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Biology Year 13 > Photosynthesis (11) > Flashcards

Photosynthesis (11) Flashcards

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1
Q

Where does the light-independent reaction occur?

A

stroma

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2
Q

Where does the light-dependent reaction occur?

A

thylakoids

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3
Q

What is the role of light in photoionisation?

A
  • Chlorophyll molecules absorb energy from photons of light
  • 2 electrons are ‘excited’ (raised to a higher energy level) causing them to be lost from the chlorophyll
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4
Q

What are the 7 stages of the light-dependent reaction?

A

1) Chlorophyll molecules absorb energy from photons of light
2) 2 electrons are ‘excited’ (raised to a higher energy level) causing them to be lost from the chlorophyll
3) electrons released from chlorophyll move down series of carrier proteins embedded in thylakoid membrane
4) undergo series of redox reactions which releases energy at decreasing energy levels
5) energy used to join ADP and Pi to form ATP
6) photolysis of water produces oxygen, electrons and protons
7) NADP reduced by electrons and hydrogen

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5
Q

How is a proton concentration gradient established during chemiosmosis?

A

some energy released from ETC is coupled to the active transport of hydrogen ions from stroma to thylakoid space

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6
Q

How does chemiosmosis produce ATP during the LDR?

A

hydrogen ions move down concentration gradient from thylakoid space to stroma via the channel protein ATP synthase

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7
Q

What are the 3 main stages of the calvin cycle?

A

1) carbon fixation
2) reduction
3) regeneration

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8
Q

What is the role of ATP synthase?

A

catalyses reaction between ADP + Pi to form ATP

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9
Q

What is the role of chlorophyll in photolysis?

A
  • absorbs light energy
  • loses electrons
  • accepts electrons from water
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10
Q

What is the role of light in photolysis?

A

light energy splits water molecules

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11
Q

What is the equation for photolysis of water?

A

2 H2O — 4H+ + 4e- + O2

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12
Q

What happens to the 4 hydrogen ions from photolysis of water?

A
  • move out of thylakoid space via ATP synthase
  • used to reduce NADP
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13
Q

What happens to the 4 electrons from photolysis of water?

A

replace electrons lost from chlorophyll

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14
Q

What happens to the oxygen from photolysis of water?

A

used for respiration or diffuses out of leaf as waste gas

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15
Q

What is the equation for reducing NADP?

A

NADP + 2H+ + 2e- > NADPH

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16
Q

Where is NADP reduced?

A

stroma

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17
Q

What catalyses the reaction for reducing NADP?

A

dehydrogenase enzymes

18
Q

What do dehydrogenase enzymes do?

A

catalyses reaction to reduce NADP

19
Q

Where are the 2 hydrogen ions from for reducing NADP?

A

from photolysis of water

20
Q

What do the 2 electrons in reducing NADP do?

A

act as final electron acceptor in ETC

21
Q

What are the 6 steps of the light-independent reaction?

A

1) CO2 enters leaf through stomata + combines with RuBP, catalysed by rubisco
2) forms unstable 6C compound that breaks down into 2 GP (3C compound)
3) 2 GP is reduced to 2 triose phosphate using 2 NADPH and energy from 2 ATP
4) forms 2 NADP and 2 ADP
5) 5/6 carbons from triose phosphate forms compound RuP
6) RuBP is regenerated from RuP using energy from 1 ATP

22
Q

What happens to 1carbon from TP?

A

leaves cycle and is converted into useful organic molecules e.g. glucose

23
Q

What is the role of ATP in the LIR?

A

reduction of GP to triose phosphate
provides phosphate group to convert RuP to RuBP

24
Q

What is the role of NADPH in LIR?

A

this coenzyme transports electrons needed for reduction of GP to triose phosphate

25
Q

What is the structure of chloroplasts?

A
  • usually disc-shaped
  • double membrane
  • thylakoids stack to form grana
  • intergranal lamellae attach thylakoids in adjacent grana
  • stroma
26
Q

What are thylakoids?

A

flattened discs

27
Q

What are intergranal lamallae?

A

tubular extensions

28
Q

What is the stroma?

A

fluid-filled matrix

29
Q

How does the structure of a chloroplast help maximise the rate of the LDR?

A
  • ATP synthase channels within granal membrane
  • large SA of thylakoid membrane for ETC
  • photosystems position chlorophyll to enable max absorption of light
30
Q

How does the structure of a chloroplast help maximise the rate of the LIR?

A
  • own DNA + ribosomes for synthesis of enzymes e.g. rubisco
  • concentration of enzymes + substrates in stroma is high
31
Q

What are 4 environmental factors that can limit the rate of photosynthesis?

A

1) light intensity for LDR
2) CO2 levels for LIR
3) temperature for enzyme-controlled steps
4) mineral + magnesium levels to maintain normal functioning of chlorophyll

32
Q

What is a limiting factor?

A

factor that determines the max rate of a reaction, even if other factors change to become more favourable

33
Q

What is the equation to calculate the Rf value?

A

distance between origin and centre of pigment spot
_______________
distance between origin and solvent front

34
Q

What are 3 agricultural practises used to overcome limiting factors?

A

1) artificial light, especially at night
2) artificial heating
3) addition of CO2 to greenhouse atmosphere

35
Q

Why do farmers use these agricultural practices?

A

to increase yield, but additional cost must be balanced with yield to ensure max profit

36
Q

How do you investigate the effect of a named variable on the rate of photosynthesis?

(3 points)

A

1) use a potometer (DV = rate of O2 production/CO2 consumption)
2) place balls of calcium alginate containing green algae in hydrogencarbonate indicator
3) colour changes from orange to magenta as CO2 is consumed and pH increases

37
Q

What is chromatography?

A

when molecules in a mixture are separated based on their relative attraction to the mobile phase (running solvent) vs the stationary phase (chromatography paper)

38
Q

How do you extract photosynthetic pigments?

A

use a pestle and mortar to grind a leaf with an extraction solvent e.g. propanone

39
Q

What is the Rf value?

A

ratio that allows comparison of how far molecules have moved in chromatography

40
Q

How can chromatography paper be used to separate photosynthetic pigments?

(4 points)

A

1) use capillary tube to spot pigment extract onto pencil origin (1cm above bottom of paper)
2) place chromatography paper in solvent (origin should be above solvent level)
3) allow solvent to run until almost touching other end of paper
4) pigments will move different distances

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