Photosynthesis Flashcards
What are the two stages of photosynthesis?
LDR and LIR
What are the four stages of LDR?
Photolysis, photoionisation, photophosphorylation and chemiosmosis
What is photolysis?
Splitting of water molecule by light to form 2H+ + 2e- + 1/2 O2
What is photoionisation?
Energy from light is passed through the PS and transferred to chlorophyll a, this causes the electrons to become excited and ejected
What is photophosphorylation?
Light is used to add a phosphate group to ADP
What is chemiosmosis?
Electrons moving through ETC release energy for active transport of H+ into the thylakoid lumen to create an electrochemical gradient, they then diffuse through ATP synthase
What is cyclic phosphorylation?
Excited electrons from PSI are passed through a series of electron carries, but are then passed back to PSI rather than NADP, it only produces small amount of ATP
What happens in the LDR?
Photolysis in thylakoid lumen. Electrons move into PSI and PSII. Photoionisation allows NADP to become NADPH with released electrons. Cytochrome moves H+ for chemiosmosis. ATP synthase creates ATP.
What happens in the LIR?
CO2 combines with RuBP (5C) under rubisco enzyme to create 2GP (3C). ATP and NADPH used to convert to 2TP (3C). ATP used and one carbon used to create sugar (6 cycles needed) and the other 5 and converted back to RuBP.
What is RuBP?
Ribulose Biphosphate is a 5 carbon compound
What is GP?
Glycerate 3-phosphate is a 3 carbon compound
What is TP?
Triose phosphate is a 3 carbon compound, it’s the reduced version of GP
How can lipids be formed from the Calvin cycle?
Glycerol (from TP) and fatty acids (from GP)
How can amino acids be formed from the Calvin cycle?
TP + Nitrate ions or ammonium ions
What are the limiting factors of photosynthesis?
Light, temperature and carbon dioxide
