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Biology > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Where does the light-dependent reaction occur in plants?

A

In the thylakoids of chloroplasts

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2
Q

Where does the light-independent reactions occur in plants?

A

In the stroma of chloroplasts

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3
Q

Explain the role of light in photoionisation

A
  • chlorophyll molecules absor energy from photons of light

- excites 2 electrons causing them to be released from the chlorophyll

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4
Q

What does exciting an electron mean?

A

Raising it to a higher energy level

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5
Q

What are the 2 main stages involved in ATP production in the light-dependent reaction?

A
  • ETC

- chemiosmosis

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6
Q

What happens in the ETC?

A

Electrons released from chlorophyll moved down a series of carrier proteins embedded in the thylakoid membrane & undergo a series of redox reaction, which releases energy

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7
Q

How is a proton concentration gradient established during chemiosmosis?

A

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

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8
Q

How does chemiosmosis produce ATP in the light-dependent stage?

A

Protons move down their concentration gradient from the thylakoid space back into the stroma via the channel protein ATP synthase

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9
Q

Explain the role of light in photolysis

A

Light energy splits molecules of water

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10
Q

What are the products of photolysis of water?

A
  • H+ ions
  • e-
  • O2
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11
Q

What happens to H+ ions in photolysis?

A

Move out of thylakoid space via ATP synthase and are used to reduce the coenzyme NADP

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12
Q

What happens to electrons in photolysis?

A

Replace electrons lost from chlorophyll

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13
Q

What happens to oxygen in photolysis?

A

Used for respiration or diffuses out of leaf as waste gas

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14
Q

How and where is reduced NADP produced in the light-dependent reaction?

A
  • NADP + 2H + 2e- -> reduced NADP
  • catalysed by dehydrogenase enzymes
  • stroma of chloroplasts
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15
Q

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

A
  • H+ ions: photolysis of water

- Electrons: NADP acts as the final electron acceptor of the ETC

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16
Q

Name the 3 main stages in the Calvin cycle

A
  • carbon fixation
  • reduction
  • regeneration
17
Q

What happens during carbon fixation?

A
  • Reaction between CO2 & RuBP catalysed by rubisco

- Forms unstable 6C intermediate that breaks down into 2x GP

18
Q

What happens during reduction in the Calvin cycle?

A
  • 2x GP are reduced to 2x TP
  • requires 2x reduced NADP & 2x ATP
  • forms 2x NADP & 2x ADP
19
Q

How does the light-independent reaction result in the production of useful organic substances?

A

1C leaves the cycles

- some of the TP is converted into useful organic molecules

20
Q

What happens during regeneration in the Calvin cycle?

A
  • after 1C leaves the cycle, the 5C compound RuP forms
  • RuBP is regenerated from RuP using an ATP
  • forms 1 ADP
21
Q

State the roles of ATP & reduced NADP in the light-independent reaction

A
  • ATP: reduction of GP to TP & provides phosphate group to convert RuP into RuBP
  • reduced NADP: coenzyme transports electrons needed for reduction of GP to TP
22
Q

How many carbon atoms in RuBP, GP & TP?

A

RuBP: 5
GP: 3
TP:3

23
Q

Describe the structure of a chloroplast

A
  • usually disc-shaped
  • double membrane
  • thylakoids
  • integranal lamellae
  • stroma
24
Q

What is a thylakoid?

A

Flattened disc that stacks to form grana

25
Q

What are intergranal lamellae?

A

Tubular extensions attach thylakoids in adjacent grana

26
Q

What is the stroma?

A

Fluid filled matrix

27
Q

How does the structure of the chloroplast maximise the rate of the light-dependent reaction?

A
  • ATP synthase channels within granal membrane
  • large surface area of thylakoid membrane for ETC
  • photosystems position chlorophyll to enable maximum absorption of light
28
Q

How does the structure of the chloroplast maximise the rate of the light-independent reaction?

A
  • own DNA & ribosomes for synthesis of enzymes like rubisco

- concentration of enzymes & substrates in stroma is high

29
Q

What is a limiting factor?

A

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

30
Q

Name 4 environmental factors that can limit the rate of photosynthesis

A
  • light intensity
  • CO2 levels
  • temperature
  • mineral/magnesium levels
31
Q

What are some common farming practices used to overcome the limiting factors affecting photosynthesis?

A
  • artificial light especially at night
  • artificial heating
  • additon of CO2 to greenhouse atmosphere
32
Q

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

A
  • to increase yield

- additional cost must be balanced with yield to ensure maximum profit

33
Q

How could a student investigate the effect of a named variable on the rate of photosynthesis?

A
  1. Use a potometer
  2. Place balls of calcium alginate containing green algae in hydrogencarbonate indicator
  3. Colour change orange -> magenta as CO2 is consumed & pH increases
34
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 the stationary phase

35
Q

Outline a method for extracting photosynthetic pigments

A

Use a peste and mortar to grind a leaf with an extraction solvent

36
Q

How can paper chromatography be used to separate photosynthetic pigments?

A
  1. Use a capillary tube to spot pigment extract into pencil start line 1cm above bottom of paper
  2. Place chromatography paper in solvent
  3. Allow solvent to run until it almost touches the end of the paper
  4. Pigments move different distances
37
Q

What are Rf values?

A
  • ratios that allow comparison of how far molecules have moved in chromatograms
38
Q

How can Rf values be calculated?

A

Distance between origin and centre of pigment spot / distance between origin and solvent front

Biology (39 decks)

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