Exercise Physiology - Bioenergetics
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What is bioenergetics?
- The body's ability to acquire, convert, store, and utilize energy
What is adenosine triphosphate (ATP)?
Immediate source of energy for all cellular activities, including muscle contraction
What is ATP broken down to?
Adenosine diphosphate (ADP)
How is ATP replenished and why does it need to be replenished?
- Replenished via other energy pathways that replace ATP as it's used;
- Needs to be replenished because only a limited amount is stored in the cell
What is the phosphagen system?
Energy pathway composed of ATP and phosphocreative (pCr) stored in muscle fibers
What does the enzyme creatine kinase do?
Through activity it helps PCr yeild its phosphate group so that it can be added to ADP to synthesize ATP
How is the phosphagen system used for exercise? What are its limitation?
- Immediately available for use by the working muscles, but is limited in its capacity to supply energy;
- During all-out-effort exercise, stored ATP and PCr in phosphagen system can only sustain activity for 30 seconds
What is the nonoxidative system referred to and why?
Referred to as anaerobic pathway because oxygen is not required for it to produce ATP
What produces ATP in the nonoxidative system?
Only carbohydrates (glucose)
What happens in the nonoxidative system as the absence of oxygen occurs?
Breakdown of carbs yeilds lactic acid (lactate), which can contribute to muscle fatigue as it accumulates.
When is the nonoxidative system the main provider of energy to the body?
Working muscles in athletic events lasting 30 seconds to 3 minutes
What is the oxidative system referred to and why?
aerobic system because the APT-producting pathway requires oxygen it to proceed
What synthesizes ATP in the oxidative system?
- Fats (lipids)
- Sometimes protein
What are the metabolic by-products of oxidative phosphorylation and what effect do they have on the muscle?
- By-products are water and carbon dioxide;
- Have no fatiguing effect on the working muscles
When is the oxidative system the main provider of energy to the body?
Activities lasting more than 3 minutes
What are the disadvantages of the oxidative system?
- Relatively slow in synthesizing ATP demaneded by exercising muscles;
- If inadequate oxygen is delivered, it depends on the nonoxidative system to produce energy resulting in lactate accumulation
What is the anaerobic threshold/lactate threshold?
The point at which energy production results in lactate accumulation due to inadequate oxygen to the muscles
What does endurance training do for ATP production and why?
- Increase the capacity of the oxidative system to produce ATP;
- Increases the storage of energy substrates (carbs/fats) used in the oxidative pathway
- Because of increased mitochondrial density, leading in increase in enzymes and other proteins involved in oxidative synthesis of ATP
What does resistance training do for ATP production and how?
- Improves that capacity of the muscle to produce ATP anaerobically;
- Increases the glycolytic enzymes used in the anaerobic pathway along with the amount of glycogen stored in the muscle
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