(7112) AP Biology Unit 3 Crash Course: Cellular Energetics!

Overview of Cellular Energetics

• Discussion on energy types and their relevance to biology.

• Major topics to be covered: Enzymes, Photosynthesis, Cellular Respiration.

Types of Energy

Kinetic Energy

• Defined as the energy of movement.

• Examples: Moving objects, heat generation through friction (rubbing hands together).

Heat Energy

• Related to the temperature; higher temperature indicates higher energy.

Chemical Energy

• Defined as the energy stored in the bonds of molecules.

• Acts as potential energy, which can be released to do work.

• Important in biological systems for energy storage and transfer.

Energy Transfer

Thermodynamics

• Science of energy transfer.

• Key Laws:

  First Law of Thermodynamics

  • Energy cannot be created or destroyed; it can only be transferred from one form to another (Conservation of Energy).

  Second Law of Thermodynamics

  • Entropy (disorder) in the universe is always increasing.

  • Example: Ice crystals (low entropy) vs. liquid water (high entropy).

Gibbs Free Energy

• Fundamental equation: ΔG = ΔH - TΔS

  • ΔG: Gibbs free energy; amount of energy available to do work.

  • ΔH: Enthalpy; total energy or potential energy system.

  • T: Temperature.

  • ΔS: Entropy; disorder in the system.

Importance of Gibbs Free Energy

• Determines if a reaction can occur spontaneously:

  • If ΔG > 0: Non-spontaneous; requires energy input.

  • If ΔG < 0: Spontaneous; energy is released and can do work.

Endergonic vs. Exergonic Reactions

• Endergonic: Reactions with positive ΔG; require energy input.

• Exergonic: Reactions with negative ΔG; spontaneous and release energy.