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A Level Biology OCR A > 18 - Respiration > Flashcards

18 - Respiration Flashcards

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1
Q

What are the 4 stages of aerobic respiration?

A
  1. Glycolysis 2. Link Reaction 3. Krebs Cycle 4. Oxidative Phosphorylation
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2
Q

What is the primary substrate used in respiration?

A

Glucose

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3
Q

What are the 3 coenzymes used in respiration?

A
  1. CoA (Coenzyme A) 2. NAD (Nicotine Adenine Dinucleotide) 3. FAD (Flavine Adenine Dinucleotide)
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4
Q

What stage of respiration uses reduced coenzymes?

A

Oxidative phosphorylation

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5
Q

What is NAD derived from?

A

Vitamin B3

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6
Q

What is FAD derived from?

A

Vitamin B2

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7
Q

What is CoA derived from?

A

Vitamin B5

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8
Q

Where does glycolysis occur?

A

In the cytosol

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9
Q

What are the three products of glycolysis?

A
  1. Pyruvate 2. ATP 3. NADH
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10
Q

Briefly summarise the reactions of glycolysis

A
  1. Two Phosphate groups from ATP attach to glucose to form hexose bisphosphate 2. Hexose bisphosphate breaks down into 2 triose phosphate molecules because it is unstable 3. Each triose phosphate has a free Pi (inorganic phosphate ions) group attach to form triose bisphosphate 4. All Phosphate are removed by ADP to form ATP, and a H atom dissociates and forms NADH (dehydrogenation). Pyruvate is what is left behind
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11
Q

What is substrate level phosphorylation?

A

The formation of ATP without using electron transport chains

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12
Q

What is glycolysis an example of?

A

Substrate level phosphorylation

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13
Q

What is the net gain of glycolysis?

A

2 ATP, 2 NADH, 2 pyruvate

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14
Q

What is the function of cristae?

A

Increase the surface area of the inner mitochondrial membrane for oxidative phosphorylation

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15
Q

What is the function of the outer mitochondrial membrane?

A

Separates the contents of the mitochondrion from the rest of the cell to allow maintenance of conditions perfect for aerobic respiration

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16
Q

What does the matrix contain?

A

Enzymes for the Krebs cycle and Link Reaction, mitochondrial DNA

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17
Q

What does the inner mitochondrial membrane contain?

A

Electron transport chains and ATP synthase

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18
Q

What is an adaptation of the intermembrane space in mitochondria?

A

Is small so allows a quick buildup of protons when they are pumped in for chemiosmosis

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19
Q

How does pyruvate enter the mitochondria?

A

Via active transport

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20
Q

What is another name for the Link Reaction?

A

Oxidative decarboxylation

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21
Q

Briefly summarise what happens in the Link Reaction?

A

CO2 is removed from pyruvate. This forms a H+ ion which reduces NAD, and leaves an acetyl group which combines with CoA to form acetyl CoA

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22
Q

Where does the Krebs Cycle occur?

A

The matrix

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23
Q

What is the Krebs Cycle also known as?

A

The Citric Acid Cycle

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24
Q

What are the products of one turn of the Krebs cycle (i.e. after inputting one acetyl CoA)?

A

2 CO2, 3 NADH, 1 FADH and 1 ATP

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25
Q

What are the products of oxidative phosphorylation for one molecule of glucose?

A

10 NAD, 2 FAD, 6 H2O, 28 ATP

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26
Q

How does oxidative phosphorylation produce ATP?

A

Hydrogen atoms on reduced coenzymes dissociate to form H+ ions and high energy electrons. These high energy electrons enter an electron transport chain, with the energy thus provided used to produce ATP via chemiosmosis.

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27
Q

Where does oxidative phosphorylation occur?

A

The inner mitochondrial membrane and intermembrane space

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28
Q

How many electron carriers are involved in the electron transport chain of oxidative phosphorylation?

A

3

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29
Q

How is water formed during oxidative phosphorylation?

A

1/2 an O2 molecule and 2 H+ ions act as electron acceptors for two low energy electrons from the electron transport chain

30
Q

How many ATP molecule can one NADH molecule synthesise?

A

2.5

31
Q

How many ATP molecule can one FADH molecule synthesise?

A

1.5

32
Q

How many ATP molecules are in theory produced by aerobic respiration and why is this not the true net gain?

A

32, but is lower in practice as active transport needed to transport pyruvate into the mitochondria

33
Q

How does cyanide kill you?

A

It readily binds to a haem group in the last electron transport chain of oxidative phosphorylation, so electrons cannot bind and oxidative phosphorylation (and therefore ATP production) are inhibited

34
Q

What type of molecule is cyanide?

A

Small and non-polar, so can pass through membranes

35
Q

Why does cyanide inhibit the Krebs Cycle and Link Reaction?

A

Lots of NADH and FADH would stockpile as they couldn’t be oxidised, so there wouldn’t be enough NAD and FAD.

36
Q

What are the three categories that organisms can be grouped into based on their dependence on oxygen?

A
  1. Obligate anaerobe 2. Facultative anaerobe 3.Obligate aerobe
37
Q

What are obligate anaerobes?

A

Organisms which cannot survive in the presence of oxygen.

38
Q

What type of organism are obligate anaerobes?

A

Mostly prokaryotes, some fungi

39
Q

What are facultative anaerobes?

A

Organisms which synthesise ATP by aerobic respiration if oxygen is present, but can switch to anaerobic respiration if necessary

40
Q

What is an example of a facultative anaerobe?

A

Yeast

41
Q

What are obligate aerobes?

A

Can only synthesise ATP in the presence of oxygen

42
Q

What is an example of a class of obligate aerobes?

A

Mammals

43
Q

Why are humans obligate aerobes even though some cells in them can be facultative anaerobes?

A

The compounds produced by anaerobic respiration in those cells must be broken down by oxygen, so the organism as a whole is an obligate aerobe

44
Q

What type of cell does lactate fermentation occur in?

A

Animal cells

45
Q

What type of cells does alcoholic fermentation occur in?

A

Yeast and some plant root cells

46
Q

Why is fermentation of pyruvate necessary in anaerobic respiration?

A

To ensure that NAD can cycle between its reduced and oxidised states, so that glycolysis can continue occurring

47
Q

Where does lactate oxidation occur in humans?

A

The liver

48
Q

What are two reasons that anaerobic respiration is not sustainable in mammals?

A
  1. It does not produce enough ATP 2. Lactate is a toxin (due to the pH change it causes which affects enzymes) and needs oxygen to break it down
49
Q

What is the word equation for anaerobic respiration involving lactate fermentation?

A

Glucose —-> Lactic Acid + Water

50
Q

What happens to NADH during fermentation?

A

It is oxidised to NAD, which is one of the molecules necessary for glycolysis

51
Q

Is lactate fermentation reversible?

A

Yes

52
Q

Is alcoholic fermentation reversible?

A

No

53
Q

What are the two stages of anaerobic respiration?

A
  1. Glycolysis 2. Fermentation
54
Q

Which enzyme catalyses the conversion of pyruvate to ethanal?

A

Pyruvate decarboxylase

55
Q

What is pyruvate converted to in alcoholic fermentation? (2 steps)

A

First ethanal, then ethanol

56
Q

What happens to ethanal in alcoholic fermentation?

A

It accepts a H atom from NADH, forming ethanol and NAD.

57
Q

Why can’t ethanolic fermentation continue indefinitely?

A

Due to the buildup of ethanol, which is a toxin as it damages plasma membranes and kills yeast if concentrations reach above about 15%

58
Q

How is respiratory quotient calculated?

A

CO2 produced/O2 consumed

59
Q

What can respiratory quotient be measured using?

A

A respirometer

60
Q

What is the approximate respiratory quotient of carbohydrates?

A

1

61
Q

What is the approximate respiratory quotient of proteins?

A

0.9

62
Q

What is the approximate respiratory quotient of lipids?

A

0.7

63
Q

Why is the RQ of lipids lower than that of glucose?

A

Because of the increased number of C-H bonds in lipids

64
Q

Why can lipids produce lots more ATP than carbohydrates per molecule?

A

Because the long fatty acid chains have lots of C-H bonds and can lead to the formation of lots of acetyl CoA, and in turn lots of ATP

65
Q

How are lipids respired?

A

Lipids are hydrolysed into fatty acids and glycerol. Glycerol can be converted to pyruvate, whilst the fatty acids can be converted to many CoA molecules

66
Q

How are proteins respired?

A

They are metabolised into amino acids, then deaminated, and can then enter the respiratory pathway (usually as pyruvate)

67
Q

Why are proteins usually only used as a respiratory substrate as a last resort?

A

They are less efficient than other substrates,this reduces the number of amino acids available to synthesise proteins, damages muscles and causes urea buildup

68
Q

What is RQ during anaerobic respiration?

A

Above 1, although this is difficult to measure

69
Q

What is human RQ during normal activity?

A

0.8-0.9

70
Q

What does the human RQ during normal activity show?

A

Shows that both lipids and carbohydrates are being used

A Level Biology OCR A (23 decks)

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