BIO 101 8a: Thermodynamics

First law of thermodynamics

energy can be transformed from one type to another, but it can’t be created or destroyed

Second law of thermodynamics

entropy is always increasing in the universe

potential energy

stored energy available to do work

high potential energy

long, weak, nonpolar bonds

low potential energy

short, strong, polar bonds

kinetic energy

the energy of motion

Gibbs free energy (G)

the amount of stored energy in a system that is available to do work

ΔG (delta G)

The change in free energy during a chemical reaction (ΔG = Gproducts - Greactants)

Exergonic reaction

a spontaneous, energetically favorable reaction where ΔG is negative; loss of free energy, increase in entropy

Endergonic reaction

a nonspontaneous, energetically unfavorable reaction where ΔG is positive; requires input of energy and decrease of entropy

ΔGº (delta G-naught)

The standard free energy change of a reaction measured under conditions

Standard conditions

reference state defined as a 1M starting concentration, a temperature of 298K, and 1atp

Equilibrium

The state in a reversible reaction where the forward and reverse reaction rates are perfectly equal; chemical concentrations stop changing

Equilibrium constant (Keq)

The unitless ratio of product concentration to reactant concentration at equilibrium

Keq > 1

The reaction favors products, making delta G-naught negative (spontaneous)

Keq < 1

The reaction favors reactants, making delta G-naught positive (nonspontaneous)

Thermodynamic Formula

ΔGº = -RTlnKeq

Energetic coupling

The process of pairing an exergonic reaction with an endergonic reaction, the energy released by the first drives the second

ATP (adenosine triphosphate)

The primary energy currency of a cell, which stores energy in phosphoanhydride bonds and transfers it using phosphate groups

phosphorylation

The addition of a phosphate group to a substrate, which raises the substrate’s potential energy

kinases

the specific class of enzymes that catalyze phosphorylation reactions

activated intermediate

a temporary, higher-energy substrate molecule generated via phosphorylation that allows an unfavorable reaction to proceed

NTPs (Nucleoside Triphosphates)

High-energy molecules whose hydrolysis drives the synthesis of macromolecules like polysaccharides, nucleic acids, and proteins

Redox reactions

reduction-oxidation processes that transfer energy by electrons between molecules

oxidation

The loss of one or more electrons (or gain of H+) from a molecule; an exergonic process

reduction

the gain of one or more electrons (or loss of H+) by a molecule; an endergonic process

Dehydrogenases

enzymes that catalyze biological redox reactions by transferring electrons and accompanying protons from a donor to an acceptor

catabolic pathway

reactants are broken down into smaller moles

anabolic pathway

smaller moles are turned into a product of large complex moles

how cells get energy

acquire molecules from the environment, uses leftover monomers as building blocks, metabolism.