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Biology: Module 5: Communication, Homeostasis and Energy > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Interrelationship between photosynthesis and respiration

A

The products of one reaction are the reactants for the other

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2
Q

Components of a chloroplast

A

Outer membrane, lamellae, grana, thylakoid, stroma, DNA

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3
Q

Where are the pigments in a chloroplast?

A

Embedded in the thylakoid membranes

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4
Q

Examples of different pigments

A

Chloropyll a, chlorophyll b, xanthophyll, carotenoids

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5
Q

Two main stages of photosynthesis

A

Light-dependent, light-independent

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6
Q

Where do the light-dependent reactions occur?

A

Thylakoid membranes

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7
Q

Where do the light-independent reactions occur?

A

Stroma

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8
Q

Structures involved in the light-dependent reactions

A

Light harvesting systems, reaction centres, photosystems

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9
Q

Components of a photosystem

A

Light harvesting system, reaction centre

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10
Q

Components of light harvesting systems

A

Chlorophyll b, xanthophylls, carotenoids, proteins

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11
Q

Role of light harvesting systems

A

Absorb light energy of different wavelengths, transfer it to the reaction centre

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12
Q

Component of reaction centres

A

Chlorophyll a

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13
Q

Role of reaction centres

A

Where the reactions of photosynthesis take place

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14
Q

Summary of the light-dependent stage

A

Light energy is absorbed and used to form ATP, NADP is reduced

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15
Q

Summary of the light-independent stage

A

Glucose made from hydrogen and carbon dioxide

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16
Q

Reactions in the light-dependent stage

A

Non-cyclic photophosphorylation, photolysis, cyclic photophosphorylation

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17
Q

How non-cyclic photophosphorylation occurs

A

Photosystem 2 absorbs light, electrons in reaction centre excited, electrons passed to electron transport chain, used to make ATP by chemiosmosis, lost electron replaced by those produced in photolysis, electrons passes to photosystem 1, passed to different electron transport chain, ATP synthesised by chemiosmosis, electrons leaving the electron transport chain are accepted with a hydrogen ion by NADP to form NADPH

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18
Q

Wavelength of light absorbed by photosystem 2

A

680nm

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19
Q

Wavelength of light absorbed by photosystem 1

A

700nm

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20
Q

How photolysis works

A

Oxygen-evolving complex catalyses the breakdown of water into protons and electrons and oxygen molecules, protons released into lumen of the thylakoids to increase proton concentration across the membrane, used in chemiosmosis

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21
Q

Equation for photolysis

A

H2O -> 2H+ + 2e- + 1/2O2

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22
Q

Role of water in the light-dependent stage

A

Can be broken down to provide electrons to replace those lost by PS2

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23
Q

Which molecules produced by the light-dependent reactions can be used as a source of energy for other metabolic processes?

A

ATP, NADPH

24
Q

What can ATP and NADPH be used for?

A

Source of energy for other metabolic processes

25
How cyclic photophosphorylation works
Electrons that leave the electron transport chain after photosystem 1 are returned to photosystem 1, no NADPH formed, ATP produced
26
How are the products of the light-dependent stage used in the Calvin Cycle?
Energy from ATP and hydrogen atom from NADPH used to convert glycerate 3-phosphate to triose phosphate
27
Reactions in the light-independent stage
Calvin Cycle, regeneration of ribulose bisphosphate
28
How the Calvin Cycle work
Carbon dioxide combines with ribulose bisphosphate which fixes the carbon dioxide, catalysed by RuBisCo, unstable six carbon intermediate formed, breaks down into 2 molecules of glycerate 3-phosphate, GP converted into triose phosphate, TP used to generate complex biological molecules or regenerate RuBp
29
Fixing
Incorporating a carbon into an organic molecules
30
Summary of the Calvin Cycle
Fixation, reduction, regeneration
31
Uses of triose phosphate
Starting material for synthesis of carbohydrates and lipids and proteins and nucleic acids, recycled to regenerate RuBP
32
Limiting factors in photosynthesis
Carbon dioxide concentration, light intensity, temperature
33
Limiting factor
A factor if, in short supply, it reduces the rate of reaction
34
Effect on photosynthesis of increased light intensity
ATP and NADPH produced at higher rate
35
Effect on photosynthesis of increased carbon dioxide concentration
Increased rate of carbon fixation, increased rate of TP production
36
Effect of temperature on photosynthesis
Increase up to a point increases rate because enzymes, decreases after the point because denaturation
37
Implications of water stress on photosynthesis
Stomata close, diffusion of CO2 stops, rate of light-independent reaction decreases, photosynthesis stops
38
Why is water not considered a limiting factor?
If water potential becomes low enough to affect the rate of photosynthesis, the plant will close its stomata and stop photosynthesis
39
Law of limiting factors
The rate of a physiological process will be limited by the factor which is in shortest supply
40
Effect of decreasing light intensity on levels of GP, RuBP and TP
Quantity of ATP and NADPH produced decreases, ATP and NADPH needed to convert GP to TP, concentration of GP increases, concentration of TP decreases, concentration of RuBP decreases as less TP to regenerate it
41
Effect of decreasing carbon dioxide concentration on levels of GP, RuBP and TP
Reduced concentrations of GP as less carbon dioxide is fixed, reduced concentration of TP, concentration of RuBP increases as still being formed from TP but not being used to fix carbon dioxide
42
Effect of increasing temperature on levels of GP, RuBP and TP
Enzymes and substrates have more kinetic energy, increased rate of reaction, higher concentrations of the molecules
43
How to measure the effect of factors on the rate of photosynthesis
Photosynthometer, leaf discs, DCPIP, algal balls
44
How photosynthometers are set up and used
Plant in boiling tube surrounded with water and sodium hydrogen carbonate solution, capillary tube in the boiling tube, syringe used to suck up bubble of gas produced by photosynthesis, bubble taken to scale, volume of bubble calculated
45
How leaf discs are used and work
Use a cork borer to prepare the leaf discs, time taken for leaf discs to rise up (Tell your sister that she's gotta rise up), they rise up because oxygen builds up inside the leaves which increases buoyancy
46
How DCPIP is used and works
DCPIP is a redox indicator, replaces NADP and is reduced using H+, time taken for colour to change can be measured
47
Colour of DCPIP when oxidised
Blue
48
Colour of DCPIP when reduced
Colourless - Green with plant stuff
49
How algal balls are set up (Sniggers)
Algal balls and hydrogen carbonate indicator solution put into sample bottles, colour of the solution changes, can be measured using a colorimeter
50
Why are carbon-hydrogen bonds important in energy release?
Weak bonds so require little energy to break, carbon and hydrogen form high energy bonds with oxygen so lots of energy released
51
Role of ATP
Universal source of energy, immediate source of energy released in small packets
52
Why is RuBisCo inefficient?
Inhibited by oxygen
53
Number of TP molecules required to regenerate a number of RuBP molecules
10 for 6
54
Why is ATP not a great energy storage molecule?
Relatively unstable, easy to remove a phosphate group
55
Tissues in the leaves that have a net uptake of carbon dioxide
Palisade and spongy mesophyll
56
Adaptations of chloroplasts
Large surface area using biconcave shape, grana give large surface area, chlorophyll and other pigments for light absorption at different wavelengths, arranged into photosystems

Biology: Module 5: Communication, Homeostasis and Energy (7 decks)

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