Bioenergetics

OBJECTIVES

  • Energy is not created or destroyed. This principle is known as The Law of Conservation of Energy.

  • Living organisms transform energy by consuming nutrients such as carbohydrates, lipids, and proteins.

    • Nutrients store energy within their chemical bonds.

    • The living body then transfers this stored energy into another chemical form that it can utilize.

By the end of this week, you will be able to:

  1. Define the first and second laws of thermodynamics.

  2. Relate these laws of physics to nutrition.

  3. Discuss the process of energy transfer and the production of ATP.

  4. Reflect on why ATP is a central energy molecule.

  5. Define the energy losses that occur between consumption and production.

  6. Compare and contrast basal metabolic rate and maintenance energy requirements.

TOPIC 4: BIOENERGETICS

  • Energy is defined as the capacity to do work.

    • Energy flow is depicted as:

    • Before Transformation: 5 units (in)

    • After Transformation: 2 units (out)

    • Stored Energy: 3 units

    • Surroundings and System flow are considered.

WORK AND HEAT ENERGY

  • Forms of Energy:

    • Chemical

    • Nuclear

    • Mechanical

    • Gravitational

    • Radiant

    • Thermal

    • Electrical

ENERGY TRANSFORMATION

  • Energy transformations occur through various processes:

    • Work

    • Heat

    • Chemical potential energy

    • Kinetic energy

PHOSPHORUS IN ENERGY TRAPPING

  • Phosphorus plays a crucial role in energy trapping.

  • ATP (Adenosine Triphosphate) provides a measure of the potential energy available for work.

  • Metabolic Products:

    • Nutrients

    • ADP (Adenosine Diphosphate)

    • ATP

    • Processes:

    • Catabolic pathways releases energy.

    • Anabolic pathways utilize energy.

FLOW OF ENERGY

  • Energy sources are categorized as follows:

    • Dietary Energy leads to ATP production (40-60%).

    • ATP is utilized for muscle contraction and various cellular activities (e.g., milk production, growth, fat deposition).

    • Internal work: Energy transfer inefficiencies.

    • External work: Less than 25% of energy expended.

    • Maintenance energy includes:

    • Respiration

    • Circulation

    • Excretion

    • Heat production from metabolic activities.

NUTRIENTS AND POTENTIAL ENERGY

  • Nutrients are essential as they contain potential energy:

    • Proteins (Amino acids)

    • Carbohydrates (Glucose)

    • Lipids (Fatty acids, Acetyl-CoA)

  • Participatory processes in energy storage/release include:

    • Citric Acid Cycle: Involves NAD+/NADH and ADP/ATP formation.

  • Chemical reactions associated with energy storage:

    • Loss of electrons signifies oxidation, while gaining electrons signifies reduction.

REDOX REACTIONS

  • An oxidizing agent causes oxidation by gaining electrons, and a reducing agent causes reduction by losing electrons.

  • Mnemonic:

    • OIL = Oxidation Is Loss

    • RIG = Reduction Is Gain

ENERGY EQUATIONS

  • For glucose metabolism:

    • C<em>6H</em>12O<em>6+6O</em>2→6CO<em>2+6H</em>2O+extheatC<em>6H</em>{12}O<em>6 + 6O</em>2 → 6CO<em>2 + 6H</em>2O + ext{heat}

  • Intermediate product: C<em>3C<em>3 Carbons; Final product: C</em>1C</em>1 Carbon.

THERMAL FATES

  • During respiration, 100% of glucose breakdown results in:

    • 59% energy is captured as ATP

    • 41% is lost as heat, showcasing inefficiencies especially when H+ leaks into mitochondria.

  • Effect of temperature regulation on metabolic processes:

    • Circulatory adjustments (e.g., vasodilation, vasoconstriction) are vital.

    • Methods include sweating, shivering, and non-shivering thermogenesis.

ENERGY REQUIREMENTS

BASAL METABOLIC RATE (BMR)

  • The greatest energy requirement for animals pertains to maintenance functions.

  • BMR calculated by:

    • extBMR=70imesextBW2/3extorextBW3/4ext{BMR} = 70 imes ext{BW}^{2/3} ext{ or } ext{BW}^{3/4}

  • Influenced by age, species, and gender.

MAINTENANCE ENERGY

  • Comprises various aspects:

    • Daily activities

    • Tissue and organ function (circulation, respiration)

    • Cellular maintenance

CALORIMETRY

  • Calorimetry is a measurement of energy defined as follows:

    • 1 calorie = the amount of heat required to raise 1 gram of water from 14.5 to 15.5 °C

    • 1000 calories = 1 kilocalorie (kcal) = 4.184 kilojoules

  • Practical applications:

    • Food labeling serves as a measure of potential energy.

COMBUSTION AND ENERGY TRANSFER

  1. Combustion of food samples yields energy as heat.

  2. A rise in water temperature reflects energy transfer from the food.

  3. A one degree change in the temperature of 1 gram of water equals 1 calorie.

ENERGY ANALYSIS IN ANIMALS

GROSS ENERGY (GE)

  • Defined as the heat of combustion.

    • Sources include:

    1. Undigested feed

    2. Enteric microbes & their products

    3. Excretions into GI tract

    4. Cellular debris from the GI tract

  • Apparent Digestible Energy (DE) & Urinary Energy relate to energy losses.

METABOLIZABLE ENERGY (ME)

  • Heat Increment (Heat of nutrient metabolism) relates to energy produced during metabolic processes, especially fermentation.

    • Net Energy (NE) is divided into maintenance energy (NEm) which refers to:

    1. Basal metabolism

    2. Voluntary activity

    3. Temperature regulation

    4. Waste formation and elimination

PRODUCTIVE ENERGY (NEp)

  • Comprises:

    1. Tissue energy (muscle, fat)

    2. Lactation and egg production

    3. Pregnancy

    4. Wool, hair, feathers

    5. Work related tasks

ENERGY FUNCTIONS IN ANIMALS: SPECIFIC EXAMPLES

  • Comparative analysis across different species regarding the utilization and need for energy- Swine, Poultry, Cats, Dogs, Ruminants.