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Exercise & Environment > Control of energy requirements of muscle > Flashcards

Control of energy requirements of muscle Flashcards

1
Q

energy flow

A
  • sunlight provides energy
  • energy trapped in organic molecules
  • organisms utilise the organic molecules to obtain energy
  • humans are 25% effcient
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2
Q

how energy efficient are humans

A

25% - rest is heat loss

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3
Q

what are the methods of providing energy to muscle without intake

A
  • ATP is immediate fuel supply
  • aerobic pathway
  • anaerobic pathway
  • long term stores in glycogen and TAG
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4
Q

muscles ATP consumption

A
  • avidly consume ATP using actomyosin ATPase and calcium pump ATPase
  • when activated, muscle metabolic rate increases more than 100-fold
  • if muscles become depleted of ATP they would go into state of rigour mortis
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5
Q

what would happen if muscles depleted of ATP

A

Rigour mortis

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6
Q

what happens to metabolic rate of muscle when activated

A

increases more than 100 fold

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7
Q

how do muscles consume ATP

A

using actomyosin ATPase and calcium pump ATPase

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8
Q

how is rigour mortis avoided

A
  • range of mechanisms to supply ATP accourding to needs of speed and endurance
  • store lots of energy within each muscle
  • range of fatigue mechanisms to ensure ATP isn’t critically depleted
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9
Q

PCr

A

phosphocreatine

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10
Q

what is ATP and PCr are measure of

A

energy turnover

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11
Q

what can be used to measure energy turnover

A

ATP and PCr

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12
Q

how to measure ATP and PCr

A

biopsy of tissue taken post exercise & rapidly frozen. then assay for

  • ATP
  • PCr
  • Lactate
  • Glycogen
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13
Q

problems with tissue biopsy for measuring energy turnover

A
  • invasive

- limited points that this can be done

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14
Q

Alternative method of assesing ATP and PCr levels

A

31P NMR spectroscopy of ATP, PCr and pH

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15
Q

pros and cons of 31P NMR spectroscopy

A

pros: non invasive and measures muscle metabolism
cons: poor time resolution and limited variation of tasks

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16
Q

what happens to ATP levels during exercise

A

they fall, but not dramatically

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17
Q

ATP stores are sufficient for work for how long

A

couple of seconds

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18
Q

how is ATP recharged

A

resynthesises from ADP by:

  • substrate level phosphorylation
  • oxidative phosphorylation
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19
Q

substrate level phosphorylation

A
  • enzyme transfers phosphate from organic P to ADP
  • from phosphocreatine OR
  • glucose (glycolysis&TCA)
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20
Q

oxidative phosphorylsation

A

energy from electrons pulled from organic molecules used to synthesis ATP

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21
Q

what is an indirect marker of muscle damage

A

creatine kinase (CPK)

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22
Q

reaction for yielding ATP from PCr

A

ADP + PCr + H+ -> Cr + ATP

enzyme: creatine kinase

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23
Q

what activates ATP synthesis using PCr

A

creatine kinase is always activated

a momentary rise in ADP is the stimulus for PCr hydrolysis

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24
Q

what is the temporal buffer for reductions in ATP

A

resynthesis of ATP using PCr

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25
Q

what does PCr buffer

A

ATP reductions
pH
partial buffer to move ~P from mitochondria to cross bridge

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26
Q

what does Pi release do

A
  • stimulates glycolysis
  • glycolysis regulates [ADP] and drives TCA
    BUT
    high Pi induces fatigue
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27
Q

what happens to muscle PCr during intermittent exercise

A

levels will oscillate

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28
Q

When does oxidate phosphorylation occur

A

cases of prolonged exercise

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29
Q

what restores PCr during recover

A

oxidate phosphorylation

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30
Q

benefit of creatine supplementation

A

if creatine stores increase, can increase energy store to longer than 10 seconds of vigorous exercise
- will also relate to faster recovery from aerobic exercise

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31
Q

2 other reactions of ADP

A

2ADP -> ATP+AMP
- myokinase reaction
AMP -> IMP + NH3

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32
Q

2ADP -> ATP+AMP

A

myokinase reaction
AMP is a metabolic byproduct and a stimulus
increase AMP acts as an energy crisis signal in muscle to activate AMP kinase

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33
Q

what is an energy crisis signal to the muscle

A

increased AMP - activates AMP kinase

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34
Q

AMP -> IMP + NH3

A

AMP can be deaminated giving inosine monophosphate and ammonia
together, creatine kinase and adenylate kinase act as a temporal buffer of ATP during anerobic contraction

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35
Q

what are the temporal buffers of [ATP] during anaerobic contraction

A

creatine kinase

adenylate kinase

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36
Q

when are creatine kinase and adenylate kinase the temporal buffers of [ATP]

A

during anaerobic contraction

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37
Q

adenylate kinase

A

catalysis the conversion of 2ADP to AMP and ATP

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38
Q

creatine kinase

A

catalysis conversion of ADP to ATP, using PCr

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39
Q

how does ATP sit in the hierarchy of energy supply

A

Instantly available but only in short supply

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40
Q

how does PCr sit in the hierarchy of energy supply

A

PCr rapidly produces ATP, and there is more PCr than ATP

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41
Q

energetic limitations of muscle power

A

maximum power output that human can achieve and sustain falls as the duration of effort increases

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42
Q

exercising for hours requires

A

lower power output over a long period of time

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43
Q

exercising for sprints requires

A

higher power output over a shorter period of time

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44
Q

method of providing energy to muscle for maintaining high rate of work once PCr supply has been exhausted

A

glycolysis

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45
Q

what is glycolysis

A

anaerobic process of degrading glucose or G1P to pyruvate and lactate

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46
Q

when does glycolysis start in exercise

A

immediately, but takes ~5s for max rate of ATP production tto be reached

47
Q

what triggers glycolysis in exercise

A

increased [ADP]

48
Q

what limits glycolysis

A

acidosis from H+ production

fatigue or Na+ depletion

49
Q

storage of glucose

A

polymers of glucose are stored as granules of glycogen in the muscle and liver. Levels of both PCr and glycogen are manipulable by diet

50
Q

Energy input and output of glycolysis

A

net = 2 ATP, 2NADH + 2H+
(2 pyruvate)
- investment phase needs 2 ATP from 1 glucose
- pay off phase produces 4 ATP and 2NADH

51
Q

how much energy from a glucose molecule is extracted by glycolysis

A

2 ATP

only 10% of energy of glucose molecule. this is a pay off for convenience of supplying high power quickly

52
Q

what happens to NADH and H+ produced by glycolysis

A

they are electron carriers that feed into mitochondria

53
Q

lactate shuttle

A
  • recruitment of TII glycolytic fibres at high exercise intensity increases lactate production
  • lactate is used as fuel by the heart and oxidative skeletal muscle, and a substrate for glucose production in the liver to recreate and store energy
54
Q

cori cycle

A

recreates and stores energy

  • glycogen in the muscle undergoes glycolysis to produce lactate
  • lactate travels in blood to the liver
  • lactate in the liver undergoes gluceoneogenesis to produce glucose
  • glucose travels in blood to muscle
55
Q

presence of lactate transporters

A

TI slow fibres: lots of MCTI lactate transporter, has a low km of 3.5 so saturates and acts as H+ regulator for lactate uptake

TII fast fibres have lots of MCT4, with high km of 35, so act to export even high levels of lactate from muscle. Important bc TII fibres involved in lots of glycolysis

56
Q

MCT4

A

expressed in TII

lactate transporter with high km 35mM to export lactate even at high levels

57
Q

MCT1

A

expressed in TI

lactate transporter with low km 3.5 so saturate and act as H+ regulator for lactate uptake

58
Q

how does glycolysis sit in heiracry of energy suppy

A

glycolysis is available fairly quickly and produces a more reasonable amount of ATP but has by products that causes acidosis which is limiting

59
Q

what is the limiting factor of glycolysis

A

how much bodies can tolerate because of H+ produced, we cannot withstand acidosis.

CHO supply is NOT the limiting factor of glycolysis

60
Q

how to provide energy to muscle for prolonged periods of work

A

2nd method of ATP synthesis

= TCA cycle and oxidative phosphorylation

61
Q

how does TCA cycle and oxidative phosphorylation provide energy

A

energy from electrons pulled from organic molecules to synthesise ATP

62
Q

what is the site of oxidative phosphorylation

A

mitochondria

63
Q

where are the enzymes for beta oxidation, TCA cycle, ETC located

A

inside mitochondira

64
Q

does TCA cycle produce lots of ATP

A

directly - No

Indirectly - yes, creates the environment fo oxidative phosphorylation which produces lots of energy :)

65
Q

does TCA cycle require oxygen

A

nope

66
Q

products of TCA cycle per 1 glucose

A

6 CO2
8 NADH + H+
2 FADH2
2 ATP

67
Q

products of TCA cycle per 1 pyruvate

A

3 CO2
4 NADH + H+
1 FADH2
1 ATP

68
Q

ATP accumulator from one glucose molecules after TCA

A

4

2 from glycolysis, 2 from TCA

69
Q

cellular respiration reaction and energy production

A

Glucose + oxygen -> carbon dioxide + water

produces energy and heat
38 ATP

70
Q

final step of oxidative phosphoryation

A

chemiosmosis

71
Q

what molecular machine drives ATP synthesis in chemiosmosis

A

ATP synthase

72
Q

where is ATP synthase

A

cristae of mitochondria

73
Q

how does ATP synthase work

A
  • H+ gradient provides the energy for ATP synthesis
  • H+ gradient develops between IMS and matrix as electrons move along the ETC
  • H+ gradient used to pump protons from the matrix to the IMS
  • [H+] is the proton motive force which creates ATP from ADP and Pi
74
Q

proton motive force

A

[H+]

75
Q

where does H+ gradient develop in ETC

A

between IMS and matrix, with H+ moving out to IMS

76
Q

IMS

A

inter membrane space

77
Q

products of oxidative phosphorylation from one glucose molecules

A 
3 ATP for every NADH
= 10 X 3
2 ATP for every FADH2
= 2 x 2
- 6 oxygen 
= 34 ATP
78
Q

ATP accumulator from one glucose molecules after oxidative phosphorylation

A

38
2 from glycolysis
2 from TCA
34 for oxidative phosphorylation

79
Q

where does oxidative phosphorylation sit in the hierarchy of energy supply

A

happens at a limited rate but produces a very large amount of ATP

80
Q

Control of cellular respiration

A

feedback allows for inhibitor or stimulation by key enzymes e.g:
phosphofructokinase is pH dependent and is inhibited in acidosis in order to limit glycolysis to maintain body’s pH set point

81
Q

when is phosphofructokinase inhibited

A

acidosis

82
Q

what does inhibition of phosphofructokinase do

A

limits glycolysis when pH id dropping to much to save from acidosis

83
Q

energy provision of long duration low power exercise

A

fatty acids undergo beta oxidation to produce actyl coA to enter the TCA cycle to feed ETC for ATP production

84
Q

where are lipid droplets for exercise fuel stored

A

muscle and can be regulated by diet and training

85
Q

what does high lipid content in muscle mean

A

opposing things:

  • obesity with danger of diabetes and CVD
  • well trained endurance athlete
86
Q

energy provided from TAG

A

18c FA gives 147 ATP
TAG has 3 FA = 441 ATP
+ 19 ATP from breakdown
= 460 ATP

87
Q

state of lipids when stored

A

dry

highly hydrophobic, typical adipocyte contains 90% of its total weight as pure TAG

88
Q

state of glycogen when stored

A

wet

hydrophilic, exists in hydrated granules and 65% of total weight is water

89
Q

what is the better energy store/ CHO or fat

A

5 x better than CHO as energy store because of their capacity /density

90
Q

how much glycogen per 1kg wet muscle

A

15-18g

91
Q

how much intramuscular fat per 1kg wet muscle

A

20g

92
Q

extramuscular fat stores

A

adipose tissue ~15kg, AKA 140,000 kcal

93
Q

where does fatty acid oxidation sit in heirarchy of energy supply

A

happens at a very limited rate but produces a huge amount of ATP

94
Q

power and capacity of anaerobic energetic processes

A

High power: PCr, glycolysis

Low capacity: limited supply

95
Q

power and capacity of aerobic energetic processes

A

low power: oxidative phosphorylation and beta oxidation

high capacity: unlimited supply

96
Q

respiratory exchange ratio

A

inform us which fuels are being used. CHO is oxidised with a RQ of 1

97
Q

why is CHO RQ 1

A

6 molecules of oxygen are used to produce glucose, which produces 6 molecules of carbon dioxide

98
Q

what is the RQ of CHO

A

1

99
Q

what is the RQ of Fat

A

0.71

100
Q

why is fat RQ 0.71

A

23 molecules of oxygen are used for fat oxidation, producing 16 molecules of carbon dioxide

101
Q

what physiological function do we match to energy demand

A

breathing and cardiac output (HR and stroke volume)

102
Q

what measure is a reflection of mitochondrial activity

A

VO2 and VCO2

103
Q

What are VO2 and VCO2 a measure of

A

mitochondrial activity and they are very trainable

104
Q

fuel supply in low intensity exercise

A

mostly FA

105
Q

fuel supply in medium intensity exercise

A

start to use TAG and glycogen

106
Q

fuel supply in high intensity exercise

A

lots of muscle glycogen

107
Q

difference between fuel source of fit and unfit person

A

unfit person first burns glycogen

fit person rapidly swithes from glycogen to uses lipolysis of FA

108
Q

glycogen sparing

A

a trained individual will burn fat preferentially when working out at the same rate as an unfit person who will burn CHO

this is an important training adaptation

109
Q

how to manipulate muscle glycogen

A

diet and exercise

high CHO can double both glycogen stores and duration before exhaustion = basis of CHO loading

110
Q

rapid, short lasting fuel supplies

A

PCr

111
Q

slower but more abundant fuel supplies for exercise

A

fat oxidation

112
Q

training will alter muscle metabolism to favour

A

fat utilisation, whilst sparing glycogen

113
Q

what helps favour aerobic respiration (fat metabolism)

A

increase in local muscle blood supply

more mitochondria

Exercise & Environment (14 decks)

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