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Biology module 5 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

What do cells use energy for?

A

Movement
Active transport
Anabolic reactions

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2
Q

What needs energy to move?

A

Cilia, Flagella, muscle fibres also needed in phagocytosis/cytokinesis.

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3
Q

What are examples of active transport that need energy?

A

Uptake of nitrates by root hair cells, loading of sucrose into phloem and selective reabsorption in the kidneys.

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4
Q

What are examples of anabolic reactions that require energy?

A

Protein synthesis, DNA synthesis.

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5
Q

What organisms are photoautotrophs?

A

Plants

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6
Q

Where do all cells get their energy from?

A

The sun

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7
Q

What do plants transfer the light energy from the sun into?

A

Stored chemical energy

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8
Q

How do plants use the energy from the sun?

A

They use the energy to fix carbon (from Carbon dioxide) to form larger organic molecules (stored chemical energy)

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9
Q

What is the usable form of energy organisms use?

A

ATP

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10
Q

What does ATP do?

A

It is the only usable form of energy so all organisms depend on it to provide energy for cellular processes.

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11
Q

Both plants and animals release energy from glucose and produce what?

A

Large amounts of ATP

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12
Q

What does ATP stand for?

A

Adenosine triphosphate

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13
Q

What is ATP made from?

A

Adenine base, ribose sugar, 3 phosphates

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14
Q

What is the role of ATP in energy transfer?

A

1 Energy from the sun is used to make small amounts of ATP
2 Energy from ATP is used to make glucose (photosynthesis)
3 Glucose is broken down to produce large quantities of ATP
4 ATP is used to power cellular processes

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15
Q

Why is it incorrect to say energy is produced?

A

It isn’t produced, it is converted from one form to another (for example, light energy to chemical energy)

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16
Q

Why is ATP not a good storage molecule?

A

ATP is only very small, doesn’t have many bonds which store the energy, less stable than organic molecules and less energy dense.

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17
Q

Why do most organisms depend directly/indirectly on photosynthesis?

A

It is the only way light energy can be converted into glucose. Glucose is needed for respiration to occur in both the photoautotrophs and the heterotrophs that eat the photoautotrophs. Without photosynthesis, respiration couldn’t occur, so ATP couldn’t be formed which is the only usable form of energy.

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18
Q

What evolved first respiration or photosynthesis?

A

Photosynthesis, in order to respire, cells require stored energy in the form of glucose. The only way to form glucose is by photosynthesis which must mean photosynthesis came first.
Oxygenetic photosynthesis evolved before free oxygen was in air which is needed for respiration so photosynthesis was first.

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19
Q

In what ways are heterotrophs dependent on photoautotrophs?

A

Heterotrophs require glucose in cells to respire and the only way to get that is by eating plants that make it in photosynthesis.
Without them there would be no glucose in the cells, so respiration couldn’t occur, so ATP couldn’t be made which is needed for cellular processes.
Plants also make Oxygen during photosynthesis which is needed for respiration.

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20
Q

What is an organ?

A

A group of specialised tissues that work together to perform a specific function.

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21
Q

Why is a leaf an organ?

A

They contain different specialised tissues that work together to photosynthesise

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22
Q

What tissues are in a leaf that help it photosynthesise?

A

Epidermis tissue contain stomata which allows the CO2 in the air to enter the leaf and be used in photosynthesis.
Mesophyll tissue contain chloroplast which contain chlorophyll which absorb the light used for photosynthesis.
Xylem tissue transports water used in photosynthesis to the leaf.
Phloem transports products of photosynthesis away from the leaf.

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23
Q

What are all the parts of the chloroplast structure?

A

Double membrane, Starch grains, Stroma fluid, Grana, 70S ribosomes, Circular DNA, Thylakoid membrane, Intergranal lamellae, Biconvex shape.

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24
Q

What is the role of the double membrane in chloroplasts?

A

Outer membrane - permeable
Inner membrane - Selectively permeable, transport proteins are present
Intermembrane space between them.

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25
Q

What is the role of the starch grains in chloroplasts?

A

Storage polysaccharide made of glucose

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26
Q

What is the role of the stroma fluid in chloroplasts?

A

Contains enzymes for the light-independent reactions of photosynthesis (Calvin cycle)

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27
Q

What are grana?

A

Stacks of thylakoids

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28
Q

What is the role of the 70S ribosomes in chloroplasts?

A

Site of protein synthesis

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29
Q

What is the role of the biconvex shape in chloroplasts?

A

Increases the surface area

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30
Q

What is the role of the circular DNA in chloroplasts?

A

Codes for proteins (enzymes such as Rubisco)

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31
Q

What is the role of the thylakoid membranes in chloroplasts?

A

Site of the light dependent reactions
Large surface area
Contains photosynthetic pigments and ATP synthase.

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32
Q

What is the role of the intergranal lamallae in chloroplasts?

A

Hold together thylakoid membranes

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33
Q

Why are leaves green?

A

Wavelengths of visible light are between 400-700nm, all can be absorbed by a leaf except green light (500-600nm), green light is reflected so plant looks green.

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34
Q

What are photosynthetic pigments?

A

Molecules that absorb light energy

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35
Q

Why do plants have a range of different pigments?

A

To absorb different wavelengths of light

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36
Q

Why do different species of plant have different colour leaves?

A

They each have different combinations of photosynthetic pigments

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37
Q

Where are primary pigments found?

A

In the thylakoid membrane

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38
Q

What are the primary pigments?

A

Both forms of chlorophyll a (P680 and P700)

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39
Q

What kind of light does chlorophyll a absorb?

A

Red and blue light

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40
Q

Why is one of the pigments called P680?

A

It absorbs red light most strongly at the wavelength 680nm

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41
Q

Why is one of the pigments called P700?

A

It absorbs red light most strongly at the wavelength 700nm

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42
Q

Why are accessory pigments needed?

A

They allow the plant to absorb a range of different wavelengths.

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43
Q

What are some examples of accessory pigments?

A

Chlorophyll b, Carotenoids, Xanthrophylls.

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44
Q

Why do leaves change colour in autumn?

A

There’s not enough photosynthesis occuring to keep making chlorophyll so it gets broken down and then the accessory pigments are visible.

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45
Q

What type of molecule is each of the photosystems?

A

Protein

46
Q

What pigment is at the reaction centre?

A

Primary pigment

47
Q

What chlorophyll a is at the reaction centre in photosystem 1?

A

Chlorophyll a P700

48
Q

What chlorophyll a is at the reaction centre in photosystem 2?

A

Chlorophyll a P680

49
Q

What is an antennae complex?

A

The layers of accessory pigments

50
Q

Why is the antennae complex arranged in a cone shape?

A

Maximises the light they recieve

51
Q

What is a photon?

A

A particle of light

52
Q

What does the photon hit to begin photosynthesis?

A

An antenna pigment

53
Q

What happens to the antenna pigment when the photon hits?

A

Energy from the photon is transferred to the next pigment by resonance energy transfer.

54
Q

What happens to electrons in the pigments that gain energy from the photon?

A

Increases to a higher energy level passing on its energy to an electron in the next pigment molecule.
Each electron returns to the pigment molecule after the energy transfer.

55
Q

What happens when the energy reaches the reaction centre?

A

Chlorophyll a emits an electron, this is called an electron transfer.

56
Q

What is the electron emitted by the reaction centre accepted by?

A

An electron acceptor

The light energy has been transferred into chemical energy (an electron)

57
Q

What is used in the light dependent reaction?

A

Light, water, ADP + Pi and NADP, electrons

58
Q

What is made during the light dependent reaction?

A

Oxygen, ATP, NADPH, H+

59
Q

What is NADP?

A

A coenzyme that accepts a hydrogen ion and 2 electrons to become reduced NADPH

60
Q

What enzyme catalyses the reduction of NADP?

A

NADP reductase

61
Q

What are the hydrogen ions made in the light dependent stage used for?

A

Reducing CO2 in the light-independent stage

62
Q

What does reduced mean?

A

Gaining e- or hydrogen

Loss of Oxygen

63
Q

What does oxidised mean?

A

Loss of e- or Hydrogen

Gaining Oxygen

64
Q

What is the electron donor that replaces the used electrons?

A

Water

2 water splits into 4H+, 2e- and O2

65
Q

What gets oxidised in the light dependent stage?

A

Water (electron donor) oxidised to Oxygen (oxidised donor)

66
Q

What gets reduced in the light dependent stage?

A

NADP (the electron acceptor) gets reduced to NADPH (the reduced acceptor)

67
Q

What type of reaction is NADP + Water

A 
Redox reaction
(water oxidised, NADP reduced)
68
Q

What is the light energy used for in the light dependent stage?

A

Make ATP from ADP+Pi by the movement of H+ ions across the membrane
Reduce NADP to NADPH
In non-cyclic, uses it to split water into protons, oxygen and electrons to replenish lost electrons.

69
Q

What is photophosphorylation?

A

Using light energy to make ATP from ADP+Pi

70
Q

What is photolysis?

A

Use of light energy to split water molecules into protons, water and electrons

71
Q

What is chemiosmosis?

A

Movement of H+ ions across a membrane down an electrochemical gradient.

72
Q

What are the main structures in non cyclic photophosphorylation?

A

Photosystem 2, Electron transport chain, Proton pump, Stroma, Photosystem 1, NADP reductase, thylakoid space, ATP synthase.

73
Q

What happens after the electron acceptor has accepted the electron?

A

The electron passes through a series of electron carrier proteins (the ETC)
Energy is released as the electron moves through the ETC.

74
Q

What is the energy released by the electrons used for?

A

Pumping hydrogen ions from the stroma into the thylakoid space.
This increases the hydrogen ion concentration in the thylakoid space

75
Q

What has happened to the electron by the time it gets to the end of the electron transport chain?

A

It has lost all of its energy from photosystem 2 as it enters the reaction centre in photosystem 1.

76
Q

What happens to the electron in photosystem 1?

A

A photon hits photosystem 1 and its energy is passed from pigment to pigment by resonance transfer. At the reaction centre an electron is emitted and accepted by a second electron acceptor.

77
Q

What happens to the re energised electron?

A

It is passed from the electron acceptor to NADP reductase

78
Q

What happens at NADP reductase?

A

NADP is reduced by the addition of a hydrogen ion and 2 electrons.

79
Q

What is the equation for NADP getting reduced?

A

NADP+ + H+ + 2e- -> NADPH

80
Q

What happens to the NADPH after it’s made in the light dependent stage?

A

Passes into the stroma to enter the light independent reactions.

81
Q

How are the electrons in photosystem 2 replenished?

A

Photolysis
Water oxidised to 4H+ ions, O2 and 2 e-
e- join ETC, O2 gets released

82
Q

Because of the proton pump, what happens in the thylakoid space?

A

There is a high concentration of H+ in the thylakoid space. An electrochemical gradient has been created.

83
Q

What happens to the H+ ions when the electrochemical gradient is set up?

A

They flow from the thylakoid space to the stroma through ATP synthase by chemiosmosis.

84
Q

What does ATP synthase do?

A

Uses the energy from the protons (proton motive force) to join ADP+Pi to form ATP.

85
Q

What does the ATP do once made at the ATP synthase?

A

It is released into the stroma to take part in the light independent reactions along with NADPH

86
Q

What is the reducing agent formed?

A

NADPH

87
Q

What would happen to photosynthesis if there was no water?

A

Water wouldn’t be oxidised so e- wouldn’t be replenished so photosystem 2 would run out. Only cyclic photophosphorylation would be able to occur.

88
Q

What is different about cyclic photophosphorylation?

A

Photosystem 2 is not used.
NADP is not reduced to NADPH instead, the electron is moved back through the proton pump so only ATP is made.
Only happens in higher plants under certain conditions.
Happens in bacteria - many only do this type.

89
Q

When does non-cyclic photophosphorylation occur?

A

In higher plants all of the time

90
Q

How is ATP used in guard cells of higher plants?

A

K+ pump requires ATP

K+ + ATP goes into guard cell so water moves into cell by osmosis making them turgid, opening the stomata.

91
Q

What type of photophosphorylation occurs in guard cells?

A

Non-cyclic

92
Q

What is fixing?

A

Taking a gas out of the atmosphere to form an organic molecule

93
Q

What are the 3 stages of the calvin cycle?

A

Carbon fixation
Reduction
Regeneration

94
Q

What is carbon dioxide fixed to in the calvin cycle?

A

Ribulose bisphosphate (RuBP)

95
Q

What enzyme is used to fix RuBP to carbon dioxide?

A

Ribulase bisphosphate carboxylase oxygenase RuBisCO

96
Q

What does the fixing of carbon dioxide form in the calvin cycle?

A

An unstable intermediate that splits into to glycerate phosphates (GPs)

97
Q

What is reduced in the calvin cycle?

A

GP

98
Q

What reduces GP in the calvin cycle?

A

2 NADPH

2 ATP is also needed

99
Q

What does the reduction of GP form?

A

Triose phosphate (TP)

100
Q

What fraction of TP is used to regenerate RuBP?

A

5/6

101
Q

What is used to regenerate RuBP?

A

2TP and ATP

102
Q

What fraction of TP is used to make glucose?

A

1/6 (only occurs after 6 cycles)

103
Q

How is NADPH a reducing agent?

A

Donates hydrogen/gets oxidised

104
Q

What is reduced in the calvin cycle?

A

Carbon dioxide in order to make glucose

105
Q

What does the carboxylase bit of RuBisCO do?

A

Adds carbon dioxide (good)

106
Q

What does the oxygenase bit of RuBisCO do?

A

Adds Oxygen (bad)

107
Q

What factors affect photosynthesis?

A

Light intensity
Carbon dioxide concentration
Temperature
(Water availability) - closes stomata when little water which stops CO2 getting into plants making CO2 concentration limiting, not water.

108
Q

What is the definition of a limiting factor?

A

A variable that is present at the least favourable value

109
Q

What is the point of the graph called when something else becomes the limiting factor?

A

The saturation point

110
Q

Why isn’t water a limiting factor?

A

When water levels are low, the stomata close which prevents carbon dioxide entering the leaf so then carbon dioxide becomes limiting. there is still enough water in the plant as stomata close.

Biology module 5 (7 decks)

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