Final_ Oxygen Consumption

Hemoglobin and Oxygen Transport

  • Hemoglobin

    • Respiratory pigment in vertebrates that enhances oxygen-loading capacity of blood.

  • Oxygen Equilibrium Curve

    • Represents the percentage of heme bound to oxygen.

    • Displays a sigmoidal shape due to positive cooperativity.

    • Can be manipulated by changes in:

      • CO2 levels

      • pH

      • Temperature

      • 2,3-Bisphosphoglycerate (2,3-BDG)

Carbon Dioxide Transport in Blood

  • CO2 Transport Mechanisms

    • CO2 is more soluble in plasma than O2, but not very soluble overall.

    • Approximately 5% of CO2 is transported dissolved in plasma.

    • CO2 binds to hemoglobin, forming carbaminohemoglobin, accounting for about 20% of transport.

    • Binding occurs not at heme groups but at amino-terminal groups of protein chains.

    • Remaining ~75% is converted to bicarbonate in red blood cells before being transported in plasma.

Role of Carbonic Anhydrase

  • Carbonic Anhydrase

    • Enzyme that catalyzes the conversion of carbon dioxide and water into carbonic acid.

    • Follows the law of mass action, where increased CO2 leads to greater bicarbonate and hydrogen ions production.

Gas Exchange Mechanisms

  • Systematic and Pulmonary Capillaries

    • Blood flow and partial pressures of CO2 and O2 are crucial in gas exchange.

    • Systemic capillaries demonstrate PCO2 = 46 mm Hg, while pulmonary capillaries show PCO2 = 40 mm Hg.

Effects of Partial Pressure

  • Haldane Effect

    • Influences how blood transports CO2 in conjunction with O2 loading/unloading related to partial pressures of O2 (PO2) and CO2 (PCO2).

Thermodynamics in Metabolism

  • 2nd Law of Thermodynamics

    • Describes how energy transformations increase disorder within isolated systems.

    • External energy sources are needed to maintain internal order within organisms.

Forms of Energy and Work in Animals

  • Energy Types

    • Animals utilize:

      • Chemical Energy from covalent bonds.

      • Electrical Energy from voltage across membranes.

      • Mechanical Energy from body motion.

    • Energy is spent on:

      • Cellular Work (metabolism, homeostasis)

      • Mechanical Motion

      • Heat (random motion, not work-capable)

Metabolic Rate Overview

  • Metabolic Rate Definition

    • Rate of converting chemical energy to heat and work, significantly dominated by heat generation.

    • Dictates food intake for maintenance and impact on ecosystems.

  • Types of Metabolic Rate

    • Basal Metabolic Rate (BMR): Measured in homeothermic animals under stress-free conditions.

    • Standard Metabolic Rate (SMR): Measured in poikilothermic animals under similar conditions.

    • Maximum Metabolic Rate (MMR): Highest oxygen consumption rate an organism can achieve.

Measuring Metabolic Rate

  • Direct Calorimetry

    • Measures heat loss from an organism at rest and during activity.

  • Indirect Calorimetry (Respirometry)

    • Infers metabolic rate from oxygen consumption and carbon dioxide production!

    • Simplified equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + 2820 kJ/mol.

Factors Affecting Metabolic Rate

  • Major Factors:

    • Physical activity intensity and ambient temperature.

  • Other factors include:

    • Ingestion of food

    • Age

    • Gender

    • Time of day

Specific Dynamic Action (SDA)

  • SDA refers to the increase in metabolic rate post-ingestion due to energy expenditure in digestion and absorption.

Allometric Scaling of Metabolic Relationships

  • Allometric Equation

    • Y = aMb,

    • Where Y is a biological variable, M is body size, and a & b are constants.

  • Example of Allometric Scaling

    • A 30g vole consumes ~175g of food per week (~600% of body weight).

    • A 1900kg rhino consumes ~650kg of food per week (~34% of body weight).

  • Metabolic Scaling

    • Energy needs in homeothermic animals don’t linearly correlate with body size, showing a negative allometric relationship.