light independent stage (calvin cycle)

Question 1

where does the light independent reaction take place

Answer 1

in the stroma

Question 2

what products does the calvin cycle use

Answer 2

-uses products of light dependent reaction:
-ATP for energy
-Reduced NADP as reducing agent

-CO2 from atmosphere or respiration for new organic compounds

Question 3

explain the first step of the calvin cycle- formation of GP/ CO2 fixation

Answer 3

-CO2 enters the leaf through stomata, diffuses into the stroma and combines with ribulose bisphosphate (RuBP) forming unstable 6C compound
-the reaction between CO2 and RuBP is catalysed by ribulose bisphosphate carboxylase (rubisco)
-the unstable 6C compound rapidly breaks down forming 2 molecules of glycerate 3-phosphate (GP)

Question 4

explain the second step of the calvin cycle; formation of TP/ CO2 reduction

Answer 4

-GP is reduced by the addition of hydrogen which comes from reduced NADP generated in the light dependent reaction (NADPH -> NADP which can be recycled in the light dependent reaction)
-energy is required to reduce GP, comes from ATP generated in light dependent reaction
(ATP -> ADP +Pi)
-results in a different 3C compound called triose phosphate (TP)

Question 5

explain the third stage of the calvin cycle: regeneration of ribulose bisphosphate

Answer 5

-only one in every six TP molecules goes on to produce carbohydrates
-other five out of six TP molecules are used to regenerate RuBP- this requires ATP (ATP-> ADP)

Question 6

what are the products of the calvin cycle

Answer 6

-TP, NADP, ADP+Pi

-1 turn= 2 TP
-3 turns= 6 TP
-6 turns needed = 12TP = 10 regenerate RuBP 2 for 6C sugar

Question 7

what are the uses of triose phosphate (TP)

Answer 7

-majority is recycled to regenerate supply of RuBP
-some TP is used to synthesise amino acids, fatty acids and glycerol
-some glucose is converted to sucrose, strach or cellulose

Question 8

-identify the enzyme that catalyses the fixation of carbon dioxide
-identify the first stable product of carbon dioxide fixation
-identify the compound that is regenerated in the calvin cycle so that more co2 can be fized
-name different polysaccharides that can be synthesised from the end products of the light independent stage of photosynthesis

Answer 8

-RubisCo
-GP
-RuBP
-starch, amylose, amylopectin and cellulose