Topic 5A: Photosynthesis and Respiration

Question 1

What are properties of ATP?

Answer 1

• Releases energy in small amounts
• Simple reaction
• Quickly remade
• Supply to where needed

Question 2

What are coenzymes?

Answer 2

• Aids an enzyme
• Transfers chemical groups from one molecule to another

Question 3

Where does the light dependent reaction happen?

Answer 3

• Thylakoid membrane

Question 4

What are properties of the thylakoid membrane?

Answer 4

• Contains chlorophyll
• Large SA to absorb light

Question 5

How does the light dependent reaction begin?

Answer 5

• Photoionisation - light absorbed by chlorophyll photo system 2 - electrons are excited and leave the chlorophyll and are accepted by an electron acceptor

Question 6

What happens to electrons from the electron acceptor?

Answer 6

• Chemiosmosis - electrons move down electron transport chain - release energy - used to make ATP - electrons move to chlorophyll photo system 1

Question 7

How do electrons move from chlorophyll PS 1?

Answer 7

• Electrons excited by light energy again and leave
• Move down second electron transport chain - move to NADP - final electron acceptor

Question 8

What is photolysis of water?

Answer 8

• Electrons replace those lost from chlorophyll
• protons (H+) reduce NADP to NADPH with electrons
• O2 released as byproduct

Question 9

What are the stages of chemiosmosis?

Answer 9

1. Electrons lose energy as the move down the electron transport chain
2. This energy is used to actively transport protons into the thylakoid
3. A proton gradient is made so protons diffuse back in through ATP synthase
4. Energy from this movement converts ATP + Pi —> ATP

Question 10

What is photo phosphorylation?

Answer 10

• Forming ATP from ADP + Pi in photosynthesis

Question 11

What is non cyclic photo phosphorylation?

Answer 11

• normal
• produces ATP, NADPH, O2

Question 12

What is cyclic photo phosphorylation?

Answer 12

• Only produces ATP
• Electrons passed back to chlorophyll PS2 to recycle without making NADPH

Question 13

Where does the light independent reaction happen?

Answer 13

• Stroma

Question 14

What are the properties of the stroma?

Answer 14

• Contains enzymes
• Short diffusion distance to grand for ATP and NADPH

Question 15

Describe the light independent reaction

Answer 15

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

Question 16

How are products from the light independent reaction used?

Answer 16

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

Question 17

How is light intensity a limiting factor of photosynthesis?

Answer 17

• More light = more rate
• Then plateaus as another factor is limiting
• More light = more excited electrons - LDR

Question 18

How is light intensity regulated in glasshouses?

Answer 18

• Light in through glass in day
• Lamps at night
• LEDs = less expensive

Question 19

How does temperature affect the rate of photosynthesis?

Answer 19

• 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

Question 20

How is temperature regulated in glasshouses?

Answer 20

• Heating and cooling system for optimum temp
• Circulation for even temp
• Energy trapped from the sun warms air

Question 21

How is CO2 conc a limiting factor?

Answer 21

• Inc - inc rate - for LIR
• Plateaus - something else is limiting

Question 22

How is CO2 changed in glasshouses?

Answer 22

• Burn propane in CO2 generator

Question 23

How does water affect photosynthesis?

Answer 23

• Too little - no photolysis
• Too much - waterlogged - reduces mineral uptake

Question 24

Where does glycolysis happen?

Answer 24

• cytoplasm

Question 25

Describe glycolysis

Answer 25

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

Question 26

What is the net gain of ATP in glycolysis?

Answer 26

2 ATP

Question 27

What is after glycolysis in aerobic respiration - where does it happen?

Answer 27

Link reaction Mitochondrial matrix

Question 28

Describe the link reaction

Answer 28

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

Question 29

Where does the Krebs cycle happen?

Answer 29

Mitochondrial matrix

Question 30

Describe the Krebs cycle

Answer 30

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

Question 31

What reactions are in the Krebs cycle?

Answer 31

From 6C to 4C - series of oxidation reduction reactions

Question 32

What phosphorylation is this?

Answer 32

- Substrate level - enzyme related

Question 33

What are the steps of the electron transport chain for respiration?

Answer 33

1. FADH + NADH attach to 1st electron carrier on cristae - release electrons H+ and NAD + FAD recycled 2. Electrons move down carriers in redox reactions - releases energy 3. Energy actively transports protons into inter membrane space - forms proton gradient 4. Protons diffuse back into matrix - through ATP synthase - release energy (ADP +Pi -> ATP) 5. O2 = final electron acceptor - combines with protons and electrons to form water

Question 34

What phosphorylation is this?

Answer 34

Oxidative

Question 35

Why is anaerobic respiration used?

Answer 35

- 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

Question 36

How does anaerobic respiration happen in plants?

Answer 36

- pyruvate —> ethanol + CO2 (NADH -> NAD)

Question 37

How does anaerobic respiration happen in animals?

Answer 37

- Pyruvate —> lactate ( NADH -> NAD)

Question 38

Which type of respiration produces more ATP?

Answer 38

- Aerobic = 38 ATP - Anaerobic = 2 ATP (from glycolysis only)