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IB Biology > 2.9 Photosynthesis > Flashcards

2.9 Photosynthesis Flashcards

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1
Q

What is photosynthesis?

A

The process where cells synthesise organic compounds from inorganic molecules in the presence of sunlight

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2
Q

What does photosynthesis require?

A

A photosynthetic pigment

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3
Q

What is an example of a photosynthetic pigment?

A

Chlorophyll

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4
Q

Where can photosynthesis occur?

A

Only in certain organisms eg plants and certain bacteria

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5
Q

What do photosynthetic organisms use to create chemical energy?

A

Light energy from the sun

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6
Q

What are the two ways that chemical energy can be used?

A

Directly by the organism
or
Used to synthesise organic compounds

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7
Q

How do animals consume the organic compounds?

A

As food

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8
Q

How do animals release the stored energy from organic compounds?

A

Via cell respiration

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9
Q

What is photosynthesis the reverse of?

A

Cell respiration

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10
Q

What type of synthesis is photosynthesis?

A

Anabolic

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11
Q

What is the electromagnetic spectrum?

A

The range of all possible frequencies of electromagnetic radiation

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12
Q

What are colours?

A

Different wavelengths of white light

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13
Q

What is the range of wavelengths of colours?

A

700nm - 400nm
Red to violet

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14
Q

What are the colours of the visible spectrum from longest to shortest wavelength?

A

Red
Orange
Yellow
Green
Blue
Indigo
Violet

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15
Q

Where does the sun emit its peak power?

A

In the visible region of the electromagnetic spectrum

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16
Q

What is the wavelength range of visible light?

A

400nm - 700nm

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17
Q

What is chlorophyll?

A

A green pigment found in photosynthetic organisms that is responsible for light absorption

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18
Q

What happens when chlorophyll absorbs light?

A

It releases electrons which are used to synthesise ATP

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19
Q

What does each different chlorophyll molecules have their own of?

A

Absorption spectra

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20
Q

Where does chlorophyll absorb light most strongly?

A

In the blue portion of the visible spectrum

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21
Q

Where does chlorophyll absorb light second most strongly?

A

By the red portion

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22
Q

Where does chlorophyll reflect light most strongly?

A

In the green portion of the visible spectrum

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23
Q

What are the two components of a typical chlorophyll molecule?

A

Chlorin ring and hydrocarbon tail

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24
Q

What does the absorption spectrum indicate?

A

The wavelengths of light absorbed by each pigment

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25
Q

What does the action spectrum indicate?

A

The overall rate of photosynthesis at each wavelength of light

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26
Q

What do pigments absorb as a source of energy for photosynthesis?

A

Light

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27
Q

There is a strong correlation between the cumulative absorption spectra of all pigments and what?

A

The action spectrum

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28
Q

Where are there two main peaks in the absorption and action spectra?

A

Large peak in the blue region
Smaller peak in the red region

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29
Q

Where does the absorption and action spectra display a trough?

A

In the green/yellow region

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30
Q

What are the two steps of the photosynthesis process?

A

Light dependent reactions and light independent reactions

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31
Q

What does the light dependent reaction convert light energy from the sun into?

A

Chemical energy (ATP)

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32
Q

What does the light independent reactions use the chemical energy to synthesise?

A

Organic compounds

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33
Q

During the light dependent reaction what results in the production of ATP?

A

Light being absorbed by chlorophyll

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34
Q

As well as chlorophyll what else absorbs light?

A

Water

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35
Q

During the light dependent reactions, what happens to the water that absorbs light?

A

It is split to produce oxygen and hydrogen

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36
Q

What is it called what light splits water?

A

Photolysis

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37
Q

What is released as a waste product during the light dependent reactions?

A

Oxygen

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38
Q

Where is oxygen released during the light dependent reaction?

A

From the stomata

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39
Q

What are used during the light dependent reactions?

A

Hydrogen and ATP

40
Q

During the light independent reaction what is transferred to the site of the light independent reaction?

A

ATP and hydrogen

41
Q

How is ATP and hydrogen carried to the site of the light independent reaction?

A

By NADPH

42
Q

What combines with what to form complex organic compounds during light independent reactions?

A

Hydrogen combines with carbon dioxide

43
Q

What does ATP do in light independent reactions?

A

Power anabolic reactions and fix carbon molecules together

44
Q

What doe photosynthetic organisms benefit from to absorb light?

A

The combined action of many pigments

45
Q

What is chromatography?

A

An experimental technique by which mixtures can be separated

46
Q

What is the mobile phase of chromatography?

A

A mixture is dissolved in a fluid

47
Q

What is the stationary phase of chromatography?

A

When the mixture is passed through a static material

48
Q

What causes the mixture to separate in chromatography?

A

The different components of the mixture travel at different speeds

49
Q

How do you calculate the Rf value?

A

distance component travels / distance solvent travels

50
Q

What are the two most common techniques for separating photosynthetic pigments?

A

Paper chromatography and thin layer chromatography

51
Q

What is paper chromatography?

A

Uses paper (cellulose) as the stationary bed

52
Q

What is thin layer chromatography?

A

Uses a thin layer of absorbent which runs faster and has better separation

53
Q

What does the law of limiting factors say about when a chemical process depends on more than one essential condition being favourable?

A

The rate of reaction will be limited by the factor that is nearest its minimum value

54
Q

What are the three main favourable conditions photosynthesis is dependent on?

A

Temperature
Light intensity
Carbon dioxide concentration

55
Q

What controls photosynthesis?

A

Enzymes

56
Q

What are enzymes sensitive to?

A

Temperature fluctuations

57
Q

Why does the reaction rate increase as temperature increases?

A

Reactants have greater kinetic energy and more collisions occur

58
Q

What happens to the rate of photosynthesis when the experiment goes above a certain temperature and why?

A

It will decrease as enzymes begin to denature

59
Q

What does chlorophyll absorb?

A

Light

60
Q

What happens to the reaction rate as light intensity increases and why?

A

It will increase as more chlorophyll are being photo-activated

61
Q

Why will photosynthetic rate plateau at a certain light intensity?

A

As all available chlorophyll are saturated with light

62
Q

Does different wavelengths of light have different or the same effect on the rate of photosynthesis?

A

Different effects

63
Q

What is the carbon dioxide involved in the fixation of in photosynthesis?

A

The fixation of carbon atoms to form organic molecules

64
Q

What happens to the reaction rate when carbon dioxide concentration increases and why?

A

It increases as more organic molecules are being produced

65
Q

Why will the photosynthetic reaction plateau at a certain concentration of CO2?

A

As the enzymes responsible for carbon fixation are saturated

66
Q

How can photosynthesis be measured directly?

A

Via the uptake of CO2 or the production of O2?

67
Q

How can photosynthesis be measured indirectly?

A

Via a change in biomass

68
Q

What may influence levels of Co2 and O2?

A

The relative amount of cell respiration happening in the tissue

69
Q

How can carbon dioxide uptake be measured?

A

By placing leaf tissue in an enclosed space with water

70
Q

How can water free of dissolved carbon dioxide be produced?

A

By boiling and cooling water

71
Q

What is produced when carbon dioxide interacts with water molecules and what is their impact?

A

Bicarbonate and hydrogen ions which changes the pH

72
Q

What does increased uptake of CO2 by the plant do in the experiment with the leaf?

A

Reduce the amount in the solution and increase the alkalinity

73
Q

What are the two instruments to measure carbon dioxide levels?

A

A probe and a data logger

74
Q

How can oxygen production be measured?

A

By submerging a plant in an enclosed water filled space attached to a sealed gas syringe

75
Q

What are the two ways an experiment can be measured when measuring O2 production?

A

A change in meniscus level on the syringe
or
the time takes for submerged leaf discs to surface

76
Q

How can glucose production be measured?

A

By a change in the plants weight

77
Q

What is required prior to measuring biomass and why?

A

The plant tissue to be completely dehydrated to ensure water content is not accounted for

78
Q

What is an alternative method to measuring biomass that does not include measuring the weight?

A

To determine the change in starch levels

79
Q

How can starch be identified?

A

Via iodine staining

80
Q

How can starch be quantitated?

A

Using a colorimeter

81
Q

What is the one significant source of oxygen gas in the known universe?

A

Biological photosynthesis

82
Q

Before the evolution of photosynthetic organisms how was any free oxygen produced?

A

Chemically captured and stored

83
Q

How long ago did photosynthetic organisms begin to saturate the environment with oxygen?

A

2.3 billion years ago

84
Q

When photosynthetic prganisms began to produce oxygen where were there changes?

A

In the earth’s atmosphere
Oceans
Rock deposition
Biological life

85
Q

What did earths oceans initially have?

A

High levels of dissolved iron

86
Q

Why did earths oceans initially have high levels of dissolved iron?

A

Released from the crust by underwater volcanic vents

87
Q

What happens when iron reacts with oxygen gas?

A

A chemical reaction to form an insoluble precipitate known as iron oxide

88
Q

What happened when the iron in the ocean was completely consumed?

A

Oxygen gas started accumulating in the atmosphere

89
Q

What was earths atmosphere like for the first 2 billion years?

A

Anoxic (oxygen free)

90
Q

What is the current concentration of oxygen gas within the atmosphere?

A

Approximately 20%

91
Q

What are the ocean deposits formed by dissolved iron and oxygen gas called?

A

Banded iron formations

92
Q

What happens as banded iron formations deposition slowed in oceans?

A

Iron rich layers started to form on land due to the rise in atmospheric O2 levels

93
Q

Why will you not find banded iron formations in sedimentary rock younger than 1.8 billion years old?

A

It reflects the the time when oxygen levels caused the near complete consumption of dissolved iron levels

94
Q

What is free oxygen toxic to?

A

Obligate anaerobes

95
Q

What may have wiped out obligate anaerobes?

A

Increase in O2 levels

96
Q

What was a critical determinant to the evolution of aerobically respiring organisms?

A

Rising O2 levels

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