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Questions and Answers
What process converts excess nutrients into fat for storage?
What is the main function of NAD and FAD in cellular metabolism?
Which of the following best describes glycolysis?
During cellular respiration, what percentage of chemical energy in food is harnessed to do work?
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What triggers the entry of glucose from the bloodstream into muscle cells during exercise?
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Which metabolic pathway does not directly require oxygen?
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What role do enzymes play in chemical reactions?
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What is a crucial requirement for aerobic metabolism?
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What is the primary function of homeostasis in living organisms?
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Which of the following best describes a steady-state condition?
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What is the main goal of negative feedback in physiological processes?
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In which scenario is positive feedback most commonly observed?
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What is the role of oxygen in cellular processes during exercise?
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Which of the following is an example of a negative feedback mechanism?
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How does homeostasis differ from a steady-state?
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Which enzyme is primarily associated with the glycolysis process?
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What triggers the negative feedback loop in thermoregulation?
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During the first few seconds of exercise, which energy system is primarily utilized?
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Why do trained individuals have a lower Oâ‚‚ deficit during exercise?
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Which mechanism exemplifies the concept of positive feedback?
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What occurs during EPOC at the end of exercise?
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What is the primary fuel source for high-intensity, short-duration exercises?
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What physiological responses occur as a result of elevated epinephrine and norepinephrine during exercise?
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How does the body shift fuel sources as exercise intensity increases?
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Which hormone decreases during exercise to promote energy mobilization?
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What is one of the primary roles of glucagon during exercise?
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Which hormone is primarily responsible for increasing during intense and prolonged exercise?
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What physiological response occurs due to low blood sugar during exercise?
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Which of the following best describes the role of catecholamines during intense exercise?
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What does the crossover concept primarily explain?
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What factor does the 'shift' in fuel sources during exercise depend on?
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What role does glucose play in fat utilization during exercise?
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Which hormone is known for stimulating lipolysis?
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What happens when there is no glucose available during exercise?
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What process allows lactate to be utilized as a substrate for glucose production?
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What is the primary energy source utilized by the body during prolonged exercise?
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How does a hormone know which tissue to act upon?
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Study Notes
Homeostasis
- The process by which living organisms regulate their internal environment to maintain a stable, constant condition, despite external changes.
- Crucial for survival and proper functioning.
Examples of Homeostasis
- Body temperature regulation (thermoregulation): Sweating to cool down, shivering to warm up.
- Blood glucose regulation (via insulin and glucagon): Insulin lowers blood glucose, glucagon raises blood glucose.
- Maintenance of blood pressure: The body adjusts blood vessel diameter and heart rate to maintain blood pressure within a healthy range.
Steady State
- A condition where a variable remains constant over time, but requires continuous energy input to maintain it.
- Difference from Equilibrium: Equilibrium means no energy input is needed for stability.
Homeostasis vs. Steady State
- Homeostasis: Internal stability maintained by feedback systems.
- Steady State: Constant condition maintained by energy-dependent processes.
- Both are essential for proper biological function.
Nervous System and Endocrine System
- Nervous System: Rapid communication using electrical signals.
- Endocrine System: Slower communication using hormones.
- Both systems contribute to maintaining homeostasis.
Feedback Mechanisms
-
Negative Feedback: Reverses a change to bring the system back to its normal state.
- Example: Body temperature regulation: Sweating cools down the body, shivering warms it up.
- Main Goal: Stability.
-
Positive Feedback: Amplifies a change, making it more extreme.
- Example: Childbirth: Oxytocin release strengthens contractions until delivery.
- Main Goal: Acceleration.
- Differences: Negative feedback brings things back to normal, while positive feedback moves things forward until a specific goal is reached.
Bioenergetics
- Glycogenesis: Storing glucose as glycogen in the liver and muscles.
- Lipogenesis: Converting excess nutrients into fat and storing in fat cells.
Glucose Entry into Muscle Cells
- Stimulus: Muscle contractions (during exercise).
- Mechanism: Glucose enters from the bloodstream into muscle cells.
Oxidation
- Removal of an electron.
- A molecule that loses hydrogen also loses an electron and is "oxidized."
Energy from Food
- 25% of chemical energy in food is harnessed to perform cellular work (donated to Pi and ADP to form ATP).
- 75% of chemical bond energy is released as heat (combusted, cannot be used for work).
Enzymes
- Proteins that accelerate chemical reactions without being changed by the reaction.
- Act like catalysts.
Phosphocreatine
- High energy compound that can donate a phosphate group to ADP to make ATP.
- Important for short bursts of intense exercise.
- Promotes muscle growth and efficient recovery from physical activity.
Anaerobic Metabolism (Glycolysis):
- Occurs in the cytoplasm of the cell.
- Glucose is broken down into pyruvate without oxygen.
- Yields ATP and NADH.
Aerobic Metabolism (3 Stages):
- Glycolysis: Glucose to pyruvate in the cytoplasm.
- Citric Acid Cycle (Krebs Cycle): Pyruvate is further broken down in mitochondria, yielding ATP, NADH, and FADH2.
- Oxidative Phosphorylation (Electron Transport Chain and Chemiosmosis): Energy from NADH and FADH2 is used to generate ATP in the mitochondria, requiring oxygen.
NAD and FAD
- Nicotinamide Adenine Dinucleotide (NAD): Important electron carrier; gains an electron during oxidation and becomes NADH.
- Flavin Adenine Dinucleotide (FAD): Similar role to NAD; gains an electron during oxidation and becomes FADH2.
- Both act like batteries storing and transferring energy.
Oxidative Phosphorylation
- Harvests energy from NADH and FADH2 to convert it to ATP and water.
- This is where oxygen is used.
Role of Oxygen in Aerobic Metabolism:
- Crucial for life.
- Allows cells to produce enough energy (ATP) to maintain vital processes.
Key Regulatory Enzymes
- PCR: Creatine Kinase (CK)
- Glycolysis: Phosphofructokinase (PFK)
- Krebs Cycle: Isocitrate dehydrogenase
Creatine Kinase (Phosphocreatine System)
- Location: Muscle cells.
- Function: Catalyses the transfer of a phosphate group from phosphocreatine to ADP to form ATP.
- Importance: Provides quick energy for short bursts of activity.
Phosphofructokinase-1 (PFK-1) (Glycolysis)
- Location: Cytoplasm.
- Function: Important regulatory enzyme in glycolysis; controls the rate-limiting step.
- Importance: Regulates the production of ATP from glucose.
Isocitrate Dehydrogenase (Krebs Cycle)
- Location: Mitochondria.
- Function: A key regulatory enzyme in the Krebs cycle; plays a role in generating NADH.
- Importance: Controls the conversion of isocitrate to alpha-ketoglutarate, a step involved in the production of ATP and reducing equivalents.
Exercise Metabolism
- VOâ‚‚ Max: The maximum amount of oxygen that can be consumed and utilized by the body during intense exercise.
- Oâ‚‚ Deficit: Occurs at the beginning of exercise; your body needs more oxygen than it can deliver immediately.
- EPOC (Excess Post-Exercise Oxygen Consumption): Elevated oxygen consumption during recovery after exercise.
Oâ‚‚ Deficit at the Beginning of Exercise
- Muscles are using more oxygen than the body can supply.
- Body relies on anaerobic metabolism for energy initially.
- Contributing factors: Inadequate oxygen delivery to muscles, mobilization of energy stores, and increased metabolic rate.
EPOC at the End of Exercise
- Occurs after exercise to restore the body to its resting state.
- Causes: Increased metabolic rate to replenish energy stores, remove metabolic byproducts (like lactic acid), and maintain elevated body temperature.
- Consequences: Continued oxygen consumption even after exercise stops, leading to a higher oxygen consumption rate than at rest.
Trained Individuals vs. Untrained Individuals
- Trained individuals: Have a lower oxygen deficit because their bodies are more efficient at delivering oxygen to working muscles during exercise.
- Trained individuals: Have a higher VOâ‚‚max due to improved cardiovascular and muscular systems.
Oâ‚‚ Consumption and Energy Systems During Exercise
- First 1-5 seconds: ATP via Phosphocreatine system.
- Exercise longer than 5 seconds, but less than 10 minutes: 100% aerobic metabolism.
- Prolonged exercise: A combination of aerobic and anaerobic systems.
Fuel Sources During Exercise
- Carbohydrates: Primary fuel source for high-intensity, short-duration exercise.
- Fat: Primary fuel source for low-to-moderate intensity, longer-duration exercise.
- Amino Acids: Minor fuel source, used during prolonged endurance exercise or when carbohydrate stores are depleted.
Crossover Concept
- As exercise intensity increases, the body shifts from primarily using fat as a fuel to using carbohydrates (glucose).
- Key Factor: Exercise intensity.
- Shift Point: The intensity at which this change occurs, influenced by factors like fitness level and exercise duration.
Hormonal Response to Exercise
- Hormones: Chemical messengers that regulate various bodily functions.
- Target Cells: Specific cells that have receptors for the hormone.
- Specificity: Hormones bind to specific receptors on target cells to trigger specific responses.
Hormones Important in Exercise
- Cortisol: Stress hormone, increases during intense and prolonged exercise.
- Growth Hormone: Promotes muscle growth and recovery, increases during high-intensity exercise.
- Catecholamines (Epinephrine/Norepinephrine): Increase during exercise, enhance energy availability and physiological responses.
- Insulin: Decreases during exercise to mobilize energy stores, potentially increases post-exercise for recovery.
- Glucagon: Increases during exercise to maintain blood sugar levels by mobilizing energy stores from the liver.
Gluconeogenesis
- The process of producing glucose from non-carbohydrate sources, such as amino acids and glycerol.
- Occurs in the liver.
- Gluconeogenesis is important for maintaining blood sugar levels during prolonged exercise.
Maintaining Blood Glucose Levels During Exercise
- Crucial for providing energy to muscles, preventing fatigue, and supporting brain function.
- Low blood glucose: Stimulates the pancreas to release glucagon, which promotes glycogenolysis in the liver, raising blood glucose levels.
- Hormones that raise blood glucose: Glucagon, cortisol, growth hormone, and epinephrine.
Lactate
- During Exercise: Lactate can accumulate in muscle cells as a byproduct of anaerobic metabolism.
- Effects: Can be used as a substrate for gluconeogenesis in the liver or oxidized in muscle cells.
- Significance: Contributes to blood glucose regulation and energy production during exercise.
Role of Protein in Exercise
- Primary Function: Tissue growth, repair, and maintenance.
- Energy Source: A secondary energy source, used when other fuel sources are low.
Hormonal Pathways
- Hormones as Keys: They bind to specific receptors on target cells.
- Target Cells as Locks: Only cells with matching receptors respond to the hormone.
- Binding: The hormone binds to the receptor to trigger a response.
- Triggering a Response: The hormone-receptor binding activates a signaling cascade within the cell, leading to specific effects.
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Description
Test your knowledge on the process of homeostasis and its significance in maintaining a stable internal environment for living organisms. This quiz covers key concepts such as thermoregulation, blood glucose regulation, and the distinction between homeostasis and steady state.
