Calvin Cycle

Question 1

What is Calvin Cycle?

Answer 1

1. Process of autotrophs to make sugar for them to grow.
2. 2nd part of photosynthesis that makes glucose from CO2 using chemical energy from ATP and NADPH.
3. It happens in the stroma of the chloroplast.

Question 2

Importance of Calvin cycle. Product and need.

Answer 2

Product: Glyceraldehyde-3-phosphate (G3P) is formed later on.

Need: A cycle of three times to make one molecule of G3P from 3 molecules of CO2

Question 3

To make carbohydrate, the chloroplast needs:

Answer 3

•3 molecules of CO2
•6 molecules of NADPH
•9 molecules of ATP

Question 4

Reactions/phases inside Calvin Cycle:

Answer 4

•Carbon Fixation
•Reduction
•Regeneration of RuBP

Question 5

What happens in phase 1 of Calvin cycle?

Answer 5

Carbon Fixation:

• Merging of CO2 (inorganic carbon molecule) into an organic molecule.

• CO2 is attached to a 5 carbon sugar molecule with the help of RuBP carbolase (rubisco)

• Product: Six-carbon sugar (extremely unstable and immediately splits in half).

• It forms two molecules of a 3-phosphoglycerate (3-carbon)

Question 6

______ is the most abundant protein in the chloroplast and probably on Earth.

Answer 6

RuBP Carbolase

Question 7

In reduction phase, what happens?

Answer 7

Phase 2: REDUCTION

• A phosphate group from ATP is attached to each 3-phosphoglycerate by an enzyme, forming 1, 3-phosphoglycerate.
• To produce Glyceraldyde-3-phosphate G3P, NADPH swoops in and reduces
  1,3- biphosphogycerate.
• The produced six G3Ps by the Calvin Cycle, five are recycled to give three molecules of RuBP.
• Of the six G3P’s produced, only one G3P leaves the cycle to be packaged for use by the cell. It needs two molecules of G3P to make one molecule of glucose.
• The products formed during the Calvin cycle, ADP and NADP+ , will then be brought back to the thylakoid membrane and then will enter the light reactions.
  Inside the thylakoid, they will be
  recharged’ with energy and become ATP and NADPH.

Question 8

What is in the final phase of Calvin cycle?

Answer 8

PHASE 3: REGENERATION OF RuBP

• Five molecules of Glyceraldyde-3-phosphate G3P shall undergo complex enzymatic reactions to produce three molecules of Ribulose Biphosphate (RuBP).
• The cell needs another three molecules of ATP, but also provides another set of Ribulose Biphosphate (RuBP) to continue the cycle.
• G3P after its release from the cycle,
  The two Glyceraldyde-3-phosphate G3Ps can combine to form six-carbon sugar. They could either be glucose or fructose (C6H1206).
• glucose + fructose = sucrose
• Starch: Formed when glucose is connected in chains
• lipid/protein synthesis: G3P can still be used.

Question 9

True or false:

The sugar produced in the Calvin Cycle is not the six-carbon Glucose that we are familiar with. The product in the Calvin Cycle is a three-carbon sugar known as G3P. The glucose is formed later on.

Answer 9

True

Question 10

True or false:

There is a need for the Calvin Cycle to ‘spin’ six times to make one molecule of G3P from three molecules of CO2.

Answer 10

False, only three times.