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photosynthesis Flashcards

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1
Q

Photosynthesis is …

photosynthesis takes place in …

A

Photosynthesis is a series of reactions that use energy from the Sun to convert carbon dioxide (CO2) into carbohydrates. These reactions take place in chloroplasts of plant and algal cells.

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2
Q

The importance of photosynthesis

Photosynthesis is one of the most important reactions for life.
The reaction converts …
This chemical energy is stored in …
Chemical energy can then be transferred to …

A

The importance of photosynthesis

Photosynthesis is one of the most important reactions for life.
The reaction converts light energy into chemical energy.
This chemical energy is stored in carbohydrates (e.g. glucose) and other biological molecules.
Chemical energy can then be transferred to all other organisms by consuming plants.

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3
Q

Photosynthesis equation

The equation for photosynthesis is:

The reaction requires … to take place.

A

Photosynthesis equation

The equation for photosynthesis is:
Carbon dioxide + water → oxygen + glucose
6CO2 + 6H2O → 6O2 + C6H12O6
The reaction requires light energy to take place.

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4
Q

Stages of photosynthesis

Photosynthesis can be broken down into two main stages:

A

Stages of photosynthesis

Photosynthesis can be broken down into two main stages:
Stage 1: light-dependent reaction.
Stage 2: light-independent reaction.

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5
Q

Light-dependent reaction

The light-dependent reaction is the ___ stage of photosynthesis.
The reaction is initiated when …

A

Light-dependent reaction

The light-dependent reaction is the first stage of photosynthesis.
The reaction is initiated when light energy is absorbed by chlorophyll in the chloroplasts.

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6
Q

Light-independent reaction

The ____ stage of photosynthesis does not require … to take place. It is also called the Calvin cycle.
The Calvin cycle cannot happen without the …

A

Light-independent reaction

The second stage of photosynthesis does not require light energy to take place. It is also called the Calvin cycle.
The Calvin cycle cannot happen without the light-dependent reaction.

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7
Q

Diagram of a chloroplast

draw it

A

Diagram of a chloroplast

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8
Q

what is the stroma.

Starch grains in the stroma are where … are stored.

A

The space within chloroplasts is called the stroma.

Starch grains in the stroma are where carbohydrates produced during photosynthesis are stored.

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9
Q

Thylakoids are …
These stacks of thylakoids form …
Grana are linked together by … The resulting structures are called …

A

Thylakoids are fluid-filled sacs that are stacked up inside chloroplasts.
These stacks of thylakoids form structures called grana (singular = granum).
Grana are linked together by thylakoid membranes. The resulting structures are called lamellae (singular = lamella).

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10
Q

Lamellae

… (lamellae) contain photosynthetic pigments.
There are different kinds of photosynthetic pigments. Each pigment has evolved to …
Examples of photosynthetic pigments include:
-
-
-

A

Lamellae

Thylakoid membranes (lamellae) contain photosynthetic pigments.
There are different kinds of photosynthetic pigments. Each pigment has evolved to absorb specific wavelengths (colours) of visible light.
Examples of photosynthetic pigments include:
Chlorophyll a.
Chlorophyll b.
Carotene.

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11
Q

what’s a photo system?
There are two types of photosystems used in photosynthesis:
-
-
Both photosystems play an important role in …

A

Photosystems

Within the thylakoid membranes, photosynthetic pigments are attached to proteins. Together they are called a photosystem.
There are two types of photosystems used in photosynthesis:
Photosystem I (PSI).
Photosystem II (PSII).
Both photosystems play an important role in the light-dependent reaction.
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12
Q

Features of chloroplasts:

Starch grains

Lamella

Photosystem

Thylakoids

Stroma

A

Features of chloroplasts:

Starch grains

Lamella

Photosystem

Thylakoids

Stroma

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13
Q

Features of chloroplasts:

Starch grains

A

Grains located in the stroma where carbohydrates synthesised during photosynthesis are stored.

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14
Q

Lamella

A

Lamella

Membrane that links grana together.

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15
Q

Photosystem

A

Photosystem

Protein and photosynthetic pigment attached together in the thylakoid membrane. Together they absorb light energy.

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16
Q

Thylakoids

A

Thylakoids

Fluid-filled sacs that are stacked up inside chloroplasts to form grana.

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17
Q

Stroma

A

Stroma

The space within chloroplasts.

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18
Q

The first step of the light-dependent reaction is …

what does the first step of the LDR cause?

A

The first step of the light-dependent reaction is the absorption of light energy by chlorophyll. This causes photoionisation, which is the release of electrons.

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19
Q

Light absorption

4 points

A

Light absorption

Light energy absorbed by chlorophyll in photosystem
Absorbing light energy excites the electrons within the photosystem.
The electrons are now in a more excited state and causes them to be released from the chlorophyll.
Chlorophyll is now considered to be photoionised.

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20
Q

Energy from photoionisation

The photoionisation of chlorophyll results in …
This energy is used in photosynthesis to drive three reactions:
-
-
-
These three reactions are necessary for ____ to take place

A

Energy from photoionisation

The photoionisation of chlorophyll also results in a release of energy.
This energy is used in photosynthesis to drive three reactions:
Photophosphorylation - production of ATP from ADP and inorganic phosphate.
Reduction - production of reduced NADP from NADP.
Photolysis - splitting of water into protons, electrons and oxygen.
These three reactions are necessary for photosynthesis to take place

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21
Q

During the light-dependent reaction, ___ and ___ are produced. In this process …

A

During the light-dependent reaction, ATP and reduced NADP are produced. In this process electrons are transferred down the electron transfer chain and protons pass across the membranes of chloroplasts.

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22
Q

Electron transport chain

Light energy excites electrons in chlorophyll and the electrons are moved to …
… are released from the chlorophyll and transferred to …
Electron carriers are ___ located in …
When high-energy electrons are released they are …
The series of electron carriers is called …

A

Electron transport chain

Light energy excites electrons in chlorophyll and the electrons are moved to a higher energy level (they are high-energy electrons).
High-energy electrons are released from the chlorophyll and transferred to an electron carrier.
Electron carriers are proteins located in the thylakoid membranes.
When high-energy electrons are released they are transferred along a chain of electron carriers.
The series of electron carriers is called the electron transport chain (ETC).

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23
Q

The proton gradient

As the electrons move down the ETC, they …
This energy …
The protons are being transported … and this requires ___
As protons build up inside the thylakoids, … forms across the thylakoid membrane because …

A

The proton gradient

As the electrons move down the ETC, they lose energy.
This energy pumps protons from the stroma into the thylakoids. The protons are being transported against their concentration gradient and this requires energy.
As protons build up inside the thylakoids, a proton gradient forms across the thylakoid membrane because the concentration of protons inside the thylakoids is greater than in the stroma.

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24
Q

Chemiosmosis

The protons diffuse ___ the concentration gradient across the thylakoid membrane through the … enzyme.
As protons diffuse through the ___, ___ is released.
This energy …
This process is called ___.

A

Chemiosmosis

The protons diffuse down the concentration gradient across the thylakoid membrane through the ATP synthase enzyme.
As protons diffuse through the ATP synthase, energy is released.
This energy converts ADP and inorganic phosphate to ATP.
This process is called chemiosmosis.

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25
Q

Reduced NADP

When light energy is absorbed, … are released.
Some electrons are transferred directly to ___. They are not passed along the ___
The electrons … to produce reduced NADP.

A

Reduced NADP

When light energy is absorbed, high-energy electrons are released.
Some electrons are transferred directly to NADP. They are not passed along the ETC.
The electrons react with a proton in the stroma to produce reduced NADP.

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26
Q

Photolysis

___ can be replaced by photolysis.
In this process, light energy splits ____ into …
The electrons can then replace …

A

Photolysis

Electrons can be replaced by photolysis.
In this process, light energy splits water into protons, electrons and oxygen.
The electrons can then replace those released when light is absorbed.

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27
Q

Define Cyclic Photophosphorylation

A

Cyclic Photophosphorylation

Cyclic photophosphorylation only involves photosystem I. The main ways in which cyclic differs from non-cyclic photophosphorylation are that no NADP is reduced, electrons are continuously recycled and no photolysis takes place.

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28
Q

Non cyclic photophosphorylation produces …

A

Reduced nadp

And atp

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29
Q

The etc is located in …

A

The etc is located in the thykloid memebrane

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30
Q

Reduced nadp is produced when …

A

Reduced nadp is produced when light is absorbed by PSI

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31
Q

Electrons r not always recycled in …

A

Electrons r not always recycled in non cyclic photophosphorylation

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32
Q

Both types of phosphorylation produce ATP

A

Both types of phosphorylation produce ATP

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33
Q

Different pigments of chlorophyll absorb …

A

Different pigments of chlorophyll absorb different wavelengths of light.

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34
Q

Plants use different pigments as an adaptation to their environment.
E.g. Plants that typically grow in the shade use pigments…

A

Plants use different pigments as an adaptation to their environment.
E.g. Plants that typically grow in the shade use pigments that are well-adapted to wavelengths that can pass through other plants.

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35
Q

The light-independent reaction (the Calvin cycle) takes place in … This reaction uses …

A

The light-independent reaction (the Calvin cycle) takes place in the stroma of the chloroplast. This reaction uses ATP, reduced NADP, CO2 and ribulose bisphosphate to produce triose phosphates.

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36
Q

1) Carbon fixation

A

1) Carbon fixation

When CO2 diffuses into the leaves through stomata, it combines with ribulose bisphosphate (RuBP) to give an unstable 6-carbon compound.
This is the first reaction in the Calvin cycle and it is catalysed by an enzyme, rubisco.
The unstable 6-carbon molecule rapidly splits into two molecules of glycerate 3-phosphate (GP).
The combination of CO2 with RuBP is described as carbon fixation.

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37
Q

2) Reduction of glycerate 3-phosphate

A

2) Reduction of glycerate 3-phosphate

The two molecules of GP are then reduced to triose phosphates (TP).
This reaction is driven by energy from two molecules of ATP and protons from two molecules of reduced NADP.
The ATP and reduced NADP are provided by the light-dependent reaction and are recycled after they have been used.
One out of every six TP molecules is converted into hexose sugars but most continue in the Calvin cycle.

38
Q

3) Regeneration of RuBP

A

3) Regeneration of RuBP

Five out of every six TP molecules are not converted into sugars. These are used to regenerate RuBP.
This reaction is driven by one molecule of ATP which is then recycled in the light-dependent reaction.
The formation of RuBP from TP allows the Calvin cycle to continue.

39
Q

Glycerate 3-phosphate is reduced to triose phosphate by which two molecules?

A

1
ATP
2
Reduced NADP

40
Q

Five out of every six triose phosphate molecules are … These molecules are used to …The regeneration reaction is driven by ..

A

Five out of every six triose phosphate molecules are not converted to sugars. These molecules are used to regenerate ribulose bisphosphate. The regeneration reaction is driven by one molecule of ATP.

41
Q

Triose phosphate (TP) and glycerate 3-phosphate (GP) molecules produced in the Calvin cycle are converted into ..

A

Triose phosphate (TP) and glycerate 3-phosphate (GP) molecules produced in the Calvin cycle are converted into useful organic substances. These are essential for plant survival.

42
Q

Triose phosphate (TP) and glycerate 3-phosphate (GP) molecules produced in the Calvin cycle are converted into useful organic substances:

A

Hexose sugars (monomers) are produced from two molecules of triose phosphate.
E.g. Glucose.
Hexose sugars can be joined together to form larger carbohydrates (polymers).
E.g. Starch, cellulose.

43
Q

Triose phosphate (TP) and glycerate 3-phosphate (GP) molecules produced in the Calvin cycle are converted into useful organic substances.

A

Lipids are made from glycerol and fatty acid chains.
Both components of lipids are synthesised from the products of the Calvin cycle:
Triose phosphates are used in the synthesis of glycerol.
Fatty acids are formed from glycerate 3-phosphate.

44
Q

Triose phosphate (TP) and glycerate 3-phosphate (GP) molecules produced in the Calvin cycle are converted into useful organic substances.

A

Amino acids

Glycerate 3-phosphate is used in the synthesis of some amino acids

45
Q

What type of sugars are produced from two molecules of triose phosphate (TP)?

A

What type of sugars are produced from two molecules of triose phosphate (TP)?

Hexose sugars

46
Q

The first stage in the Calvin cycle is … It is catalysed by … and produces … This compound then …

A

The first stage in the Calvin cycle is carbon fixation. It is catalysed by the enzyme Rubisco and produces an unstable 6-carbon molecule. This compound splits into two molecules of glycerate 3-phosphate.
1 / 1

47
Q

The four key factors affecting the rate of photosynthesis are:

A

The four key factors affecting the rate of photosynthesis are:

Temp

Light intensity

Carbon dioxide concentration

Chlorophyll concentration

48
Q

Initially, the rate of photosynthesis increases as the temperature increase. Above about__°C, the rate starts to fall.
Enzymes such as ___ play an important role in photosynthesis.
At low temperatures, enzymes have less … and r less likely to … This means …
Above the optimum temperature, enzymes will …

A

Initially, the rate of photosynthesis increases as the temperature increase. Above about 45°C, the rate starts to fall.
Enzymes such as rubisco play an important role in photosynthesis.
At low temperatures, enzymes have less kinetic energy and are less likely to successfully collide with the substrate. This means fewer enzyme-substrate complexes are formed.
Above the optimum temperature, enzymes will denature and the rate of photosynthesis will fall.

49
Q

intensity

Increasing light intensity increases the rate of photosynthesis because …
In low light intensities … cannot take place. This causes …
… are necessary to convert …
Without reduced NADP and ATP …

A

intensity

Increasing light intensity increases the rate of photosynthesis because more energy is provided.
In low light intensities the light-dependent reaction cannot take place. This causes levels of reduced NADP and ATP to fall.
Reduced NADP and ATP are necessary to convert GP to TP and to regenerate RuBP.
Without reduced NADP and ATP the Calvin cycle cannot take place and rate of photosynthesis declines.

50
Q

Increasing the CO2 concentration increases the rate of photosynthesis.
At high CO2 concentrations …
If the rate of the Calvin cycle increases, …
Very high CO2 concentrations can cause ___ to open wider causing …

A

Increasing the CO2 concentration increases the rate of photosynthesis.
At high CO2 concentrations, there is more carbon available for fixation in the Calvin cycle.
If the rate of the Calvin cycle increases, more GP and TP is produced and more RuBP is regenerated.
Very high CO2 concentrations can cause stomata to open wider causing more water to be lost.
Too much water loss will then cause the stomata to close and the rate of photosynthesis to slow again.

51
Q

High chlorophyll concentration gives a high rate of photosynthesis.
If there is more chlorophyll, light can … This will cause …

A

High chlorophyll concentration gives a high rate of photosynthesis.
If there is more chlorophyll, light can be absorbed at a faster rate. This will cause the light-dependent reaction rate to increase.

52
Q

If carbon dioxide concentration is increased from___% to___%, the rate of photosynthesis increases

A

If carbon dioxide concentration is increased from 0.04% to 0.4%, the rate of photosynthesis increases

53
Q

Farming and Photosynthesis
Commercial agricultural practice

-

-
-

-

A

Farming and Photosynthesis
Commercial agricultural practice

Light intensity
High intensity is optimal
Lamps provide light at night

Temperature
25oC is optimal
Heating and cooling systems
Glasshouses

CO2 concentration
0.4% is optimal
CO2 added to the air

54
Q

What is the approximate optimum temperature range to maximise plant yields?

A

10-40°c

55
Q

How are Rf values calculated?

A

How are Rf values calculated?

Distance travelled from spot / distance travelled by solvent

56
Q

The technique used to identify which pigments are in leaves of different plants is called ___. This technique allows us to identify what …

A

The technique used to identify which pigments are in leaves of different plants is called chromatography. This technique allows us to identify what wavelengths of light a plant can absorb.

57
Q

Investigating Dehydrogenase Activity in Chloroplasts
During the light-dependent reaction, ..

A dehydrogenase enzyme catalyses this reaction. This experiment will monitor dehydrogenase activity by using …

A

Investigating Dehydrogenase Activity in Chloroplasts
During the light-dependent reaction, NADP is reduced to NADPH. A dehydrogenase enzyme catalyses this reaction. This experiment will monitor dehydrogenase activity by using DCPIP, a redox indicator.

58
Q

DCPIP

In this investigation, a blue dye (DCPIP) is used to …
This means that it is blue in the oxidised state and colourless in its …
When electrons are released by the chlorophyll, DCPIP will change from …

A

DCPIP

In this investigation, a blue dye (DCPIP) is used to monitor the rate of dehydrogenase activity. DCPIP is a redox indicator.
This means that it is blue in the oxidised state and colourless in its reduced state.
When electrons are released by the chlorophyll, DCPIP will change from blue to colourless.

59
Q

Extracting chloroplasts

Put __cm3 of … into a beaker.
Tear … into small pieces and put the pieces into the isolation medium in the beaker.
Do NOT put pieces of the midrib or the leaf stalk into the beaker.
Half fill a large beaker with___ and place …
When carrying out this step, all solutions and apparatus should be kept … and the extraction should be carried…

A

Extracting chloroplasts

Put 50 cm3 of isolation medium into a beaker.
Tear eight spinach leaves into small pieces and put the pieces into the isolation medium in the beaker.
Do NOT put pieces of the midrib or the leaf stalk into the beaker.
Half fill a large beaker with ice and place a small beaker on top of the ice.
When carrying out this step, all solutions and apparatus should be kept as cold as possible and the extraction should be carried out as quickly as possible.

60
Q

Suspending chloroplasts

Put 3 layers of___ over the top of the filter funnel and wet with the … Rest the filter funnel in …
Pour the … into the blender and blend for__ seconds. Pour the blended mixture …
Pour your blended mixture through the muslin in the …Carefully squeeze the muslin to assist the filtering process.
Label this filtrate which is in the small beaker on ice as …

A

Suspending chloroplasts

Put 3 layers of muslin over the top of the filter funnel and wet with the isolation medium. Rest the filter funnel in the small beaker on the ice.
Pour the spinach and isolation medium into the blender and blend for 15 seconds. Pour the blended mixture back into the beaker.
Pour your blended mixture through the muslin in the filter funnel. Carefully squeeze the muslin to assist the filtering process.
Label this filtrate which is in the small beaker on ice as ‘chloroplast suspension’.

61
Q

Set up tubes A and B

Label five test tubes A, B, C, X and Y and stand them in the large beaker. Put the lamp about ___ away so that all tubes are___. Set up tubes A and B as follows:
Tube A - …
Tube B - …
Tubes A and B are control experiments. Leave both tubes until the end of your investigation

A

Set up tubes A and B

Label five test tubes A, B, C, X and Y and stand them in the large beaker. Put the lamp about 10 cm away so that all tubes are illuminated. Set up tubes A and B as follows:
Tube A - 5 cm3 DCPIP solution + 1 cm3 water + 1 cm3 chloroplast suspension. Immediately wrap the tube in aluminium foil to exclude light.
Tube B - 5 cm3 DCPIP solution + 1 cm3 water + 1 cm3 isolation medium.
Tubes A and B are control experiments. Leave both tubes until the end of your investigation.

62
Q

Tube C is for you to use as a standard to ..

A

Set up tube C as follows:
Tube C - 6 cm3 water + 1 cm3 chloroplast suspension.
Tube C is for you to use as a standard to help you to determine when any colour change is complete.

63
Q

Set up tube X as follows:
Tube X -
Add 1 cm3 chloroplast suspension to tube X, quickly ___ the contents and start … Use tube C to help you determine …
Repeat this step ..

A

Set up tube X as follows:
Tube X - 5 cm3 DCPIP solution + 1 cm3 water in the tube.
Add 1 cm3 chloroplast suspension to tube X, quickly mix the contents and start the timer.
Record in seconds how long it takes for the contents of tube X to change colour from blue-green to green. Use tube C to help you determine when the colour change is complete.
Repeat this step four more times.

64
Q

Set up tube Y as follows:
Tube Y -
Add _ cm3 of … to tube Y, quickly mix the contents and start the timer.
Record in seconds how long it takes for the contents of tube Y to change colour from … Use___ to help you determine when the colour change is complete.
Repeat this step four more times.

A

Set up tube Y as follows:
Tube Y - 5 cm3 DCPIP solution + 1 cm3 ammonium hydroxide.
Add 1 cm3 chloroplast suspension to tube Y, quickly mix the contents and start the timer.
Record in seconds how long it takes for the contents of tube Y to change colour from blue-green to green. Use tube C to help you determine when the colour change is complete.
Repeat this step four more times.

65
Q

Record your data in a suitable table.

At the end of your investigation, …

A

Record your data in a suitable table.

At the end of your investigation, record the colour of the mixtures in tubes A and B.

66
Q

Chloroplast suspension is produced by …

A

Chloroplast suspension is produced by filtering blended spinach

67
Q

Tube y contains

A

Dcpip solution and ammonium hydroxide

68
Q

Investigating Dehydrogenase Activity

This experiment can be used to see …

A

Investigating Dehydrogenase Activity

This experiment can be used to see how environmental conditions influence the rate of dehydrogenase activity.

69
Q

Investigating Dehydrogenase Activity
This experiment can be used to see how environmental conditions influence the rate of dehydrogenase activity. Examples of environmental conditions that could be investigated are:

A

Investigating Dehydrogenase Activity
This experiment can be used to see how environmental conditions influence the rate of dehydrogenase activity. Examples of environmental conditions that could be investigated are:

Light intensity

Temperatures

Chlorophyll concentration

70
Q

Light intensity

A

Light intensity

Change the distance of the test tubes from a light source.

71
Q

Temperature

A

Temperature

Incubate the test tubes in a water bath of varying temperatures.

72
Q

Chlorophyll concentration

A

Chlorophyll concentration

Place varying volumes of chloroplast suspension in different test tubes.

73
Q

What is another name that can be given to the second stage of photosynthesis?

A

The calvin cycle

74
Q

Where in the chloroplast does the Calvin cycle take place?

A

Where in the chloroplast does the Calvin cycle take place?

Stroma

75
Q

Which process replaces the electrons released from photosystem II when light is initially absorbed?

A

Which process replaces the electrons released from photosystem II when light is initially absorbed?

Photolysis

76
Q

Which two molecules are directly produced in the Calvin cycle?

A 
Trios phosphate (TP)
Glycerate 3-phosphate (GP)
77
Q

In which kind of membrane are Photosystems I and II located?

A

In which kind of membrane are Photosystems I and II located?

Thylakoid

78
Q

High light intensities can be dangerous for a plant as reactive oxygen species may be produced.

What process allows a plant to use light energy and produce ATP even when there is no NADP+?

A

High light intensities can be dangerous for a plant as reactive oxygen species may be produced.

What process allows a plant to use light energy and produce ATP even when there is no NADP+?

Cyclic Photophosphorylation

79
Q

DCPIP is used as a redox indicator (turning from blue to colourless when it is reduced). DCPIP can be used to quantify the activity of the enzyme NADP+ dehydrogenase under different light intensities.

How could you set up a control experiment and why might you do this?

A

Wrapping a test tube in aluminium foil or replacing the chloroplast suspension with buffer solution. Both of these serve as control experiments.

The purpose of a control is to validate your results by proving that the change you are observing is not caused by other factors.

By covering the tube in aluminium foil you are hoping to show that the colour change only occurs when there is light present. By using the buffer you are showing that chloroplasts are required for the colour change.

80
Q

Which experimental technique could be used to isolate chlorophyll a from chlorophyll b in order to test the absorption wavelengths of each pigment?

A

Which experimental technique could be used to isolate chlorophyll a from chlorophyll b in order to test the absorption wavelengths of each pigment?

Chromatography

81
Q

Scientists studied the rate of carbon dioxide uptake by grape plant leaves. Grape leaves have stomata on the lower surface but no stomata on the upper surface.
The scientists recorded the carbon dioxide uptake by grape leaves with three different treatments:
Treatment 1 − No air-sealing grease was applied to either surface of the leaf.
Treatment 2 − The lower surface of the leaf was covered in air-sealing grease that
prevents gas exchange.
Treatment 3 − Both the lower surface and the upper surface of the leaf were covered in air–sealing grease that prevents gas exchange.

The scientists measured the rate of carbon dioxide uptake by each leaf for 60 minutes in light and then for 20 minutes in the dark.

(a) Suggest the purpose of each of the three leaf treatments

Treatment 1 …

Treatment 2 …

Treatment 3 …

A

Treatment 1 : no grease means stomata r open

Treatment 2 : grease on lower surface seals stomata so no co2 diffuses thru

Treatment 3 : grease on both surfaces stops all co2 uptake

82
Q

Describe the results shown for Treatment 1. (Rate of co2 drops after 60 mins)

A

Describe the results shown for Treatment 1.

(Mean rate of) carbon dioxide uptake was constant and fell after the light turned off;

uptake started to fall at 60 minutes and reached lowest at 80 minutes

83
Q

The stomata close when the light is turned off.

Explain the advantage of this to the plant

A

The stomata close when the light is turned off.
Explain the advantage of this to the plant.

Cos waters lost thru stomata
Closure prevents water loss
This maintains water content of cells

84
Q

Treatment 2 shows that even when the lower surface of the leaf is sealed there is still some uptake of carbon dioxide.
Suggest how this uptake of carbon dioxide continues.

A

Treatment 2 shows that even when the lower surface of the leaf is sealed there is still some uptake of carbon dioxide.
Suggest how this uptake of carbon dioxide continues.

Carbon dioxide uptake) through the upper surface of the leaf / through cuticle.

85
Q

In both Treatment 1 and Treatment 2, the uptake of carbon dioxide falls to zero when the light is turned off.
Explain why.

A

No use of carbon dioxide in photosynthesis (in the dark);

there is now a diffusion gradient for carbon dioxide out of leaf (due to respiration)

86
Q

Q2.A student investigated the effect of different wavelengths of light on the rate of photosynthesis.
What measurements should the student have taken to determine the rate of photosynthesis?

A

Oxygen production / concentration and time

87
Q

Other than temperature and pH, give two factors which should be kept constant during this investigation

A

Other than temperature and pH, give two factors which should be kept constant during this investigation

Intensity of light and time

88
Q

The student did not use a buffer to maintain the pH of the solution.
Explain what would happen to the pH of the solution during this investigation.

A

student did not use a buffer to maintain the pH of the solution.
Explain what would happen to the pH of the solution during this investigation.

Ph increases

As more co2 is removed for photosynthesis

89
Q

Figure 2 shows the student’s results.

Suggest and explain why the rate of photosynthesis was low between 525 nm and 575 nm wavelengths of light.

A

Figure 2 shows the student’s results. Figure 2
Suggest and explain why the rate of photosynthesis was low between 525 nm and 575 nm wavelengths of light.

Less absorption
Light required for light dependant reactions
Represents green light

90
Q

Chloroplasts contain chlorophyll a and chlorophyll b. Scientists found tobacco plants with a mutation that caused them to make more chlorophyll b than normal tobacco plants. They investigated the effect of this mutation on the rate of photosynthesis.

The scientists carried out the following investigation.
• They grew normal and mutant tobacco plants. They grew some of each in low light intensity and grew others in high light intensity.
• They isolated samples of chloroplasts from mature plants of both types.
• Finally, they measured oxygen production by the chloroplasts they had isolated from
the plants.
The figure below shows the scientists’ results.

Explain why the scientists measured the rate of production of oxygen in this investigation.

The scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants in all light intensities.
Explain how these data support this suggestion.

A

The scientists carried out the following investigation.
• They grew normal and mutant tobacco plants. They grew some of each in low light intensity and grew others in high light intensity.
• They isolated samples of chloroplasts from mature plants of both types.
• Finally, they measured oxygen production by the chloroplasts they had isolated from
the plants.
The figure below shows the scientists’ results.

Explain why the scientists measured the rate of production of oxygen in this investigation.

Oxygen produced in light-dependent reaction;
The faster (oxygen) is produced, the faster the light-dependent reaction

At all light intensities, chloroplasts from mutant plants:

  1. Have faster production of ATP and reduced NADP;
  2. (So) have faster / more light-independent reaction;
  3. (So) produce more sugars that can be used in respiration;
  4. (So) have more energy for growth
91
Q

Q5.Farmland previously used for growing crops was left for 30 years and developed into woodland. During this period, ecologists recorded an increase in the diversity of birds in the area.
(a) Name the process that resulted in the development of woodland from farmland.

Explain the increase in the diversity of birds as the woodland developed.

A

Succession

Greater variety / diversity of plants
More food sources / more varieties of food;
Greater variety / more habitats / niches;

92
Q

Explain why CO2 uptake is a measure of net productivity.

A

Explain why CO2 uptake is a measure of net productivity.

Shows gross photosynthesis

biology a level (14 decks)

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