A.Bioenergetics
➢ Glucose, starch, and fat all energy-rich, but the bonds must be broken in order for the energy to be released
➢ First Law of Thermodynamics: Energy cannot be created or destroyed. The sum of energy in the universe is constant.
➢ Second Law of Thermodynamics: Energy transfer leads to less and less organization. The universe tends towards entropy
➢ Types of Reactions
- Exergonic
■ Products have less energy than the reactants
■ Energy is given off during the reaction
■ Ex. oxidation of molecules in mitochondria
- Endergonic
■ Require an input of energy
■ Products have more energy than reactants
■ Ex. plants’ use of $CO_2$ and water to form sugars
B. Gibbs Free Energy
➢ $ΔG=ΔH-TΔS$
- T=temperature
- H=enthalpy (measure of energy in a thermodynamic system)
- S=entropy
- Change in the Gibbs free energy of a reaction determines whether the reaction in
favorable (spontaneous, negative) or unfavorable (nonspontaneous, positive) - Used to figure out if, without adding energy, the reactants will stay as they re or be converted to products
➢ Spontaneous Reactions
- Occur without a net addition of energy
- $ΔG<0$=exergonic
- $ΔG>0$=endergonic
■ Only occur if energy is added
➢ Activation Energy - Even though exergonic reactions release energy, the reaction still needs energy to start off with
■ Reactants must first go into transition state before turning into products
■ Activation energy is the energy needed to achieve the transition state
■ Bonds must be broken before new bonds can form