Energy Metabolism and Muscle Contraction Overview

Coupled reactions

Two separate chemical reactions that are linked together, used to form ATP.

Aerobic metabolism

The presence of oxygen in the metabolic process.

Anaerobic metabolism

The absence of oxygen in the metabolic process.

Substrates of aerobic metabolism

Glucose/glycogen, fats, and protein (as a last resort).

Location of aerobic metabolism

In the mitochondria.

Substrates converted into glucose

Lactate and amino acids.

Muscle breakdown for energy

Occurs during starvation or ultra-prolonged exercise.

ATP-CP system

The energy system that uses creatine phosphate only.

Duration of ATP-CP energy

0-15 seconds.

Lactate system

The system that follows ATP-CP and uses glucose only.

Location of anaerobic metabolism

In the cytosol.

Energy yield from NAD reduction

3 ATP.

Energy yield from FAD reduction

2 ATP.

ATP production from GTP

1 ATP.

Macronutrient breakdown of a normal diet

55% carbs, 30% fats, 15% protein.

High-fat diet effect on performance

Increases reliance on fat, decreases duration.

High-carb diet effect on performance

Increases reliance on carbs, increases duration.

Beneficiaries of a high-carb diet

Endurance athletes.

Phases of recovery

Fast (alactacid) and slow (lactacid).

Restoration during fast phase of recovery

Everything except removal of lactic acid.

Slow phase of recovery

Oxygen is used to remove/recycle lactate.

Factors affecting muscle glycogen restoration

Diet (especially high-carb intake post-exercise).

Time to restore most glycogen stores

10 hours (full restoration takes ~46 hours).

Glycogen supercompensation

Also known as carbohydrate loading.

Layers of skeletal muscle

Epimysium, perimysium, endomysium.

Initiation of muscle contraction

Action potential from a neuron.

Neurotransmitter released during contraction

Acetylcholine.

Organelle releasing Ca²⁺

Sarcoplasmic reticulum.

Ca²⁺ binding during contraction

Binds to troponin.

Formation when actin and myosin couple

Actomyosin.

Energy source for muscle contraction

ATP → ADP + Pi + energy.

Muscle relaxation process

Ca²⁺ is pumped out; actomyosin dissociates into actin and myosin.

Isometric contraction

Tension develops without a change in muscle length.

Isokinetic contraction

Tension develops at a constant speed; requires special equipment.

Isotonic contraction

Tension remains the same while muscle length changes.

Eccentric contraction

Tension while the muscle lengthens (e.g., lowering a weight).

Concentric contraction

Tension while the muscle shortens (e.g., lifting a weight).