2.13 - The Calvin Cycle

Question 1

What does one turn of the Calivin Cycle require?

Answer 1

• 3 CO2
• 9 ATP
• 6 NADPH

Question 2

What does one turn of the Calivin Cycle produce?

Answer 2

• 1 3C sugar: G3P
  (glyeraldehyde 3-phosphate)

Question 3

How many turns of the Calvin Cycle does it take to make one molecule of glucose?

glucose = 6C

Answer 3

It takes 2 turns.
1 G3P (3C) + 1 G3P (3C) = 6C glucose

Question 4

What is the name of the starting molecue in the Calvin Cycle?

Answer 4

Ribulose bisphosphate
RuBP

Question 5

What is the name of the enzyme that splits the 6C molecule at the begining of the Calvin’s cycle?

Answer 5

Rubisco

Question 6

What are the 3 stages of the Calvin Cycle?

Answer 6

1) Carbon Fixation
2) Reduction
3) Regeneration of RuBP

Question 7

What is the name of the 3C molecule that results from the splitting in half of a molecule during the Calvin Cycle?

Answer 7

3-phosphoglycerate
3PG
or PGAL

Question 8

Describe what happens in the first phase of the Calvin Cycle, Carbon Fixation.

Answer 8

• CO2 is combined with a 5 carbon molecule called RuBP. That forms an unstable 6C molecule that imediatley splits in half to form two 3C moleclues. 3PG
• This occurs b/c of Rubisco which is the enzyme responsible for this

Question 9

Describe what happens in the second phase of the Calvin Cycle, Reduction.

Answer 9

• Energy from ATP (made during light rxns) is used to transfer high energy e-, carried by NADPH, into molecules
• 3PG/PGAL (the 3C molecule) is converted into G3P

Question 10

Why do plants have so many Rubisco enzymes?

Answer 10

This is due to the fact that rubisco large and is a slow working enzyme. Therefore, to attempt to speed things up[, plants have a lot of it in their leaves

Question 11

Describe what happens in the third phase of the Calvin Cycle, Rgeneration of RuBP.

Answer 11

• Only 1 of 6 G3P molecules produced are released (for the purpose of making glucose and carbohydrates)
• the remaining 5 G3P molecules are rearranged back into RuBP to keep the cycle going
• 5 x 3C G3P -> 3 x 5C RuBP

Question 12

How many RuBP molecules are there in one turn the Calvin Cycle?

Answer 12

There are 3 RuBP molecules.
( 3 x 5C molecules)

Question 13

How many CO2 molecues go into one turn the Calvin Cycle?

Answer 13

3 CO2 molecues enter one roation of the cycle