Photosynthesis Revision Notes
Importance of Photosynthesis
Importance of Photosynthesis
-6CO2 + 6H2O → C6H12O6 + 6O2
- endothermic reaction (light energy used to produce ATP. ATP is then used to synthesise glucose)
-Energy is needed for:
Anabolic reactions (smaller molecules → bigger molecules – photosynthesis)
Active transport (nitrates from soil into root hair cell)
Movement (skeletal, flagella and cilia need energy to move)
Photosynthesis and Respiration
-Photosynthesis = endothermic (light energy used to produce ATP. ATP is then used to synthesise glucose)
6CO2 + 6H2O → C6H12O6 + 6O2
-Respiration = exothermic (glucose broken down and the energy forms ATP)
C6H12O6 + 6O2 → 6CO2 + 6H2O
-the products of one reaction are raw materials for the other
Carbon Fixation
-where CO2 is converted into sugars (endothermic and require electrons)
-helps to regulate concentration of CO2 in atmosphere and oceans
Compensation Point
-where the rate of photosynthesis = rate of respiration (no net loss of carbohydrates)
- at a high light intensity – plants that are used to the shade reach optimum rate quicker than plants that are used to light
-plants respire all the time but only photosynthesis in day
Autotroph vs Heterotroph
-Autotroph – uses light or chemical energy and inorganic molecules to synthesise complex organic molecules
-Heterotroph – ingest and digest complex organic molecules releasing chemical potential energy (gain nutrients)
-Photoautotroph – uses light energy as source to make its own food
Structure of Chloroplasts
-2-10μm long
- 2 Reactions can take place:
Light Dependant Reaction – in thylakoid membrane
Light Independent Reaction – in the stroma
Grana
-stacks of thylakoids (increases surface area)
-increased surface area needed for photosystems (convert light → ATP)
-Products of Light Dependant Reaction pass easily to Light Independent Reaction
Stroma
-fluid filled matrix
-contains enzymes needed in the Light Independent Reaction, small ribosomes, starch grains and loops of DNA
Photosynthetic Pigments and Photosystem
-photosystem = reaction centre (primary pigment) + light harvesting clusters (accessory pigments)
-accessory pigments pass light to primary pigment
-primary pigment – chlorophyll a
-accessory pigments – chlorophyll b, carotenoids
Chlorophyll A
-P700 = Photosystem I – peak absorption of 700nm
-P680 = Photosystem II – peak absorption of 680nm
Spectra
Absorption Spectrum = the relative absorption of different wavelengths of light
Action Spectrum = the relative effectiveness of wavelengths and photosynthesis
Importance of Photosynthesis
Importance of Photosynthesis
-6CO2 + 6H2O → C6H12O6 + 6O2
- endothermic reaction (light energy used to produce ATP. ATP is then used to synthesise glucose)
-Energy is needed for:
Anabolic reactions (smaller molecules → bigger molecules – photosynthesis)
Active transport (nitrates from soil into root hair cell)
Movement (skeletal, flagella and cilia need energy to move)
Photosynthesis and Respiration
-Photosynthesis = endothermic (light energy used to produce ATP. ATP is then used to synthesise glucose)
6CO2 + 6H2O → C6H12O6 + 6O2
-Respiration = exothermic (glucose broken down and the energy forms ATP)
C6H12O6 + 6O2 → 6CO2 + 6H2O
-the products of one reaction are raw materials for the other
Carbon Fixation
-where CO2 is converted into sugars (endothermic and require electrons)
-helps to regulate concentration of CO2 in atmosphere and oceans
Compensation Point
-where the rate of photosynthesis = rate of respiration (no net loss of carbohydrates)
- at a high light intensity – plants that are used to the shade reach optimum rate quicker than plants that are used to light
-plants respire all the time but only photosynthesis in day
Autotroph vs Heterotroph
-Autotroph – uses light or chemical energy and inorganic molecules to synthesise complex organic molecules
-Heterotroph – ingest and digest complex organic molecules releasing chemical potential energy (gain nutrients)
-Photoautotroph – uses light energy as source to make its own food
Structure of Chloroplasts
-2-10μm long
- 2 Reactions can take place:
Light Dependant Reaction – in thylakoid membrane
Light Independent Reaction – in the stroma
Grana
-stacks of thylakoids (increases surface area)
-increased surface area needed for photosystems (convert light → ATP)
-Products of Light Dependant Reaction pass easily to Light Independent Reaction
Stroma
-fluid filled matrix
-contains enzymes needed in the Light Independent Reaction, small ribosomes, starch grains and loops of DNA
Photosynthetic Pigments and Photosystem
-photosystem = reaction centre (primary pigment) + light harvesting clusters (accessory pigments)
-accessory pigments pass light to primary pigment
-primary pigment – chlorophyll a
-accessory pigments – chlorophyll b, carotenoids
Chlorophyll A
-P700 = Photosystem I – peak absorption of 700nm
-P680 = Photosystem II – peak absorption of 680nm
Spectra
Absorption Spectrum = the relative absorption of different wavelengths of light
Action Spectrum = the relative effectiveness of wavelengths and photosynthesis
