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AQA Biology > 5.1 Photosynthesis > Flashcards

5.1 Photosynthesis Flashcards

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1
Q

Where does the light dependent reaction occur in plants?

A

Thylakoids of the chloroplasts

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2
Q

Where does the light independent reaction occur in plants?

A

Stroma of the chloroplasts

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3
Q

Explain the role of light of photoionisation.

A

Chlorophyll molecules absorb energy from photons of light
This raises 2 electrons to a higher energy level to release them from the chlorophyll

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4
Q

Name the 2 main stages involved in ATP production in the LDR.

A
  1. Electron Transfer Chain (ETC)
  2. Chemiosmosis
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5
Q

What happens in the ETC?

A

Electrons released from chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane
Undergo a series of redox reactions to release energy

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6
Q

How is a proton concentration gradient established during chemiosmosis?

A

Some energy released from ETC is coupled to the active transport of H+ ions from stroma into thylakoid space

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7
Q

How does chemiosmosis produce ATP in the light dependent stage?

A

H+ ions move down their concentration gradient from thylakoid space into stroma via the channel protein ATP synthase

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8
Q

What does ATP synthase catalyse?

A

ADP + Pi -> ATP

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9
Q

Explain the role of light in photolysis.

A

Splits molecules of water

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10
Q

Give the equation for the photolysis of water.

A

2H₂O -> 4H⁺ + 4e⁻ + O₂

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11
Q

What happens to the H⁺ produced in the photolysis of water?

A

Move out of thylakoid space via ATP synthase
Used to redyce the coenzyme ATP

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12
Q

What happens to the e⁻ produced in the photolysis of water?

A

Replace electrons lost from chlorophyll

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13
Q

What happens to the O₂ produced in the photolysis of water?

A

Used for respiration or diffuses out of leaf as waste gas

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14
Q

Where is reduced NADP produced in the LDR?

A

Stroma of chloroplasts

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15
Q

How is reduced NADP produced in the LDR?

A

NADP + 2H⁺ + 2e⁻ -> reduced NADP
Catalysed by dehydrogenase

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16
Q

Where do H⁺ ions used to reduce NADP come from?

A

Photolysis of water

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17
Q

Where do electrons used to reduce NADP come from?

A

NADP acts as the final electron acceptor of the ETC

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18
Q

Name the 3 stages of the Calvin Cycle.

A

Carbon fixation
Reduction
Regeneration

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19
Q

What happens during carbon fixation in the Calvin cycle?

A

Reaction between CO₂ & RuBP catalysed by rubisco
Forms unstable 6C intermediate that breaks down into 2GP

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20
Q

What is meant by RuBP?

A

Ribulose BisPhosphate

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21
Q

What is meant by GP?

A

Glycerate 3-Phosphate

22
Q

What happens during reduction in the Calvin cycle?

A

2GP are reduced to 2TP
Requires 2NADP & 2ATP
Forms 2NADP & 2ADP

23
Q

What is meant by TP?

A

Triose Phosphate

24
Q

How does the LIR result in the production of useful organic substances?

A

1C leaves the cycle

25
Q

What happens during regeneration in the Calvin cycle?

A

1C leaves the cycle
5C compound RuP forms
RuBP is regenerated from RuP using 1ATP
Forms 1ADP

26
Q

State the role of ATP in the LIR.

A

Reduction of GP to TP
Provides phosphate group to convert RuP into RuBP

27
Q

State the role of reduced NADP in the LIR.

A

Coenzyme transports electrons needed for reduction of GP to TP

28
Q

What number of carbon atoms does RuBP have?

A

5

29
Q

What number of carbon atoms does GP have?

A

3

30
Q

What number of carbon atoms does TP have?

A

3

31
Q

Describe the structure of a chloroplast.

A

Disc-shaped
Double membrane
Thylakoids
Intergranal lamellae
Stroma

32
Q

What are the thylakoids of a chloroplast?

A

Flattened discs stack to form grana

33
Q

What are the intergranal lamellae of a chloroplast?

A

Tubular extensions attach thylakoids in adjacent grana

34
Q

What is the stroma of a chloroplast?

A

Fluid-filled matrix

35
Q

How does the structure of a chloroplast maximase the rate of the LDR?

A

ATP synthase channels within granal membrane
Large SA of thylakoid membrane for ETC
Photosystems position chlorophyll to enable maximum absorption of light

36
Q

How does the structure of a chloroplast maximase the rate of the LIR?

A

Own DNA & ribosomes for synthesis of enzymes e.g. rubisco
Concentration of enzymes & substrates in stroma is high

37
Q

Define limiting factor.

A

Factor that determines maximum rate of a reaction, even if other factors change to become more favourable

38
Q

Name 4 environmental factors that limit the rate of photosynthesis.

A

Light intensity
CO₂ levels
Temperature
Mineral/magnesium levels

39
Q

What part of photosynthesis does light intensity affect?

A

Light dependent stage

40
Q

What part of photosynthesis do CO₂ levels affect?

A

Light dependent stage

41
Q

What part of photosynthesis does temperature affect?

A

Enzyme controlled steps

42
Q

What part of photosynthesis do mineral levels affect?

A

Normal functioning of chlorophyll

43
Q

Outline some common agricultural practices used to overcome the effect of limiting factors in photosynthesis.

A

Artificial light
Artificial heating
Addition of CO₂ to greenhouse atmosphere

44
Q

Why do farmers try to overcome the effect of limiting factors?

A

Increase yield
Additional cost balanced with yield to ensure maximum profit

45
Q

State the purpose and principle of paper chromatography.

A

Molecules in a mixture are separated based on their relative attraction to the mobile phase vs stationary phase

46
Q

Outline a method for extracting photosynthetic pigments.

A

Using a pestle and mortar to grind a leaf with an extraction solvent

47
Q

Outline how paper chromatography can be used to separate photosynthetic pigments.

A

Use capillary tube to spot pigment extract onto pencil origin
Place chromatography paper in solvent with origin above solvent level
Allow solvent to run until almost at other end of paper
Pigments move different distances

48
Q

Where does the origin line go?

A

1cm above bottom of paper

49
Q

Why is origin line drawn in pencil?

A

Pencil isn’t soluble

50
Q

What are Rf values?

A

Ratios that allow comparison of how far molecules have moved in chromatograms

51
Q

How are Rf values calculated?

A

Distance to origin/distance to solvent front

AQA Biology (43 decks)

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