… In the light-independent reactions, the plant uses carbon dioxide (CO2) and the ATP and NADPH from the light-dependent reactions to produce a sugar called  glucose (C6H12O6) 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 component All other organisms can use this sugar for energy

8. Cont ….. There are three phases to the light-independent  reactions , collectively called the Calvin cycle carbon fixation Reduction regeneration

9. Carbon fixation A series of reactions outline the cycle: The cycle begins when carbon dioxide (CO2) from the atmosphere enters plant cells An  enzyme  called rubisco  catalyzes  the first reaction, where CO2 binds to a specific 5-carbon molecule called ribulose-1,5-bisphosphate (RuBP).

10. Cont …. This reaction creates a 6-carbon molecule which then splits into two 3-carbon molecules This part of the cycle is a form of carbon fixation This just means that inorganic carbon is converted to organic molecules, like sugar.

11. Reduction 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 to 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

12. Cont ….. Three turns of the cycle are needed for one G3P molecule to exit the cycle Glucose is made of 6 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

13. Regeneration ATP is used to convert the leftover G3P into the molecules that can bind incoming carbon dioxide and restart the cycle

14. Chemical equation for the Calvin cycle The overall chemical equation for the Calvin cycle is: 3 CO 2  + 6 NADPH + 5 H 2 O + 9  ATP  → glyceraldehyde-3-phosphate (G3P) + 2 H +  + 6 NADP +  + 9 ADP + 8 Pi (Pi = inorganic phosphate)

15. Summary The reactions of the Calvin cycle add carbon (from  carbon dioxide  in the atmosphere) to a simple  five -carbon molecule called RuBP These reactions use chemical energy from NADPH and  ATP  that were produced in the  light reactions The final product of the Calvin cycle is  glucose

16. Thank you