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Exercise Physiology > Chapter 3/4: Bioenergetics and Exercise Metabolism > Flashcards

Chapter 3/4: Bioenergetics and Exercise Metabolism Flashcards

1
Q

1 g of carbohydrates yields

A

4 kcal of energy

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2
Q

1 g of fat yields

A

9.5 kcal of energy

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3
Q

1 g of protein yields

A

4 kcal of energy

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4
Q

storage form and location for carbohydrates

A

glycogen in the liver & muscle

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5
Q

define glycogenesis. performed by what enzyme?

A

synthesis of glycogen by glycogen synthase

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6
Q

define glycogenolysis. performed by what enzyme?

A

breakdown of glycogen to glucose by glycogen phosphorylase

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7
Q

define gluconeogenesis

A

synthesis of glucose from non-carb sources (e.g. amino acids or lactate)

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8
Q

define glycolysis

A

breakdown of glucose to pyruvate or lactate; mediated by the rate-limiting enzyme phosphofructose kinase

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9
Q

storage form and location for fats

A

stored as triglycerides in muscle and adipose tissue

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10
Q

define lipogenesis

A

synthesis of triglycerides from glycerol and free fatty acids

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11
Q

define lipolysis. performed by what enzyme?

A

breakdown of triglycerides into glycerol and free fatty acids by lipases

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12
Q

which component of triglycerides is not an important muscle fuel during exercise?

A

glycerol

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13
Q

define beta-oxidation

A

breakdown of free fatty acids to acetyl coA, which then enters the Krebs cycle

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14
Q

when are proteins used as an energy source?

A

extreme endurance races or starvation

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15
Q

how are proteins used as an energy source?

A

muscles can directly metabolize branch chain amino acids and alanine; the liver can convert alanine to glucose

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16
Q

define lactate shuttle

A

lactate produced in one tissue and transported to another is converted to acetyl-CoA and enters the Krebs cycle

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17
Q

define Cori cycle

A

lactate can be converted to glucose in the liver

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18
Q

how much ATP do we have in storage?

A

store only small amounts (~100 g) until needed; body must constantly synthesize new ATP

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19
Q

does the synthesis of ATP require oxygen

A

can occur in the presence or absence of oxygen

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20
Q

formula for the synthesis of ATP

A

ADP + Pi + energy —> ATP

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21
Q

formula for the breakdown of ATP

A

ATP + water (ATPase) —> ADP + Pi + energy

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22
Q

3 ATP synthesis pathways

A

1) ATP-PC system
2) glycolysis
3) oxidative phosphorylation

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23
Q

does the ATP-PC system require oxygen

A

no; anaerobic

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24
Q

ATP yield of the ATP-PC system

A

1 mol ATP / 1 mol phosphocreatine

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25
Q

duration (of energy) provided by the ATP-PC system

A

1-5 sec of maximal exercise (striking matches)

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26
Q

when is the ATP-PC pathway used

A

used to reassemble ATP because ATP stores are limited

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27
Q

what can phosphocreatine NOT be used for? what can it be used for?

A

PC cannot be used for cellular work, but it can be used to reassemble ATP

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28
Q

what does the ATP-PC system provide energy for

A

muscular contraction at the onset of exercise and during short-term, maximal exercise

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29
Q

does glycolysis need oxygen?

A

no; anaerobic

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30
Q

ATP yield of glycolysis

A

2-3 mol ATP / 1 mol substrate

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31
Q

duration (of energy) for glycolysis ?

A

intense exercise longer than 5 seconds

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32
Q

substrate and products of glycolysis

A

breakdown of glucose to 2 pyruvic acid or 2 lactic acid

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33
Q

what is the difference between using glucose and glycogen as the substrate for glycolysis?

A

if you use glucose, you must convert it to glucose-6-phosphate, which requires the input of 1 ATP

if you use glycogen, the phosphate is already present on the glucose and doesn’t require any ATP input

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34
Q

where does glycolysis occur

A

cytoplasm

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35
Q

rate limiting enzyme for glycolysis

A

phosphofructose kinase

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36
Q

pros of glycolysis

A

allows muscles to contract with limited O2, permits shorter term, higher-intensity exercise (up to 45 sec) than oxidative metabolism can sustain (because it is much faster)

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37
Q

cons of glycolysis

A

low ATP yield, inefficient use of substrate, lack of O2 converts pyruvate acid to lactic acid which increase H+ conc. and impairs glycolysis and muscle contraction

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38
Q

why is pyruvate converted to lactate at the end of glycolysis?

A

the conversion of pyruvate to lactic acid converts one NADH to NAD+ which allows glycolysis to continue (also donates H+ to pyruvate to make lactic acid)

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39
Q

what happens to lactic acid immediately?

A

dissociates into lactate and H+, which changes pH

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40
Q

does oxidative phosphorylation require oxygen

A

yes, aerobic

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41
Q

ATP yield of oxidative phosphorylation

A

depends on the substrate
32 ATP/ glucose
33 ATP / glycogen
100+ ATP / 1 FFA

42
Q

duration (of energy) provided by oxidative phosphorylation

A

steady supply for hours

43
Q

where does oxidative phosphorylation occur

A

mitochondria

44
Q

3 steps of oxidation of carbohydrates

A

1) glycolysis
2) Krebs cycle
3) electron transport chain

45
Q

what is the energy yield of the Krebs cycle? for one molecule of glucose?

A

3 NADH, 1 FADH2, 1 GTP
but runs through 2 acetyl-coA so 6 NADH, 2 FADH2, 2 GTP

46
Q

energy equivalents of NADH and FADH2

A

2.5 ATP per NADH
1.5 ATP per FADH2

47
Q

how does the electron transport chain generate ATP?

A

H+ carried to electron transport chain via NADH and FADH molecules, where H+ electrons travel down the chain creating a conc. gradient, H+ combines with O2 to form H2O; conc gradient is used to make ATP

48
Q

energy breakdown of oxidation of a carbohydrate

A

glycolysis: +2 or +3 ATP
GTP from Krebs: +2 ATP
10 NADH = +25 ATP
2 FADH = +3 ATP

49
Q

which is faster, oxidation of fat or oxidation of carbs?

A

oxidation of carbs

50
Q

beta-oxidation substrates and products

A

converts free fatty acids to acetyl-coA so that it can enter the Krebs cycle

51
Q

how much ATP does B-oxidation cost?

A

2 ATP

52
Q

does oxidation of fats or oxidation of carbs require more oxygen?

A

oxidation of fats

53
Q

how many ATP are generated per B-oxidation cycle?

A

14 ATP

54
Q

how to calculate net yield of ATP from beta oxidation of a free fatty acid

A

total ATP = (n-1)*14 + 10 - 2
where n = number of acetyl CoA molecules

55
Q

list the energy systems in order of fastest rate of ATP generation to slowest rate of ATP generation

A

ATP-PC, glycolysis, CHO oxidation, fat oxidation

56
Q

list the energy systems in order of most maximal available energy to least maximal available energy

A

fat oxidation, CHO oxidation, glycolysis, ATP-PC

57
Q

formula for respiratory exchange rate (RER)
what conditions have to be met for this formula to be used?

A

R = volume of CO2 produced / volume of O2 consumed
subject must have reached steady state

58
Q

R for fat

A

= 16 CO2/ 23 O2 = 0.70

59
Q

R for carbohydrate

A

= 6 CO2/ 6 O2= 1.00

60
Q

is it physiologically possible for R to be outside the range 0.70-1.00?

A

yes, VO2 will not change but VCO2 can change if the body uses the bicarbonate buffering reaction to create CO2

61
Q

during the rest-to exercise transition, what pathways initially produces ATP?

A

ATP-PC system and glycolysis

62
Q

how quickly does oxygen uptake reach steady state? what pathway of ATP production is used once steady state is reached?

A

1-4 minutes; aerobic ATP production

63
Q

what is the oxygen deficit?

A

lag in oxygen uptake at the beginning of exercise; O2 demand > O2 consumed

64
Q

how does training change the oxygen deficit?

A

faster rise in VO2 curve and steady state is reached earlier; energy requirement can be met by oxidative ATP production at the onset of exercise

65
Q

what does having a lower oxygen deficit result in?

A

less lactate and H+ formation & less PC depletion

66
Q

what kind of energy systems contribute more during short-term, high-intensity activities?

A

anaerobic energy systems (ATP-PC and glycolysis)

67
Q

what kind of energy systems contribute more during long-term, low-intensity exercise?

A

aerobic energy systems (oxidative phosphorylation)

68
Q

where does energy come from during the first 1-5 seconds of short-term, high-intensity exercise?

A

ATP-PC system

69
Q

where does energy come from after 5 seconds during short-term, high-intensity exercise?

A

shifts to ATP production via glycolysis

70
Q

where does energy come from when an event last longer than 45 seconds during short-term, high-intensity exercise?

A

ATP production through ATP-PC, glycolysis, and aerobic systems

71
Q

percent contribution of aerobic/anaerobic sources at 60 seconds of short-term, high-intensity exercise?

A

70% anaerobic, 30% aerobic

72
Q

percent contribution of aerobic/anaerobic sources at 2-3 mins of short-term, high-intensity exercise?

A

50% anaerobic, 50% aerobic

73
Q

where does energy come from during prolonged exercise (> 10 mins) in a cool environment?

A

primarily aerobic metabolism, steady state oxygen uptake can generally be maintained during submaximal exercise (below lactate threshold)

74
Q

describe the concept of upward drift

A

there is an upward drift in oxygen uptake over time in hot and humid environments, steady state is not obtained

75
Q

what is upward drift due to?

A

rising body temp, and increasing Epi and NE

76
Q

during prolonged, low intensity exercise, how does fuel selection change?

A

shift from CHO metabolism to fat metabolism

77
Q

why does fuel selection shift towards fats during prolonged, low-intensity exercise?

A

increased rate of lipolysis via lipases which is stimulated by rising levels of Epi

78
Q

during prolonged exercise at the same intensity, how does fuel utilization of trained athletes differ from those less fit?

A

trained athletes use more fat and less CHO

79
Q

during graded exercise, what energy source is primarily used?

A

ATP production primarily from aerobic metabolism

80
Q

how does oxygen uptake change during a graded exercise with increasing work rate?

A

oxygen uptake increases linearly until VO2 max is reached

81
Q

what is VO2 max? what is it influenced by?

A

“physiological ceiling” for delivery of O2 to muscles; influenced by genetics and training

82
Q

2 physiological factors influencing VO2 max

A

1) maximum ability of cardiorespiratory system to deliver oxygen to the muscle
2) ability of muscles to use oxygen to produce ATP aerobically

83
Q

what is the primary fuel for low intensity exercise (<30% VO2 max)?

A

fats

84
Q

what is the primary fuel used for high-intensity exercise (>70% VO2 max)?

A

carbs

85
Q

describe the crossover concept

A

the shift from fat to carb metabolism as exercise intensity increases

86
Q

why does the crossover concept happen?

A

1) recruitment of fast muscle fibers that are better equipped to metabolize carbs than fats
2) increasing blood levels of Epi stimulate glycogenolysis

87
Q

how does training affect the crossover concept?

A

increases utilization of fat and sparing of plasma glucose and muscle glycogen (crossover shifts right)

88
Q

what is the lactate threshold?

A

work rate at which blood lactic acid rises systematically during graded exercise

89
Q

where does the lactate threshold appear for untrained subjects?

A

50-60% VO2 max

90
Q

where does the lactate threshold appear for trained subjects?

A

65-85% VO2 max

91
Q

what may contribute to the sudden increase in blood lactate levels?

A

accelerated glycolysis, recruitment of fast-twitch fibers, and reduced rate of lactate removal

92
Q

how is lactate threshold useful in planning training programs?

A

training near (just below) lactate threshold is effective in shifting the lactate threshold to the right

93
Q

how can you use lactate threshold to estimate a 10k race time?

A

1) plot blood lactate vs VO2, determine VO2 at Lactate threshold
2) plot VO2 vs running speed, determine speed at lactate threshold
3) race pace at 5 m/min above LT
4) 10k time (min) = 10,000m/ (speed at LT m/min + 5 m/min)

94
Q

what is the underlying issue in McArdle’s disease

A

cannot synthesize enzyme glycogen phosphorylase, inability to breakdown muscle glycogen

95
Q

do lactate levels rise in McArdle’s patients?

A

no

96
Q

why can’t McArdle’s patients oxidize more fat?

A

reduced rate of glycolysis —> reduced production of pyruvate —> reduced Krebs cycle intermediates —> reduced fat oxidation

97
Q

when is the highest rate of fat oxidation reached?

A

just before lactate threshold

98
Q

what is excess post-exercise oxygen consumption (EPOC)

A

O2 consumed > O2 demand

99
Q

factors contributing to the rapid portion of EPOC

A

resynthesis of PC in muscle & restoration of muscle and blood oxygen stores

100
Q

factors contributing to the slow portion of EPOC

A

lactate conversion to glucose, elevated body temp, post-exercise elevation of HR and breathing, elevated hormones

Exercise Physiology (25 decks)

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