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Photosynthesis - Coggle Diagram
Photosynthesis
Light-dependent reactions
happen in the thylakoid membrane of the chloroplast
cyclic photophosphorylation
only uses photosystem I
makes ATP but doesn't make NADPH
step 1:
light is absorbed by photosystem I and passed to the photosystem I primary pigment (p700)
step 2:
an electron in the pigment gets excited to a higher energy level and is emitted from the chlorophyll (photoactivation)
step 3:
the electron captured by an electron carrier and is passed down the electron transport chain before passing back to the chlorophyll molecule in photosystem I
step 4:
as the electrons pass along the chain they lose energy, and this energy is used to transport H+ ions from the stroma to the thylakoid lumen, which creates a concentration gradient
step 5:
the H+ ions diffuse down the concentration gradient via ATP synthase, and this provides energy to add a phosphate onto ADP and form ATP (chemiosmosis)
step 6:
the ATP is passed to the light-independent reactions
non-cyclic photophosphorylation
uses both photosystem I and photosystem II
makes ATP and NADPH
step 1:
light is absorbed by photosystem II and passed to the photosystem II primary pigment (p680)
step 2:
an electron in the pigment gets excited to a higher energy level and is emitted from the chlorophyll (photoactivation)
step 3:
the electron captured by an electron carrier and is passed down the electron transport chain before being passed to photosystem I
step 5:
to replace the electron that was transferred to photosystem I, photosystem II splits water molecules into H+ ions and electrons (photolysis), and this is catalysed by an enzyme called the oxygen-evolving complex
step 6:
at the same time as photoactivation in photosystem II, photoactivation also happens in photosystem I
step 7:
the excited electrons from photosystem I passes along the electron transport chain
step 8:
these electrons combine with H+ ions (formed in photolysis) and NADP to form NADPH
step 4:
chemiosmosis occurs
step 9:
the ATP and NADPH formed move into the stroma for the light-independent reactions
Light-independent reactions
happen in the stroma of the chloroplast
the Calvin cycle
step 1:
CO2 reacts with ribulose bisphosphate/ RuBP (5 carbons) to form an unstable 6 carbon intermediate, and this is catalysed by the enzyme rubisco. This is called 'carbon fixation' because the CO2 isn't polluting the air anymore
step 2:
the unstable 6 carbon intermediate immediately breaks down into 2 molecule of glycerate-3-phosphate (3 carbons)
step 3:
energy from ATP and hydrogen from NADPH are used to reduce the glycerate-3-phosphate into 2 molecules of triose phosphate (3 carbons)
step 4:
1/6 of the triose phosphate produced is used to make useful organic compounds, such as lipids, carbs and amino acids
step 5:
5/6 of the triose phosphate produced is used to regenerate the RuBP that we started with, and this requires ATP