photosynthesis 2

Question 1

what is another name for light independent reactions?

Answer 1

calvin cycle

Question 2

the calvin cycle/light independent reaction takes place where?

Answer 2

in the thylakoid membrane

Question 3

light independent reactions can be split into 3 phases which are?

Answer 3

carbon fixation, reduction, regeneration of the co2 acceptor

Question 4

the carbohydrate produced directly from the calvin cycle is?

Answer 4

not glucose. it is a 3 carbon sugar called glyceraldehyde 3 phosphate. G3P

Question 5

for the net synthesis of 1 molecule of g3p, the cycle must take place?

Answer 5

3 times

Question 6

phase 1: carbon fixation?

Answer 6

the calvin cycle incorporates each co2 molecule one at a time by attaching it to a 5 carbon sugar called ribulose biphosphate rubp. the enzyme that catalyzes this first step is rubp carboxylase oxygenase or rubisco. the product of the reaction is 6 carbon intermediate it splits in half forming two molecules of 3- phosphoglycerate.

Question 7

phase 2: reduction?

Answer 7

each molecule of 3-phosphoglycerate recieves an additional phosphate group from atp become 1,3-biphosphoglycerate. Next, a pair of electrons donated from nadph reduces 1,3 biphosphoglycerate which loses a phosphate group becoming glyceraldehyde 3 phosphate.

Question 8

important note

Answer 8

for every 3 molecules of co2 that enter the cycle, there are 6 molecules of g3p formed.
only one molecule of g3p can be counted as a net gain because the rest are required to complete the cycle.
- one molecule exits the cycle to be used by the plant cell but the other 5 must be recycled to regenerate the 3 molecules of rubp.

Question 9

phase 3: regeneration of the co2 acceptor rubp?

Answer 9

in a series of reactions, the carbon skeletons of 5 molecules of g3p are rearranged into 3 molecules of rubp. to accomplish this, the cycle spends 3 more molecules of atp.

Question 10

the calvin cycle produces ___ molecule of g3p from ___ x co2 molecules that enter the cycle

Answer 10

1 molecule g3p from 3 molecule co2

Question 11

to make 1 g3p __ molecules of atp are needed and ___ molecules of nadph are needed

Answer 11

9 atp, 6 nadph

Question 12

what is g3p used for?

Answer 12

g3p can combine with g3p to form glucose: can be linked together to form starch/cellulose