CH11 Photosynthesis Flashcards
Where does light-dependant reaction occur
Thylakoids of chloroplasts
Where does the light-independent reaction take place
Stroma of chloroplasts
Role of light in photoionisation
Chlorophyll absorb energy from photons of light
This excited 2 electrons (raises them to a higher energy level)
Causing them to be released from the chlorophyll
2 main stages in ATP production in LDR
Electron transfer chain
Chemiosmosis
What happens in electron transfer chain (ETC)
Electrons released from chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane and undergo a series of redox reactions, releasing energy
How is a proton concentration gradient established during chemiosmosis
Some energy released from ETC is coupled to the AT of H+ ions from the stroma into the thylakoid space
How does chemiosmosis produce ATP in the LDR
H+ ions move down their concentration gradient from the thylakoid space into the stroma via the channel protein ATP synthase
ATP synthase catalyses:
ADP + Pi –> ATP
What is photolysis
The splitting of water into 2 electrons 2 protons and oxygen gas
What happens to products of photolysis
H+ = Move out of thylakoid space via ATP synthase and are used to reduce coenzyme NADP e- = Replace electrons lost from chlorophyll O2 = Used for respiration or diffuses out of leaf as waste gas
How and where is reduced NADP produced in LDR
NADP + 2H+ + 2e- –> reduced NADP
Catalysed by dehydrogenase enzymes
Stroma of chloroplasts
Where do H+ ions and electrons used to reduce NADP come from
H+ = photolysis of water e- = NADP is final electron acceptor in ETC
3 main stages of Calvin Cycle
Carbon fixation
Reduction
Regeneration
What occurs during carbon fixation
Reaction between CO2 and (RuBP) catalysed by rubisco
Forms unstable 6C intermediate which breaks down into 2x GP
What happens during reduction
2x GP reduced to 2x TP
Requires 2 reduced NADP and 2 ATP
Forms 2 NADP and 2 ADP
How does LDR result in production of useful organic substances
1C leaves the cycle
Some TP converted into useful organic molecules
What happens during regeneration
After 1C leaves the cycle, the 5C compound RuP forms
RuBP is regenerated from RuP using 1 ATP
Forms 1 ADP
Roles of ATP and reduced NADP in LiR
ATP - Reduction of GP to TP and provides phosphate to convert RuP to RuBP
NADP - coenzyme transports electrons needed for reduction of GP to TP
State number of carbons in RuBP
GP
TP
RuBP - 5
GP - 3
TP - 3
Describe. structure of chloroplast
Disc-shaped
Double membrane
Thylakoids - flattened discs stack to form grana
Intergranal lamellae - tubular extensions attach thylakoids to in adjacent grana
Stroma - fluid-filled matrix
How does structure of chloroplast maximise rate of LDR
ATP synthase channels within granal membrane
Large SA of thylakoid membrane for ETC
Photosystems position chlorophyll to enable maximum light absorption
How does structure of chloroplast maximise rate of LiR
Own DNA and ribosomes for synthesis of enzymes - rubisco
Concentration of enzymes and substrates in stroma is high
Define limiting factor
Factor that determines maximum rate of a reaction, even if other factors change to become more favourable
Name 4 environmental factors that can limit rate of photosynthesis
Light intensity - LDR
CO2 levels - LiR
Temperature - Enzymes
Mineral levels - maintain normal functioning of chlorophyll
Common agricultural practices to overcome limiting factors
Artificial light
Artificial heating
Addition of CO2 to greenhouses
Why to farmers try to overcome limiting factors
Increase yield
Additional cost must be balanced to ensure profit
Method for extracting photosynthetic pigment
Use a pestle and mortar to grind leaf with an extraction solvent - propanone
How paper chromatography can be used to separate photosynthetic pigment
Use capillary tube to spot pigment extract onto pencil line 1cm above bottom of paper
Place chromatography paper in solvent
Allow solvent to run until it almost touches the other end of paper
What are Rf values - how are they calculated
Ratios that allow comparison of how far molecules move in chromatograms - Distance between origin and centre of pigment spot / distance between origin and solvent front
