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Topic 5) Energy Transfers In & Between Organisms > 5.1 - Photosynthesis & Respiration > Flashcards

5.1 - Photosynthesis & Respiration Flashcards

1
Q

Where do light-dependent reactions occur in chloroplasts?

A

In the thylakoids

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2
Q

Where do light-independent reactions occur in chloroplasts?

A

In the stroma

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3
Q

What does chloroplasts own DNA (cpDNA) code for?

A

Ribosomal RNA

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4
Q

Why does cpDNA code for ATP synthase?

A

Allow protons to move across the membrane.

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5
Q

What is the balanced chemical equation for photosynthesis?

A

6CO2 + 6H2O + Energy ——> C6H12O6 + 6O2

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6
Q

Why is photosynthesis an example of a metabolic pathway?

A

The process occurs in a series of small reactions controlled by enzymes.

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7
Q

What is the balanced chemical equation for aerobic respiration?

A

C6H12O6 + 6O2 ——> 6CO2 + 6H2O + Energy

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8
Q

What is meant by the compensation point of light intensity?

A

Particular level (different for different species of plants) of light intensity at which the rate of photosynthesis exactly matches the rate of respiration.

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9
Q

How to work out the compensation point?

A

Measure rate at which oxygen is produced & used by a plant at different light intensities.
Because photosynthesis produces oxygen & respiration uses it, compensation point is light intensity at which oxygen is being used as quickly as it’s being produced (therefore, net zero oxygen).

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10
Q

What is light intensity usually measured in?

A

Umoles m^-2 s^-1

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11
Q

What are thylakoids?

A

Fluid-filled sacs which are stacked up in the chloroplast into structures called grana.

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12
Q

What is a granum?

A

Singular of grana
Stack of thylakoids

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13
Q

How are grana linked together?

A

By bits of thylakoid membrane called lamellae.

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14
Q

What are photosynthetic pigments?

A

Coloured substances that absorb light energy needed for photosynthesis.
Found in thylakoid membranes
Attached to proteins

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15
Q

What is a photosystem?

A

Photosynthetic pigments attach to proteins.
The protein & pigment is known as a photosystem.

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16
Q

How many photosystems are used by plants to capture light energy?

A

2

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17
Q

What wavelength of light does Photosystem I absorb best?

A

700 nm

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18
Q

What wavelength of light does Photosystem II absorb best?

A

680 nm

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19
Q

What is the stroma?

A

Gel-like substance
Within the inner membrane of the chloroplast
Surrounding the thylakoids

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20
Q

What does the stroma contain?

A

Enzymes, sugars & organic acids. Carbohydrates produced by photosynthesis that aren’t used straight away are stored as starch grains in the stroma.

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21
Q

What are redox reactions?

A

Reactions that involve oxidation & reduction.

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22
Q

What does it mean if something is reduced?

A

It has gained electrons (e-)
May have gained hydrogen, or lost oxygen

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23
Q

What does it mean if something is oxidised?

A

It has lost electrons (e-)
May have lost hydrogen or gained oxygen

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24
Q

Oxidation of one molecule always involves…

A

reduction of another molecule

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25
Q

What are coenzymes?

A

Molecule that aids the function of an enzyme,
By transferring a chemical group from one molecule to another.

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26
Q

Name a coenzyme used in photosynthesis.

A

NADP

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27
Q

What is the overall function of NADP?

A

To transfer hydrogen from one molecule to another
Meaning it can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule.

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28
Q

What 2 stages make up photosynthesis?

A
  1. Light-dependent reaction
  2. Light-independent reaction (the Calvin cycle)
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29
Q

Where does the light-dependent reaction take place?

A

In the thylakoid membranes of chloroplasts

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30
Q

What is photoionisation?

A

In light-dependent reaction,
Light energy is absorbed by chlorophyll in the photosystems
This energy excites electrons in chlorophyll, giving them more energy
Eventually causing them to be released from the chlorophyll molecule = photoionisation
The chlorophyll molecule is now a positively charged ion

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31
Q

The energy resulting from photoionisation of chlorophyll is used for what 3 things:

A

1) Photophosphorylation
2) Making reduced NADP from NADP
3) Photolysis

32
Q

What is the function of phosphorylation?

A

To make ATP from ADP and inorganic phosphate
It’s the process of adding phosphate to a molecule using light

33
Q

What do **electron carriers* link?

A

Photosystems
Forming an electron transport chain

34
Q

What are the 3 products of non-cyclic photophosphorylation?

A

ATP
Reduced NADP
Oxygen

35
Q

What is the first stage of non-cyclic photophosphorylation?

A

Light energy excites electrons in chlorophyll:
Light energy is absorbed by PSII
Excites electrons in chlorophyll
So electrons move to higher energy level
These electrons are released from chlorophyll
And move down the electron transport chain into PSI

36
Q

What is the second stage of non-cyclic photophosphorylation?

A

Photolysis of water produces protons, electrons & oxygen:
Excited electrons that from chlorophyll leave PSII to move down electron transport chain
They must be replaced
Light energy splits water into protons (H+), electrons & oxygen = photolysis

37
Q

What is the third stage of non-cyclic photophosphorylation?

A

Energy from the excited electrons makes ATP:
Excited electrons loose energy as they move down electron transport chain
This energy is used to transport protons into thylakoid so that is has higher concentration of protons than in thestroma
Forms proton gradient across thylakoid membrane
Protons move down gradient into stroma,
Via enzyme ATP synthase (embedded in thylakoid membrane)
Energy from this movement combines ADP & Pi to from ATP

38
Q

What is the fourth stage of non-cyclic photophosphorylation?

A

Energy from the excited electrons generated reduced NADP:
Light energy is absorbed by PSI
Exciting electrons again to an even higher energy level
Electrons are then transferred to NADP, along with a proton from the stroma
To form reduced NADP

39
Q

Remember a proton is just another word for a…

A

Hydrogen ion

40
Q

What does the chemiosmotic theory describe?

A

Process of electrons flowing down electron transport chain
Creating a proton gradient across membrane
To drive ATP synthesis

41
Q

What is the function of cyclic photophosphorylation?

A

To produce ATP

42
Q

How is cyclic photophosphorylation different from non-cylcic?

A

Only produces ATP
Only used PSI

43
Q

Outline cyclic phosphorylation.

A

Electrons from chlorophyll molecules are passed back into PSI via electron carriers
Meaning electrons are recycled & can repeatedly flow through PSI
Process doesn’t produce reduced NADP or oxygen
Only produces small amounts of ATP

44
Q

What is another name for the light-independent reaction?

A

The Calvin cycle

45
Q

Where does the Calvin cycle take place?

A

In the stroma of the chloroplasts

46
Q

What is the overall function of the Calvin cycle?

A

To make triose phosphate
From carbon dioxide & ribulose bisphosphate
In order to make glucose & other useful organic substances

47
Q

How many carbons does ribulose bisphosphate contain?

A

5

48
Q

What is the first stage of the Calvin cycle?

A

Formation of glycerate 3-phosphate

49
Q

What does RuBP stand for?

A

Ribulose bisphosphate

50
Q

Outline the formation of glycerate 3-phosphate.

A

CO2 enters leaf through stomata, and diffuses into stroma (in chloroplast)
Combines with RuBP through condensation reaction, catalysed by enzyme rubisco
Gives an unstable 6-carbon compound, which quickly breaks down
Into 2 molecules of the 3-carbon compound, GP.

51
Q

What does GP stand for?

A

Glycerate 3-phosphate

52
Q

What is the second stage of the Calvin cycle?

A

Formation of triose phosphate

53
Q

What does TP stand for?

A

Triose phosphate

54
Q

Outline the formation of TP

A

Hydrolysis of ATP (from LDR) provides energy to reduce GP,
To a different 3-carbon compound, TP
Reaction also requires H+ ions
Which come from reduced NADP (from LDR)
Reduced NADP is recycled into NADP

55
Q

What happens to TP produced in the LIR?

A

1/6 is converted into useful organic compounds (e.g. glucose)
5/6 used to regenerate RuBP

56
Q

How is one hexose sugar made?

A

By joining two molecules of TP together.

57
Q

How many turns does the Calvin cycle need to make to produce one hexose sugar?

A

Six

58
Q

How is RuBP regenerated?

A

2 x TP (3C) —> 1 x RuBP (5C)
Uses rest of ATP produced by LDR (converted into ADP + Pi for energy) -coupled reaction
Also produces useful organic compound (1C)

59
Q

What is respiration in short?

A

The process that allows cells to produce ATP from glucose.

60
Q

Where do the reactions in aerobic respiration take place?

A

Mitochondria

61
Q

The cristae in the inner membrane of the mitochondrion…

A

Provide a large surface area to maximise respiration.

62
Q

What is a coenzyme?

A

Molecule that aids the function of an enzyme by transferring a chemical group from one molecule to another

63
Q

Name the 3 coenzymes used in respiration.

A

NAD
Coenzyme A
FAD

64
Q

What can NAD and FAD both do?

A

Transfer hydrogen from one molecule to another, meaning they can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule.

65
Q

What does coenzyme A transfer?

A

Acetate

66
Q

What are the 4 stages of aerobic respiration?

A

1) Glycosis
2) The link reaction
3) The Krebs cycle
4) Oxidative phosphorylation

67
Q

Where does glycolysis take place?

A

In the cytoplasm of cells

68
Q

What are the 2 stages of glycolysis?

A

1) Phosphorylation
2) Oxidation

69
Q

In short, what is phosphorylation?

A

The process of adding phosphate to a molecule.

70
Q

Outline phosphorylation.

A

-glucose is phosphorylated
-using a phosphate ion from an ATP molecule
-creates 1 glucose phosphate molecule + 1 ADP molecule
-ATP then used to add another phosphate
-forming hexose bisphosphate
-which is then split into 2 triose phosphates (TP)

71
Q

In short, what happens in the oxidation stage of glycolysis?

A

TP is oxidised, releasing ATP

72
Q

Outline oxidation.

A

-triose phosphate is oxidised (loses hydrogen)
-forming 2 pyruvate molecules
-NAD collects hydrogen ions, forming 2 reduced NAD
-4 ATP are produced (but 2 used in phosphorylation) = net gain of 2 ATP

73
Q

Where do the products of glycolysis go? : 2 reduced NAD

A

To oxidative phosphorylation

74
Q

Where do the products of glycolysis go? : 2 pyruvate

A

Actively transported into the mitochondrial matrix for use in the link reaction.

75
Q

Where do the products of glycolysis go? : 2 ATP (net gain)

A

Used for energy

Topic 5) Energy Transfers In & Between Organisms (3 decks)

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