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Biology > 17.3 Photosynthesis > Flashcards

17.3 Photosynthesis Flashcards

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1
Q

What is photosynthesis?

A

The process in which energy in the form of light from the sun, is used to build large complex organic molecules, such as glucose.

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2
Q

What happens in photosynthesis?

2 points

A
  • light energy is transformed into chemical energy.

- Trapped in the bonds of the complex organic molecules produced.

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3
Q

What are autotrophic organisms?

A

Organisms that can photosynthesis.

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4
Q

How do heterotrophs obtain organic molecules?

A

They obtain complex organic molecules by eating other autotrophic and heterotrophic organisms.

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5
Q

How are the network of membranes present in chloroplasts suitable for their role?

2 points

A
  • Provide large surface area

- To maximise absorption of light essential for the first set of photosynthesis.

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6
Q

In chloroplast what is light absorbed by and where is it found?

2 points

A
  • Chlorophyll (complex of pigments)

- Embedded within thylakoid membranes.

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7
Q

What is the stroma?

A

The site of many chemical reactions resulting in the formation of complex organic molecules.

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8
Q

What do pigment molecules do?

A

Absorb specific wavelengths (colours) of light and reflect others.

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9
Q

Why do different pigments have different colours?

A

Different pigments absorb and reflect different wavelengths of light.

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10
Q

What is the primary pigment in photosynthesis?

A

Chlorophyll a

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11
Q

What does chlorophyll absorb and reflect?

A
  • absorbs red and blue light.

- reflects green light.

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12
Q

Why are there different shades and colours of leaves?

A

-Different combination of pigments.

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13
Q

Where are other pigments(accessory pigments) other than chlorophyll a ?

A

-Chlorophyll b, carotenoids and xanthophyll are embedded in thylakoid membranes.

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14
Q

What is light harvesting system also known as?

A

Antennae complex

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15
Q

What is the role of light harvesting system?

2 points

A
  • Absorb or harvest light energy.

- of different wavelengths, and transfer quickly and efficiently to reaction centre.

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16
Q

Where is chlorophyll a located?

A

Reaction centre

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17
Q

What is the reaction centre primary reaction centre?

A

Where the reactions involved in photosynthesis take place.

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18
Q

What forms light harvesting systems?

A

Pigments like, carotenoids,xanthophylls, chlorophyll b and proteins.

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19
Q

What is the photo system? And what structure is it?

A

What the light harvesting system and reaction centre is collectively known as.

Funnel-shaped

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20
Q

What is a feature of photo systems that-maximises absorption of light?

A

The reaction centre is surrounded by the light harvesting system.

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21
Q

What is chromatography used for in photosynthesis?

A

To separate different pigments in plant extracts.

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22
Q

What is the mobile phase?

A

The solution containing a mixture of pigments.

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23
Q

What is the stationary phase?

A

A thin layer of silica gel applied to glass.

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24
Q

Due to the pigment moving at different rates what happens?

A

This results in the pigments being separated, as they move through silica gel.

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25
Q

What is the retention value equation?

A

Distance travelled by component./distance travelled by solvent.

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26
Q

List the apparatus you would use, and outline the process you would follow to separate a mixture of plant pigments.

9 points

A
  • Small strip of TLC plate.
  • Grind leaves with organic solvent(Propanone).
  • Apply drop of extract to TLC near to one end.
  • Repeat until concentrated spot produced.
  • Place TLC strip in test tube.
  • Put solvent into test tube, so level of solvent below spot.
  • Ensure strip not touching sides of tube.
  • Leave solvent to run up strip
  • Remove TLC strip before solvent reaches top of strip.
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27
Q

Describe what happens in light dependent stage in photosynthesis?

2 points

A
  • Energy from sunlight is absorbed and used to form ATP.

- Hydrogen from water is used to reduce coenzyme NADP to reduced NADP.

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28
Q

Describe what happens in light independent stage?

A

-Hydrogen from reduced NADP and CO2, used to build organic molecules (glucose, lipids, amino acids).

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29
Q

What supplies energy for light independent reaction?

A

ATP

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30
Q

Which photo system absorbs light at higher wavelength?

2 points

A
  • Photosystem 1(700nm)

- Whereas for photosystem 2 it’s (680nm)

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31
Q

What happens first at PS2?

3 points

A
  • The light absorbed excites electrons at the reaction centre of photo systems.
  • The excited electrons are released from reaction centre of PS2 and are passed to an electron transport chain.
  • ATP produced by process of chemiosmosis.
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32
Q

What replaces electrons lost from photosystem 2?

A

Replaced from photolysis of water molecules, broken down using energy from sun. (Chapter 17.4)

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33
Q

What happens in PS1

2 points

A
  • Excited electrons released from reaction centre and passed to another electron transport chain.
  • ATP is again produced by chemiosmosis.
34
Q

What replaces electrons lost from PSI?

A

The electrons that have just traveled along the first electron transport chain, after being released from PS11.

35
Q

What happens to the electrons leaving the electron transport chain following PS1?

2 points

A
  • They are accepted along with a hydrogen by the coenzyme NADP.
  • Forming reduced NADP.
36
Q

What is the need for reduced NADP?

2 points

A
  • Provides hydrogen/reducing power in production of organic molecules. (E.g glucose)
  • In light independent stage
37
Q

What is photolysis?

A

When water is split into hydrogen ions, electrons and oxygen molecules using energy from the sun.

38
Q

What catalyses photolysis the breakdown of water?

A

The oxygen-evolving complex present in PS2.

39
Q

Photolysis reaction equation?

A

H20= 2H+ + 2e- + 1/2 O2

40
Q

Why is water along with light and CO2 a raw material of photosynthesis?

A

The electrons released from photolysis replaces electrons lost from reaction centre in PS2.

41
Q

What is the byproduct of photolysis?

A

Oxygen gas

42
Q

What happens to the protons produced in photolysis?

4 points

A
  • Protons released into lumen of thylakoids increasing concentration along membranes.
  • They move back through membrane down concentration gradient and electrochemical gradient.
  • This drives formation of more ATP.
  • Once hydrogen ions return to stroma , they combine with NADP and an electron from PS1 to form reduced NADP.
43
Q

Why is this process useful? Other than the production of reduced NADP.

2 points

A
  • Removes hydrogen ions from stroma.

- Helps to maintain the proton gradient across thylakoid membranes.

44
Q

Describe cyclic photophosphorylation in PS1.

3 points

A
  • Electrons leaving transport chain after PS1 can be returned to PS1.
  • Instead of being used to form reduced NADP.
  • This means PS1 can still lead to production of ATP, without any electrons being supplied from PS2.
45
Q

Where does light independent stage of photosynthesis take place?

A

-In stroma of chloroplast.

46
Q

What is the raw material used in light independent stage of photosynthesis? And what else from products of light dependent stage is required?

3 points

A
  • Co2
  • Reduced NADP
  • ATP
47
Q

Describe what happens in Calvin cycle concisely?

2 points

A

-Organic molecules like glucose produced.

In a series of reactions collectively known as Calvin cycle.

48
Q

What are the 3 stages of the Calvin cycle?

A
  • Fixation-Co2 fixed(Incorporated into organic molecule)
  • Reduced-GP to To by addition of hydrogen from reduced NADP, using energy from ATP.
  • Regeneration-RuBp regenerated from recycled TP.
49
Q

How does CO2 enter the stroma?

A
  • Enters intercellular spaces within spongy mesophyll , of leaves by diffusion.
  • From atmosphere through stomata.
  • It diffuses into cells, and into the stroma of chloroplast.
50
Q

What happens in fixation?

A
  • Co2 combines with 5-carbon molecule(Ribulose biphosphate).
  • Carbon is fixed which means incorporated into organic molecule.
  • Unstable 6 carbon intermediate produced.
51
Q

What catalyses fixation?

A
  • Ribulose bisphosphate carboxylasee (RuBIsCo).

- Unstable 6 carbon intermediate produced.

52
Q

Why is RuBIsCo seen as inefficient? (The most abundant enzyme and is key enzyme of photosynthesis.)

A
  • Competitively inhibited by oxygen.

- So a lot needed to carry out photosynthesis successfully.

53
Q

How is GP produced?

A
  • Unstable 6-carbon intermediate formed immediately breaks down.
  • Forming GPx2 molecules (glycerate 3-phosphate) 2 3 carbon molecules.
54
Q

What happens in reduction?

A
  • GP reduced into another 3-carbon molecule TP.

- Using hydrogen atom from reduced NADP and energy supplied by ATP.

55
Q

What do you know about triose phosphate?

A
  • 3 carbon sugar
  • Majority recycled to regenerate RuBp so Calvin cycle can continue.
  • Starting point for synthesis of many complex biological molecules.
56
Q

What happens in regeneration of RuBp?

A
  • For one glucose molecule to be produced 6CO2 molecules have to enter Calvin cycle,so full turns of cycle.
  • 2 TP molecules removed to make glucose molecule.

-10 TP molecules used to regenerate six RuBp.
(Used in 6 turns of cycle.)

-Energy supplies by ATP.

57
Q

Explain why photorespiration is not something commercial producers would encourage?

A
  • less carbon fixed
  • Less Organic molecules synthesised.
  • Reduced yield
58
Q

Suggest why plants evolved with such important enzyme RuBisCo vein inhibited by oxygen?

A
  • Photosynthesis produces oxygen.

- No oxygen in atmosphere when plants begun to evolve.

59
Q

Describe photorespiration?

A
  • Low humidity+high temperature= high transpiration(too much water lost.)
  • Stomata closes and photosynthesis still happens.
  • O2 produced and co2 concentrations decrease.
  • O2 is competitive inhibitor of RuBIsCo producing phosphoglycolate.
  • Phosphoglycolate- toxic 2-carbon molecule, converted into other organic molecule, energy from ATP needed.
  • 25 percent of products of Calvin cycle lost in photorespiration.
60
Q

Define photophosphorylation?

A
  • Synthesis of ATP./Addition of phosphate to ADP.

- Using energy from light.

61
Q

Explain why photosynthesis stops when pants exposed to green light only?

A
  • Green light reflected.
  • No energy for light independent stage.
  • No ATP and reduced NADP for light independent stage.
62
Q

What is meant by the term fixation?

A
  • Inorganic carbon

- Added to organic molecule.

63
Q

Where does light independent stage of photosynthesis take place?

A

-In stroma of chloroplast.

64
Q

What is the raw material used in light independent stage of photosynthesis? And what else from products of light dependent stage is required?

3 points

A
  • Co2
  • Reduced NADP
  • ATP
65
Q

Describe what happens in Calvin cycle concisely?

2 points

A

-Organic molecules like glucose produced.

In a series of reactions collectively known as Calvin cycle.

66
Q

What are the 3 stages of the Calvin cycle?

A
  • Fixation-Co2 fixed(Incorporated into organic molecule)
  • Reduced-GP to To by addition of hydrogen from reduced NADP, using energy from ATP.
  • Regeneration-RuBp regenerated from recycled TP.
67
Q

How does CO2 enter the stroma?

A
  • Enters intercellular spaces within spongy mesophyll , of leaves by diffusion.
  • From atmosphere through stomata.
  • It diffuses into cells, and into the stroma of chloroplast.
68
Q

What happens in fixation?

A
  • Co2 combines with 5-carbon molecule(Ribulose biphosphate).
  • Carbon is fixed which means incorporated into organic molecule.
  • Unstable 6 carbon intermediate produced.
69
Q

What catalyses fixation?

A
  • Ribulose bisphosphate carboxylasee (RuBIsCo).

- Unstable 6 carbon intermediate produced.

70
Q

Why is RuBIsCo seen as inefficient? (The most abundant enzyme and is key enzyme of photosynthesis.)

A
  • Competitively inhibited by oxygen.

- So a lot needed to carry out photosynthesis successfully.

71
Q

How is GP produced?

A
  • Unstable 6-carbon intermediate formed immediately breaks down.
  • Forming GPx2 molecules (glycerate 3-phosphate) 2 3 carbon molecules.
72
Q

What happens in reduction?

A
  • GP reduced into another 3-carbon molecule TP.

- Using hydrogen atom from reduced NADP and energy supplied by ATP.

73
Q

What do you know about triose phosphate?

A
  • 3 carbon sugar
  • Majority recycled to regenerate RuBp so Calvin cycle can continue.
  • Starting point for synthesis of many complex biological molecules.
74
Q

What happens in regeneration of RuBp?

A
  • For one glucose molecule to be produced 6CO2 molecules have to enter Calvin cycle,so full turns of cycle.
  • 2 TP molecules removed to make glucose molecule.

-10 TP molecules used to regenerate six RuBp.
(Used in 6 turns of cycle.)

-Energy supplies by ATP.

75
Q

Explain why photorespiration is not something commercial producers would encourage?

A
  • less carbon fixed
  • Less Organic molecules synthesised.
  • Reduced yield
76
Q

Suggest why plants evolved with such important enzyme RuBisCo vein inhibited by oxygen?

A
  • Photosynthesis produces oxygen.

- No oxygen in atmosphere when plants begun to evolve.

77
Q

Describe photorespiration?

A
  • Low humidity+high temperature= high transpiration(too much water lost.)
  • Stomata closes and photosynthesis still happens.
  • O2 produced and co2 concentrations decrease.
  • O2 is competitive inhibitor of RuBIsCo producing phosphoglycolate.
  • Phosphoglycolate- toxic 2-carbon molecule, converted into other organic molecule, energy from ATP needed.
  • 25 percent of products of Calvin cycle lost in photorespiration.
78
Q

Define photophosphorylation?

A
  • Synthesis of ATP./Addition of phosphate to ADP.

- Using energy from light.

79
Q

Explain why photosynthesis stops when pants exposed to green light only?

A
  • Green light reflected.
  • No energy for light independent stage.
  • No ATP and reduced NADP for light independent stage.
80
Q

What is meant by the term fixation?

A
  • Inorganic carbon

- Added to organic molecule.

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