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Biology Eduqas A Level > A2C1 - Chapter 2 - Photosynthesis > Flashcards

A2C1 - Chapter 2 - Photosynthesis Flashcards

(46 cards)

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1
Q

What is the overall equation for photosynthesis?

A

6CO2 + 6H2O –> C6H12O6 + 6O2

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2
Q

What are the two stages of photosynthesis?

A

Light Dependant Reaction
Light Independant Reaction

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3
Q

What happens in the Light Dependant Stage of Photosynthesis?

A

Light energy is converted into chemical energy as the photolysis of water releases protons and electrons producing ATP via photophosphorylation and reduce the co-enzyme NADP.

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4
Q

What is Light-independant stage (aka calvin cycle) in photosynthesis?

A

This is where ATP and NADPH from the light-dependant reaction reduce carbon dioxide to produce glucose.

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5
Q

What is photophosphorylation?

A

An endergonic reaction bonding a phosphate ion to a molecule of ADP using energy from light, making ATP.

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6
Q

What is a chloroplast?

A

An organelle found in plants and green algae that is the site of photosynthesis.

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7
Q

Describe the structure of a chloroplast.

A
  • Double membrane= Chloroplast envelope
  • Grana = Stacks of flattened disks (thylakoids) that contain PSI and PSII, electron transport chain and ATP synthase.
    Grana = Connected by intergranal lamellae
    Stroma = Fluid-filled matrix containing enzymes
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8
Q

Where are chloroplasts located in an angiosperm leaf?

A

Mainly found in the palisade layer.

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9
Q

How are chloroplasts adapted for photosynthesis?

A
  • Thylakoids give a large surface area for light-dependant reactions.
  • Photosynthetic pigments arranged into photosystems to maximise light-absorption.
  • Stroma directly surrounds grana - products of photosynthesis diffuse directly into the stroma.
  • Contain their own DNA and ribosomes.
  • Inner chloroplast membrane is less permeable than the outer layer, enabling the control over the movement of substances.
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10
Q

How are angiosperm leaves adapted for photosynthesis?

A
  • Large surface area to maximise light absorption.
  • Thin to reduce the diffusion distance for CO2.
  • Upper epidermis is transparent allowing light to strike mesophyll layers.
  • Palisade cells densely packed and contain many chloroplasts.
  • Air spaces reduce the diffusion distance for CO2.
  • Stomata allow CO2 to diffuse into the leaf.
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11
Q

What is a transducer? Why are chloroplasts described as transducers?

A

Something that converts one type of energy into another.
Chloroplasts transduce light energy into the chemical energy of ATP.

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12
Q

What is a photosynthetic pigment?

A

Molecule present in chloroplasts that absorbs light energy for photosynthesis.
Absorbs specific wave wavelengths of light and reflects others.

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13
Q

Give some examples of photosynthetic pigments.

A

Chlorophyll a and b
Beta carotene
Xanthophylls

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14
Q

What is the purpose of chromatography?

A

To separate different components from a mixture.

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15
Q

State the equation used to calculate Rf (retention value).

A

Rf = Distance of Component/Distance of Solvent

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16
Q

Definition of Photosynthesis.

A

A complex metabolic pathway that synthesises organic molecules from Carbon Dioxide and Water in the presence of light. Overall:
6CO2 + 6H2O –> C6H12O6 + 6O2

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17
Q

What is a photosystem?

A
  • Protein complex consisting of an antenna complex and reaction centre.
  • The photosystem is involved in the absorption of light and transfer of electrons in photosynthesis.
  • PSI and PSII.
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18
Q

How do PSI and PSII differ?

A

They absorb different wavelengths of light.

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19
Q

Describe the process of light harvesting in photosynthesis.

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A
  • Antenna complex absorbs light energy of varying wavelengths and transfers it quickly and efficiently to the reaction centre.
  • Energy absorbed by two chlorophyll a molecules which emit ‘excited’ electrons.
20
Q

What is an absorption spectrum?

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A

A graph showing how much light energy is absorbed at different wavelengths.

21
Q

What is an action spectrum?

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A

A graph of the rate of photosynthesis against each wavelength of light absorbed by a pigment.

22
Q

Describe the light-dependant stage of photosynthesis.
what, where, what happens?

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A
  • The first stage of photosynthesis
  • Takes place in the thylakoids of the chloroplast.
  • Uses light energy to produce ATP, reduced NADP and oxygen.
23
Q

State the sources of electrons for the electron transport chain.

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A

Cyclic and non-cyclic photophosphorylation.

24
Q

Define non-cyclic photophosphorylation.

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A

The formation of ATP and NADP involving both photosystems.

25
Outline Non-Cyclic photophosphorylation.
- Involves PSI and PSII. - Excited electrons enter the electron transport chain to form ATP. - NADP acts as final electron acceptor and is reduced. - Water is photolysed to compensate for electrons lost from PSII.
26
What is the purpose of non-cyclic photophosphorylation?
Produces ATP and reduced NADP (NADPH) for the calvin cycle.
27
Define cyclic photophosphorylation.
The formation of ATP involving PSI only, where NADP is not reduced.
28
Outline cyclic photophosphorylation.
- Involves PSI only (no electrons are supplied by PSII here) - Excited electrons enter the electron transport chain to produce ATP and then return to PSI.
29
What is the purpose of cyclic photophosphorylation?
Produces additional ATP to meet surplus energy demands of the cell.
30
How does chemiosmosis produce ATP in the light dependant stage?
Protons flow down their concentration gradient from the thylakoid space into the stroma via ATP synthase. ATP synthase phosphorylates ADP to form ATP as protons flow through it.
31
Describe photolysis.
The splitting of a molecule of water in the presence of light (energy from the sun) that occurs during the light-dependant stage of photosynthesis. This produces protons, electrons and oxygen.
32
What happens to the products of photolysis?
H+ is used in proton pumping to reduce NADP. e- replaces electrons lost during PSII from chlorophyll a reaction centre. O2 is a biproduct used for respiration or it diffuses out the leaf as a waste gas.
33
Explain how the electron transport chain results in the production of reduced NADP.
NADP acts as the final electron acceptor hence it is reduced.
34
Describe the light-independant stage of photosynthesis. (5) (Not the steps)
- Second stage of photosynthesis. - Produces glucose. - No requirement for light energy. - Located in stroma. - Uses CO2 and the products of the light-dependant stage to build organic molecules.
35
What is the light independant stage known as?
The Calvin Cycle
36
Name the 3 main stages of the Calvin Cycle.
1. Carbon Fixation 2. Reduction 3. Regeneration
37
What happens during the fixation of the Calvin Cycle?
Reaction of CO2 and RUBP catalysed by RuBisCo. This forms an unstable 6C intermediate that breaks into 2 molecules of G3P (glycerate-3-phosphate).
38
What happens during reduction of the Calvin Cycle? (what is reactants, products/formed, required and when does it occur)
2 G3Ps form 2TPs (Triose Phosphates) This requires 2x NADPH and 2ATPs formed during the light-dependant reaction. Forms 2x NADP and 2x ATP once done. These then go and enter the light-dependant reaction again.
39
What happens during regeneration of the Calvin Cycle?
After 1C leaves the cycle, the 5C compound RuP forms (Ribulose Phosphate). RuBP is regenerated from RuP using an ATP. As the 1 ATP is used, it forms 1 ADP.
40
How are nutrients produced as a result of photosynthesis?
The formation of amino acids from GP (requires nitrates and sulfates) TP molecules used to produce sugars eg: glucose, fructose and sucrose.
41
What is a limiting factor?
A variable limiting the rate of a particular reaction.
42
Name the factors affecting the rate of photosynthesis. What stage do they limit? (5)
Light Intensity = Light-dependant stage. Light Wavelength = absorption by chlorophyll. CO2 Concentration = Light-independant stage. Temperature = enzyme controlled reactions (Carbon fixation). pH = enzyme controlled reactions.
43
Describe the role of nitrogen in plant metabolism.
Synthesis of amino acids, nucleotides and chlorophyll.
44
What does Nitrogen deficiency in plants cause?
Stunted Growth Chlorosis (yellowing of the leaves due to insufficient chlorophyll production).
45
Describe the role of magnesium in plant metabolism.
Central component of chlorophyll.
46
What does magnesium deficiency in plants cause?
Chlorosis (yellowing of the leaves due to insufficient chlorophyll production)

Biology Eduqas A Level (10 decks)

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