Photosynthesis Biology A2 Flashcards
What is a coenzyme?
An enzyme that aids the function of other enzymes by transferring the chemical groups between the molecules being reacted.
What is the coenzyme associated with photosynthesis? ?
What is the coenzyme associated with photosynthesis? ?
What are the three key events in the light-dependent stage of photosynthesis?
Photoionisation
Photolysis
and Chemiosmotic Theory
How is light energy and chlorophyll used in photoionisation?
When chlorohyll molecules absorb light energy it boosts the energy within the electrons in the chlorophyll. This causes the electrons to leave the chlorophyll molecule, causing the chlorophyll molecule to become ionised. These electrons are then passed along “electron carrier” molecules by a series of oxidation and reduction reactions. The electrons lose a bit of energy with each reaction, and this “scrap” energy is then use to phosphorylate ADP to ATP.
How is light energy used in photolysis?
It is needed to split water into H+ and OH- ions. After photoionisation occurs, chlorophyll molecules are short of electrons and require more so they can continue to absorb light energy. These are provided when water is split into H+ and OH- ions in photolysis.
How are the products in photolysis used to support the Calvin Cycle?
Photolysis produces both electrons and protons. The protons exit the thylakoids to aid the calvin cycle in the stroma. Here, they bond with NADP to create reduced NADP. This is then used in the reduction stage of the calvin cycle, when the NADP releases H+ ions to turn Glycerate 3 Phosphate to Triose Phosphate.
What are the three products of the light dependent reaction of photosynthesis used in the calvin cycle?
H+ ions, NADP and ADP/ATP.
What is stage one of the calvin cycle?
Carbon Fixation
What is the main (intended) input product of the calvin cycle and output product of the calvin cycle?
Input product- Carbon Dioxide
Output Product- Glucose
What is the name of the starting compound in the Calvin Cycle?
Ribulose Bisphosphate
What happens during the Carbon fixation stage of the calvin cycle
Clues
- CO2, RuBP, 2x GP, Rubisco
Carbon Dioxide enters the leaf via the stomata and then enters the stroma of the chloroplasts. This then binds with the starting compound of the calvin cycle, Ribulose Bisphosphate. This is then broken down into 2 Glycerate 3 phosphate molecules (a three carbon compound). This entire reaction is catalysed by a substance called Ribulose Bisphosphate Carbulose
What products from the light dependent reaction are used in the reduction stage of the calvin cycle?
ATP and Reduced NADP
What happens in the reduction stage of the Calvin Cycle?
GP →→→→ requires energy from ATP and H+ ions from NADP →→→→ TP
The 3 carbon molecule made in the former section of the calvin cycle (glycerate 3 phosphate) must be converted into another 3 carbon compound. In order to do this, it must require energy. ATP from the light dependent reaction is therefore hydrolysed to release this energy. H+ ions are also required to change the Glycerate 3 phosphate into triose phosphate (TP). These ions are obtained from the (reduced) NADP+, so the H+ ions are released, and the NADP+ can now be recycled as normal NADP. The Triose Phosphate is then used to make glucose (as well as other substances)
What is the third stage of the calvin cycle?
RuBP Regeneration
What happens in RuBP regeneration?
Clue—
TP x5 →→→→ energy from ATP hydrolysis →→→→ RuBP
AS RuBP is the starter compound of the calvin cycle, it must be regenerated each cycle. It does this using the Triose Phosphate made in the reduction phase. Only one of the 6 TP molecules made in three turns of the calvin cycle is used to create glucose (along with one other TP molecule from after another three cycles). The other five (after 3 cycles or ten after six cycles) are used to regenerate the RuBP. It does this through energy released from ATP hydrolysis.
