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Biology > 5.2.2 - Respiration > Flashcards

5.2.2 - Respiration Flashcards

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1
Q

What can respiration be said to be ?

A

The reverse of photosynthesis

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2
Q

Where is the energy trapped in glucose molecules ?

A

In the carbon hydrogen bonds

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3
Q

What is released when the C-H bonds break in glucose ?

A

Energy is released

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4
Q

What is the energy in glucose used for ?

A
  • Energy is used for the synthesis of ATP by chemiosmosis
  • ATP is constantly being used up and synthesised
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5
Q

What is the first stage of respiration ?

A

Glycolysis

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6
Q

Where does glycolysis occur ?

A

In the cytoplasm of the cell

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7
Q

What type of a process is glycolysis ?

A
  • It is an anaerobic process
    • It does not require oxygen
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8
Q

What happens in glycolysis (brief) ?

A
  • Glucose is split into two pyruvate molecules
  • ATP and reduced NAD are also produced
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9
Q

What are the 4 stages in glycolysis ?

A
  • Phosphorylation 1
  • Lysis
  • Phosphorylation 2
  • Dehydrogenation and formation of ATP
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10
Q

What happens in the first phosphorylation in glycolysis ?

A
  • Two phosphates, released from two ATP molecules, are attached to glucose
  • Forms hexose bisphophate
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11
Q

What happens in the lysis stage in glycolysis ?

A

The molecule is destabilised and splits into two TP molecules

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12
Q

What happens in the second phosphorylation in glycolysis ?

A
  • Another phosphate group is added to each TP
  • Forms two triose bisphosphate molecules
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13
Q

Where do the phosphates come from in the second phosphorylation stage ?

A

Come from free inorganic phosphate ions present in the cytoplasm

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14
Q

What happens in the dehydrogenation and formation of ATP in glycolysis ?

A
  • Two triose bisphosphate molecules are oxidised by the removal of hydrogen atoms
  • Forming two pyruvate molecules
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15
Q

What happens to the two hydrogen molecules that are released from the dehydrogenation of Triose Bisphosphate ?

A
  • NAD coenzymes accept the removed hydrogens
  • They are then reduced and form two reduced NAD molecules
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16
Q

How many ATP molecules are produced in glycolysis ?

A

4

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17
Q

What is the overall net ATP yield of glycolysis ?

A

2

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18
Q

What is glycolysis an example of ?

A

Substrate level phosphorylation

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19
Q

What is substrate level phosphorylation ?

A

The formation of ATP without the involvement of an electron transport chain

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20
Q

Where do the remainder of the aerobic reactions of cellular respiration take place ?

A

They take place in the mitochondria

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21
Q

What is the role of the outer mitochondrial membrane ?

A
  • It separates the contents of the mitochondrion from the rest of the cell
  • It creates a cellular compartment with ideal conditions for aerobic respiration
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22
Q

What is the role of the matrix ?

A
  • It contains enzymes for the Krebs cycle and the Link reaction
  • It contains mitochondrial DNA
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23
Q

What is the role of the inner mitochondrial membrane ?

A

It contains electron transport chains and ATP synthase

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24
Q

What is the role of the intermembrane space ?

A
  • Proteins are pumped into this space by the electron transport chain
  • The space is small so the concentrations build up quickly
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25
Q

What are the cristae ?

A

They are projections of the inner membrane which increase the surface area available for oxidative phosphorylation

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26
Q

What is the first step in the aerobic respiration ?

A

Oxidative decarboxylation

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27
Q

What is oxidative decarboxylation sometimes called ?

A

The link reaction

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28
Q

Why is it called the link reaction ?

A

It is the step that links anaerobic glycolysis to the aerobic steps of respiration

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29
Q

Where does pyruvate enter into ?

A

Mitochondrial matrix

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30
Q

How would pyruvate enter the mitochondrial matrix ?

A

Active transport via specific carrier proteins

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31
Q

What does pyruvate undergo once in the mitochondrial matrix ?

A

Oxidative decarboxylation

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32
Q

What is oxidative decarboxylation ?

A

Carbon dioxide is removed along with hydrogen

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33
Q

What happens to the hydrogen that is removed from pyruvate ?

A

It is accepted by NAD

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34
Q

What does NAD turn into once it accepts the hydrogen from pyruvate ?

A
  • Reduced NAD
  • NADH
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35
Q

What is left after oxidative decarboxylation occurs ?

A

Acetyl group

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36
Q

What happens to the acetyl group that is left?

A
  • It is bound to coenzyme A
  • This forms Acetylcoenzyme A
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37
Q

What is the role of Acetyl CoA ?

A

It delivers the acetyl group to the Krebs Cycle

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38
Q

Where is the NADH used ?

A

In oxidative phosphorylation to synthesise ATP

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39
Q

What happens to the carbon dioxide that was produced as a result of the decarboxylation ?

A

It will either diffuse away and be removed or be used as a raw material in photosynthesis

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40
Q

Where does the krebs cycle take place ?

A

Mitochondrial matrix

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41
Q

What does each krebs cycle result in ?

A

The breakdown of an acetyl group

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42
Q

What processes are involved in the Krebs cycle ?

A
  • Decarboxylation
  • Dehydrogenation
  • Substrate level phosphorylation
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43
Q

What picks up the H atoms that are released in the krebs cycle ?

A

Coenzymes NAD and FAD

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44
Q

What happens to the CO2 released in the krebs cycle ?

A

It is a by product

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45
Q

What happens to the ATP released in the krebs cycle ?

A

It is available for use by energy requiring processes within the cell

46
Q

When are the reduced NAD and reduced FAD used ?

A

In oxidative phosphorylation (the final oxygen requiring step of aerobic respiration)

47
Q

What does acetyl combine with when it enters the krebs cycle ?

A

Oxaloacetate (4C molecule)

48
Q

What does the reaction between acetyl and oxaloacetate form ?

A

A six carbon molecule called citrate

49
Q

What happens to the citrate molecule once it is formed ?

A

It undergoes decarboxylation and dehydrogenation

50
Q

What is formed after the decarboxylation and dehydrogenation of a citrate molecule ?

A
  • One reduced NAD
  • CO2
  • 5 carbon compound
51
Q

What happens to the 5 carbon molecule in the krebs cycle ?

A

It undergoes further decarboxylation and dehydrogenation reactions

52
Q

What is eventually regenerated in the krebs cycle ?

A

Oxaloacetate

53
Q

What is released in one cycle of Krebs ?

A
  • 2 CO2
  • 1 ATP
  • 1 FADH2
  • 3 NADH
54
Q

What is released in two cycle of Krebs ?

A
  • 4 CO2
  • 2 ATP
  • 2 FADH2
  • 6 NADH
55
Q

Why will two cycle of Krebs occur ?

A

Because there were originally 2 pyruvate molecules

56
Q

Why are coenzymes required in respiration ?

A

To transfer protons, electrons and functional groups between the enzyme catalysed reactions

57
Q

Which reactions are necessary in respiration ?

A

Redox reactions

58
Q

Why are coenzymes really important in redox reactions ?

A

Without coenzymes transferring electrons and protons between these reactions many respiratory enzymes would be unable to function

59
Q

What are the two main coenzymes in the Krebs Cycle ?

A
  • NAD
  • FAD
60
Q

What do FAD and NAD do ?

A

They accept protons and electrons released during the breakdown of glucose in respiration

61
Q

What are the differences between NAD and FAD ?

A
  • NAD takes part in all of cellular respiration whereas FAD only takes part in the krebs cycle
  • NAD accepts one hydrogen and FAD accepts two hydrogens
  • NADH results in the synthesis of 3 ATP molecules whereas FADH2 results in the synthesis of 2 ATP molecules
62
Q

Where are coenzymes normally derived from ?

A

Vitamins

63
Q

Where do the hydrogens from reduced NAD and reduced FAD go ?

A

They are delivered to ETCs

64
Q

Where are the electron transport chains in oxidative phosphorylation ?

A

They are present in the membranes of the cristae of the mitochondria

65
Q

What do hydrogen atoms dissociate into at the cristae ?

A

Hydrogen ions and high energy electrons

66
Q

What are electrons used for after they dissociate from hydrogen atoms ?

A

They are used in the synthesis of ATP by chemiosmosis

67
Q

How is energy released at the cristae ?

A

During redox reactions as the electrons reduce and oxidise electron carriers as they flow along the ETC

68
Q

What is energy used to create in oxidative phosphorylation ?

A

A proton gradient leading to the diffusion of protons through ATP synthase resulting in the synthesis of ATP

69
Q

What happens at the end of the ETC ?

A

The electrons combine with hydrogen ions and oxygen to form water

70
Q

What is the final electron acceptor in the ETC ?

A
  • Oxygen
  • The ETC cannot operate unless oxygen is present
71
Q

What is oxidative phosphorylation ?

A

The phosphorylation of ADP to form ATP, this is dependent on electrons moving along ETCs, which is dependent on the presence of oxygen

72
Q

What is substrate level phosphorylation ?

A

The production of ATP involving the transfer of a phosphate group from a short lived, highly reactive intermediate

73
Q

How is oxidative phosphorylation different from substrate level phosphorylation ?

A

Oxidative phosphorylation couples the flow of protons down the electrochemical gradient through ATP synthase to the phosphorylation of ADP to produce ATP

74
Q

Comparison of ATP production between aerobic respiration and fermentation

A
  • Aerobic respiration is 38 molecules of ATP
  • Fermentation is 2 molecules of ATP
75
Q

What are obligate anaerobes ?

A

They cannot survive in the presence of oxygen

76
Q

What category do obligate anaerobes fall under ?

A

Almost all of them are prokaryotes

77
Q

What are facultative anaerobes ?

A

They synthesis ATP by aerobic respiration if oxygen is present, but can switch to anaerobic respiration in the absence of oxygen

78
Q

Give an example of a facultative anaerobe

A

Yeast

79
Q

What are obligate aerobes ?

A

They can only synthesise ATP in the presence of oxygen

80
Q

What is fermentation ?

A

It is the process by which complex organic compounds are broken down into simpler inorganic compounds, without the use oxygen or the involvement of an ETC

81
Q

How much ATP does fermentation produce ?

A
  • Much less than aerobic respiration
  • 2 ATP molecules compared to 38 ATP
82
Q

How is the ATP in fermentation produced ?

A

Via substrate level phosphorylation

83
Q

What is alcoholic fermentation ?

A
  • It occurs in yeast and some plant root cells
  • end products are ethanol and carbon dioxide
84
Q

What is lactate fermentation ?

A
  • It results in the production of lactate
  • Carried out in animal cells
85
Q

What does no oxygen at the end of the ETC lead to ?

A
  • No final electron acceptor
  • No synthesis of ATP as chemiosmosis stops
  • NAD and FAD can no longer be regenerated
  • Decarboxylation and oxidation of pyruvate stops
  • Krebs cycle comes to a halt as there are no coenzymes
86
Q

What does pyruvate act as in mammals ?

A
  • It can act as a hydrogen acceptor
  • Taking the H from NADH
87
Q

What enzyme catalyses the formation of reduced NAD in lactate fermentation ?

A

Lactate dehydrogenase

88
Q

What is the pyruvate converted to in lactate fermentation ?

A

Lactate (Lactic Acid)

89
Q

What is regenerated in lactate fermentation ?

A

NAD

90
Q

What can lactate be converted back into ?

A

Glucose

91
Q

Where is lactate taken to ?

A

Liver

92
Q

What are the two reasons that mean that lactate fermentation cannot occur indefinitely ?

A
  • Reduced quantity of ATP produced would not be enough to maintain vital processes for a long period of time
  • Accumulation of lactic acid causes the pH to fall and proteins to denature
    • e.g. respiratory enzymes and muscle filaments
93
Q

Is alcoholic fermentation a reversible process ?

A

No

94
Q

What happens in alcoholic fermentation ?

A
  • Pyruvate is converted into ethanal
  • The ethanal then accepts a H from NADH to become ethanol
95
Q

Which enzyme catalyses alcoholic fermentation ?

A

Pyruvate decarboxylase

96
Q

What is regenerated in alcoholic fermentation ?

A

NAD

97
Q

What does NAD act as once regenerated in alcoholic fermentation ?

A

It can continue to act as a coenzyme and glycolysis can continue

98
Q

What are respiratory substrates ?

A

Substrates that can be broken down in order to release energy for the synthesis of ATP

99
Q

Give an example of a respiratory substrate

A

Triglycerides

100
Q

What happens to the glycerol before undergoing oxidative decarboxylation ?

A
  • It is first converted to pyruvate
  • Producing an acetyl group which is picked up by coenzyme A, forming acetyl CoA
101
Q

What do the fatty acids in a triglyceride lead to the formation of ?

A

50 acetyl CoA molecules result in the synthesis of up to 500 ATP molecules

102
Q

Compare the energy release between alcohol, carbohydrates, lipids and proteins

A
  • Alcohol contains more energy than carbohydrates but less than lipids
  • Proteins are roughly equivalent to carbohydrates
103
Q

What is a respiratory quotient ?

A

It is calculated by dividing the volume of carbon dioxide released by the volume of oxygen taken in during respiration of that particular substrate

104
Q

How is a respiratory quotient measured ?

A

Using a simple piece of apparatus called a respirometer

105
Q

Why do lipids produce more ATP in respiration than carbohydrates ?

A

This is because they have a greater proportion of carbon-hydrogen bonds than carbohydrates

106
Q

What do lipids need to break them down, given that they have more bonds ?

A
  • They need more oxygen to break them down
  • They release relatively less carbon dioxide
107
Q

Relative RQ’s for carbs, proteins and lipids

A
  • Carbs = 1
  • Protein = 0.9
  • Lipids = 0.7
108
Q

How can we identify the type of substrate being used for respiration ?

A

By measuring the volume of oxygen taken in and carbon dioxide released, and calculating RQ

109
Q

What is the RQ range during normal activity ?

A

0.8 to 0.9

110
Q

What is the RQ range during anaerobic respiration ?

A

Increases above 1

111
Q

What happens to proteins before they enter the respiratory pathway ?

A

They have to be hydrolysed to amino acids and then the amino acids have to be deaminated before they enter

112
Q

How do deaminated amino acids enter the respiratory pathway ?

A

Via pyruvate

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