BIOL362-weeks 1-2

Animal Energetics Overview

Aims of the Lecture

• Understanding the importance of metabolism for organisms

• Historical context of energetics study

• Basics of biochemistry related to energy metabolism

• Comparison of aerobic vs anaerobic metabolism

• Factors affecting metabolic rate related to ecology and evolution

• Measurement methodologies for animal metabolism

• Theories on the evolution of increased metabolic rates

Defining Life and Metabolism

• Definition of Life:

  • Ability to replicate

  • Presence of metabolism (specifically energy metabolism)

• Energy Metabolism: A cellular attribute where various physiological systems support energy metabolism.

Understanding Energy

What is Energy?

• Defined by the formula: E = mc² (mass x speed of light²)

• Types of Energy:

  • Capacity to do work (Force x Distance)

  • Capacity to increase order in a system

• Laws of Thermodynamics:

  • First Law: Energy cannot be created or destroyed, only transformed.

  • Second Law: Entropy (disorder) of an isolated system will always increase, leading to useful energy converting to heat.

Entropy and Its Implications

• Entropy: Measure of disorder in a system

  • Characteristics:

    • Ordered systems = low entropy

    • Disordered systems = high entropy (solid < liquid < gas)

    • Heat release info significance for work and order preservation

Energy Needs in Animals

• Animals maintain order in a battle against entropy

• As heterotrophs, they consume other organisms for energy.

Energy Sources and Metabolism

Stored Energies in Animals

• Examples include:

  • H2O + CO2

  • Oxygen (O2)

  • Food types (fats, carbohydrates, proteins)

• Metabolism reflects energy conversion from substrates:

  • O2 consumption correlates with CO2 production and heat, affecting metabolic rates.

Aerobic vs Anaerobic Metabolism

• Fuels for Aerobic Metabolism:

  • Glucose: C6H12O6 + 6O2 → 6CO2 + 6H2O (RQ = 1.0)

  • Lipids: C16H32O2 + 23O2 → 16CO2 + 16H2O (RQ = 0.7)

  • Amino Acids: RQ = 0.8

  • Glycogen vs. Lipids: Lipids contain higher stored energy (6x more than 1g of glycogen).

Efficiency of Energy Production

• ATP Source: Produced mainly through oxidative phosphorylation in mitochondria.

• Electron Transport Chain plays a crucial role in ATP production using O2 and releasing CO2.

Measuring Metabolic Rate

• Measured via direct/indirect calorimetry methods:

  • Direct: Heat produced

  • Indirect: O2 used or CO2 produced

• Bomb Calorimetry: Measures food energy levels.

Factors Affecting Metabolic Rates

• Varied factors include:

  • Temperature, time of day, sleep cycles, digestive state, noise, posture, activity.

Evolution of Metabolic Rates

• Higher metabolic rates generally relate to improved aerobic capacities.

• Different metabolic strategies adapt depending on environmental conditions (aerobic vs anaerobic).

Stress and Metabolism

• Chronic stress increases metabolic rates due to higher baseline hormone levels.

Summary of Energy Expenditure Concepts

• Energy Expenditure (EE): Rate of CO₂ production multiplied by the Respiratory Quotient (RQ).

• The DLW method helps in understanding metabolic rates over extended periods.

Physiological Adaptations to Metabolic Challenges

• Acclimatization impacts thermal tolerance levels and metabolic rates in response to temperature changes.

• Examples include adaptations in tropical vs arctic mammals to withstand temperature extremes.