2.1 Introduction to Energy + 2.2 Activation Energy & Enzymes

What is thermodynamics?

• The study of the flow of energy in systems

• First Law of Thermodynamics:

  • Energy cannot be created or destroyed, but can be converted from one form to another

• Second Law of Thermodynamics:

  • Energy transfers are never 100% efficient

  • Always accompanied by a loss of energy in the form of heat

What is energy?

• The ability to:

  • Do work

  • Bring about a change

What are the two states of energy?

• Kinetic

  • Energy of motion

• Potential

  • Stored energy

What are the different forms of energy?

• Thermal

  • Heat

• Electrical

  • Flow of charged particles

• Nuclear

  • Radioactive decay

• Light

  • Waves of photons

• Sound

  • Mechanical waves moving through air

• Chemical

  • Potential energy stored in chemical bonds

  • Only type of energy organisms can use

    • Glucose contains chemical potential energy stored in its covalent bonds

Organisms need energy every second. What for?

• Active transport

  • Nerve transmission

  • Homeostasis

  • Muscle contraction

• Anabolic reactions

  • Synthesis reactions

  • Endothermic

  • Energy provided by hydrolysis of ATP

• Catabolic reactions

  • Release of stored chemical potential energy in bonds

  • Exothermic

  • Digestion/cellular respiration

• Organisms depend on the ability to transfer energy in & out of their cells

• Energy is transferred mostly through redox reactions

What is entropy?

• A measurement of the degree of disorder and randomness in a system

• The higher the more random

• In a closed system it always increases

• Entropy and energy are inversely related

  • Higher entropy = lower amount of available energy to do work

• If a reaction increases the randomness of the universe, the reaction will occur spontaneously

What is activation energy (E_A)?

• Energy required to initiate a reaction

  • For chemical reaction

    • It helps destabilize existing bonds

    • Increases entropy

    • Is usually in the form of heat

What are enzymes?

• Biological catalysts

• Proteins

• Have specific 3° structure

• Initiates and speeds up reactions

How do enzymes work?

1. Substrate binds to enzyme’s active site

2. After binding they form the enzyme-substrate complex which decreases E_A

3. When the enzyme and substrate react, the chemical bonds in the substrate weaken which causes them to link together

4. The chemical reaction at the active site leads to the formation of a different molecule (product)

5. The product is then released and the enzyme returns to its original state

What do the rates of reaction depend on?

• Temperature

• Concentration

• Pressure