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IB Biology > 8.2 Cell respiration > Flashcards

8.2 Cell respiration Flashcards

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1
Q

What is ATP?

A

A high energy molecule that functions as an immediate power source for cells

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2
Q

What does one molecule of ATP contain three of?

A

Three covalently bonded phosphate groups

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3
Q

What do the three covalently bonded phosphate groups store in their bonds?

A

Potential energy

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4
Q

Why is ATP a readily reactive molecule that contains high energy bonds?

A

Because phosphorylation makes molecules less stable

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5
Q

What happens to the energy when ATP is hydrolysed?

A

It is stored in the terminal phosphate bond and released for used by the cell

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6
Q

What are the two functions of ATP in the cell?

A
  • functions as the energy currency of the cell by releasing energy when hydrolysed to ADP
  • transfers phosphate groups to other organic molecules
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7
Q

What is ATP synthesised from?

A

ADP

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8
Q

What are two sources of energy used to synthesise ATP?

A

Solar energy
Oxidative processes

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9
Q

What is solar energy?

A

Photosynthesis converts light energy into chemical energy that is stored as ATP

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10
Q

What are oxidative processes?

A

Cell respiration breaks down organic molecules to release chemical energy that is stored as ATP

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11
Q

What is cell respiration?

A

The controlled release of energy from organic compounds to produce ATP

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12
Q

What does anaerobic respiration involve?

A

The incomplete breakdown of organic molecules for a small yield of ATP
No oxygen is required

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13
Q

What does aerobic respiration involve?

A

The complete breakdown of organic molecules for a larger yield of ATP
Oxygen is required

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14
Q

How does the breakdown of organic molecules occur?

A

Via a number of linked processes

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15
Q

What does staggering the breakdown into several processes do?

A

Reduces the energy requirements

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16
Q

What happens to released energy during the overall breakdown of organic molecules?

A

It is transferred to activated molecules via redox reactions

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17
Q

How is chemical energy transffered when organic molecules are broken down by cell respiration?

A

Redox reactions

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18
Q

What do redox reactions involve?

A

The oxidation of one chemical species and the reduction of another

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19
Q

What do most redox reactions typically involve?

A

The transfer of electrons, hydrogen or oxygen

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20
Q

What is reduction?

A

Gain of electrons/ hydrogens or the loss of oxygen

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21
Q

What is oxidation?

A

The loss of electrons/ hydrogen or the gain of oxygen

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22
Q

What does cell respiration transfer to carrier molecules?

A

Hydrogen atoms and electrons

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23
Q

What is the energy stored in the organic molecule transferred with to the carrier proteins?

A

Protons and electrons

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24
Q

What are carrier molecules called?

A

Hydrogen carriers or electron carriers

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25
Q

What is the most common hydrogen carrier?

A

NAD+

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26
Q

What is an example of a less common hydrogen carrier?

A

FAD

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27
Q

What do hydrogen function to do?

A

Transport the electrons to the cristae of the mitochondria

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28
Q

What is the site of the electron transport chain?

A

The cristae

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29
Q

What does the electron transport chain use the energy transferred by the carriers to do?

A

Synthesise ATP

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30
Q

What type of respiration can generate ATP from hydrogen carriers?

A

Aerobic respiration

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31
Q

What is the main organic compound used in cell respiration?

A

Carbohydrates

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32
Q

Why are lipids not preferentially used in cell respiration?

A

As they are harder to transport and digest

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33
Q

Why are proteins not preferentially used in cell respiration?

A

As they release potentially toxic nitrogenous compounds when broken down

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34
Q

What is the first step in the controlled breakdown of carbohydrates?

A

Glycolysis

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35
Q

Where does glycolysis occur?

A

In the cytosol of the cell

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36
Q

What is the main point of glycolysis?

A

A hexose sugar is broken down into two molecules of pyruvate

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37
Q

What are the four key events of glycolysis?

A

Phosphorylation
Lysis
Oxidation
ATP formation

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38
Q

What happens at the phosphorylation stage of glycolysis?

A

A hexose sugar is phosphorylated by two molecules of ATP to form a hexose biphosphate

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39
Q

How does the phosphorylation in glycolysis affect the molecule?

A

It makes it less stable and more reactive
Prevents diffusion out of the cell

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40
Q
A
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40
Q

What happens at the lysis stage of glycolysis?

A

The hexose bisphosphate is split into two triose phosphates

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41
Q

What happens at the oxidation stage of glycolysis?

A

Hydrogen atoms are removed from each of the 3C sugars via oxidation to reduce NAd+ to NADH

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42
Q

What is produced at the oxidation stage of glycolysis?

A

Two molecules of NADH

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43
Q

In ATP formation in glycolysis, what is some of the energy released from the sugar intermediates used to do?

A

Directly synthesise ATP

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44
Q

In ATP formation at glycolysis what is the direct synthesis of ATP called?

A

Substrate level phosphorylation

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45
Q

What is produced during glycolysis by substrate level phosphorylation?

A

4 molecules of ATP

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46
Q

What two reactions have occurred in glycolysis?

A

Glucose has been broken down into two molecules of pyruvate
Two hydrogen carriers have been reduced via oxidation

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47
Q

What is the net total of ATP molecules produced in glycolysis?

A

Two

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48
Q

What type of process is glycolysis?

A

An anaerobic process

49
Q

Depending on the availability of oxygen what are the two processes pyruvate may be subjected to?

A

Aerobic respiration which results in the further production of ATP
or
Fermentation where no more ATP is produced

50
Q

Where is the pyruvate transported to after glycolysis if oxygen is present?

A

The mitochondria for further breakdown

51
Q

What does the further oxidation after glycolysis generate?

A

Large numbers of reduced hydrogen carriers

52
Q

What can reduced hydrogen carriers release in the presence of oxygen?

A

Their stored energy to synthesise more ATP

53
Q

What three processes occur in aerobic respiration?

A

The link reaction
Krebs cycle
The electron transport chain

54
Q

Where does the pyruvate remain if oxygen is not present?

A

The cytosol

55
Q

What is pyruvate converted into in animals if no oxygen is present?

A

Lactic acid

56
Q

What is pyruvate converted into in plants and yeast if no oxygen is present?

A

Ethanol and carbon dioxide

57
Q

Is the conversion of pyruvate in none oxygen conditions reversible?

A

Yes

58
Q

Why is the conversion of pyruvate in non oxygen conditions important?

A

To ensure that glycolysis can continue to produce small amounts of ATP

59
Q

In the absence of oxygen what will glycolysis quickly deplete to prevent further glycolysis?

A

Available stocks of NAD+

60
Q

What type of reaction does fermentation of pyruvate involve?

A

A reduction reaction that oxidises NADH

61
Q

What is the first stage of aerobic respiration?

A

The link reaction

62
Q

What does the link reaction do?

A

Transports pyruvate into the mitochondria

63
Q

What does aerobic respiration use available oxygen to do?

A

Further oxidise the sugar molecule for a greater yield of ATP

64
Q

Why is the link reaction named that way?

A

Because it links the products of glycolysis with the aerobic processes of the mitochondria

65
Q

In the link reaction, where is pyruvate transported into?

A

The mitochondrial matrix

66
Q

In the link reaction, how is the pyruvate transported into the mitochondrial matrix?

A

By carrier proteins on the mitochondrial membrane

67
Q

In the link reaction, what does the pyruvate lose?

A

A carbon atom which forms a carbon dioxide molecule

68
Q

In the link reaction, what does the now 2C compound form?

A

An acetyl group when it loses hydrogen atoms via oxidation

69
Q

In the link reaction what does the acetyl compound combine with?

A

Coenzyme A to form acetyl coenzyme A

70
Q

How many times does the link reaction occur per molecule of glucose?

A

Two

71
Q

Why does the link reaction need to go twice?

A

As glycolysis splits glucose into two pyruvate molecules

72
Q

What does the link reaction produce per glucose molecule?

A

2x acetyl CoA
2xNADH + H+
2x Co2

73
Q

What is the second stage of aerobic respiration?

A

The Krebs cycle

74
Q

Where does the kreb cycle occur?

A

In the matrix of the mitochondria

75
Q

What happens in the krebs cycle?

A

acetyl CoA transfers its acetyl group to a 4C compound to make a 6C compound

76
Q

Once the coenzyme A is released what can it do?

A

It can return to the link reaction to form another molecule of acetyl CoA

77
Q

In the krebs cycle what is broken down to form the original 4C compound?

A

The 6C compound

78
Q

What are the reactions that occur in the Krebs cycle?

A

Two carbon atoms are released via decarboxylation to form two molecules of carbon dioxide
Multiple oxidation reactions result in the reduction of hydrogen carriers
One molecule of ATP is produced directly via substrate level phosphorylation

79
Q

Why does the krebs cycle occur twice?

A

As the link reaction produces two molecules of acetyl CoA

80
Q

What are the products of the Krebs cycle?

A

4x Co2
2x ATP
6x NADH + H+
2x FADH2

81
Q

What is the final stage of aerobic respiration?

A

The electron transport chain

82
Q
A
83
Q

Where is the electron transport chain stage located?

A

In the inner mitochondrial membrane

84
Q

Where is the electron transport chain stage located?

A

In the inner mitochondrial membrane

85
Q

What is the inner mitochondrial membrane arranged into?

A

Folds/Cristae

86
Q

What does the folds increase?

A

Surface area available for the transport chain

87
Q

What does the electron transport chain release in order to synthesise ATP?

A

The energy stored within the reduced hydrogen carriers

88
Q

Why is it called oxidative phosphorylation?

A

As the energy to synthesise ATP is derived from the oxidation of hydrogen carriers

89
Q

What are the three steps of oxidative phosphorylation?

A
  • proton pump create an electrochemical gradient
  • ATP synthase uses the subsequent diffusion of protons to synthesise ATP
  • oxygen accepts electrons and protons to form water
90
Q

When generating a proton motive force, what causes the release of high energy electrons and protons?

A

The hydrogen carriers are oxidised

91
Q

When generating a proton motive force, where are the high energ electrons transferred to?

A

The electron transport chain

92
Q

What does the electron transport chain consist of?

A

Several transmembrane carrier proteins

93
Q

As electrons pass through the electron transport chain, what do they lose?

A

Energy

94
Q

In the electron transport chain, how is the energy that is lost from the electrons used?

A

By the chain to pump protons from the matrix

95
Q

What creates an electrochemical gradient in the electron transport chain?

A

The accumulation of H+ ions within the inter membrane space

96
Q

What does the proton motive force cause H+ ions to dd?

A

To move down their electrochemical gradient and diffuse back into the matrix

97
Q

What is the diffusion of protons called?

A

Chemiosmosis

98
Q

What facilitates chemiosmosis?

A

The transmembrane enzyme ATP synthase

99
Q

What do H+ ions trigger as they move through ATP synthase?

A

The molecular rotation of the enzyme which synthesises ATP

100
Q

What must happen in order for the electron transport chain to continue functioning?

A

The de-energised electrons must be removed

101
Q

In the electron transport chain, what does oxygen act as?

A

The final electron acceptor

102
Q

Why does oxygen remove the de-energised electrons in the electron transport chain?

A

To prevent the chain from becoming blocked

103
Q

What does oxygen bind with to form water?

A

Free protons in the matrix

104
Q

What does removing matrix protons maintain?

A

The hydrogen gradient

105
Q

In the absence of oxygen, what cannot happen?

A

Hydrogen carriers cannot transfer energised electrons to the chain and ATP production is halted

106
Q

How much ATP is produced per glucose consumed?

A

36 ATP

107
Q

Where are 32 ATP produced?

A

In the electron transport chain

108
Q

What do hydrogen carriers produce different amounts of ATP depend on?

A

Where they donate electrons to the transport chain

109
Q

Mitochondria are the ____ of the cell?

A

Power plants

110
Q

What do aerobic prokaryotes use to perform oxidative phosphorylation?

A

The cell membrane

111
Q

What are mitochondria once though to have been?

A

Independent prokaryotes that were internalised by eukaryotes

112
Q

What are the proof of mitochondria via endosymbiosis?

A
  • double membrane structure
  • own circular DNA and 70S ribosomes
  • metabolic processes are susceptible antibiotics
113
Q

What are the five key structures of the mitochondria?

A

Outer membrane
Inner membrane
Cristae
Intermembrane space
Matrix

114
Q

What is the outer membrane?

A

The outer membrane contains transport proteins that enable the shuttling of pyruvate from the cytosol

115
Q

What is the inner membrane?

A

Contains the electron transport chain and ATP synthase

116
Q

What is the Cristae?

A

The inner membrane is arranged into folds that increase the SA:Vol ratio

117
Q

What is the intermembrane space?

A

Small space between membranes maximises hydrogen gradient upon proton accumulation

118
Q

What is the matrix?

A

Central cavity that contains appropriate enzymes and a suitable pH for the Krebs cycle to occur

119
Q

What may cause the appearance of a mitochondrion in electron micrographs?

A

Depending on where the cross-section occurs

120
Q

What is electron tomography?

A

A technique by which the 3D internal structure of a sample can be modelled

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