Topic 5A: Photosynthesis and Respiration Flashcards
What are properties of ATP?
- Releases energy in small amounts
- Simple reaction
- Quickly remade
- Supply to where needed
What are coenzymes?
- Aids an enzyme
- Transfers chemical groups from one molecule to another
Where does the light dependent reaction happen?
- Thylakoid membrane
What are properties of the thylakoid membrane?
- Contains chlorophyll
- Large SA to absorb light
How does the light dependent reaction begin?
- Photoionisation - light absorbed by chlorophyll photo system 2 - electrons are excited and leave the chlorophyll and are accepted by an electron acceptor
What happens to electrons from the electron acceptor?
- Chemiosmosis - electrons move down electron transport chain - release energy - used to make ATP - electrons move to chlorophyll photo system 1
How do electrons move from chlorophyll PS 1?
- Electrons excited by light energy again and leave
- Move down second electron transport chain - move to NADP - final electron acceptor
What is photolysis of water?
- Electrons replace those lost from chlorophyll
- protons (H+) reduce NADP to NADPH with electrons
- O2 released as byproduct
What are the stages of chemiosmosis?
- Electrons lose energy as the move down the electron transport chain
- This energy is used to actively transport protons into the thylakoid
- A proton gradient is made so protons diffuse back in through ATP synthase
- Energy from this movement converts ATP + Pi —> ATP
What is photo phosphorylation?
- Forming ATP from ADP + Pi in photosynthesis
What is non cyclic photo phosphorylation?
- normal
- produces ATP, NADPH, O2
What is cyclic photo phosphorylation?
- Only produces ATP
- Electrons passed back to chlorophyll PS2 to recycle without making NADPH
Where does the light independent reaction happen?
- Stroma
What are the properties of the stroma?
- Contains enzymes
- Short diffusion distance to grand for ATP and NADPH
Describe the light independent reaction
Calvin Cycle
5C RuBP
CO2 joins - catalysed by rubisco
2x3C GP
Forms 2x3C Triose Phosphate —> reduced using NADPH -> NADP and energy from ATP -> ADP + Pi
How are products from the light independent reaction used?
1/6 used to produce organic molecules e.g. glucose
5/6 go back to become RuBP using phosphate from ATP -> ADP + Pi
Reaction must happen 6 times for one glucose molecule
How is light intensity a limiting factor of photosynthesis?
- More light = more rate
- Then plateaus as another factor is limiting
- More light = more excited electrons - LDR
How is light intensity regulated in glasshouses?
- Light in through glass in day
- Lamps at night
- LEDs = less expensive
How does temperature affect the rate of photosynthesis?
- Inc temp = faster rate - inc collision rate
- Too hot - enzymes denature - rate slows
- only affects LIR - enzymes
- Too hot - stomata close - less CO2 in
- Affects membrane permeability - for proton gradient
How is temperature regulated in glasshouses?
- Heating and cooling system for optimum temp
- Circulation for even temp
- Energy trapped from the sun warms air
How is CO2 conc a limiting factor?
- Inc - inc rate - for LIR
- Plateaus - something else is limiting
How is CO2 changed in glasshouses?
- Burn propane in CO2 generator
How does water affect photosynthesis?
- Too little - no photolysis
- Too much - waterlogged - reduces mineral uptake
Where does glycolysis happen?
- cytoplasm
Describe glycolysis
6C glucose - phosphorylation with ATP -> ADP + Pi
6C glucose phosphate - phosphorylated again (ATP -> ADP +Pi)
Unstable 6C molecule - splits
2x3C triose phosphate - oxidised (NAD-> NADH & 4ADP+4Pi -> 4ATP)
2x3C pyruvate
What is the net gain of ATP in glycolysis?
2 ATP
What is after glycolysis in aerobic respiration - where does it happen?
Link reaction
Mitochondrial matrix
Describe the link reaction
3C pyruvate - reduced and loses a C ( CO2 released & NAD -> NADH)
2C acetate - gains coenzyme A
2C acetyl coenzyme A
Happens twice for each glucose - 2x pyruvate made
Where does the Krebs cycle happen?
Mitochondrial matrix
Describe the Krebs cycle
2C acetyl coenzyme A
6C acid (releases CO2 & NAD -> NADH
5C acid (releases CO2, NAD -> NADH, FAD -> FADH & ATP)
4C acid —> back round to acetyl coenzyme A
What reactions are in the Krebs cycle?
From 6C to 4C - series of oxidation reduction reactions
What phosphorylation is this?
- Substrate level - enzyme related
What are the steps of the electron transport chain for respiration?
- FADH + NADH attach to 1st electron carrier on cristae - release electrons H+ and NAD + FAD recycled
- Electrons move down carriers in redox reactions - releases energy
- Energy actively transports protons into inter membrane space - forms proton gradient
- Protons diffuse back into matrix - through ATP synthase - release energy (ADP +Pi -> ATP)
- O2 = final electron acceptor - combines with protons and electrons to form water
What phosphorylation is this?
Oxidative
Why is anaerobic respiration used?
- Alternative pathway - pyruvate accepts H from NADH
- Allows regeneration of NAD to drive glycolysis to happen again
- Generates a small amount of ATP to provide energy until aerobic respiration can begin again
How does anaerobic respiration happen in plants?
- pyruvate —> ethanol + CO2
(NADH -> NAD)
How does anaerobic respiration happen in animals?
- Pyruvate —> lactate
( NADH -> NAD)
Which type of respiration produces more ATP?
- Aerobic = 38 ATP
- Anaerobic = 2 ATP (from glycolysis only)
