energy for muscular activity ch 7

What does muscle contraction require?

Energy — must be sufficient in both amount and rate to sustain contraction.

What are the three energy systems in the body?

1. Immediate Energy (Phosphagen System); 2. Short-Term Energy (Glycolytic System); 3. Long-Term Energy (Oxidative System)

What molecule fuels all biochemical processes in the body?

Adenosine Triphosphate (ATP)

Why is ATP called the "energy currency" of the body?

It provides energy directly to fuel muscle contractions and other cellular processes.

What happens during ATP hydrolysis?

ATP → ADP + P + energy (used for muscle contraction)

How is ATP resynthesized?

ADP + P → ATP (using energy from carbohydrates, fats, or proteins)

Is the phosphagen system aerobic or anaerobic?

Anaerobic (does not require oxygen)

What molecule donates a phosphate to ADP to form ATP in this system?

Creatine Phosphate (CP)

What type of activity uses the phosphagen system?

Short-duration, very high-intensity activities (e.g., shot put, sprinting, weightlifting)

How long can the phosphagen system sustain high-intensity effort?

7–12 seconds at very high intensity or 15–30 seconds at moderate intensity

What are the characteristics of the phosphagen system?

Produces large amounts of energy quickly, recovers fast, relies on limited CP stores, depletes rapidly, and requires rest to recover.

What is another name for the glycolytic system?

Anaerobic Lactic System

What process breaks down glucose to form ATP without oxygen?

Glycolysis

How many ATP are produced from one glucose molecule in glycolysis?

2 ATP

What is the primary fuel for the glycolytic system?

Carbohydrates (from foods like pasta, bread, fruits, vegetables)

What are the two possible fates of pyruvic acid in glycolysis?

High rate (no oxygen): → Lactic acid; Low rate (with oxygen): → Pyruvate

What are the by-products of the glycolytic system?

Lactic acid and hydrogen ions

What causes the "burning" sensation in muscles during intense exercise?

Accumulation of hydrogen ions from lactic acid production

How is lactate cleared from the body?

Metabolized by the heart, liver, and muscles

What changes occur in the body with endurance training (glycolytic system)?

Higher anaerobic threshold, faster removal of lactic acid, increased muscle blood flow and capillaries, and improved lactate metabolism.

Is the oxidative system aerobic or anaerobic?

Aerobic (requires oxygen)

What fuels are used by the oxidative system?

Carbohydrates, fats, and proteins

Where does oxidative energy production occur in the cell?

Mitochondria (with enzymes and coenzymes)

What are the main biochemical pathways of the oxidative system?

1. Krebs Cycle (Citric Acid Cycle); 2. Electron Transport Chain (ETC)

How much ATP is produced in the oxidative system?

Between 36–147 ATP per molecule of fuel

What are the requirements for the oxidative system to function efficiently?

Sufficient mitochondria, adequate oxygen supply, and proper enzyme activity

What is VO₂ max?

The maximum rate at which oxygen can be consumed during intense exercise (a measure of aerobic power)

What are the characteristics of the oxidative system?

Produces ATP slowly but efficiently, best for long-duration moderate-intensity activities, requires oxygen, and produces low lactic acid levels.

What limits the oxidative system?

The rate of oxygen delivery and availability

What are the benefits of endurance training on the oxidative system?

Increased vascularization, better oxygen delivery, more and larger mitochondria, improved enzyme function, higher fat utilization, and higher VO₂ max.

How do the three energy systems interact during exercise?

They all contribute energy, but in different proportions depending on activity duration and intensity.

Which systems dominate in short-term, high-intensity exercise?

Phosphagen and glycolytic systems

Which system dominates in long-duration, low- to moderate-intensity exercise?

Oxidative system

Around what duration does the body shift between glycolytic and oxidative dominance?

Around 6–9 minutes of high-intensity exercise (roughly half glycolytic, half oxidative)

Which energy system is most important overall?

The oxidative system — it supports a wide range of activities and recovers efficiently.

What determines which energy system is used most?

The duration and intensity of the activity.