paper 2: Photosynthesis Flashcards
what is meant by the terms oxidation and reduction
oxidation: losss of electron or hydrogen
reduction: gain of electrons or hydrogen
state the chemical equation photosynthesis
carbon dioxide + water —-> glucose + oxygen
draw a chloroplast and label the structure
what are the names of the 2 stages of photosynthesis
light dependent reaction, light independent reaction
where in the chloroplast does each stage of photosynthesis take place
thylakoid membrane, stroma
describe the steps of the light dependent reaction
- photoionisation: chlorophyll absorbs light. electrons are exited to a higher eergy level and lost from chlorophyll
- photolysis: light splits water into electrons, protons and oxygen. the chlorophyll reagins its lost electrons from the split water. oxygen is given off as a waste product.
- electron transfer chain: electrons from chlorophyll are passed down a series of electron carriers in the thylakoid membrane via redox reactions. electrons lsoe enrgy and the enrgy is then used to pump protons across the thylakoid membrane forming a proton gradient.
- formation of ATP: protons diffuse back through the thylakoid membrane via ATP synthase down their electrochemical gradient (chemiosmosis). the energy from this forms ATP from ADP + Pi
- reducing NADP: the electron from the electron transfer chain and H reduce NADP to make reduced NADP
name the 2 products that are made in the light dependent reaction that are used in the light independent reaction
ATP and reduced NADP
draw a diagrm detailing the light dependent reaction
describe the reactions which occur in the light independent reaction
- occurs in stroma of chloroplasts
- carbon dioxide reacts with RuBP
- produces 2 molecules of GP
- catalysed by rubisco
- GP is reduced to 2 molecules of triose phosphate
- using hydrogen from reduced NADP
- using energy from the hydrolysis of ATP
- triose phosphate is converted to organic molecules such as glucose and amino acids.
- 5 carbons from triose phsophate is used to regenerate RuBP via phosphorylation by ATP.
what is the name of the enxyme which catalyses tthe reaction between CO2 and RuBP
rubisco
how does photosynthesis increase growth of the plant
- glucose is produced - which is respired to produce ATP which is hydrolysed to release energy
- energy is used to synthesise new molecules like proteins
- beta glucose is used to make cellulose in cell walls
- lipids prodcused can be used to make phospholipids and form new phospholipid bilayers
- amino acids are used to form enzymes needed for growth
in the abscence of light, levels of GP increase at first and then level off. explain why
- oxygen and redcued NADP are no longer made in light dependent reaction
- GP increases as CO2 continues to react with RuBP to make GP but GP is no longer being reduced to triose phosphate
- GP then levels off as RuBP is not being regenerated
- so GP no longer made as CO2 has no RuBP to react with
what are the three limiting factors which effect the rate of photosynthesis
light intensity
temperature
CO2 conc.
how does light intensity speed up the rate of photosynthesis
- higher light intensity means more light dependent reaction so more ATP and redcued NADP produced so more GP redcued to triose phosphate in light independant reaction
how does temperature increase he rate of photosynthesis
light independant reaction happens faster as enzymes have more kinetic energy so more enzyme-substrate complexes form
