Thermodynamics

Definition

Thermodynamics is the branch of physics that deals with the relationship between heat, work, temperature, and energy. It describes the transfer of energy as it relates to the physical and chemical changes that occur in a system.

5 Must Know Facts For Your Next Test

1. The first law of thermodynamics states that energy can be converted from one form to another, but it cannot be created or destroyed.
2. The second law of thermodynamics states that the entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.
3. Thermodynamic processes are classified as either endothermic (absorbing heat) or exothermic (releasing heat).
4. Enzymes are biological catalysts that lower the activation energy required for chemical reactions, thereby increasing the rate of those reactions.
5. The free energy change of a reaction determines whether a reaction will occur spontaneously (negative free energy change) or require an input of energy (positive free energy change).

Review Questions

• Explain how the laws of thermodynamics relate to energy, matter, and enzymes.
  • The first law of thermodynamics states that energy can be converted from one form to another, but not created or destroyed. This is relevant to energy transformations in living systems, where energy from food is converted into chemical energy, mechanical energy, and heat. The second law of thermodynamics, which states that entropy (disorder) tends to increase, helps explain why enzymes are necessary to catalyze reactions and maintain the highly ordered state of living organisms. Enzymes lower the activation energy required for reactions, allowing them to occur more readily and efficiently, despite the natural tendency towards increased entropy.
• Describe the role of Gibbs free energy in determining the spontaneity and direction of chemical reactions in biological systems.
  • Gibbs free energy is a measure of the useful work that can be extracted from a system at constant temperature and pressure. The change in Gibbs free energy (ΔG) determines whether a reaction will occur spontaneously (ΔG < 0) or require an input of energy (ΔG > 0). In the context of enzymes and biological systems, the free energy change of a reaction is crucial in understanding the energetics and feasibility of various metabolic pathways. Enzymes can catalyze reactions with positive ΔG values by coupling them to other reactions with negative ΔG values, thereby driving the overall process in a favorable direction.
• Analyze how the principles of thermodynamics influence the structure and function of enzymes in biological systems.
  • The structure and function of enzymes are directly influenced by the principles of thermodynamics. Enzymes are biological catalysts that lower the activation energy required for chemical reactions, thereby increasing the rate of those reactions. This is essential for maintaining the highly ordered state of living organisms, as it counteracts the natural tendency towards increased entropy (disorder) as described by the second law of thermodynamics. Furthermore, the free energy change (ΔG) of a reaction determines whether it will occur spontaneously or require an input of energy. Enzymes can catalyze reactions with positive ΔG values by coupling them to other reactions with negative ΔG values, allowing the overall process to proceed in a favorable direction. This optimization of energy transformations is a key aspect of the structure and function of enzymes in biological systems.

Related terms

Enthalpy:

The total energy of a system, including the internal energy and the work done by or on the system.

Entropy:

A measure of the disorder or randomness in a system, which tends to increase over time as energy is transformed.

Gibbs Free Energy: A measure of the useful work that can be extracted from a system at constant temperature and pressure.