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A level Biology > Unit 3.2 - Photosynthesis uses light energy to synthesise organic molecules > Flashcards

Unit 3.2 - Photosynthesis uses light energy to synthesise organic molecules Flashcards

1
Q

Location of photosynthesis

A

Chloroplasts

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2
Q

What do chloroplasts contain that absorb light energy?

A

Photosynthetic pigments

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3
Q

What do the photosynthetic pigments of chloroplasts do?

A

Absorb light energy at particular wavelengths of light

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4
Q

Photosynthetic pigments in chloroplasts

A

Xanthophylls
Carotene
Chlorophyll a
Chlorophyll b

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5
Q

Where are chloroplasts found?

A

In mesophyll tissues

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6
Q

Where predominantly in mesophyll tissues are chloroplasts found?

A

In the palisade mesophyll cells

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7
Q

Which other mesophyll tissue apart from the palisade mesophyll contains some chloroplasts?

A

Spongey mesophyll

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8
Q

Adaptations of leaves for photosynthesis

A

Large surface area
Thin
Air spaces in spongy mesophyll
Palisade cells are packed with chloroplasts and arranged with their long axes perpendicular to the surface
Cuticle and epidermis are transparent
Palisade mesophyll cells are elongated and densely arranged in layers

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9
Q

What does the large surface area of a leaf allow it to do?

A

Capture as much light as possible

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10
Q

Why has a leaf adapted to be thin for photosynthesis?

A

Allows light to penetrate through the leaf

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11
Q

Why do chloroplasts rotate and move within mesophyll cells?

A

Move into the best position for maximum absorption of light

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12
Q

What do the air spaces in the spongey mesophyll of leaves allow to happen?

A

Allows CO2 to diffuse to photosynthesising cells

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13
Q

Why are palisade cells packed with chloroplasts and arranged with their long axes perpendicular to the surface?

A

To capture as much light as possible

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14
Q

Why are the cuticle and epidermis of a leaf transparent?

A

So that light penetrates to the mesophyll

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15
Q

Why have leaves adapted so that palisade mesophyll cells are elongated and densely arranged in layers?

A

Can accommodate a large number and no cross walls to prevent light from penetrating through the cell = capture as much light as possible

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16
Q

What’s the main purpose of photosynthesis?

A

To synthesise carbohydrates by taking in simple inorganic compounds like CO2 and H2O and combining them to make complex carbohydrates

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17
Q

What’s the purpose of the starch granule in chloroplasts?

A

Glucose phosphorylised during photosynthesis is stored here as starch

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18
Q

Where are the photosynthetic pigments in chloroplasts?

A

Thylakoids

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19
Q

What are thylakoids?

A

Internal membranes of chloroplasts

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20
Q

How would thylakoids appear on an electron microscope photo?

A

Stained black

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21
Q

What’s a stack of thylakoids known as?

A

Granum

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22
Q

How are granum connected in chloroplasts?

A

By lamellae

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23
Q

What is the stroma of a chloroplast?

A

Fluid filled space

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24
Q

What provide evidence for the endosymbiotic theory of chloroplasts in chloroplasts? Explain

A

Circular DNA, like in prokaryotes
Theory states that Chloroplasts and mitochondria in eukaryotic cells were once free-living aerobic, prokaryotic organisms, that were then ingested by a large anaerobic, prokaryotic bacteria

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25
Q

What does the endosymbiotic theory suggest?

A

Theory states that Chloroplasts and mitochondria in eukaryotic cells were once free-living aerobic, prokaryotic organisms, that were then ingested by a large anaerobic, prokaryotic bacteria

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26
Q

Primary pigment in chloroplasts

A

Chlorophyll A

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27
Q

Accessory pigments in chloroplasts

A

Chlorophyll B
Carotenoids

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28
Q

What are the pigments chlorophyll B and carotenoids known as in chloroplasts?

A

Accessory pigments

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29
Q

What does a light absorption spectrum show?

A

The relative absorbance of light at different wavelengths by the photosynthetic pigments

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30
Q

Why does each photosynthetic pigment in chloroplasts have an absorption spectrum?

A

Different pigments absorb more light energy at certain wavelengths

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31
Q

What’s an absorbance spectrum?

A

A graph which shows how much light is absorbed by a pigment at different wavelengths of light

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32
Q

What does each photosynthetic pigment in chloroplast have on the light absorption spectrum?

A

Its peak absorbance at a different wavelength

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33
Q

Which colours does the absorbance of chlorophyll a peak at?

A

Red and blue

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34
Q

What does more light being absorbed by a photosynthetic pigment lead to?

A

Higher rate of photosynthesis

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35
Q

Why do chloroplasts contain multiple photosynthetic pigments?

A

Having more than one pigment increases the number of wavelengths of light that are absorbed by the leaf

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36
Q

Which photosynthetic pigment is involved in the reactions that lead to the synthesis of ATP in chloroplasts?

A

Chlorophyll A

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37
Q

Why do we perceive plants to be green?

A

The light that’s reflected from the leaf is green, whilst the other wavelengths of light are absorbed by the leaf
Chlorophyll A does not absorb wavelengths of green and yellow (indicated by a very low degree of light absorption from about 500 to 600nm).
As the primary pigment, there;s more chlorophyll A than the other types of pigment

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38
Q

Which type of pigment is there the most of in chloroplasts?

A

Chlorophyll A

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39
Q

Why is there barely any light absorption in one part of the light absorption spectrum?

A

One theory is that when the plants were evolving, they evolved pigments that absorb light that was reflected by other living bacteria at the time, not absorbed by those too

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40
Q

Action spectrum

A

Show the rate of photosynthesis at different wavelengths of light

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41
Q

Which 2 types of spectrum show a very strong correlation when overlayed?

A

An action spectrum and an absorption spectrum

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42
Q

How can we guess that the wavelengths of light absorbed by photosynthetic pigments are actually used for photosynthesis?

A

If you overlay an action spectrum onto an absorption spectrum, the peaks show a very close correlation

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43
Q

What simple device can be used for measuring the rate of photosynthesis?

A

Photosynthetometer

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44
Q

What is a photosynthetometer used for?

A

Measuring the rate of photosynthesis

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45
Q

How do we set up and use a photosynthetomer?

A

Aquatic plant in a CO2 source, and a light source and a filter for different colours
Observe how much O2 is produced at different wavelengths of light by observing the bubbles produced

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46
Q

Who devised an experiment to show the action spectrum of photosynthesis?

A

Thomas Englemann

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47
Q

What did Englemann’s experiment determine?

A

Which wavelengths of light were used most for photosynthesis

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48
Q

How did Englemann complete his experiment?

A

Placed the photosynthetic filamental algae Spirogyra in a suspension of motile aerobic (oxygen seeking) bacteria
Used a prism to refract white light into its constituent rainbow colours
Under the microscope, he could observe where on the colour spectrum on the slide there were large numbers of bacteria where they had swam towards the spirogyra in the middle of the slide

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49
Q

What were the results of Englemann’s experiment and what did this mean?

A

Large numbers of bacteria in the red part of the spectrum (+few in the blue part)
This is where there is the highest rate of photosynthesis, therefore the bacteria moves there to obtain more oxygen

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50
Q

Why did some regions on the spectrum have less bacteria moving towards the filamental algae spirogyra during Englemann’s experiment?

A

These are the regions where the algae weren’t absorbing much light energy, therefore there was less photosynthesis, so less O2 produced, so less bacteria here

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51
Q

2 types of electron microscope

A

Transmission
Scanning

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52
Q

Transmission electron microscope

A

Electrons are fired through the sample

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53
Q

Scanning electron microscope

A

Looks at the surface of the thing that’s studied

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54
Q

Do any electron microscope photos have colour? Why?

A

No, as electrons all have the same wavelength

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55
Q

Where are photosystems found?

A

Embedded in the thylakoid membrane of chloroplasts

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56
Q

Where exactly are photosynthetic pigments located?

A

In photosystems embedded in the thylakoid membranes of chloroplasts

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57
Q

What’s the name for the simplified diagram of a photo system?

A

Antenna complex

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58
Q

What’s the purpose of a photosystem?

A

To capture visible light energy

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59
Q

What is a photosystem geared towards?

A

Channelling the energy that strikes the photosystem to the reaction centre

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60
Q

What does the primary pigment reaction centre of a photosystem always have?

A

A molecule of chlorophyll A

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61
Q

Where is a molecule of chlorophyll A always found in a photosystem?

A

In the primary pigment reaction centre

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62
Q

Accessory pigments in a photosystem

A

Xanthophylls
Carotenes
Chlorophyll b

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63
Q

Light harvesting

A

When photosynthetic pigments absorb light energy

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64
Q

Name for when photosynthetic pigments absorb light energy

A

Light harvesting

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65
Q

How is light harvesting achieved?

A

By antenna complexes within the thylakoid membranes of the chloroplasts

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66
Q

Why are there a range of pigments in photosystems?

A

Allow a range of wavelengths to be absorbed

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67
Q

Describe the process occurring inside a photosystem

A

Photons of light strike photosystem
Absorbed by accessory pigments
Transferred through the photosystem to the reaction centre
Energy is absorbed by chlorophyll A n the reaction centre

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68
Q

How many molecules of chlorophyll a does the reactions centre of a photosystem contain?

A

2

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69
Q

What happens when chlorophyll a molecules absorb light energy in the reaction centre of a photosystem?

A

They emit high energy electrons that got excited

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70
Q

What does the emitting of high energy electrons from the reaction centre of a photosystem lead to?

A

The light dependent stage of photosynthesis

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71
Q

What’s the purpose of the proteins associated with the antenna complex?

A

Prevent the light energy from escaping from the antenna complex

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72
Q

What are the 2 main stages of photosynthesis?

A

The light dependent stage
The light independent stage

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73
Q

Where does the light dependent stage of photosynthesis occur?

A

In the thylakoid membrane

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74
Q

2 types of reaction centre involved in the light dependent stage

A

Photosystem I
Photosystem II

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75
Q

Absorption peak of photosystem I and hence other name

A

700nm
P700

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76
Q

Absorption peak of photosystem II and hence other name

A

680nm
P680

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77
Q

Which two processes take place at the same time during the light dependent stage?

A

Non-cyclic photophosphorylation
Cyclic photophosphorylation

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78
Q

Which type of photophosphorylation in the light dependent stage involves 2 photosystems and what are they?

A

Non-cyclic photophosphorylation
PS I and PS II

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79
Q

Non-cyclic photophosphorylation

A
  1. At PS II, light energy comes in as a photon
  2. This is absorbed by PS II
  3. Energy is directed to the reaction centre
  4. The energy energises an electron at the reaction centre
  5. The high energy electron is emitted
  6. The electron from PS II is captured by an electron acceptor
  7. At the same time, light energy strikes PS I
  8. Electron is emitted from PS I
  9. This electron is captured by another electron acceptor
    = 2 excited electrons absorbed by electron acceptors
  10. Returning to PS II, the electron from the acceptor goes down an electron transport chain
  11. The energy from the electron is used for the phosphorylation of ADP to ATP to synthesise ATP via Chemiosmosis
  12. At the end of the electron transport chain, an electron is passed to PS I, as it’s lost an electron, and is absorbed by chlorophyll A
  13. The electron from PS I is captured by an electron acceptor
  14. The electron is combined with a proton to reduce NADP to NADPH
    (Remember NAD is involved in respiration, NADP is involved in photosynthesis)
  15. The products of non-cyclic phosphorylation are therefore ATP and reduced NADP, which go on to take part in the light independent stage of photosynthesis
  16. The electron that was transferred from PS II to PS I needs to be replaced
  17. This electron comes from water
  18. In a process called photolysis (also in the thylakoid), water is split using sunlight energy
  19. Gives out 2 electrons, 2 protons and 1/2 a molecule of O2 (an atom of O2)
    H20 —> 2e- + 2H+ + 1/2O2
  20. Th electron is used to give an electron back to PS II
  21. The protons combine with the electrons from PS I to reduce NADP
  22. The oxygen is given off as O2 gas
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80
Q

Photolysis

A

Water is split using sunlight energy

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81
Q

Photolysis equation

A

H2O —> 2e- + 2H+ + 1/2O2
(Reverse of the reaction at the end of the electron transport chain)

82
Q

Why is non-cyclic photophosphorylation called “non-cyclic”?

A

The electron does not return to its origin - PS II ends up an electron short, so photolysis must occur

83
Q

Which photosystems does cyclic phosphorylation of the light dependent stage of photosynthesis use?

A

Just PS I

84
Q

Explain cyclic photophosphorylation during the light dependent stage of photosynthesis

A
  1. Light entry strikes PS I
  2. PS I absorbs the photon of light (at 680nm)
  3. Light energy excites an electron to form a high energy electron
  4. The electron is captured by an electron acceptor
  5. The electron passes through the electron transport chain
  6. The electron’s energy is therefore used to pump protons from the stroma into the thylakoid space, creating an electrochemical gradient
  7. Protons return to the stroma through the ATP synthetase complex
  8. ADP is phosphorylated to ATP
  9. The electron (now at a lower energy state) is passed back to PS I
  10. The only product of cyclic phosphorylation is therefore just ATP
85
Q

Why is cyclic photophosphorylation known as “cyclic”?

A

The electron originates from PS I and returns to PS I

86
Q

Compare the products of cyclic photophosphorylation and non-cyclic photophosphorylation

A

Cyclic = ATP only
Non-cyclic = NADPH and ATP

87
Q

Compare the photosystems of cyclic photophosphorylation and non-cyclic photophosphorylation

A

Cyclic = PS I only
Non-cyclic = PS I and PS II

88
Q

Compare whether photolysis occurs during cyclic photophosphorylation and non-cyclic photophosphorylation

A

Cyclic = no photolysis
Non-cyclic = photolysis

89
Q

Is oxygen produced during cyclic or non-cyclic phosphorylation?p

A

Non-cyclic

90
Q

What is the point of photolysis?

A

Provides an electron for PS II

91
Q

What occurs during photolysis?

A

Molecules of water absorb light energy and are split to form electrons, protons and oxygen

92
Q

Where is the water for photolysis?

A

The thylakoid space

93
Q

Where do the electrons produced during photolysis go?

A

Passed to PS II to replace those lost during non-cyclic phosphorylation

94
Q

What are the protons produced during photolysis used for?

A

To reduce NADP

95
Q

How does NADP become reduced?

A

Each NADP molecule picks up two protons and two electrons to become reduced

96
Q

What happens to the oxygen produced during photolysis?

A

Diffuses out of the chloroplast as a waste product

97
Q

Products of the light dependent stage of photosynthesis

A

ATP and reduced NADP

98
Q

What are the products of the light dependent stage of photosynthesis essential for?

A

The light independent stage or Calvin cycle

99
Q

Where does the light independent stage of photosynthesis occur?

A

In the stroma of the chloroplast

100
Q

Where does the light independent stage occur

A

In the stroma of the chloroplast

101
Q

Summarise what occurs dung the light independent stage

A

CO2 is fixed into carbohydrate

102
Q

“Fixing” CO2

A

Takes CO2 from the air and combines it with a complex organic compound

103
Q

Other word for the light independent stage

A

The Calvin cycle

104
Q

What does the light independent stage make use f?

A

The products of the light dependent stage

105
Q

Describe the light independent stage/Calvin cycle

A

1.) CO2 is taken up by 5C ribulose bisphosphate (RUBP)
2.) forms an unstable 6C compound —> unstable hexose (6C)
3.) unstable hexose instantly splits into 2 molecules of 3C glycerate-3-phosphate (GP)
4) this is all catalysed by the enzyme rubisco
5.) glycerine-3-phosphate then undergoes reduction. ATP and reduced NADP (from the light dependent stage, during non-cyclic phosphorylation) reduce GP to 3C triose phosphate (TP)
6.) some of the TP i converted into glucose, but most of the TP is converted into RUBP (using energy from ATP) - this regeneration of RUBP allows the light independent stage to continue

106
Q

Which enzyme is involved in Calvin’s cycle?

A

Rubisco

107
Q

What is the light independent stage dependent on and how can we prove this?

A

The light dependent stage as ATP and reduced NADP (the products of the light dependent stage) are used to reduce glycerate-3-phosphate, and later on ATP is used to convert TP to RUBP

108
Q

What can the glucose generated during the Calvin cycle then be used for?

A

Amino acids, starch and lipids (molecules needed by plants)

109
Q

How is glucose converted into amino acids?

A

Combined with nitrates

110
Q

How is glucose converted into starch?

A

Built up and stored

111
Q

How is glucose converted into lipids?

A

Chemically converted

112
Q

What is the problem with rubisco?

A

Inefficient

113
Q

What has to be done as rubisco is inefficient?

A

Lots of it needs to be produced

114
Q

What are the names of the 4 stages of the Calvin cycle?

A

Carboxylation phase
Reduction phase
Synthesis phase
Regeneration phase

115
Q

How many time does Calvin’s cycle have to occur for 1 molecule of glucose to be synthesised? Why?

A

6 times, as every time the cycle makes 1 complete turn, 1 carbon atom is added to the compounds made during the Calvin cycle

116
Q

Describe Calvin’s experiment to discover the Calvin cycle

A

1.) used Chlorella algae (a photosynthetic protist)
2.) placed on a thin glass vessel —> the lollipop vessel
3.) algae as given plenty of light, CO2 and hydrogen carbonate (HCO3-) containing normal carbon (12C) —> this allowed the algae to photosynthesise
4.) at the start of the experiment, the carbon compounds were replaced with compounds containing radioactive carbon (14C)
5.) as the algae photosynthesised, it absorbed the 14C and fixed it through the Calvin cycle
6.) at 5 second time intervals, a sample of chlorella was placed into hot ethanol to top all enzymatic reactions (ethanol denatures the enzymes). - creates a “snapshot” of that moment in the cycle
7. )the carbon compounds were then separated by chromatography and the compounds containing 14C identified by autoradiography - this allows us to see where and when radioactivity appears and their sequence to find the order of the Calvin cycle

117
Q

What was used during Calvin’s experiment?

A

Chlorella algae (a photosynthetic protist)

118
Q

Vessel used during Calvin’s experiment?

A

Lollipop vessel

119
Q

Radioactive carbon used during Calvin’s experiment

A

14C

120
Q

What was chlorella placed in every 5 seconds during Calvin’s experiment and why?

A

The ethanol
Denatured the enzymes so stops all enzymatic reactions to create a “snapshot”

121
Q

How was the chromatography completed during Calvin’s experiment?

A

The solvent would run through the chromatography paper and would then be turned so that the compounds separate

122
Q

What was used to see the radioactivity on the chromatography paper used during Calvin’s experiment?

A

Autoradiograms - use a photosynthetic film to see radioactivity

123
Q

How can radioactivity be seen on an autoradiogram?

A

From a black patch

124
Q

What was seen after 5 seconds on the autoradiograms during Calvin’s experiment?

A

More labelled glycerate-3-phosphate than any other compound - this indicates that glycerate-3-phosphate is the first product of carbon fixation

125
Q

What was seen after 30 seconds on the autoradiograms during Calvin’s experiment?

A

A range of different labelled compounds occur, showing the intermediate and final products of the light independent reactions

126
Q

Factors that affect the rate of photosynthesis

A

Light intensity
Carbon dioxide concentration
Temperature

127
Q

Law of limiting factors

A

The rate of a metabolic process which relies on several factors is limited by the factor which is present at its least favourable level (lowest)

128
Q

Why is the law of limiting factors true for photosynthesis?

A

Think - the rate of photosynthesis is affected by light intensity, CO2 concentration and temperature all at the same time, but is limited by the factor at its lowest level

129
Q

At which concentrations of CO2 is the concentration of CO2 in the atmosphere limiting the rate of photosynthesis?

A

Between 0 and 0.1%

130
Q

How do we know that the concentration of CO2 in the atmosphere is the limiting factor of photosynthesis att concentrations between 0 and 0.1%?

A

If the concentration of CO2 is increased, the rate of photosynthesis will increase, so it must be a limiting factor

131
Q

What happens to the rate of photosynthesis when the concentration of CO2 in the atmosphere is raised beyond 0.1% and why?

A

The rate of photosynthesis doesn’t increase anymore, as another factor must be limiting the rate of photosynthesis

132
Q

Why does the rate of photosynthesis decrease at lower CO2 levels?

A

CO2 is needed during the light independent stage (Calvin cycle)
Low concentration = lower rate of Calvin cycle (even if there’s sufficient light, ATP, NADPH e.t.c)

133
Q

What is the atmospheric level of CO2?

A

0.04% (not optimal)

134
Q

Could the rate of photosynthesis in our current atmosphere be higher? Explain

A

Yes, as the concentration of CO2 is at 0.04%, which isn’t optimal

135
Q

How can farmers increase their yield by increasing the rate of photosynthesis for their crops?

A

Place more CO2 in greenhouses, as the 0.04% concentration in our atmosphere currently isn’t the optimal level

136
Q

CO2 source example

A

Sodium hydrogen carbonate

137
Q

How can we measure the effect of light intensity on the rate of photosynthesis?

A

Use the right set up and measure the oxygen production production at different light intensities

138
Q

What’s the purpose of the beaker of water in the light intensity experiment?

A

To keep the temperature constant

139
Q

Area of a light bulb

A

4pir^2

140
Q

How is light intensity calculated?

A

Power
———
Area

141
Q

Table headings for the light intensity experiment to measure the rate of photosynthesis

A

Distance between the pondweed and light source
Light intensity
Number of bubbles given off in 1 minute

142
Q

Equipment for measuring the effect of light intensity on the rate of photosynthesis

A

Lamp (light source)
Ruler
Elodea (pondweed)
Beaker of water
Thermometer
Test tube containing a CO2 source (e.g - sodium hydrogen carbonate)

143
Q

What happens to a plant as a light source is moved further away from it?

A

It receives less light energy

144
Q

Why does a plant receive less light energy as the light source is moved further away from it?

A

The intensity of light is lower as it’s spread out over a larger surfed area (inverse square law)

145
Q

How do we know if light intensity is the limiting factor of the rate of photosynthesis?

A

If you were to increase it, the rate of photosynthesis would still increase

146
Q

What were used to act as heat filters during Calvin’s experiment?

A

Glass screens between the lamp and the lollipop apparatus

147
Q

What were placed between the lamp and the lollipop apparatus during Calvin’s experiment and why?

A

Glass screens
Act as heat filters

148
Q

At low temperatures, how does increasing the temperature affect the rate of photosynthesis?

A

The rate increases in more or less direct proportion

149
Q

What happens to the rate of photosynthesis when it rises above a certain temperature?

A

The rate drops to zero

150
Q

Why does the rate of photosynthesis drop to zero above a certain temperature?

A

The temperature affects the activity of the enzymes catalysing photosynthesis reactions, especially during the light independent stage.
Above a certain temperature, the enzymes will denature

151
Q

Unit of light intensity + explanation

A

Foot - candles
(Distance unit, intensity unit)

152
Q

Point on a CO2 exchange against light intensity graph where it flattens off

A

Light saturation point

153
Q

Light compensation point

A

The light intensity at which the volume of gases used and produced by photosynthesis and respiration are equal
(Photosynthesis = respiration)

154
Q

What do plant cells do as well as photosynthesise?

A

Respire

155
Q

What do plant cells do as they respire?

A

Produce CO2

156
Q

What do plants do with the CO2 they produce when respiring?

A

Use it for photosynthesis

157
Q

What happens in terms of respiration and photosynthesis at very low light intensities?

A

The rate of photosynthesis is lower than the rate of respiration, therefore the plant gives out CO2

158
Q

What happens above the light compensation point?

A

The rate of photosynthesis increases as the plant is using more CO2 than that produced

159
Q

What happens to the photosynthetic rate AT the light compensation point?

A

The rate doesn’t increase - it becomes zero

160
Q

Why is Mg2+ important?

A

It’s one of the inorganic ions needed by plants to survive, as it’s an essential component of chlorophyll

161
Q

How is magnesium absorbed?

A

As Mg2+

162
Q

Where is Mg2+ transported?

A

In the xylem

163
Q

Function of Mg2+

A

Chlorophyll production
Activation of ATPase

164
Q

What is magnesium needed by?

A

All tissues, especially the leaves

165
Q

Which molecule does magnesium form a part of?

A

The chlorophyll molecule

166
Q

What ones magnesium deficiency cause?

A

Chlorosis

167
Q

Where does chlorosis begin?

A

Between the veins of older leaves

168
Q

What happens during chlorosis?

A

Existing magnesium in the plant is mobilised and chlorophyll is broken down and transported to newly formed leaves

169
Q

What does chlorosis cause?

A

The yellowing of old leaves

170
Q

What is nitrogen essential for?

A

Photosynthesis and plant growth

171
Q

How is nitrogen absorbed by plants?

A

By the roots as nitrate ions by active transport

172
Q

What is nitrogen used for?

A

To synthesise amino acids, nucleic acids and nucleotides such as ATP
(Remember - plants synthesis their own complex organic molecules)

173
Q

What different ways is nitrogen transported in a plant?

A

As nitrates in the xylem
As amino acids in the phloem

174
Q

Where in the plant is nitrogen transported as nitrates?

A

In the xylem

175
Q

Where in the plant is nitrogen transported as amino acids?

A

In the phloem

176
Q

What is nitrogen transported as in the xylem?

A

Nitrates

177
Q

What is nitrogen transported as in the phloem?

A

Amino acids

178
Q

Symptoms of nitrogen deficiency

A

Reduced growth of all organs
Chlorosis (yellowing of leaves due to inadequate chlorophyll production)

179
Q

Why does chlorosis cause the yellowing of leaves?

A

Inadequate chlorophyll production

180
Q

Where does chlorosis first appear?

A

In older leaves

181
Q

What do we use when extracting chloroplasts and why?

A

Ice cold solution to slow down any enzyme reactions

182
Q

Which stage is the only stage of photosynthesis to involve CO2?

A

Light independent stage

183
Q

Minerals taken up from soil

A

Nitrogen
Phosphate
Magnesium

184
Q

What’s synthesised with a nitrogen source?

A

Amino acids

185
Q

What’s synthesised with a phosphate source?

A

Phospholipids

186
Q

What’s synthesised with both a nitrogen and a phosphate source?

A

Nucleotides

187
Q

What’s synthesised with magnesium?

A

Chlorophyll

188
Q

Why would we use a black paper cover in an experiment about plant minerals?

A

Exclude light
Prevent the growth of algae
Algae would absorb mineral ions from the solution

189
Q

What does distilled water lack?

A

Minerals

190
Q

2 Purposes of hot methanol in Calvin’s experiment

A

Kill algae and stop reactions at a precise time
Acts as a solvent to extract chemicals

191
Q

Why do we need heat filters in Calvin’s experiment?

A

Light source produces heat
Increased rate
Denatured enzymes

192
Q

When using chromatogram to compare with autoradiograms of known substances, what must be kept the same?

A

Solvent
Paper
Temperature

193
Q

Why must the solvent be kept the same when comparing chromatogram with autoradiograms of known substances during Calvin’s experiment?

A

Different solubility of substances in different solvents

194
Q

Why must the paper be kept the same when comparing chromatogram with autoradiograms of known substances during Calvin’s experiment?

A

Substances could travel different distances

195
Q

Why must the temperature be kept the same when comparing chromatogram with autoradiograms of known substances during Calvin’s experiment?

A

Can affect solubility

196
Q

Blue wavelengths of light

A

450nm

197
Q

Red wavelengths of light

A

670nm - 680nm

198
Q

Green wavelength of light

A

550nm

199
Q

Which light has the most energy?

A

Blue light

200
Q

What happens to the wavelength of light energy when its being passed form pigment to pungent in the antenna complex and why?

A

Its wavelength is being changed so that it’s the right wavelength to be absorbed by chlorophyll a

201
Q

Enzymes involved in a Krebs cycle + explain

A

Decarboxylase enzymes for decarboxylation
Dehydrogenase enzymes for dehydrogenation

A level Biology (26 decks)

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