Pack 16 - Photosynthesis Flashcards
What are the two reactions for photosynthesis?
Light Dependant Reaction
Light Independent Reaction
Describe the light dependent reaction?
light is absorbed by chlorophyll and a pair of electrons gain energy
the electrons leave the chlorophyll are taken up by a molecule called an electron carrier
loss of electrons oxidises chlorophyll molecule - this is photoionisation
the electrons pass through series of electron carriers in a series of REDOX reactions
electron carriers form an electron transport chain located in membrane of thylakoid
electrons lose energy at each carrier
during photophosphorylation the energy that comes from the electrons is used to combine an inorganic phosphate with ADP to form ATP via a H+ ion gradient
molecule of water splits into hydrogen ions (proton and electrons) and oxygen - this is photolysis
electrons from photolysis are used back in the chlorophyll
the protons from photolysis react with NADP (along with the electrons at the end of the electron transport chain) to form NADPH
How do the H+ ions diffuse back into the stroma after being pumped out when the electron moves through the ETC?
Via special protein complexes that contain the enzyme ATP synthase
Describe the light independent reaction
Ribulose Biosphosphate is carboxylated into 2 glycerate and 3-phosphate
In a reduction reaction 2 glycerate and 3-phosphate changes to 2 triose phosphate (organic substances)
During the reduction 2ATP changes to 2ADP+2pi and NADH changes to NAD
2 triose phosphate undergoes phosphorylation changing back to ribulose biosphosphate
During the phosphorylation 2 ADP+ 2pi changes to 2ATP
What are some environmental factors that would limit photosynthesis?
light intensity - increased light intensity = increased photosynthesis
pH - at too high/low pH’s enzymes in the plant denature causing photosynthesis to decrease
temperature - between 10 degrees and 35 degrees is the optimum temperature
CO2 concentration - decreased CO2 = decreased photosynthesis
