A revision summary of OCR A level Biology Photosynthesis 5.2.1
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
Photosynthesis – light energy is converted into chemical energy to Cyclic phosphorylation
synthesise organic molecules. (Inorganic to organic) 1. Only PSⅠ(P680)
6CO2 + 6H2O C6H12O6 + 6O2 Respiration 2. Light energy excited e- to higher energy level
Carbon Dioxide + Water Glucose + Oxygen - Uses O2 3. 2e- pass into ETC (Fe2+ containing proteins
- Light energy trapped by chlorophyll molecules used to drive produced from accept & donate 2e- in redox reactions)
synthesis. photosynthesi 4. ETC generates small amount of ATP
- Compensation point – respiration & photosynthesis in plant occur s 5. 2e- leaving ETC are recycled & returned to PSⅠ
at same rate = no net gain/ loss of carbohydrate. - Organic Cyclic Non-cyclic
Autotrophs – synthesis organic molecules from inorganic molecules molecules Molecules? Inorganic Inorganic
Chemoautotrophs – oxidise ammonia to nitrate (nitrifying bacteria) broken into organic organic
Photoautotrophs – use light & CO2 to create sugars and complex inorganic PSⅠ? Yes Yes
carbs (plants) - Energy PSⅡ? No Yes
Respiration Photosynthesis released used Where Recycled in ETC
Molecul Inorganic to organic Organic to inorganic to synthesis does ETC
es ATP PSⅠget e-?
Reactan Glucose & oxygen Water & carbon dioxide - CO2 produced Where Photolysis -
ts used in does PSⅡ H2O
Product Water & carbon dioxide Glucose & oxygen photosynthesi get e-?
s s. Products? ATP ATP, rNADP,
Reaction Exothermic – release Endothermic – trap energy O2,
Grana - made of stacks of thylakoids =
↑membrane SA
Stroma - enzymes for catalysis of LD reactions &
holds LD stage products.
Lipid droplets – pplipid bilayer
Photosystem – protein embedded within thylakoid membrane.
Primary Pigment is Chlorophyll-a in reaction centre absorbs red/green
- Fatty acid tail (can embed itself CSM)
- Mg2+ ion can lose electrons.
- PSⅠ – has chlorophyll P700 (max absorption at 700nm)
- PSⅡ – has Chlorophyll P680 (max absorption at 680nm)
Accessory pigments - chlorophyll-b, xanthophyll, carotenoids
- Each absorb specific freq of wavelengths
- pass photons of light energy to primary pigment
- Allow for maximum absorption of light.
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