Bio1 Wed 9/30 Chemical Reactions in Cells and Organisms

+ continuation of 9/28 lecture Interactions Between Molecules

What are Van der Waals interactions? What causes them?

temporary weak attractive forces between any kind of molecule, as a result of random electron movement and displacement

What are hydrophilic vs hydrophobic molecules?

Hydrophilic molecules can form hydrogen bonds and easily dissolve in water.

Hydrophobic molecules typically contain nonpolar covalent bonds so they cannot form hydrogen bonds and do not dissolve very well in water. They tend to clump because water will orient around aggregates of nonpolar molecules.

What are reversible reactions?

reactions in which both the forward and reverse reactions occur, so the net direction depends on the rates of the forward and reverse reactions

Most biological processes are reversible reactions

Equilibrium State

the point in a reversible reaction where the forward and reverse reactions happen at equal rates

This represents the most energetically favorable/lowest-energy state, with the highest entropy.

When is a reaction spontaneous?

When it can proceed without adding any external energy. The reaction must have a negative Gibbs energy, aka results in a higher entropy.

The reaction that is spontaneous from left to right is non-spontaneous from right to left.

How do you calculate equilibrium constant K_eq? What does it mean?

• The [ ] square brackets denote the concentrations in mol/L.

K_eq = 1 indicates that the equilibrium mixture contains equal amounts of reactant and product.

K_eq < 1 indicates that the equilibrium mixture contains higher concentrations of reactant than product.

K_eq > 1 indicates that the equilibrium mixture contains higher concentrations of product than reactant.