Photosynthesis ( light independent reaction)

Question 1

Describe the Calvin Cycle

Answer 1

CARBON FIXATION - Rubisco enzyme catalyses the reaction of RuBP with CO2 to produce 2x Glycerate-3-Phosphate (G-3-P).
REDUCTION - NADPH reduces G-3-P into 2x Triose Phosphate (TP) with energy being provided by ATP.
REGENERATION - 2 x TP are converted into organic compounds e.g. glucose OR ATP is used to convert TP into RuBP for more turns of the Calvin cycle.

Question 2

How many carbon atoms in Ribulose Bisphosphate (RuBP)?

Answer 2

5

Question 3

What is produced from the reaction of RUBP and carbon dioxoide?

Answer 3

6 carbon molecule

Question 4

How many turns of the Calvin cycle take place to produce 1 molecule of glucose?

Answer 4

6

Question 5

What happens to NADPH in the LIR?

What does the product then do?

Answer 5

Gets oxidised

Provides electrons for G3P to get reduced to turn into TP

Question 6

What happens to the ATP from the LDR?

Answer 6

Gets turned back into ADP to Pi which releases energy to turn G3P into TP

Question 7

Does the Calvin Cycle require light to function?

Answer 7

No

BUT

The reactions will stop eventually in the absence of light because essential ATP and NADPH from light reactions will run out.

Question 8

During the light-independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how. (6 marks)

Answer 8

Carbon dioxide combines with ribulose bisphosphate / RuBP;
Produces two glycerate-3-phosphate / GP;
GP reduced to triose phosphate / TP;
Using reduced NADP; and…
…Using energy from ATP;
Triose phosphate converted to glucose / RuBP / ribulose bisphosphate

Question 9

Where is rubisco found?

Answer 9

stroma (of chloroplast

Question 10

A decrease in the activity of the enzyme rubisco would limit photosynthesis - why?

Answer 10

Less carbon dioxide reacts with RuBP

so

Less GP