Chemistry: Energy and Reactions

Study Notes

Energy is the ability to promote change or do work.
Energy exists in two forms: kinetic energy, associated with movement, and potential energy, due to structure or location.
Chemical energy, the energy stored in molecular bonds, is a form of potential energy.

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, but can be transformed from one type to another.
The second law of thermodynamics describes the transfer of energy from one form to another, which increases the entropy (degree of disorder) of a system.
Entropy increases as less energy becomes available to promote change.

Enzymes are biological catalysts that speed up the rate of chemical reactions without being consumed in the process.
Enzymes have a high specificity for their substrate, meaning they only interact with specific molecules.
The lock-and-key model describes the interaction of an enzyme and substrate where only the correct key (substrate) will fit into the lock (enzyme).
Induced fit, however, involves a conformational change in both the enzyme and substrate upon binding, further enhancing the reaction.

Saturation: An enzyme's rate of reaction reaches a plateau when all active sites are occupied by substrate (Vmax).
Michaelis constant (Km): The substrate concentration where the reaction velocity is half maximal. A high Km indicates a lower affinity between the enzyme and substrate.

Competitive Inhibition: A molecule binds to the active site of an enzyme, inhibiting the substrate from binding, which increases the apparent Km.
Noncompetitive Inhibition: An inhibitor binds to an allosteric site (a site other than the active site), lowering the Vmax but not impacting the Km.

Metabolism is the sum of all chemical reactions that occur within a living organism.
Anabolism is the building of complex molecules from simpler ones.
Catabolism is the breakdown of complex molecules into simpler ones.
Organic molecules are constantly recycled through metabolic pathways, ensuring a continuous supply of nutrients.
During degradation, nucleic acids are broken down into their nucleotide monomers which can be recycled to synthesize new nucleic acids or used as energy sources.
Ribozymes are catalytic RNA molecules that can act as enzymes.