Carbon reactions Flashcards
What happens to atmospheric CO2 every year
> 10% reduced to carbohydrate by photosynthetic organisms
How much nitrogen gas in atmosphere
78%
How much oxygen gas in atmosphere
21%
How much argon in atmosphere
1%
How much carbon dioxide in atmosphere
0.04% (trace gas)
Carbon reactions
Accelerate in presence of light but can occur without it - used NADPH and ATP from light reactions, take place in stromal matrix of chloroplast
How was Calvin Benson cycle discovered
By using 14CO2 in pulse-chase experiments - use 2D paper chromatographic techniques and radioautography comparisons made with organic compound controls- spots eluted from paper and identified with MS and IR spec.
When was radioactivity seen in PGA
After 5s in COOH, after 30s two other carbons became labelled
What is the CO2 acceptor
Expect 2C acceptor but instead 5C - ribulose-1,5-bisphosphate
What does calvin cycle require
ATP, NADPH, CO2, RuBP, RuBisCO
How many turns of the calvin cycle produces 1 glucose
6
Plant carbohydrate stores
- Starch (amylose) similar to glycogen (chloroplasts) 2. Sucrose (cytosol)
How many ATPs used for six rounds of calvin cycle
18
How many ATps used for C4 Calcin cycle
30
What is the most abundant protein in nature
Rubisco
Role of magnesium and CO2
Mg2+ with CO2 at lysine –> carbamate. Activates bound RuBP so that it can react with substrate CO2
Photorespiration
Rubisco can’t distinguish fully between CO2 and O2 - gets worse at higher temperatures
What does photorespiration produce
Phosphoglycolate (toxic) and 3-phosphoglycerate
How do we deal with the oxygenation problem
C4 pathway
