Thermodynamics and Energy in Biological Reactions

Energy

the capacity of something to cause change

Thermodynamics

the study of the energy transformations that occur in a collection of matter

First Law of Thermodynamics

States that the total amount of energy in a system (a collection of matter) is constant.

Second Law of Thermodynamics

States that every energy transfer or transformation increases the disorder (entropy) of the universe

Entropy

a measure of disorder, or randomness, of the environment

Free Energy (G)

the portion of the total energy in a reaction that a cell can use to carry out some process.

Change in Free Energy (AG)

can tell us if energy is released or consumed during the course of a chemical reaction

Endergonic Reactions

If AG > 0, energy input is required for the reaction to occur

Exergonic Reactions

If AG < 0, the reaction will happen spontaneously

Activation Energy (EA)

Minimum amount of energy required to start any chemical reaction

Enzymes

Biological catalysts that lower the activation energy (EA) for reactions

Active Site

the place on or in the enzyme where the chemical reaction is catalyzed

Cofactors

Atoms and other molecules that associate with certain enzymes in order to help catalyze the reaction

Coenzymes

Organic cofactors that are necessary for the function of certain enzymes

Metabolism

Sum total of all chemical reactions that take place in an organism

Anabolism

the portion of metabolism concerned with synthesizing biomolecules.

Catabolism

the portion of metabolism concerned with degrading biomolecules.

Gibbs Free Energy

G = change in Gibbs free energy

Ribozymes

Made of RNA molecules that provide structure and catalyze the formation of peptide bonds.

Sucrase

enzyme that breaks down sucrose into monosaccharides

Reforming the Phosphate

Bond

captures energy.

Hydrolysis of ATP

Breaking a phosphate bond releases energy.

Adenosine Diphosphate (ADP)

the product formed when ATP loses a phosphate group

Adenosine Triphosphate (ATP)

a nucleotide that functions as a cellular energy carrier

Noncompetitive (Allosteric)

Inhibitors

Bind to a site other than the active site and cause a change in shape of the active site

Competitive Inhibitors

Resemble the actual substrate, but do not actually undergo a chemical reaction

Feedback Inhibition

The accumulation of some end product slows down or stops the process that created it in the first place

Catalase

peroxisomal enzyme

Hexokinase

enzyme that functions during the first step of glucose breakdown