Metabolic Pathways

Question 1

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

Answer 1

Muscles convert chemical energy into mechanical work.

Question 2

How do muscles generate ATP?

Answer 2

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

Question 3

What is ATP, and what does it stand for?

Answer 3

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

Question 4

What happens to ATP during muscle contraction?

Answer 4

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

Question 5

What is the significance of the hydrolysis of ATP?

Answer 5

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

Question 6

Write the equation that represents the breakdown of ATP.

Answer 6

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

Question 7

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

Answer 7

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

Question 8

Where is the primary site for generating ATP in muscles?

Answer 8

The mitochondria.

Question 9

What energy pathways do mitochondria in muscles utilize?

Answer 9

Aerobic pathways that require oxygen.

Question 10

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

Answer 10

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

Question 11

Name the three types of muscle fibers discussed.

Answer 11

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

Question 12

Which muscle fiber type has the highest mitochondrial density?

Answer 12

Type-I fibers.

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

What is the concentration of ATP in resting muscle?

Answer 18

Approximately 8 millimolar.

Question 19

What is the rate of ATP consumption in resting muscle?

Answer 19

About 1 millimole per kilogram per minute.

Question 20

How much ATP can heavily contracting muscle consume?

Answer 20

Up to 240 millimoles per kilogram per minute.

Question 21

Name some processes that consume ATP in resting muscle.

Answer 21

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

Question 22

What additional ATP-consuming process occurs in contracting muscle?

Answer 22

Myosin ATPase hydrolyzes ATP to power mechanical work.

Question 23

How do ATP levels remain stable during heavy contraction?

Answer 23

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

Question 24

What are the three major pathways for ATP regeneration?

Answer 24

Phosphocreatine, anaerobic glycolysis, and oxidative phosphorylation.

Question 25

How does phosphocreatine regenerate ATP?

Answer 25

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

Question 26

How quickly can phosphocreatine power activity?

Answer 26

For about 10 seconds.

Question 27

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

Answer 27

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

Question 28

What is anaerobic glycolysis?

Answer 28

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

Question 29

What transports glucose into the muscle during exercise?

Answer 29

Glucose transporters recruited by insulin and during exercise.

Question 30

How many ATP does anaerobic glycolysis produce?

Answer 30

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

Question 31

Why does anaerobic glycolysis have a limit?

Answer 31

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

Question 32

What is oxidative phosphorylation?

Answer 32

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

Question 33

What is the relationship between oxygen consumption and oxidative phosphorylation?

Answer 33

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

Question 34

Where do the TCA cycle and electron transport chain occur?

Answer 34

In the mitochondria.

Question 35

What is the maximum power of phosphocreatine for ATP regeneration?

Answer 35

36 kilocalories per minute.

Question 36

What is the maximum capacity of phosphocreatine?

Answer 36

About 11 kilocalories.

Question 37

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

Answer 37

About 5 to 10 seconds.

Question 38

What is the maximum capacity of anaerobic glycolysis?

Answer 38

About 15 kilocalories before depletion.

Question 39

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

Answer 39

About 2 to 3 minutes.

Question 40

What is the maximum capacity of oxidative phosphorylation?

Answer 40

Approximately 2,000 kilocalories.

Question 41

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

Answer 41

Oxidative phosphorylation.

Question 42

What is the dominant energy pathway during most daily activities?

Answer 42

Oxidative phosphorylation.

Question 43

What fuel sources can be used for oxidative phosphorylation?

Answer 43

Glucose (carbohydrates), lipids, and proteins.

Question 44

How is glucose stored in the muscle?

Answer 44

As glycogen.

Question 45

What happens to pyruvate during oxidative phosphorylation?

Answer 45

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

Question 46

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

Answer 46

About 36 ATP molecules.

Question 47

What is the total energy capacity from muscle glycogen?

Answer 47

Approximately 500 kilocalories.

Question 48

What is lipolysis?

Answer 48

The breakdown of lipids into free fatty acids and glycerol.

Question 49

How do free fatty acids contribute to ATP regeneration?

Answer 49

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

Question 50

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

Answer 50

About 130 ATP molecules.

Question 51

How do proteins enter the oxidative phosphorylation pathway?

Answer 51

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

Question 52

What is the energy capacity from muscle protein?

Answer 52

Approximately 24,000 kilocalories.

Question 53

When is protein used as a significant energy source?

Answer 53

During periods of starvation.

Question 54

What happens to proteins during starvation?

Answer 54

They can undergo gluconeogenesis and significant muscle protein breakdown.

Question 55

Describe the general pathway for carbohydrates in oxidative phosphorylation.

Answer 55

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

Question 56

Describe the general pathway for lipids in oxidative phosphorylation.

Answer 56

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.

Question 57

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

Answer 57

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

Question 58

What do all fuel sources ultimately do in oxidative phosphorylation?

Answer 58

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

Question 59

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

Answer 59

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

Question 60

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

Answer 60

Anaerobic pathways.

Question 61

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

Answer 61

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

Question 62

What fuels are primarily used during low-intensity exercise?

Answer 62

Plasma-free fatty acids and muscle triglycerides.

Question 63

How does fuel source contribution change with increased exercise intensity?

Answer 63

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

Question 64

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

Answer 64

Predominantly intramuscular sources and lipids.

Question 65

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

Answer 65

Free fatty acids and lipids.

Question 66

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

Answer 66

A combination of phosphocreatine and anaerobic glycolysis.

Question 67

What is the primary fuel source during endurance events?

Answer 67

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

Question 68

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

Answer 68

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

Question 69

What is the significance of oxidative phosphorylation in energy production?

Answer 69

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

Question 70

How do energy pathways integrate during physical activity?

Answer 70

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

Question 71

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

Answer 71

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

Question 72

What happens to ATP consumption during high-power activities?

Answer 72

ATP is consumed quickly, primarily using phosphocreatine for regeneration.

Question 73

How do anaerobic glycolysis and phosphocreatine function together in exercise?

Answer 73

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

Question 74

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

Answer 74

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

Question 75

What adaptations occur in anaerobic training?

Answer 75

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

Question 76

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

Answer 76

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

Question 77

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

Answer 77

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

Question 78

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

Answer 78

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

Question 79

What happens to glycogen stores with increased training?

Answer 79

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

Question 80

What cardiovascular adaptations occur due to training?

Answer 80

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

Question 81

How does heart rate change with training during submaximal exercise?

Answer 81

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

Question 82

What ventilatory changes occur with training?

Answer 82

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.

Question 83

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

Answer 83

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

Question 84

How do catecholamine levels change with training during exercise?

Answer 84

Catecholamine levels decrease, which helps in preserving glycogen stores.

Question 85

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

Answer 85

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

Question 86

How does training impact oxygen delivery to muscles?

Answer 86

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

Question 87

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

Answer 87

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

Question 88

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

Answer 88

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

Question 89

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

Answer 89

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

Question 90

What happens to heart rate during detraining?

Answer 90

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

Question 91

How does stroke volume change with bed rest?

Answer 91

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

Question 92

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

Answer 92

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

Question 93

How does blood volume affect cardiovascular function during detraining?

Answer 93

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

Question 94

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

Answer 94

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

Question 95

What is the effect of detraining on muscle condition?

Answer 95

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

Question 96

What musculoskeletal changes can result from prolonged bed rest?

Answer 96

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

Question 97

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

Answer 97

Increased risk of falls and fractures.

Question 98

What pulmonary issues can arise from bed rest?

Answer 98

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

Question 99

How does the a-vO2 difference change during detraining?

Answer 99

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

Question 100

What overall effects does bed rest have on the body?

Answer 100

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

Question 101

How does bed rest affect muscle endurance?

Answer 101

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

Question 102

What role does norepinephrine play during detraining?

Answer 102

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

Question 103

What contributes to the decline in peak VO2 during detraining?

Answer 103

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