lesson 10 light independent reactions

Question 1

what is the calvin cycle

Answer 1

• the calvin cycle is the reactions that convert inorganic carbon dioxide from the atmosphere to the three carbon organic molecule G3P
• for every 12 molescules of G3P made, two are used to make glucose and other high energy compounds
• (important) the cycle spends the energy of atp and the reducing power of electrons carried by NADPH produced in the light dependent reactions to make the sugar
• can occur in the absence or presence of light.

Question 2

how many turns of cycle produce g3p

Answer 2

three turns = 1 net g3p
- each turn of the calvin cycle “fixes” one carbon
- (carbon fixation important) this means the conversion of inorganic carbon (co2 cause it only has carbon and not carbon and hydrogen) to organic compounds
- for the net synthesis of one g3p molecule, the cycle must take place three times, fixing 3 molescules of co2
- to make one glucose, this would require six cycles and the fixation of 6 co2 molecules
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Question 3

what are steps of calvin cycle

Answer 3

1. carbon fixation phase
2. reduction phase
3. regeneration of RuBP

Question 4

1. carbon fixation phase. what is it

Answer 4

-each co2 molecule is attached to a five-carrbon sugar which is RuBP.
- this is caalyzed by RuBP carboxylase or RUBISCO(allows for the first reaction of calvin cycle. ((without rubisco, plants wouldnt be able to take co2 and make sugar out of it))
- the six-carbon intermediate splits in half to form two moelcules of 3 phosphoglycerate per co2.

Question 5

2. reduction phase. what is it

Answer 5

• each 3 phosphoglycerate recieves another phosphate group from atp to form 1,3 biphosphoglycerate.
• a pair of electrons from NADPH reduces each 1,3 biphosphoglycerate to g3p.

Question 6

g3p information to know

Answer 6

• three turns of calvin cycle = six molecules of g3p.
  – one g3p leaves the cycle and may eventually go on to produce glucose.
  – the remaining five g3p molescules move onto the third phase of the cycle in which RuBP is replenished to keep the cycle going
• G3P is also commonly referred to as PGAL

Question 7

3. REGENERATION OF RuBP. what is it

Answer 7

• the five remaining g3p (3c) molescules are rearranged to form three RuBP (5c) molecules.
• to do this, the cycle must spend three more molecules of ATP (one per RuBP) to complete the cycle and prepare for the next one.

Question 8

the net synthesis of one g3p

Answer 8

• the calvin cycle consumes nine atp and six NADPH.
  it costs 3 atp and two NADPH per Co2

Question 9

g3p - a crucial molecule in the … plant metabolism

Answer 9

a great deal for the g3p that leaves the calvin cycle is transported out of the chloroplast and into the cytoplasm to produce sucrose.
g3p is also sued to produce:
starch, cellulose,
corn oil, safflower oil and olive oil
- g3p + nitrogen -> amino acids

Question 10

overall reaction

Answer 10

3 co2 + 3 rubp + 9atp + 6nadph –> 1 g3p + 3rubp + 9atp + 6nadp+ + 8 Pi
(3 rubp cancel out)