Download Photosynthesis Continued (part 3)

Photosynthesis
Continued (part 3)
Quick Re-cap
Where does photosynthesis occur?
How many stages are included in the process of
photosynthesis? What are they and where do they occur?
Explain the light-dependent reaction.
Chemiosmosis
Remember this picture:
Chemiosmosis
At position B (the electron transport chain), H+ ions are being
pulled across the membrane.
These ions are unable to escape the lumen except through
highly specialized proteins called ATP synthase complexes
As H+ ions rush through these complexes, they release energy
ATP synthase then uses this energy to convert ADP to ATP
Chemiosmosis
This process of creating ATP using the energy from an H+ ion
gradient is called chemiosmosis
Stage 3: The Calvin Cycle
The last stage of photosynthesis is carbon fixation
This is where high energy organic molecules are formed from
CO2
It is referred to the Calvin cycle in honour of Melvin Calvin who
discovered this pathway
Memorize
Me!
Stage 3: The Calvin Cycle
The Calvin cycle uses ATP molecules and high energy
electrons carried by NADPH from the light dependent
reactions
It uses these molecules to create G3P (a sugar that is used to
create glucose)
3 ATPs and 2 NADPHs are consumed for every CO2 that
enters the cycle
Stage 3: The Calvin Cycle
This means that 18 ATP and the electrons and protons carried
by 12 NADPH molecules are needed to create one simple
sugar molecule like glucose!
In order to operate, the Calvin cycle needs CO2 to be readily
available in the stroma of the chloroplast
https://www.youtube.com/watch?v=0UzMaoaXKaM
Summary of Events
1. Light Dependent Reaction
- Light strikes photosystem II
- Electrons are energized and ready to go
- Photolysis occurs replacing electrons that are moving on to
stage 2
Summary of Events
2. Electron Transport and ATP Synthesis
- Electrons travel down the transport chain losing energy
until they reach photosystem I
- Electrons are energized again and are used to form NADPH
from NADP+ through a redox reaction
- Chemiosmosis occurs transporting H+ ions through ATP
synthase complexes to create ATP
Summary of Events
3. Calvin Cycle
- ATP and NADPH are used from previous steps to turn CO2
into glucose and other sugars
- C02 is changed into G3P which is used to make glucose
https://www.youtube.com/watch?v=sQK3Yr4Sc_k