Metabolic Pathways Flashcards
What is the primary function of muscles in relation to energy?
Muscles convert chemical energy into mechanical work.
How do muscles generate ATP?
Muscles and tissues catabolize fuel to break it down and regenerate ATP, which is the energy currency of the cell.
What is ATP, and what does it stand for?
ATP stands for adenosine triphosphate, consisting of an adenosine group and three phosphate groups.
What happens to ATP during muscle contraction?
ATP is broken down into ADP (adenosine diphosphate) and a free phosphate group.
What is the significance of the hydrolysis of ATP?
The hydrolysis of ATP releases free energy, which powers muscular contraction.
Write the equation that represents the breakdown of ATP.
ATP + water → ADP + free phosphate + free energy.
What is the role of free energy released from ATP hydrolysis in muscles?
It is used by the muscle to produce force and facilitate movement.
Where is the primary site for generating ATP in muscles?
The mitochondria.
What energy pathways do mitochondria in muscles utilize?
Aerobic pathways that require oxygen.
How are capillaries positioned in relation to muscle fibers and mitochondria?
Capillaries are closely positioned near mitochondria to supply blood and oxygen to the muscles.
Name the three types of muscle fibers discussed.
Type-I fibers, Type-IIa fibers, and Type-IIb fibers.
Which muscle fiber type has the highest mitochondrial density?
Type-I fibers.
How does mitochondrial density correlate with oxidative enzymes in muscle fibers?
Type-I fibers have the highest oxidative enzymes, while Type-IIb fibers have the lowest.
What is the relationship between capillary density and muscle fiber types?
Type-I fibers have the highest capillary density, while Type-II fibers have the lowest.
What is the fatigue resistance of Type-I fibers compared to Type-IIb fibers?
Type-I fibers are the most fatigue-resistant, while Type-IIb fibers are the most fatigable.
How do Type-I and Type-IIb fibers differ in force generation?
Type-I fibers generate force slowly and resist fatigue, whereas Type-IIb fibers generate force quickly and are more fatigable.
What is a key takeaway regarding muscle fiber types and their metabolic properties?
Different muscle fiber types have different metabolic properties that influence their mechanical performance.
What is the concentration of ATP in resting muscle?
Approximately 8 millimolar.
What is the rate of ATP consumption in resting muscle?
About 1 millimole per kilogram per minute.
How much ATP can heavily contracting muscle consume?
Up to 240 millimoles per kilogram per minute.
Name some processes that consume ATP in resting muscle.
Ion pumps (like sodium-potassium pump), calcium pumps, RNA and protein synthesis, fuel storage, transport of substances, and cell signaling pathways.
What additional ATP-consuming process occurs in contracting muscle?
Myosin ATPase hydrolyzes ATP to power mechanical work.
How do ATP levels remain stable during heavy contraction?
ATP is replenished at a similar rate to its consumption through three major pathways.
What are the three major pathways for ATP regeneration?
Phosphocreatine, anaerobic glycolysis, and oxidative phosphorylation.
How does phosphocreatine regenerate ATP?
Through the reaction: ADP + phosphocreatine + proton → ATP + creatine.
How quickly can phosphocreatine power activity?
For about 10 seconds.
What is the role of phosphocreatine in ATP levels during rapid ATP consumption?
It acts as a buffer and shuttles phosphate groups from mitochondria to myofibrils
What is anaerobic glycolysis?
The breakdown of carbohydrates to pyruvate and eventually lactate without consuming oxygen.
What transports glucose into the muscle during exercise?
Glucose transporters recruited by insulin and during exercise.
How many ATP does anaerobic glycolysis produce?
Two or three ATP, depending on whether glucose or glycogen is the source.
Why does anaerobic glycolysis have a limit?
Due to lactate buildup causing acidosis, which can inhibit cellular functions.
What is oxidative phosphorylation?
A process that uses a fuel source and oxygen to form ATP and produce carbon dioxide and water.
What is the relationship between oxygen consumption and oxidative phosphorylation?
The rate of oxygen consumption is proportional to the workload performed, measuring aerobic capacity.
Where do the TCA cycle and electron transport chain occur?
In the mitochondria.
What is the maximum power of phosphocreatine for ATP regeneration?
36 kilocalories per minute.
What is the maximum capacity of phosphocreatine?
About 11 kilocalories.
How long does it take for anaerobic glycolysis to reach its maximum rate?
About 5 to 10 seconds.
What is the maximum capacity of anaerobic glycolysis?
About 15 kilocalories before depletion.
How long does it take for oxidative phosphorylation to reach maximum rate?
About 2 to 3 minutes.
What is the maximum capacity of oxidative phosphorylation?
Approximately 2,000 kilocalories.
Which energy pathway is the dominant one during most daily activities?
Oxidative phosphorylation.
What is the dominant energy pathway during most daily activities?
Oxidative phosphorylation.
What fuel sources can be used for oxidative phosphorylation?
Glucose (carbohydrates), lipids, and proteins.
How is glucose stored in the muscle?
As glycogen.
What happens to pyruvate during oxidative phosphorylation?
It is transferred to the mitochondria for use in the TCA cycle and electron transport chain.
How many ATP molecules are generated from one molecule of glucose?
About 36 ATP molecules.
What is the total energy capacity from muscle glycogen?
Approximately 500 kilocalories.
What is lipolysis?
The breakdown of lipids into free fatty acids and glycerol.
How do free fatty acids contribute to ATP regeneration?
They undergo beta oxidation, producing smaller substrates that enter the TCA cycle and electron transport chain.
How many ATP molecules can be generated from one molecule of palmitic acid?
About 130 ATP molecules.
How do proteins enter the oxidative phosphorylation pathway?
At various points along glycolysis, the TCA cycle, and the electron transport chain, depending on the protein source.
What is the energy capacity from muscle protein?
Approximately 24,000 kilocalories.
When is protein used as a significant energy source?
During periods of starvation.
What happens to proteins during starvation?
They can undergo gluconeogenesis and significant muscle protein breakdown.
Describe the general pathway for carbohydrates in oxidative phosphorylation.
Carbohydrates are broken down into glucose 6 phosphate, then glycolysis to pyruvic acid, acetyl-CoA, TCA cycle, and electron transport chain.
Describe the general pathway for lipids in oxidative phosphorylation.
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.
How do proteins contribute to the nitrogen pool during oxidative phosphorylation?
Proteins are broken down and generate nitrogen that can enter the metabolic pathways at different stages.
What do all fuel sources ultimately do in oxidative phosphorylation?
They provide energy to convert ADP and free phosphate into ATP.
What is the relationship between exercise duration and the energy pathways used?
Short, high-intensity activities rely more on anaerobic pathways, while longer-duration activities rely more on aerobic pathways.
During maximal exercise lasting a few seconds, which energy pathway is primarily used?
Anaerobic pathways.
What happens to the reliance on aerobic pathways as exercise duration increases?
The reliance on aerobic pathways increases because anaerobic pathways have limited capacity.
What fuels are primarily used during low-intensity exercise?
Plasma-free fatty acids and muscle triglycerides.
How does fuel source contribution change with increased exercise intensity?
Lower intensity relies more on lipids, while higher intensity increases reliance on carbohydrates like muscle glycogen and plasma glucose.
In the context of exercise duration, what is primarily utilized at rest?
Predominantly intramuscular sources and lipids.
As exercise duration increases, what fuel source becomes more prominent?
Free fatty acids and lipids.
For a 200 to 400-meter sprint, what energy pathways are primarily used?
A combination of phosphocreatine and anaerobic glycolysis.
What is the primary fuel source during endurance events?
A combination of phosphocreatine, anaerobic glycolysis, and oxidative phosphorylation.
How does the intensity of exercise affect the dominant fuel source?
As intensity increases, carbohydrates become the dominant fuel source; for lower intensity and longer duration, lipids are predominant.
What is the significance of oxidative phosphorylation in energy production?
It allows the use of various fuel sources to regenerate ATP, especially during longer-duration activities.
How do energy pathways integrate during physical activity?
Different pathways are utilized depending on the intensity and duration of the activity, transitioning from anaerobic to aerobic systems.
What do plots of exercise intensity and duration show about energy sources?
Higher intensity leads to more carbohydrate use, while longer duration favors lipid utilization.
What happens to ATP consumption during high-power activities?
ATP is consumed quickly, primarily using phosphocreatine for regeneration.
How do anaerobic glycolysis and phosphocreatine function together in exercise?
They work together to quickly regenerate ATP during activities of moderate duration and high intensity.
What are the two main types of training discussed in this segment?
Anaerobic training (high-intensity, short duration) and aerobic training (low-intensity, longer duration).
What adaptations occur in anaerobic training?
Increased ATP concentration, phosphocreatine (PCr), creatine, muscle glycogen, and the quantity and activity of key glycolytic enzymes.
Why is an increase in glycolytic enzymes important during anaerobic training?
They are essential for breaking down glucose to power anaerobic glycolysis and the conversion of glucose to pyruvate for oxidative phosphorylation.
What metabolic changes occur with low-intensity, longer-duration training?
Increased number and volume of mitochondria, increased fat oxidation at rest and during submaximal exercise, and decreased reliance on glucose.
How does training affect the use of fats and carbohydrates during exercise?
Increased reliance on fat and decreased reliance on glucose at submaximal exercise intensity.
What happens to glycogen stores with increased training?
Training allows for preservation of glycogen stores, enhancing endurance due to the lower capacity of glycogen compared to lipids.
What cardiovascular adaptations occur due to training?
Increased ventricular volume, greater stroke volume, increased cardiac output, decreased heart rate at rest and submaximal exercise, and improved vasodilation capacity.
How does heart rate change with training during submaximal exercise?
Heart rate decreases at rest and during submaximal exercise, although maximum heart rate remains largely unchanged.
What ventilatory changes occur with training?
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.
Why is an increase in mitochondrial volume important for aerobic training?
It enhances oxidative phosphorylation, which is crucial for energy production during aerobic activities.
How do catecholamine levels change with training during exercise?
Catecholamine levels decrease, which helps in preserving glycogen stores.
What is the effect of training on the oxidation of carbohydrates at maximum exercise?
There is an increased ability to oxidize carbohydrates, along with an increase in glycogen content.
How does training impact oxygen delivery to muscles?
Increased capacity for vasodilation enhances oxygen-rich blood delivery to active muscles.
How does training change the balance between tidal volume and respiratory rate during exercise?
Training increases tidal volume while decreasing the reliance on respiratory rate, improving efficiency in oxygen diffusion.
What is the overall goal of metabolic adaptations due to training?
To enhance energy efficiency, increase endurance, and improve overall physical performance.
What is the impact of 30 days of bed rest on VO2 max?
There can be a 25% decline in VO2 max after 30 days of bed rest.
What happens to heart rate during detraining?
Heart rate increases at rest and during submaximal exercise after bed rest.
How does stroke volume change with bed rest?
Stroke volume declines, leading to greater reliance on heart rate to maintain cardiac output at submaximal levels.
What changes occur in the balance between the parasympathetic and sympathetic nervous systems during detraining?
There is a decrease in parasympathetic nervous system activity, with variable changes in sympathetic nervous system activity.
How does blood volume affect cardiovascular function during detraining?
Changes in blood volume lead to decreased central venous pressure, resulting in decreased cardiac filling and a reduction in stroke volume.
What are the peripheral effects of bed rest on the cardiovascular system?
Loss of capillaries and decreased capacity for vasodilation, which reduces blood delivery to skeletal muscles and impacts oxygen delivery.
What is the effect of detraining on muscle condition?
Muscle atrophy, decreased muscle protein synthesis, weakness, and decreased muscle endurance occur.
What musculoskeletal changes can result from prolonged bed rest?
Changes in muscle length leading to joint contractures and loss of bone mineral density.
What is a significant risk associated with decreased bone mineral density due to bed rest?
Increased risk of falls and fractures.
What pulmonary issues can arise from bed rest?
Atelectasis (collapse of alveoli) and increased risk of pneumonia.
How does the a-vO2 difference change during detraining?
Potential changes in the a-vO2 difference can occur due to decreased oxygen delivery from peripheral effects.
What overall effects does bed rest have on the body?
Bed rest leads to significant changes across all systems of the body, affecting cardiovascular, muscular, pulmonary, and overall physiological function.
How does bed rest affect muscle endurance?
There is a decrease in muscle endurance as a result of detraining.
What role does norepinephrine play during detraining?
There is greater responsiveness to beta receptor activation and norepinephrine, which can influence cardiovascular responses.
What contributes to the decline in peak VO2 during detraining?
Increased heart rate, decreased stroke volume, and potential changes in the a-vO2 difference contribute to the decline in peak VO2.
