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What are the three main pathways for ATP resynthesis?
What are the three main pathways for ATP resynthesis?
During exercise, how does the rate of ATP replenishment change compared to rest?
During exercise, how does the rate of ATP replenishment change compared to rest?
Which of the following is the smallest fuel store in a lean individual?
Which of the following is the smallest fuel store in a lean individual?
What is the net ATP gain from glycolysis?
What is the net ATP gain from glycolysis?
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What is the enzyme responsible for breaking down glycogen into glucose?
What is the enzyme responsible for breaking down glycogen into glucose?
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What determines the rate at which muscle will take up glucose from the blood?
What determines the rate at which muscle will take up glucose from the blood?
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Which process does not utilize oxygen?
Which process does not utilize oxygen?
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What is the role of mitochondria in replenishing depleted phosphocreatine (PCr) stores?
What is the role of mitochondria in replenishing depleted phosphocreatine (PCr) stores?
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Which enzyme is considered rate-limiting in the glycolysis pathway?
Which enzyme is considered rate-limiting in the glycolysis pathway?
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How many ATP are produced during glycolysis when glucose is converted to pyruvate?
How many ATP are produced during glycolysis when glucose is converted to pyruvate?
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What are the two primary fates of pyruvate after glycolysis?
What are the two primary fates of pyruvate after glycolysis?
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What does oxidation mean in metabolic terms?
What does oxidation mean in metabolic terms?
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What role do NADH and FADH2 play in cellular metabolism?
What role do NADH and FADH2 play in cellular metabolism?
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Why is lactate formation beneficial during glycolysis?
Why is lactate formation beneficial during glycolysis?
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What is the main purpose of the citric acid cycle?
What is the main purpose of the citric acid cycle?
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What type of carbohydrate is maltose classified as?
What type of carbohydrate is maltose classified as?
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What is the primary function of muscle glycogen during physical activity?
What is the primary function of muscle glycogen during physical activity?
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How does liver glycogen primarily function during periods of fasting?
How does liver glycogen primarily function during periods of fasting?
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Which carbohydrate loading method has notable disadvantages?
Which carbohydrate loading method has notable disadvantages?
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What is primarily indicated by the glycemic index (GI) of a carbohydrate source?
What is primarily indicated by the glycemic index (GI) of a carbohydrate source?
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Which of the following benefits is associated with carbohydrate ingestion 1-4 hours before exercise?
Which of the following benefits is associated with carbohydrate ingestion 1-4 hours before exercise?
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What is the effect of carbohydrate intake during long-duration exercise?
What is the effect of carbohydrate intake during long-duration exercise?
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What is the optimal ratio of glucose to fructose for maximizing carbohydrate oxidation during exercise?
What is the optimal ratio of glucose to fructose for maximizing carbohydrate oxidation during exercise?
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What is the recommended approach for maximizing carbohydrate oxidation during exercise?
What is the recommended approach for maximizing carbohydrate oxidation during exercise?
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Which of the following is a disadvantage of consuming solid carbohydrates during exercise?
Which of the following is a disadvantage of consuming solid carbohydrates during exercise?
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What is a negative aspect of liquid carbohydrate supplementation during exercise?
What is a negative aspect of liquid carbohydrate supplementation during exercise?
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During what time frame does the rapid phase of glycogen synthesis occur after exercise?
During what time frame does the rapid phase of glycogen synthesis occur after exercise?
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What is the relationship between insulin and glycogen synthesis during the second phase after exercise?
What is the relationship between insulin and glycogen synthesis during the second phase after exercise?
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What is the recommended carbohydrate intake for athletes during heavy training?
What is the recommended carbohydrate intake for athletes during heavy training?
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Where is the greatest storage of fat found in the body?
Where is the greatest storage of fat found in the body?
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Which enzyme is primarily responsible for lipolysis?
Which enzyme is primarily responsible for lipolysis?
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Which of the following steps is not part of the fat metabolism process?
Which of the following steps is not part of the fat metabolism process?
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What is the crossover point in energy sourcing during exercise?
What is the crossover point in energy sourcing during exercise?
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How does successful endurance training affect the crossover point?
How does successful endurance training affect the crossover point?
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What role do mitochondrial enzymes play in fat oxidation?
What role do mitochondrial enzymes play in fat oxidation?
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What happens to brain metabolism when switching to a low carb, high fat diet?
What happens to brain metabolism when switching to a low carb, high fat diet?
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Where are ketone bodies formed and from which macronutrient?
Where are ketone bodies formed and from which macronutrient?
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Why are protein needs increased on a high fat, low carbohydrate diet?
Why are protein needs increased on a high fat, low carbohydrate diet?
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Which medical condition may benefit from a low carbohydrate, high fat diet?
Which medical condition may benefit from a low carbohydrate, high fat diet?
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What is one proven effect of the low carbohydrate, high fat diet on athletes' exercise metabolism?
What is one proven effect of the low carbohydrate, high fat diet on athletes' exercise metabolism?
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Study Notes
ATP Resynthesis Pathways
-
Phosphagen system: Creatine phosphate (PCr) is used to quickly regenerate ATP.
- Occurs in the cytoplasm of muscle cells.
- Provides energy for short bursts of intense activity (e.g., weightlifting, sprinting).
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Glycolysis: Breakdown of glucose into pyruvate, producing a net of 2 ATP molecules.
- Occurs in the cytoplasm of muscle cells.
- Important for moderate-intensity exercise lasting up to 3 minutes.
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Oxidative phosphorylation: Series of metabolic reactions occurring in the mitochondria.
- Uses oxygen to generate ATP from glucose, pyruvate, and fatty acids.
- Provides energy for long-duration, low-intensity activities (e.g., jogging, cycling).
Creatine Supplementation
- Creatine supplementation can temporarily increase PCr stores in muscles.
- Effective for improving performance in activities requiring short bursts of high intensity.
Glycolysis Details
- Inputs: Glucose.
- Outputs: 2 pyruvate molecules, 2 ATP, and 2 NADH.
- Key Enzyme: Phosphofructokinase (PFK) is the rate-limiting enzyme.
- Sources of glucose: Muscle glycogen, blood glucose (maintained by liver glycogen and food intake).
- Glucose uptake: Influenced by insulin, exercise intensity, and GLUT-4 transporter.
Pyruvate Fates
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Lactate formation: Occurs when oxygen supply is limited.
- Used to maintain a fast rate of glycolysis.
- Oxidative metabolism: Enters the mitochondria for further energy production.
The Citric Acid Cycle
- Occurs in the mitochondria.
- Breaks down pyruvate to generate energy.
- Produces ATP, NADH, and FADH2 which are used in the electron transport chain.
The Electron Transport Chain
- Occurs in the mitochondria.
- Uses electrons from NADH and FADH2 to generate a proton gradient.
- This gradient is used to produce ATP.
- Requires oxygen as the final electron acceptor.
Carbohydrate Digestion and Absorption
- Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose).
- Disaccharides: Two simple sugars linked together (e.g., sucrose, lactose, maltose).
- Polysaccharides: Long chains of simple sugars (e.g., starch, glycogen).
- Dietary fiber: Indigestible carbohydrates, contribute to digestive health.
Muscle vs. Liver Glycogen
- Muscle glycogen: Provides energy directly to muscle cells.
- Liver glycogen: Regulates blood glucose levels, supplying glucose to the bloodstream during fasting or low energy conditions.
Carbohydrate Loading
- Classical method: Depletes glycogen stores followed by high-carbohydrate intake.
- Modified method: Gradual carbohydrate increase over several days.
- Disadvantages of classical method: May lead to muscle fatigue and discomfort.
Glycemic Index (GI)
- Measure of how quickly a food raises blood glucose levels.
- High GI foods are rapidly digested and absorbed.
- Low GI foods are digested and absorbed more slowly.
Carbohydrate Intake Recommendations Before Exercise
- 1-4 hours before exercise: High-carbohydrate meals or snacks (e.g., pasta, potatoes, fruit) to maximize glycogen storage and provide glucose for intestinal absorption.
Carbohydrate Intake During Exercise
- Duration and intensity: Crucial factors determining the need for carbohydrate intake during exercise.
- Liquid form: Provides rapid absorption and gastric emptying.
- Solid form: More energy dense but can cause slower digestion.
- Combined forms: Mixes of liquid and solid forms of carbohydrates.
Glycogen Resynthesis after Exercise
- Rapid phase: Occurs within the first 2 hours after exercise.
- Slow phase: Occurs from 2 to 24 hours after exercise.
Factors Affecting Glycogen Resynthesis Rate
- Insulin: Increases glucose uptake and glycogen synthesis.
- GLUT-4: Transporter responsible for glucose uptake in muscle cells.
- Glycogen synthase: Enzyme that catalyzes glycogen synthesis.
Carbohydrate Intake Recommendations After Exercise
- Immediate: Consume carbohydrates to facilitate glycogen resynthesis.
- Later events: Consume carbohydrates to ensure adequate glycogen stores for subsequent exercise.
Daily Carbohydrate Recommendations for Athletes
- Moderate to heavy training: 5-10 grams of carbohydrate per kilogram of body weight per day.
Fat Metabolism
- Lipolysis: Breakdown of triglycerides into fatty acids and glycerol.
- Key enzyme: Hormone-sensitive lipase (HSL).
- Activation: Triggered by hormones (e.g., adrenaline, cortisol) and low insulin levels.
- Transport: Fatty acids are transported in the bloodstream bound to albumin.
Crossover Concept
- As exercise intensity increases, the body relies more on carbohydrates as a primary source of fuel.
- The crossover point is when 50% of energy is derived from carbohydrates and 50% from fat.
- Endurance training shifts the crossover point to the right, allowing athletes to utilize fat as fuel for longer periods.
Fat Oxidation and Training
- Mitochondrial adaptation: Increases in mitochondrial enzymes improve oxidative capacity.
- Cellular transport: Improved uptake of fatty acids from the bloodstream.
- Cardiovascular improvements: Increased blood flow and oxygen delivery to muscles.
Low-Carb, High-Fat Diet
- Adaptation: Liver produces ketone bodies from fatty acid breakdown.
- Brain fuel: Ketones become the primary energy source for the brain.
- Increased protein needs: Glycogen stores are depleted, leading to increased protein breakdown to provide energy.
Ketone Bodies
- Formed in the liver from fatty acids.
- Used as an alternative fuel source by tissues like the brain.
LCHF Effects on Exercise Performance
- Increased fat oxidation: Spares glycogen stores allowing for longer endurance.
Medical Conditions
- Epilepsy: Low-carb, high-fat diets may reduce seizures.
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Description
Explore the various pathways of ATP resynthesis including the phosphagen system, glycolysis, and oxidative phosphorylation. Learn how creatine supplementation can enhance performance in high-intensity activities and its impact on muscle energy. This quiz is ideal for students studying exercise physiology or related fields.
