Bioenergetics: Energy Transformations and Thermodynamics

Energy

Capacity to do work or produce change.

Joule (J)

SI unit of energy; equivalent to Nm or Ws.

Calorie (cal)

Energy to heat 1g water by 1°C.

1 cal

Equals 4.184 Joules.

Potential Energy

Stored energy in a specific form.

Kinetic Energy

Energy of motion; harnessed potential energy.

Biologic Work

Energy used for cellular processes.

Mechanical Work

Energy for muscle contraction and cell division.

Chemical Work

Energy for synthesizing molecules.

Transport Work

Energy for moving substances across membranes.

Electrical Work

Energy for transporting charged particles.

First Law of Thermodynamics

Energy cannot be created or destroyed.

Conservation of Energy

Energy transforms without being depleted.

Entropy

Measure of disorder in a system.

Second Law of Thermodynamics

Energy transformations increase universe's entropy.

Gibbs Free Energy (G)

Energy available to do work in a system.

Spontaneous Process

Occurs with a decrease in Gibbs Free Energy.

Equilibrium Constant (Keq)

Ratio of products to reactants at equilibrium.

Coupled Reactions

Linking reactions to drive non-spontaneous processes.

Dynamic Steady State

Balance between production and consumption in systems.

Enzymes

Biological catalysts that speed up reactions.

Activation Energy

Energy required to initiate a chemical reaction.

Lock and Key Mechanism

Enzyme specificity based on substrate shape.

Exergonic Reaction

Releases free energy; spontaneous process.

Endergonic Reaction

Requires energy input; non-spontaneous process.

Heat Loss

Energy dissipated as heat during transformations.

Biochemical Catalysis

Enzymes lower activation energy for reactions.

Non-equilibrium Thermodynamics

Living systems never reach equilibrium.

Thermodynamic Equilibrium

State where reactants and products are balanced.

High Enthalpy Food

Energy-rich food with low entropy.

Low Enthalpy Waste

Energy-poor waste with high entropy.