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A2 BIO UNIT3 > 3.3 Respiration > Flashcards

3.3 Respiration Flashcards

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1
Q

Define aerobic respiration

A
  • the release of large amounts of energy made available as ATP from the breakdown of molecules with oxygen as the terminal electron acceptor
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2
Q

Define anaerobic respiration

A
  • the breakdown of molecules in the absence of oxygen releasing relatively little energy making a small amount of ATP by substrate-level phosphorylation
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3
Q

Define oxidative phosphorylation

A
  • inner membranes of mitochondria in aerobic respiration
  • energy for making ATP comes from oxidation-reduction reactions and is released in the transfer of electrons along a chain of electron carrier molecules
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4
Q

Define photophosphorylation

A
  • thylakoid membranes of the chloroplast
  • energy from light and is released in transfer of electrons along electron carrier molecules
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5
Q

Define substrate-level phosphorylation

A
  • phosphate groups transferred from donor molecules
  • ie ADP to ATP
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6
Q

Describe briefly the key stages of respiration

A
  • glycolysis - occur in cytoplasm and generates pyruvate, ATP and reduced NAD
  • link reaction - occur n matrix of mitochondria. Pyruvate converted to acetyl coenzyme A, reduced NAD and CO2
  • Krebs cycle - mitochondrial matrix generates CO2 and reduced NAD and FAD
  • electron transport chain - cristae of inner mitochondrial membrane, ADP to ATP
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7
Q

Aerobic & anaerobic equation

A

glucose + oxygen —> carbon dioxide + water (+ energy)

glucose —> lactic acid (+ energy)

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8
Q

Where does glycolysis happen?

A
  • occurs in cytoplasm because glucose cannot pass through the mitochondria as enzymes not present
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9
Q

Define anabolic and catabolic

A

Anabolic: build
Catabolic: break

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10
Q

What happens when H+ is lost and gained?

A
  • gain = reduce
  • lose = oxidise
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11
Q

Overall glycolysis equation

A

Glucose + 2NAD + 2ADP + 2Pi ——> 2 pyruvate + 2NADred + ATP

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12
Q

Properties of phosphorylated glucose

A
  • more reactive due to lower Ea
  • more polar so less likely to diffuse
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13
Q

Outline glycolysis

A
  • glucose molecule phosphorylated by addition of 2Pi groups using 2 molecules of ATP to make hexose diphosphate
  • hexose diphosphate converted to 2x triose phosphate, 3C sugar and glyceraldehyde-3-phosphate
  • 2 triose phosphate are dehydrogenated, oxidising to pyruvate
  • hydrogen atoms transferred to NAD, a hydrogen carrier molecule, making reduced NAD which releases energy for 4 molecules of ATP
  • net gain of 2 ATPs from each molecule of glucose
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14
Q

Draw glycolysis

A
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15
Q

Outline link reaction

A
  • pyruvate diffuses from cytoplasm into mitochondrial matrix
  • pyruvate is dehydrogenated and hydrogen released is accepted by NAD to form reduced NAD
  • pyruvate is decarboxylated which leaves 2 carbon acetate group which combines with coenzyme A to make acetyl coenzyme A which enters krebs
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16
Q

Overall link reaction equation

A

Pyruvate + NAD + CoA ——> AcCoA + NADred + CO2

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17
Q

Draw link reaction

A
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18
Q

Outline Krebs cycle

A
  • acetyl CoA enters Krebs cycle by combining with 4C acid to make citric acid
  • 6C acid is dehydrogenated making reduced NAD and decarboxylated to make CO2 and 5C acid
  • 5C acid is dehydrogenated to make reduced NAD and FAD and decarboxylated to make 4C acid
  • 4C combine with AcCoA to repeat
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19
Q

How many times does decarboxylated occur

A

2

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20
Q

How many times does decarboxylation occur

A

4

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21
Q

What does each turn of the Krebs cycle produce?

A
  • one ATP
  • 3x redNAD
  • 1x redFAD
  • 2x CO2
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22
Q

What enzyme reduces NAD

A

Dehydrogenase

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23
Q

Draw krebs

A
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24
Q

Products of krebs per glucose

A
  • 2x ATP
  • 6x NADred
  • 2x FADred
  • 4x CO2
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25
Q

What is the acceptor molecule in krebs?

A

Oxaloacetate

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26
Q

What is the final electron acceptor in krebs?

A

Oxygen

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27
Q

Why does the ETC only work while O2 is present?

A
  • oxygen is the final electron acceptor and removes H from NADred to make water
28
Q

Explain why if no oxygen is available, the Krebs cycle and link reaction stop

A
  • NAD needs to be oxidised to get reduced to NADH
29
Q

Outline the anaerobic and aerobic pathways (whiteboard)

A

anaerobic
Glycolysis —> fermentation —> 2ATP per glucose

aerobic
Glycolysis —> Krebs cycle —> ETC —> 38ATP per glucosw

30
Q

Where does glycolysis take place?

A

Cytoplasm

31
Q

Where does ETC and krebs take place?

A

Mitochondria

32
Q

Aerobic respiration products

A

38 ATP
CO2 and H2O

33
Q

Anaerobic respiration products

A

2 ATP
Lactic acid

34
Q

Why is the max yield of ATP never quite achieved

A
  • cost of moving pyruvate and ADP into the mitochondrial matrix
  • proton gradient compromised by proton leakage across inner mitochondrial membrane
  • molecules leak through membrane
35
Q

Efficiency of ATP production equation

A

Energy made available
——————————————— x100
Energy released in combustion

36
Q

Difference between aerobic and anaerobic respiration

A
  • only glycolysis can take place in anaerobic
37
Q

Explain the 2 diff anaerobic pathways to remove hydrogen from reduced NAD

A
  • animals: pyruvate is the hydrogen acceptor and converted to lactate, regenerating NAD. if O2 becomes available then lactate can be respired to carbon dioxide and water
  • microorganisms: pyruvate converted to carbon dioxide and to ethanal, a hydrogen acceptor, by decarboxylase. Ethanal reduced to ethanol in alcoholic fermentation
    —> irreversible so if not broken down it accumulates to toxic levels
38
Q

How can lipids be used as a respiratory substrate?

A
  • fat can be hydrolysed to glycerol and fatty acids
  • glycerol is phosphorylated with ATP, dehydrogenated with NAD and converted to triose phosphate which enters glycolysis
39
Q

Why might lipids be good as an alternative respiration pathway?

A
  • produce large number of ATP molecules
  • depending in chain length
    —> more C so meow CO2 produced than can be removed
    —> more H so more reduced NAD and FAD therefore more ATP
    —> more H so more H2O produced - metabolism
40
Q

Why might lipids be good as an alternative respiration pathway?

A
  • produce large number of ATP molecules
  • depending in chain length
    —> more C so meow CO2 produced than can be removed
    —> more H so more reduced NAD and FAD therefore more ATP
    —> more H so more H2O produced - metabolism
41
Q

Outline the use of protein as a respiratory substrate

A
  • in prolonged starvation, tissue protein is mobilised to supply energy
  • protein is hydrolysed to amino acids which are delaminated in the liver
  • amino converted to urea and excreted
  • residue converted to AcCoA, pyruvate and other Krebs intermediates before being oxidised
42
Q

Where is the ETC located?

A

Cristae of the inner mitochondrial membranes

43
Q

How do hydrogen atoms enter the ETC?

A
  • coenzymes NAD and FAD
44
Q

Briefly outline the ETC

A
  1. Electrons from NADred and FADred pass through electron carriers to make water
  2. Protons from NADred and FADred are pumped into intermembrane space and flow back through ATP synthetase
  3. ATP formation
45
Q

Explain the passage of electrons in the ETC

A
  • NADred donates electrons of H atoms to the first of a series of electron carriers
  • electrons provide energy for first proton pump and protons from H are carried into intermembrane spaces
  • electrons pass along chain of carrier molecules providing energy for proton pumps

2H+ + 2e- + 1/2O2 —> H2O

46
Q

Explain the passage of protons in ETC

A
  • inner membrane is impermeable to protons so accumulate in intermembrane space
  • proton conc in intermembrane > matrix so gradient of conc & charge is set up
  • protein complexes in membrane are associated with ATP synthetase and allow protons to diffuse through channels

ADP + Pi —> ATP + H2O

  • protons combine with electrons to form water
47
Q

How does oxidative phosphorylation result in ATP production?

A
  • inner membrane of mitochondria in aerobic respiration
  • energy from redox released from electron transfer along ETC
  • flow of protons down electrochemical gradient through ATP synthetase
48
Q

Draw alcoholic fermentation

A
49
Q

2 types of enzymes involved in the conversion of pyruvate to AcCoA

A
  • dehydrogenase
  • decarboxylase
50
Q

What could be deduced if oxygen consumption was low with pyruvate as a substrate?

A
  • pathway to link is not working
  • no reduced NAD for ETC
51
Q

What could be deduced if there was a build up of any one of the Krebs cycle intermediates?

A
  • enzymes catalysing conversion of molecules are not functional
52
Q

Explain why there is a raised blood lactate level in many patients with mitochondrial disease

A
  • Krebs not working
  • pyruvate levels increase
  • excess converted to lactate
53
Q

State where the Krebs cycle takes place

A

Matrix of mitochondria

54
Q

Describe briefly what happens to a molecule of carbon dioxide removed

A
  • diffuses out of mitochondria into blood
  • carried out at hydrogen carbonate ion
  • breathed out
55
Q

Describe the way in which reduced NAD is produced in the Krebs cycle

A
  • removal of H ions by dehydrogenation
  • series of reactions
  • NAD to NADH2
56
Q

Explain what happens to the reduced NAD under anaerobic conditions and why this is essential for glycolysis to continue

A
  • pyruvate used to form lactic acid
  • regenerate to NAD
57
Q

Explain biochemical reasons for anaerobic conversion to lactate

A
  • allows reduced NAD to be converted back to NAD
  • allowing ATP production by oxidative phosphorylation
  • which enables glycolysis
58
Q

Explain why the two hydrogen acceptors NAD and FAD lead to the production of different numbers of ATP molecules

A
59
Q

Enzymes for alcoholic fermentation

A
  • pyruvate decarboxylase & ethanol dehydrogenase
60
Q

Enzyme for lactic fermentation

A
  • lactate dehydrogenase
61
Q

Stages of the biochemical pathway in the cytoplasm that produced reduced NAD

A
  • glycolysis
  • dehydrogenation when triose phosphate to pyruvate
62
Q

Why are fats not the main source of energy in muscles?

A
  • more CO2 than can be removed
  • more O2 needed to reduce NAD
63
Q

Where does the link reaction occur

A

Mitochondrial matrix

64
Q

Number of molecules formed in link using NADH

A

3

65
Q

Molecules of ATP produced in krebs using NADH

A

6

66
Q

Molecules of ATP made in Krebs using FADH

A

2

A2 BIO UNIT3 (3 decks)

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