3.5.1 Photosynthesis Flashcards
Where do the LDR and LIR take place
LDR - thylakoid
LIR - stroma
Explain the role of light in photoionisation
Pigment absorbs energy from light
Excites 2 electrons and they are released and go down electron transfer chain
What happens in the electron transfer chain (ETC)
Electrons released from pigment move down a series of carrier proteins in thylakoid membrane, undergo a series of redox reactions which releases energy
How is a H+ gradient established
Some energy from ETC is used to actively transport H+ from stroma into thylakoid space
How is ATP produced in LDR
H+ moves down conc gradient from thylakoid space into stroma via ATP synthase. ATP synthase catalyses ADP+Pi -> ATP
Explain the role of light in photolysis
Light energy splits molecules of water
2H2O –> 4H+ + 4e- + O2
What happens to products of photolysis of water
H+ moves out thylakoid by ATP synthase to LIR
e- replaces electrons lost from pigment
O2 - respiration or diffuses out as waste
How and where is NADP produced in LDR
NADP + H+ + 2e- –> NADPH
Stroma
Describe what happen between RuBP and CO2
Reaction between RuBP and CO2 is catalysed by rubisco
Forms 2x GP
Describe what happens to GP
Using energy released from ATP and H+ from NADPH, GP is reduced into 2x triose phosphate
How does the LIR result in growth
1 carbon leaves the cycle each time
eg some of the TP is converted into useful organic molecules eg hexose sugar
What happens to TP in LIR
After 1C leaves the cycle, RuBP reforms using phosphate from ATP
Describe the structure of a chloroplast
Disc shaped
Double membrane
Thylakoids - flattened discs stack to form grana
Lamellae
Stroma
How does the structure of the chloroplast maximise the rate of LDR
Large SA of thylakoid membrane for ETC
Photosystems position chlorophyll to enable maximum absorption of light
ATP synthase channels within granal membrane
How does the structure of the chloroplast maximise the rate of the LIR
Own DNA and ribosomes for synthesis of enzymes eg rubisco
Conc 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
3 environmental factors that can limit the rate of photosynthesis
Light intensity
Co2 levels
Temperature
Common agricultural processes used to overcome limiting factors
Artificial light
Artificial heating
Addition of CO2 to greenhouse atmosphere
Why do farmers try to overcome the effect of limiting factors
To increase yield
Additional cost must be balanced with yield to ensure maximum profit
Outline a method for extracting photosynthetic pigments
Use a pestle and mortar to grind a leaf with an extraction solvent eg propanone
Outline how paper chromatography can be used to separate photosynthetic pigments
Use a capillary tube to spot pigment extract onto pencil origin line
Place chromatography paper in solvent
Allow solvent to run until it nearly reaches end of paper
State the number of carbon atoms in RuBP, GP, TP
RuBP = 5
GP = 3
TP =3
