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A Level Biology > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

What is photosynthesis?

A

The conversion of light energy from the sun into a chemical energy store in the form of glucose.

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2
Q

What type of feeders are plants?

A

Autotrophs

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3
Q

What is aerobic respiration?

A

The release of energy, by converting ATP to ADP.

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4
Q

What is the formula of photosynthesis?

A

ENERGY
6CO(2) + 6H(2)O —————> C(6)H(12)O(6) + 6O(2)
Chlorophyll

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5
Q

What is the formula of aerobic respiration?

A

C(6)H(12)O(6) + 6O(2) ————> 6CO(2) + 6H(2)O + energy

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6
Q

Describe the action and absorption spectrum (discuss pigment)

A

Leaves absorb high levels of blue and red light and low levels of green light.

This would suggest that the leaves would be reflecting the green light.

This also suggests that leaves contains different pigments.

This would suggest that both blue and red pigment will be identifiable on chromatography paper.

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7
Q

Harnessing light energy:
What are two different types of pigment?

A
  • Primary Pigment: Two forms of chlorophyll a
  • Accessory Pigment: Other forms of chlorophyll a, chlorophyll b, carotenoids and xanthrophylls
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8
Q

What are photosystems?

A

Pigments that are arranged into light harvesting clusters called photosystems.

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9
Q

What is photo-excitation?

A

Photons (package of light energy) boost electrons up to higher energy levels. As electrons move back to a lower energy level, energy is emitted and transferred to accessory pigment. This allows energy to move towards the primary pigment in the reaction centre.

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10
Q

What are the 2 different types of photosystems?

A

Photosystem I
Photosystem II

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11
Q

Describe photosystem I

A

This photosystem is arranged around a molecule of ‘chlorophyll a’ with a peak absorption of 700nm (nanometers). This reaction centre is known as P700.

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12
Q

Describe photosystem II

A

This photosystem is arranged around a molecule of ‘chlorophyll a’ with a peak absorption of 680nm. This reaction centre is known as P680.

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13
Q

What is photolysis

A

The breaking down of water by light

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14
Q

Describe the formula of photolysis

A

light
2H(2)O ————> O(2) + 4H+ + 4e-

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15
Q

Describe the quantity of light energy needed to split one water molecule.

A

Water is a very stable molecule and it requires energy from 4 photons of light to split 1 water molecule.

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16
Q

What is photophosphorylation?

A

Light energy used to generate ATP from ADP and an inorganic phosphate group.

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17
Q

What are processes involved in the light dependent stage?

A
  • Non-cyclic photophosphorylation
  • Cyclic photophosphorylation
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18
Q

What are processes involved in light independent stage?

A

Calvin cycle

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19
Q

Describe the process of non-cyclic photophosphorylation

A
  1. Water is broken down by light energy - photolysis, creating products of electrons, protons (hydrogen ions) and oxygen, as a waste product which diffuses out of the chloroplast.
  2. The protons fill the stroma, while the electrons are in Photosystem II (P680).
  3. The electrons, which now have energy, as they have been excited, travel towards photosystem I, through the electron transport chain.
  4. As the electrons travel towards photosystem I, they pass through the proton pump giving it energy.
  5. This allows the proton pump to actively transport H+ ions from an area of low concentration - the stroma - into an area of higher concentration - the thylakoid membrane.
  6. The H+ ions then travel to a coenzyme called ATP synthase, before using it to travel from the thylakoid lumen to the stroma.
  7. As it travels through ATP synthase, the electrons are used to convert ADP and a phosphate molecule into ATP.
  8. The electrons that have been captured by electron acceptors at Photosystem II are excited by light energy that has been harvested by Photosystem II.
  9. These electrons are then used to convert NADP to reduced NADP.
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20
Q

Describe the process of cyclic photophosphorylation

A
  1. Electrons at Photosystem I are excited by light energy harvested by Photosystem I.
  2. They then travel back in the electron transport train to before the proton pump.
  3. The electrons then pass through the electron transport train past through the proton pump, where it gives energy.
  4. This is used to actively transport hydrogen ions (H+) from an area of lower concentration - stroma, to an area of higher concentration - thylakoid lumen.
  5. The hydrogen ions then travel to a coenzyme called ATP synthase, where it uses to be transported back into the stroma.
  6. When hydrogen ions (H+) travel through the ATP synthase protein, it is used to create ATP from ADP and a phosphate molecule.
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21
Q

What products are produced from non-cyclic photophosphorylation?

A

ATP
Reduced NADP

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22
Q

What products are produced from cyclic photophosphorylation?

A

ATP

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23
Q

How are electrons captured into photosystem I during cyclic photophosphorylation?

A

The electrons are captured on electron acceptors

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24
Q

What is the peak absorption of Photosystem I?

A

700nm (nanometers) - meaning it is known as P700

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25
Q

What is the peak absorption of Photosystem II?

A

680nm (nanometers) - meaning it is known as P680.

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26
Q

Is photolysis involved in cyclic photophosphorylation?

A

No

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27
Q

Is photolysis involved in non-cyclic photophosphorylation?

A

Yes

28
Q

Where does cyclic photophosphorylation get its first electron donor?

A

Photosystem I - P700

29
Q

Where does non-cyclic photophosphorylation get its first electron donor?

A

Water

30
Q

What is the last electron acceptor in cyclic photophosphorylation?

A

Photosystem I (P700)

31
Q

What is the last electron acceptor in cyclic photophosphorylation?

A

NADP

32
Q

What are the products of cyclic photophosphorylation?

A

ATP

33
Q

What are the products of non-cyclic photophosphorylation?

A

ATP, reduced NADP and oxygen (waste)

34
Q

What photosystems are involved in non-cyclic photophosphorylation?

A
  • Photosystem I
  • Photosystem II
35
Q

What photosystems are involved in cyclic photophosphorylation?

A
  • Photosystem I
36
Q

Name the molecules involved in the Calvin Cycle?

A

RuBP
GP
TP
(RuBisCO)

37
Q

What is the process called that is involved in light independent reactions?

A

The Calvin cycle

38
Q

Describe the process of the Calvin Cycle

A
  1. Carbon binds with RuBP (5-Carbon), using RuBisCO - the enzyme - which forms an unstable intermediate (6-Carbon).
  2. Due to its instability, it breaks into 2 separate molecules of GP (3-Carbon).
  3. ATP and reduced NADP produced during the light dependent stages are then used to convert GP to TP.
  4. TP can be used to create carbohydrates, lipids and amino acids, however 5/6 TP molecules are used the regenerate RuBP - this process requires ATP.
39
Q

Describe the relationship between RuBisCO and oxygen

A

RuBisCO is inhibited by oxygen so it is needed in large amount.

40
Q

What is an autotroph?

A

An organism that can fix carbon to produce organic molecules

41
Q

What is a heterotroph?

A

Relies on organic molecules to supplied by another organism - e.g. plants

42
Q

In what ways do heterotroph organisms are dependent on plants?

A
  • Animals obtain organic material from plants.
  • Plants produce oxygen during photosynthesis which can be used by heterotrophs.
  • Animals obtain glucose that is used for respiration in plants.
43
Q

What is an advantage of a plant having a range of accessory pigments in photosystems?

A

A range of different wavelengths can be absorbed by the different pigments.

44
Q

What are two different polysaccharides that can be synthesised from the end products of the light-independent stage of photosynthesis?

A
  • Starch
  • Cellulose
45
Q

How is Grana adapted to its function?

A
  • Contains pigments such as ‘chlorophyll a’.
  • Contains a large surface area in a small volume for light dependent reactions.
46
Q

What are the different parts of a chloroplasts?

A
  • Thylakoid
  • Stroma
  • Grana
  • Outer membrane
  • Inner membrane
  • Stroma lamellae
  • Thylakoid lumen
  • Inter-membrane space
47
Q

What is a thylakoid of a chloroplast?

A

Traps light energy and turns it into chemical energy forms. Contains cylindrical grana stacks made up of membranous discs piled one on top of the other.

48
Q

What is a Stroma lamellae of a chloroplast?

A

Wraps around the grana, connecting to thylakoids within the stack.

49
Q

What is the outer membrane of a chloroplast?

A

Contains porins and therefore freely permeable to small molecules.

50
Q

What is the inter-membrane space of a chloroplast?

A

The region in between the outer membrane and the inner membrane. This is where nucleotide phosphorylation occurs.

51
Q

What is the thylakoid lumen of a chloroplast?

A

It is a continuous aqueous phase enclosed by the thylakoid membrane.

52
Q

What is the inner membrane of a chloroplast?

A

Impermeable to ions and metabolites, therefore able to regulate what moves in and out of the chloroplast.

53
Q

What is the stroma of a chloroplast?

A

The site of many chemical reactions, resulting in the formation of complex organic molecules.

54
Q

What is a granum (grana) in a chloroplast?

A

This is a structural unit of the thylakoid membrane network. It is composed of multiple flattened membrane forming a stacked arrangement of a cylindrical shape.

55
Q

In what way have plants adapted their structure to living in sunlight?

A
  • Increased number of chloroplast
  • More grana
  • Larger palisade mesophyll
56
Q

What are different types of accessory pigments?

A
  • Chlorophyll b
  • Xanthrophylls
  • Carotenoids
57
Q

What does RuBisCO stand for?

A

Ribulose Biphosphate Carboxylase

58
Q

What can fat droplets found in the chloroplast be used for?

A

Membrane formation

59
Q

What type of photophosphorylation would be stopped by the inhibition of Photosystem II?

A
  • Non-cyclic photophosphorylation

Cyclic photophosphorylation would still occur

60
Q

What process produces carbon dioxide in the plant?

A

Respiration

61
Q

What are 3 limiting factors in plants?

A
  • Temperature
  • Light energy
  • Carbon Dioxide concentration
62
Q

Describe what effect low light intensities would have on the production of GP, TP, RuBP

A

Low light intensity:

  • Increased levels of GP as the isn’t ATP and reduced NADP from light dependent reaction.
  • Decreased levels of TP, as GP cannot be converted in to TP.
  • Decreased levels of RuBP due to the lack of TP being formed.
63
Q

Describe what effect high light intensities would have on the production of GP, TP, RuBP

A

High light intensities:

  • Decreased levels of GP, as there is plenty of ATP and reduced NADP being produced from light dependent reactions, meaning GP is converted into TP.
  • Increases levels of TP as GP can be converted to TP, due to ATP and reduced NADP.
  • Increased levels of RuBP, as plenty of TP being produced.
64
Q

Describe what effect low carbon dioxide concentration would have on the production of GP, TP, RuBP

A
  • Decreased levels of GP, as there isn’t enough Carbon to bind to form unstable intermediates, which would then form GP.
  • Decreased levels of TP, as GP isn’t being produced.
  • Increased levels of RuBP, due to the lack of carbon to bind to form the unstable intermediate.
65
Q

Describe what effect high carbon dioxide concentration would have on the production of GP, TP, RuBP

A

High carbon dioxide concentration:

  • Increased levels of GP, as RuBP is able to bind with the carbon to form GP.
  • Increase levels of TP, as there is plenty of GP to convert to TP.
  • Decreased levels of RuBP, as there is a high carbon dioxide concentration to form GP.
66
Q

Describe what effect different temperature would have on the production of GP, TP and RuBP

A

Low temperature:

All reactions are enzyme controlled, therefore at low temperatures, the enzyme wouldn’t have enough kinetic energy, meaning GP, TP a d RuBP would all be produced in low amount.

Medium temperature:

At optimum temperature, the enzymes would have enough kinetic energy to catalyse the reactions, without denatured, meaning GP, TP and RuBP are all produced in large quantities.

High temperature:

Enzymes can become denatured at high temperatures. As all reactions are enzyme controlled, if they become denatured, it will massively affect the amount of GP, TP and RuBP being produced. As a result, low levels of GP, TP and RuBP will be made.

A Level Biology (13 decks)

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