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Biology 1B > Respiration & Photosynthesis > Flashcards

Respiration & Photosynthesis Flashcards

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1
Q

What is the first law of thermodynamics?

A

Law of energy conservation:
- Energy cannot be lost within the Universe
- Energy can be converted from one form into another

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2
Q

What is the second law of thermodynamics?

A

Every energy transfer increases the overall entropy of the universe

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3
Q

What is cellular respiration?

A

The metabolic processes by which an organism obtains energy by oxidising nutrients, and releases waste products

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4
Q

What is anabolism?

A

The use of energy to build complex molecules

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5
Q

Example of an anabolic process?

A

Protein synthesis

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6
Q

What is catabolism?

A

The breakdown of a molecule to release energy

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7
Q

Example of catabolic process?

A

The breakdown of glucose in glycolysis

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8
Q

How is energy used/released in anabolic and catabolic processes?

A

In catabolic processes, every step may not release energy, however the net energy change will be an increase; vice versa for anabolic processes

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9
Q

What is the equation for Gibbs free energy?

A

C.I Gibbs = C.I enthalpy of system - (C.I entropy of system x Temp)

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10
Q

What is the rule about the spontaneity of a reaction with regard to Gibbs energy?

A

If C.I energy is negative, the reaction will occur spontaneously

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11
Q

What is exergonic?

A

Gibbs free energy in products is lower than in reactants
Gibbs energy released
C.I gibbs is negative
Reaction can occur spontaneously

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12
Q

What is endergonic?

A

Gibbs free energy in products is higher than in reactants
Gibbs energy required
C.I is positive
Reaction cannot occur spontaneously

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13
Q

How can reactions still occur in a process, despite being endergonic?

A

Endergonic reactions can still occur if previous reactions in the process were exergonic, as long as the Gibbs energy required by the endergonic reaction is less than the Gibbs released by the exergonic reactions (so net C.I Gibbs is still negative)

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14
Q

Do enzymes change the Gibbs energy levels required in reactions?

A

No- they just lower the activation energy, allowing metabolic processes to occur

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15
Q

Are enzymes often pH-dependent?

A

Yes

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16
Q

What are enzymes regulated by?

A

Gene expression and protein modification

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17
Q

How are enzymes often inhibited?

A

By the end product of the reaction (negative feedback)

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18
Q

When does ATP release energy?

A

When the outermost phosphate group is cleaved off to form ADP

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19
Q

Why does the cleaving off of the outermost phosphate group release energy?

A

A high amount of chemical energy is stored in the phosphate group, as negative charges repel each other meaning it takes energy for them to bind in the first place; so when the phosphate group leaves, energy is released

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20
Q

What are the two ways in which ATP is formed?

A

Oxidative phosphorylation
Substrate-level phosphorylation

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21
Q

What is substrate-level phosphorylation?

A

Where a substrate with attached phosphate groups react with ADP to form ATP, in the presence of an enzyme

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22
Q

What is an example of a substrate-level phosphorylation process?

A

Glycolysis

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23
Q

What are the two aspects of oxidative phosphorylation?

A

Chemiosmosis
Electron transport chain

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24
Q

What is chemiosmosis?

A

The movement of ions down their electrochemical gradient across a semipermeable membrane

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25
Q

What can oxidative phosphorylation be seen as?

A

A biological hydraulic power station, made up of a rotor, stator, rod and knob

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26
Q

How does the rotor work in oxidative phosphorylation?

A

The rotor spins as H+ ions flow past it

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27
Q

What is the role of the stator in oxidative phosphorylation?

A

The stator holds the rotor and knob in position

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28
Q

What is the role of the rod in oxidative phosphorylation?

A

The rod turns with the rotor, and activates the knob

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29
Q

What is the role of the knob in oxidative phosphorylation?

A

The knob is made up of catalytic sites, which join the phosphate groups to ADP, forming ATP

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30
Q

Where does chemiosmosis of ATP occur?

A

Across the inner membranes of mitochondria and chloroplasts

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31
Q

What is the electron transport chain?

A

The relocation of electrons from weakly electronegative sugars to highly electronegative oxygens, releasing energy

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32
Q

What is NADH?

A

An electron currency

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33
Q

How is NADH involved in the electron transport chain?

A

NADH is involved in redox reactions to transfer H+ ions with electrons, creating a H+ gradient.
The H+ gradient is used to produce ATP via chemiosmosis

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34
Q

What are kinases?

A

Enzymes that adds/moves phosphate groups

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35
Q

What are isomerase?

A

Enzymes that convert molecules from one isomer to another

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36
Q

What are lyases?

A

Enzymes that split molecules up

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37
Q

What are dehydrogenases?

A

Enzymes that oxidises a substrate by reducing an electron acceptor

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38
Q

What are the three stages of cellular respiration?

A
  • Glycolysis
  • Krebs cycle
  • Oxidative phosphorylation
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39
Q

Where does glycolysis occur?

A

In cytosol

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40
Q

Is glycolysis aerobic or anaerobic?

A

Anaerobic (no oxygen required)

41
Q

What is the Krebs cycle also known as?

A

Citric acid cycle

42
Q

Where does the Krebs cycle occur?

A

In the mitochondria

43
Q

Is the Krebs cycle aerobic or anaerobic?

A

Aerobic

44
Q

Glycolysis and the Krebs cycle are both what type of process?

A

Substrate level phosphorylation

45
Q

Where does oxidative phosphorylation occur?

A

In the mitochondria

46
Q

Is oxidative phosphorylation aerobic or anaerobic?

A

Aerobic

47
Q

What is the initially investment of ATP required for glycolysis?

A

2 ATP

48
Q

How many ATP does glycolysis produce, and so what is the net gain?

A

Glycolysis produces 4 ATP, giving a net gain of 2

49
Q

What is glucose broken down into during glycolysis?

A

Glucose is broken down into 2 pyruvate and 2 H2O molecu;es

50
Q

Overall, what is produced from glycolysis?

A
  • 4 ATP (2 net gain)
  • 2 pyruvate
  • 2 H2O
  • 2 NADH
  • 2 H+
51
Q

What happens to the pyruvate before entering the Krebs cycle?

A

Pyruvate is prepared for the Krebs cycle by cleaving off CO2, and adding Coenzyme A.
The product is Acetyl CoA

52
Q

What is the first step of the Krebs cycle?

A

The pyruvate reacts with oxaloacetate to form citrate.
Oxaloacetate is the final product of the Krebs cycle, therefore once it is formed, it then reacts with a new pyruvate and the cycle repeats

53
Q

What is the overall process of the Krebs cycle?

A

The oxidation of citrate to oxaloacetate

54
Q

What is the products of a single Krebs cycle?

A

1 ATP
1 FADH2
3 NADH

55
Q

What is important to note about the products of the Krebs cycle with regard to the overall products of respiration?

A

A single glucose molecule produces 2 pyruvate molecules, meaning to get the overall products from respiration, the products of the Krebs cycle must be doubled.
Therefore there are 2 ATP, 2 FADH and 6 NADH produced in total from one glucose molecule

56
Q

What are the electron carriers involved in oxidative phosphorylation?

A

NADH and FADH2

57
Q

What happens to the electron carriers produced from the previous processes in respiration?

A

All previously produced electron carriers (NADH and FADH2) come to be oxidised

58
Q

What does the oxidation process of electron carriers allow for?

A

It creates a negative change in Gibbs energy, which is used to pump protons across the membrane, creating an electrochemical gradient

59
Q

What happens after the protons are pumped out in oxidative phosphorylation?

A

The H+ ions re-enter the membrane down the electrochemical gradient through ATP synthase, producing ATP via chemiosmosis

60
Q

How many electrons enter the electron transport chain per NADH

A

2 electrons

61
Q

What many ATP are produced per glucose molecule from oxidative phosphorylation?

A

26 to 28 ATP

62
Q

What happens to ATP production if there is a lack of oxygen?

A

Only anaerobic respiration (glycolysis) can occur, so only 2 ATP are produced

63
Q

What is the overall reaction for cellular respiration?

A

C6H12O6 + 6O2 -> 6H2O + 6CO2

64
Q

What is the overall process of photosynthesis?

A

Solar energy is captured and used to form ATP and NADPH.
ATP and NADPH are then used to convert CO2 into hexose phosphates

65
Q

Where are light absorbing pigments found?

A

The thylakoid

66
Q

From what does the light reaction produce O2?

A

From the splitting of two H2O molecules

67
Q

What is the H+ from H2O used for in the light reactions?

A

The H+ from H2O is used in the chemiosmotic synthesis of ATP

68
Q

What is the H- (hydride) from H2O used for in the light reactions?

A

The H- from H2O is used to reduce NADP+ to NADPH

69
Q

At what colours wavelengths does chlorophyll capture light well?

A

Blue and red wavelengths

70
Q

At what colours wavelengths does chlorophyll capture light poor?

A

Green-yellow wavelengths

71
Q

Why are leaves green?

A

Because the absorption of green light is lowest by the pigments in leaves

72
Q

What are the purpose of other pigments than chlorophyll in leaves?

A

To help absorb light at different wavelengths, that chlorophyll is poorer at absorbing

73
Q

What are three examples of other light absorbing pigments?

A
  • Carotene
  • Phycocyanin
  • Phycoerythrin
74
Q

Why do light absorbing pigments try to maintain the excited electrons (light energy) for as long as possible?

A

To give time for biochemical processes to take place

75
Q

What does the absorption of light energy convert?

A

The absorption of light energy is used to convert poor reducing agents (P680 and P700) to good reducing agents (excited molecules)

76
Q

What drives the electron flow uphill in the Z-scheme?

A

Light energy

77
Q

What is the Z-scheme?

A

A representation of the energy levels in photosystem II and photosystem I

78
Q

What occurs in photosystem II?

A

P680 (poor reducing agent) is converted to an excited state

79
Q

What occurs in photosystem I?

A

P700 (poor reducing agent) is converted to an excited state

80
Q

What is produced from the Z-scheme for every 4 electrons transferred?

A

For every 4e- transferred:
- 2 NADP+ is reduced to 2 NADPH
- 2 ATP

81
Q

How many NADPH and ATP are required for the Calvin cycle and why is this a problem?

A

For each CO2 reduced to form a carbohydrate sugar, 2 NADPH and 3 ATP are required.
This is a problem because only 2 ATP are produced from the Z-scheme, so we’re 1 short

82
Q

How is the problem of too few ATP for carbon fixing overcome?

A

Cyclic electron transport, where electrons are recycled from photosystem I to chemiosmotically produce ATP

83
Q

How are electrons recycled during cyclic electron transport?

A

Ferridoxin donates e- back via a specialised cytochrome, increasing protonmotive force and increasing ATP production

84
Q

Where does the dark reactions of photosynthesis occur and why?

A

The stroma of chloroplasts, as it contains enzymes required for CO2 fixation and sugar production

85
Q

Why is it called the dark reaction?

A

As it does not require light in order to proceed, however it is dependent on the products of the light reactions, namely NADPH, H+ and ATP

86
Q

What is the main process of the dark reactions?

A

The Calvin cycle

87
Q

What are the three stages of the Calvin cycle?

A
  • Carbon fixation
  • Reduction
  • Regeneration
88
Q

What is the main enzyme involved in the Calvin cycle?

A

RuBisCO (Ribulose bisphosphate carboxylase/oxygenase)

89
Q

What is the structure of RuBisCO?

A

Made up of 8 large and 8 small subunits

90
Q

What occurs in carbon fixation?

A

A CO2 molecule combines with five carbon RuBP, making a 6 carbon compound.
This 6 C compound quickly splits into two 3 C compounds (3-PGA).
This process is catalysed by RuBiSCO

91
Q

What happens in reduction of the Calvin cycle?

A

ATP and NADPH are used to convert 3-PGA molecules into molecules of a 3-carbon sugar(G3P)

92
Q

What happens in regeneration of the Calvin cycle?

A

One of the G3P molecules leaves to contribute to the formation of the carbohydrate molecule (commonly glucose).
The remaining G3P molecules are used to regenerate RuBP, and ATP is used in this process.

93
Q

How many turns of the Calvin cycle are required to produce one glucose molecule?

A

6 turns are needed to produce a single glucose molecule

94
Q

Out of C3 and C4 photosynthesis, which is more common?

A

The majority of plant species use C3 photosynthesis

95
Q

What is C3 photosynthesis?

A

Where the first carbon compound produced in the Calvin cycle contains three carbon atoms

96
Q

Which is more efficient, C3 or C4?

A

C4 is more efficient than C3?

97
Q

What feature of RuBiSCO is a problem with C3 photosynthesis?

A

RuBisCO aims to fix CO2, however it can also fix oxygen molecules around 20% of the time in a process called photorespiration; this costs the plant energy it could have used to photosynthesise

98
Q

How is C4 adapted to be more efficient?

A

Unique leaf anatomy in C4 plants allows CO2 to concentrate in ‘bundle sheaths’ around RuBisCO, delivering CO2 directly to RuBisCO and effectively removing its contact with oxygen (preventing photorespiration)

99
Q

What does the C4 adaption allow C4 plants to do?

A

Retain water through the ability to continue carbon fixing while stomata are closed

Biology 1B (6 decks)

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