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PT663 > Metabolic Pathways > Flashcards

Metabolic Pathways Flashcards

1
Q

What is the primary function of muscles in relation to energy?

A

Muscles convert chemical energy into mechanical work.

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2
Q

How do muscles generate ATP?

A

Muscles and tissues catabolize fuel to break it down and regenerate ATP, which is the energy currency of the cell.

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3
Q

What is ATP, and what does it stand for?

A

ATP stands for adenosine triphosphate, consisting of an adenosine group and three phosphate groups.

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4
Q

What happens to ATP during muscle contraction?

A

ATP is broken down into ADP (adenosine diphosphate) and a free phosphate group.

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5
Q

What is the significance of the hydrolysis of ATP?

A

The hydrolysis of ATP releases free energy, which powers muscular contraction.

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6
Q

Write the equation that represents the breakdown of ATP.

A

ATP + water → ADP + free phosphate + free energy.

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7
Q

What is the role of free energy released from ATP hydrolysis in muscles?

A

It is used by the muscle to produce force and facilitate movement.

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8
Q

Where is the primary site for generating ATP in muscles?

A

The mitochondria.

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9
Q

What energy pathways do mitochondria in muscles utilize?

A

Aerobic pathways that require oxygen.

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10
Q

How are capillaries positioned in relation to muscle fibers and mitochondria?

A

Capillaries are closely positioned near mitochondria to supply blood and oxygen to the muscles.

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11
Q

Name the three types of muscle fibers discussed.

A

Type-I fibers, Type-IIa fibers, and Type-IIb fibers.

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12
Q

Which muscle fiber type has the highest mitochondrial density?

A

Type-I fibers.

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13
Q

How does mitochondrial density correlate with oxidative enzymes in muscle fibers?

A

Type-I fibers have the highest oxidative enzymes, while Type-IIb fibers have the lowest.

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14
Q

What is the relationship between capillary density and muscle fiber types?

A

Type-I fibers have the highest capillary density, while Type-II fibers have the lowest.

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15
Q

What is the fatigue resistance of Type-I fibers compared to Type-IIb fibers?

A

Type-I fibers are the most fatigue-resistant, while Type-IIb fibers are the most fatigable.

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16
Q

How do Type-I and Type-IIb fibers differ in force generation?

A

Type-I fibers generate force slowly and resist fatigue, whereas Type-IIb fibers generate force quickly and are more fatigable.

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17
Q

What is a key takeaway regarding muscle fiber types and their metabolic properties?

A

Different muscle fiber types have different metabolic properties that influence their mechanical performance.

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18
Q

What is the concentration of ATP in resting muscle?

A

Approximately 8 millimolar.

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19
Q

What is the rate of ATP consumption in resting muscle?

A

About 1 millimole per kilogram per minute.

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20
Q

How much ATP can heavily contracting muscle consume?

A

Up to 240 millimoles per kilogram per minute.

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21
Q

Name some processes that consume ATP in resting muscle.

A

Ion pumps (like sodium-potassium pump), calcium pumps, RNA and protein synthesis, fuel storage, transport of substances, and cell signaling pathways.

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22
Q

What additional ATP-consuming process occurs in contracting muscle?

A

Myosin ATPase hydrolyzes ATP to power mechanical work.

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23
Q

How do ATP levels remain stable during heavy contraction?

A

ATP is replenished at a similar rate to its consumption through three major pathways.

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24
Q

What are the three major pathways for ATP regeneration?

A

Phosphocreatine, anaerobic glycolysis, and oxidative phosphorylation.

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25
Q

How does phosphocreatine regenerate ATP?

A

Through the reaction: ADP + phosphocreatine + proton → ATP + creatine.

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26
Q

How quickly can phosphocreatine power activity?

A

For about 10 seconds.

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27
Q

What is the role of phosphocreatine in ATP levels during rapid ATP consumption?

A

It acts as a buffer and shuttles phosphate groups from mitochondria to myofibrils

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28
Q

What is anaerobic glycolysis?

A

The breakdown of carbohydrates to pyruvate and eventually lactate without consuming oxygen.

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29
Q

What transports glucose into the muscle during exercise?

A

Glucose transporters recruited by insulin and during exercise.

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30
Q

How many ATP does anaerobic glycolysis produce?

A

Two or three ATP, depending on whether glucose or glycogen is the source.

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31
Q

Why does anaerobic glycolysis have a limit?

A

Due to lactate buildup causing acidosis, which can inhibit cellular functions.

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32
Q

What is oxidative phosphorylation?

A

A process that uses a fuel source and oxygen to form ATP and produce carbon dioxide and water.

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33
Q

What is the relationship between oxygen consumption and oxidative phosphorylation?

A

The rate of oxygen consumption is proportional to the workload performed, measuring aerobic capacity.

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34
Q

Where do the TCA cycle and electron transport chain occur?

A

In the mitochondria.

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35
Q

What is the maximum power of phosphocreatine for ATP regeneration?

A

36 kilocalories per minute.

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36
Q

What is the maximum capacity of phosphocreatine?

A

About 11 kilocalories.

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37
Q

How long does it take for anaerobic glycolysis to reach its maximum rate?

A

About 5 to 10 seconds.

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38
Q

What is the maximum capacity of anaerobic glycolysis?

A

About 15 kilocalories before depletion.

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39
Q

How long does it take for oxidative phosphorylation to reach maximum rate?

A

About 2 to 3 minutes.

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40
Q

What is the maximum capacity of oxidative phosphorylation?

A

Approximately 2,000 kilocalories.

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41
Q

Which energy pathway is the dominant one during most daily activities?

A

Oxidative phosphorylation.

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42
Q

What is the dominant energy pathway during most daily activities?

A

Oxidative phosphorylation.

43
Q

What fuel sources can be used for oxidative phosphorylation?

A

Glucose (carbohydrates), lipids, and proteins.

44
Q

How is glucose stored in the muscle?

A

As glycogen.

45
Q

What happens to pyruvate during oxidative phosphorylation?

A

It is transferred to the mitochondria for use in the TCA cycle and electron transport chain.

46
Q

How many ATP molecules are generated from one molecule of glucose?

A

About 36 ATP molecules.

47
Q

What is the total energy capacity from muscle glycogen?

A

Approximately 500 kilocalories.

48
Q

What is lipolysis?

A

The breakdown of lipids into free fatty acids and glycerol.

49
Q

How do free fatty acids contribute to ATP regeneration?

A

They undergo beta oxidation, producing smaller substrates that enter the TCA cycle and electron transport chain.

50
Q

How many ATP molecules can be generated from one molecule of palmitic acid?

A

About 130 ATP molecules.

51
Q

How do proteins enter the oxidative phosphorylation pathway?

A

At various points along glycolysis, the TCA cycle, and the electron transport chain, depending on the protein source.

52
Q

What is the energy capacity from muscle protein?

A

Approximately 24,000 kilocalories.

53
Q

When is protein used as a significant energy source?

A

During periods of starvation.

54
Q

What happens to proteins during starvation?

A

They can undergo gluconeogenesis and significant muscle protein breakdown.

55
Q

Describe the general pathway for carbohydrates in oxidative phosphorylation.

A

Carbohydrates are broken down into glucose 6 phosphate, then glycolysis to pyruvic acid, acetyl-CoA, TCA cycle, and electron transport chain.

56
Q

Describe the general pathway for lipids in oxidative phosphorylation.

A

Lipids are broken down into fatty acids and glycerol, undergo beta oxidation to form acetyl-CoA, enter the TCA cycle, and the electron transport chain.

57
Q

How do proteins contribute to the nitrogen pool during oxidative phosphorylation?

A

Proteins are broken down and generate nitrogen that can enter the metabolic pathways at different stages.

58
Q

What do all fuel sources ultimately do in oxidative phosphorylation?

A

They provide energy to convert ADP and free phosphate into ATP.

59
Q

What is the relationship between exercise duration and the energy pathways used?

A

Short, high-intensity activities rely more on anaerobic pathways, while longer-duration activities rely more on aerobic pathways.

60
Q

During maximal exercise lasting a few seconds, which energy pathway is primarily used?

A

Anaerobic pathways.

61
Q

What happens to the reliance on aerobic pathways as exercise duration increases?

A

The reliance on aerobic pathways increases because anaerobic pathways have limited capacity.

62
Q

What fuels are primarily used during low-intensity exercise?

A

Plasma-free fatty acids and muscle triglycerides.

63
Q

How does fuel source contribution change with increased exercise intensity?

A

Lower intensity relies more on lipids, while higher intensity increases reliance on carbohydrates like muscle glycogen and plasma glucose.

64
Q

In the context of exercise duration, what is primarily utilized at rest?

A

Predominantly intramuscular sources and lipids.

65
Q

As exercise duration increases, what fuel source becomes more prominent?

A

Free fatty acids and lipids.

66
Q

For a 200 to 400-meter sprint, what energy pathways are primarily used?

A

A combination of phosphocreatine and anaerobic glycolysis.

67
Q

What is the primary fuel source during endurance events?

A

A combination of phosphocreatine, anaerobic glycolysis, and oxidative phosphorylation.

68
Q

How does the intensity of exercise affect the dominant fuel source?

A

As intensity increases, carbohydrates become the dominant fuel source; for lower intensity and longer duration, lipids are predominant.

69
Q

What is the significance of oxidative phosphorylation in energy production?

A

It allows the use of various fuel sources to regenerate ATP, especially during longer-duration activities.

70
Q

How do energy pathways integrate during physical activity?

A

Different pathways are utilized depending on the intensity and duration of the activity, transitioning from anaerobic to aerobic systems.

71
Q

What do plots of exercise intensity and duration show about energy sources?

A

Higher intensity leads to more carbohydrate use, while longer duration favors lipid utilization.

72
Q

What happens to ATP consumption during high-power activities?

A

ATP is consumed quickly, primarily using phosphocreatine for regeneration.

73
Q

How do anaerobic glycolysis and phosphocreatine function together in exercise?

A

They work together to quickly regenerate ATP during activities of moderate duration and high intensity.

74
Q

What are the two main types of training discussed in this segment?

A

Anaerobic training (high-intensity, short duration) and aerobic training (low-intensity, longer duration).

75
Q

What adaptations occur in anaerobic training?

A

Increased ATP concentration, phosphocreatine (PCr), creatine, muscle glycogen, and the quantity and activity of key glycolytic enzymes.

76
Q

Why is an increase in glycolytic enzymes important during anaerobic training?

A

They are essential for breaking down glucose to power anaerobic glycolysis and the conversion of glucose to pyruvate for oxidative phosphorylation.

77
Q

What metabolic changes occur with low-intensity, longer-duration training?

A

Increased number and volume of mitochondria, increased fat oxidation at rest and during submaximal exercise, and decreased reliance on glucose.

78
Q

How does training affect the use of fats and carbohydrates during exercise?

A

Increased reliance on fat and decreased reliance on glucose at submaximal exercise intensity.

79
Q

What happens to glycogen stores with increased training?

A

Training allows for preservation of glycogen stores, enhancing endurance due to the lower capacity of glycogen compared to lipids.

80
Q

What cardiovascular adaptations occur due to training?

A

Increased ventricular volume, greater stroke volume, increased cardiac output, decreased heart rate at rest and submaximal exercise, and improved vasodilation capacity.

81
Q

How does heart rate change with training during submaximal exercise?

A

Heart rate decreases at rest and during submaximal exercise, although maximum heart rate remains largely unchanged.

82
Q

What ventilatory changes occur with training?

A

Greater reliance on increased tidal volume rather than increased respiratory rate at submaximal exercise, allowing better oxygen diffusion and reducing the energy cost of breathing.

83
Q

Why is an increase in mitochondrial volume important for aerobic training?

A

It enhances oxidative phosphorylation, which is crucial for energy production during aerobic activities.

84
Q

How do catecholamine levels change with training during exercise?

A

Catecholamine levels decrease, which helps in preserving glycogen stores.

85
Q

What is the effect of training on the oxidation of carbohydrates at maximum exercise?

A

There is an increased ability to oxidize carbohydrates, along with an increase in glycogen content.

86
Q

How does training impact oxygen delivery to muscles?

A

Increased capacity for vasodilation enhances oxygen-rich blood delivery to active muscles.

87
Q

How does training change the balance between tidal volume and respiratory rate during exercise?

A

Training increases tidal volume while decreasing the reliance on respiratory rate, improving efficiency in oxygen diffusion.

88
Q

What is the overall goal of metabolic adaptations due to training?

A

To enhance energy efficiency, increase endurance, and improve overall physical performance.

89
Q

What is the impact of 30 days of bed rest on VO2 max?

A

There can be a 25% decline in VO2 max after 30 days of bed rest.

90
Q

What happens to heart rate during detraining?

A

Heart rate increases at rest and during submaximal exercise after bed rest.

91
Q

How does stroke volume change with bed rest?

A

Stroke volume declines, leading to greater reliance on heart rate to maintain cardiac output at submaximal levels.

92
Q

What changes occur in the balance between the parasympathetic and sympathetic nervous systems during detraining?

A

There is a decrease in parasympathetic nervous system activity, with variable changes in sympathetic nervous system activity.

93
Q

How does blood volume affect cardiovascular function during detraining?

A

Changes in blood volume lead to decreased central venous pressure, resulting in decreased cardiac filling and a reduction in stroke volume.

94
Q

What are the peripheral effects of bed rest on the cardiovascular system?

A

Loss of capillaries and decreased capacity for vasodilation, which reduces blood delivery to skeletal muscles and impacts oxygen delivery.

95
Q

What is the effect of detraining on muscle condition?

A

Muscle atrophy, decreased muscle protein synthesis, weakness, and decreased muscle endurance occur.

96
Q

What musculoskeletal changes can result from prolonged bed rest?

A

Changes in muscle length leading to joint contractures and loss of bone mineral density.

97
Q

What is a significant risk associated with decreased bone mineral density due to bed rest?

A

Increased risk of falls and fractures.

98
Q

What pulmonary issues can arise from bed rest?

A

Atelectasis (collapse of alveoli) and increased risk of pneumonia.

99
Q

How does the a-vO2 difference change during detraining?

A

Potential changes in the a-vO2 difference can occur due to decreased oxygen delivery from peripheral effects.

100
Q

What overall effects does bed rest have on the body?

A

Bed rest leads to significant changes across all systems of the body, affecting cardiovascular, muscular, pulmonary, and overall physiological function.

101
Q

How does bed rest affect muscle endurance?

A

There is a decrease in muscle endurance as a result of detraining.

102
Q

What role does norepinephrine play during detraining?

A

There is greater responsiveness to beta receptor activation and norepinephrine, which can influence cardiovascular responses.

103
Q

What contributes to the decline in peak VO2 during detraining?

A

Increased heart rate, decreased stroke volume, and potential changes in the a-vO2 difference contribute to the decline in peak VO2.

104
Q
A

PT663 (22 decks)

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