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Paper 2 Important topics > 16 Cellular respiration > Flashcards

16 Cellular respiration Flashcards

1
Q

what are the needs for ATP?

A

active transport

chemical activation

anabolic synthesis

cellular ultrastructure

bioluminescence

exocytosis

movement (e.g. of flagella and cilia)

homeostasis

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2
Q

why is ATP considered to be the ‘universal energy currency’?

A

found in all living eukaryotic and prokaryotic cells

links energy-releasing and energy-consuming reactions

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3
Q

where does glycolysis take place? why?

A

cytosol

requires specific enzymes only found there

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4
Q

what is the function of glycolysis?

A

to oxidise glucose and split a 6C hexose into 2x 3C triose (pyruvate)

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5
Q

what is required for glycolysis?

A

1 glucose molecule

2 ATP

2 NAD+

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6
Q

what are the products of glycolysis?

A

2 pyruvate

4 ATP (gross)

2 red. NAD

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7
Q

give each stage of the conversion from a. glucose to pyruvate

A

a. glucose

glucose phosphate

fructose phosphate

fructose bisphosphate

2 glyceraldehyde 3-phosphate

2 glycerate 1,3-bisphosphate

2 glycerate 3-phosphate

2 pyruvate

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8
Q

what is phosphorylation? what is its use in glycolysis?

A

addition of a phosphate group, providing a -ve charge to the substrate (which prevents glucose diffusing out of the cel)

increases the CPE of glucose ∴ Ea of next reaction decreases

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9
Q

where does the link reaction take place? why?

A

mitochondrial matrix

CoA and other enzymes only found here

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10
Q

what is required for the link reaction?

A

1 pyruvate

1 ATP

1 ACoA

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11
Q

how does pyruvate reach the mitochondrial matrix?

A

moves across mitochondrial envelope through specialised intrinsic protein carriers via active transport

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12
Q

what are the three reactions involved in the link reaction?

A

decarboxylation

redox

dehydrogenation

[collectively oxidative decarboxylation}

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13
Q

what are the components of coenzyme A (CoA)?

A

pantothetic acid (a vitamin B complex)

ADP

-SH group (joins acetyl group to CoA)

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14
Q

what are the products of the link reaction?

A

CO(2)

acetyl CoA (aCoA)

red. NAD

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15
Q

how can fats be converted into a CoA molecule?

A

B. oxidation occurs - 2C fragments hydrolysed from hydrocarbon tails of fatty acids

each fragment can make 1 CoA

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16
Q

where does the Krebs cycle take place?

A

mitochondrial matrix

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17
Q

what is the Krebs cycle controlled/limited by?

A

substrate concentration

allosteric (non-competitive) inhibitors

end-product inhibition

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18
Q

KC: what is added to oxaloacetate to produce citrate?

A

an acetyl group from aCoA

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19
Q

KC: what is added/removed to citrate to produce a 5C intermediate?

A
  • CO(2)

+ NAD+ (producing red. NAD)

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20
Q

KC: what is added/removed to the 5C intermediate to produce a 4C intermediate?

A
  • CO(2)

+ NAD+ (producing red. NAD)

+ ADP + P(i) (producing ATP)

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21
Q

KC: what is added to the 4C intermediate to produce another 4C intermediate?

A

+ FAD (producing red. FAD)

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22
Q

KC: what is added to the second 4C intermediate to reform oxaloacetate?

A

+ NAD+ (producing red. NAD)

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23
Q

what is produced in 1 turn of the Krebs Cycle?

A

1 ATP

2 CO(2)

1 red. FAD

3 red. NAD

24
Q

what is the purpose of red. FAD and red. NAD?

A

co-enzymes

act as H carriers to the electron transport chain (eTC)

to allow production of ATP via oxidative phosphorylation

25
Q

where does oxidative phosphorylation take place?

A

cristae of inner mitochondrial membrane

26
Q

what molecules are involved in the eTC?

A

red. NAD
red. FAD

e- carriers

O2

27
Q

eTC: what are e- carriers?

A

specialised carrier globular proteins

accept/donate e-

have a quaternary structure (a prosthetic group:
- Fe3+ + e- Fe2+)

28
Q

eTC: what is the first e- carrier?

A

red. NAD dehydrogenase

29
Q

eTC: how do e- carriers pump H+ across inner mitochondrial membrane?

A

e- cause conformational change to protein structure

causes protein to pump H+ across membrane into the inter-membrane space

30
Q

eTC: how does the pumping of H+ in the eTC result in the formation of ATP?

A

pumping creates an electrochemical H+ gradient –> proton motive force

H+ diffuse back down gradient through ATP synthase channels into mitochondrial matrix

E released forms ATP from ADP and P(i)

31
Q

eTC: what is the role of oxygen?

A

to act as the final e- acceptor and combine with 2H+ and 2e- to form H(2)O

32
Q

how many ATP molecules are produced in:

  • glycolysis
  • link reaction
  • krebs cycle
  • oxidative phosphorylation

as substrate-level phosphorylation?

A
  • 4
  • 0
  • 2
  • 0
33
Q

how many ATP molecules are produced indirectly from:

  • 2 red. NAD from glycolysis
  • 2 red. NAD from link reaction
  • 6 red. NAD from Krebs cycle
  • 2 red. FAD from Krebs cycle?
A
  • 4
  • 4
  • 18
  • 4
34
Q

why is the net gain of ATP always less than the theoretical gain?

A

used for active transport of pyruvate

used to move ADP into matrix

used to shuttle red. NAD from glycolysis into mitochondria

some protons leak from the inter-membrane space ∴ reduced proton motive force ∴ less ATP made

35
Q

what is anaerobic respiration?

A

when molecules other than oxygen are used as final electron acceptors

36
Q

what is the purpose of anaerobic respiration?

A

to allow glycolysis to continue and produce 2 ATP

37
Q

what type of anaerobic respiration takes place in skeletal muscles?

A

lactate fermentation

following vigorous exercise

38
Q

outline the stages of lactate fermentation

A

H removed from red. NAD

combines with pyruvate –> lactate

NAD oxidised to NAD+ ==> NAD+ can accept more e- and glycolysis can continue

39
Q

what can result from a build up of lactate?

A

inhibition of glycolysis

cramp and fatigue in skeletal muscles

lactic acidosis

40
Q

what is the fate of lactate?

A

transported to liver in plasma

oxidised back to pyruvate by lactate dehydrogenase forming red. NAD

1/5 = respired aerobically, producing ATP in the Krebs cycle

4/5 = converted to glucose-6-phosphate and then to glycogen in glycogenesis in liver cells

41
Q

what type of anaerobic respiration takes place in yeast?

A

alcoholic fermentation

42
Q

why is yeast considered a ‘facultive anaerobe’?

A

it can survive in both anaerobic and aerobic conditions (although growth is faster in aerobic)

43
Q

outline the stages of alcoholic fermentation

A

pyruvate is decarboxylated to ethanAl and CO(2) by pyruvate decarboxylase

ethanAl acts as H+ acceptor and removes H+ from red. NAD

forming ethanOl (catalysed by ethanOl dehydrogenase)

oxidising red. NAD back to NAD+ ==> NAD+ can now accept more e- and glycolysis can continue

44
Q

why is alcoholic fermentation considered wasteful for the yeast?

A

CPE is trapped in the ethanOl ∴ it is wasted

45
Q

what is a respiratory substrate?

A

an organic molecule that can be oxidised in respiration to produce ATP

46
Q

why do different respiratory substrates produce different amounts of ATP?

A

have different amounts of hydrogen

∴ different number of H+ that can be pumped into the IMS

∴ different proton motive forces generated

∴ different numbers of ATP molecules can be produced

47
Q

name two cells that only use glucose as a respiratory substrate

A

brain cells

erythrocytes

48
Q

how are proteins converted and used as respiratory substrates?

A

excess amino acids are deaminated (removal of amino group –> converted to urea in ornithine cycle)

remainder of molecule is converted to glycogen or lipids for storage

during starvation, can be hydrolysed to release a.a.

49
Q

how are lipids converted and used as respiratory substrate?

A

triglycerides hydrolysed to 3 fatty acids and 1 glycerol

converted to glyceraldehyde

then pyruvate and respired

fatty acids broken down during B. oxidation to release acetyl groups –> join a CoA to form aCoA –> Krebs cycle

50
Q

what is the respiratory quotient (RQ)?

A

the ration of the volume of carbon dioxide evolved to that of oxygen consumed by an organism, tissue or cell in a given time

51
Q

what does the RQ indicate?

A

the type of respiratory substrate being used

52
Q

how is RQ calculated?

A

mol/vol of CO(2) evolved / mol/vol of O(2) taken up

53
Q

what is the RQ value for anaerobic conditions?

A

{infinitely large}

54
Q

what is the RQ value for carbohydrates?

A

1

55
Q

what is the RQ value for lipids?

A

0.70 - 0.72

56
Q

what is the RQ value for proteins?

A

0.80 - 0.90

57
Q

why is the RQ value for carbohydrates higher than proteins and lipids?

A

less oxygen is required to oxidise carbohydrates

Paper 2 Important topics (9 decks)

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