Topic: Respiration/Photosyn Essay - Main Points!

Q) Distinguish photophosphorylation and oxidative phosphorylation

Main points
Key idea:	Location
Photophosphorylation · occurs at thylakoid membr (of chloroplast, plant cells) Oxidative phosphorylation · occurs at inner mitochondrial membr (of mitochondria, all euk cells)
Key idea:	Energy conversion
Photophosphorylation · Light energy converted to chemical energy (in the form of ATP) Oxidative phosphorylation · Chemical energy fr glucose converted to chemical energy (in the form of ATP)
Key idea:	Source of energy for ATP synthesis
Photophosphorylation · Originates fr light Oxidative phosphorylation · Originates fr oxidation of glucose
Key idea:	Involvement of light
Photophosphorylation · Light energy absorbed by photosyn pigments (of light harvesting complexes) · Excitation & displacement of energized e fr pri pigments (of rx centres of PSI & II) · Also required for photolysis of H2O, to generate e · Ref to replenish e lost fr PS II (during non-cyclic photophosphorylation) Oxidative phosphorylation · Light not required
Key idea:	Coenzymes
Photophosphorylation · NADP reduced to NADPH during light dep · NADPH required for reduction of glycerate-3-phosphate to triose phosphate (TP) · Some TP used to syn biomolecules (e.g. starch) + rest of TP to regenerate ribulose bisphosphate (RuBP) Oxidative phosphorylation · NAD & FAD reduced to NADH & FADH2 · which carry energized e to electron transport chain (ETC), for ATP syn
Key idea:	Source of electrons
Photophosphorylation · H2O (non-cyclic photophosphorylation) · PSI (cyclic photophosphorylation) Oxidative phosphorylation · NADH + FADH2 donate e to ETC
Key idea:	Oxygen
Photophosphorylation · not required · O2 produced as byproduct during photolysis of H2O · NADP+ - last e acceptor of light dep rx Oxidative phosphorylation · O2 - last e acceptor of ETC, hence required for continuous flow of e throu ETC + subseq ATP syn
Key idea:	Water
Photophosphorylation · Source of e in non-cyclic photophosphorylation (light dep rx) Oxidative phosphorylation   · H2O – byproduct, formed when O2 combines with e & H+
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min)