28 terms

Dark reactions

How many types of light-independent reaction cycles are there? What are they?
3: C3; C4; and CAM
What is another name for the C3 cycle?
The Calvin cycle
What is the difference between the light independent reactions?
Different numbers of CO2 molecules in the first step and so, different carbon acceptor molecules.
Where does the Calvin cycle occur?
In the stroma
What is the stroma?
Internal cavity of chloroplast
What happens in the Calvin cycle?
CO2 is converted to glucose.
What does the Calvin cycle require? What are they?
ATP and NADPH; they're energy molecules.
Why make glucose?
It is versatile
What is the first phase of the Calvin cycle called?
Carbon fixation
What happens during the first step of the Calvin cycle?
CO2 is combined with RuBP
What does RuBP stand for?
Ribulose biphosphate
How many carbon atoms and how many phosphate groups does RuBP have?
5 carbon atoms and 2 phosphate groups
What is the enzyme that bonds CO2 and RuBP called?
RuBP carboxylase
What is the shortened name of RuBP carboxylase?
How many steps are in each phase?
What happens in step 2 of the Calvin cycle?
The unstable C6 molecule formed by CO2 and RuBP immediately splits into 2 PGA molecules.
What does PGA stand for?
Phosphoglyceric acid
How many carbon atoms and how many phosphorous atoms does PGA have?
3 C and 1 P
What happens in step 3?
ATP adds a phosphate group to each of the PGA molecules, converting them to BPG molecules.
What happens in step 4?
NADPH reduces BPG to PGAL, and reverts to NADP+
How many turns of the cycle are required to produce 12 PGAL molecules?
What happens in step 5, on the 6th turn of the Calvin cycle?
2 PGAL molecules combine to form a glucose, and the other 10 remain as PGALs.
What happens in step 6?
The remaining 10 PGALs combine to form 6 RuBP molecules.
How many ATP molecules are used in total during the last phase of the Calvin cycle?
Why is PGA significant in the Calvin cycle?
PGA is the first stable compound in the Calvin cycle.
What is the total energetic cost of the Calvin cycle?
18 ATPs and 12 NADPHs --> 1 glucose
During which dark reaction cycle are the stomata dependent on the daylight cycle? Why?
CAM, because that particular cycle evolved in desert plants with the purpose of water conservation. The stomata are closed during the day to prevent stored water from evaporating, but are open at night to allow for the exchange of gases.
What do the stomata control?
They allow CO2 to diffuse in, O2 to diffuse out, and water to evaporate.