8.1: Speeding Up Chemical Reactions

activation energy (Ea)

energy barrier that blocks the tendency for a chemical reaction to occur

catalysts

substances that speeds up reactions without themselves being permanently altered and allows equilibrium to be approached more quickly

• e.g enzymes

enzymes

protein that catalyzes biological reactions.

substrate

molecule that reacts in the active site in an enzyme-catalyzed reaction.

transition state

high energy state after substrate binds to enzyme which lowers Ea - begins formation of products

active site

part of tertiary structure of enzymes where substrates bind - only specific substrates bind to certain enzymes

enzyme-substrate complex

when a substrate binds to active site = held together by hydrogen bonds, electrical attraction or temp covalent bonds = gives rise to product and free enzyme

enzymes and activation energy

enzymes lower the activation energy required for a reaction to occur, thereby increasing the rate of the reaction.

enzyme-substrate reactions

substrate orientation, physical strain, chemical charge - can use multiple

substrate orientation

is the positioning of substrates in a way that facilitates the formation of a product

physical strain

when substrate binds enzyme causes bonds in substrates to stretch by putting it into unstable transition state = causes strained bonds which are easier to break

chemical charge

enzyme either adds charges or change the polarity of the bonds within that substrate which changes that substrate's state

what influences enzyme’s specificity

substrate structure, active site shape, and interactions of chemical groups at active site

induced-fit

describes how enzymes undergo a conformational change upon substrate binding, to adjust to give an optimal fit

enzyme partners

some enzymes require presence of nonprotein chemical partners to work - prosthetic groups, inorganic cofactors, coenzymes

prosthetic groups

nonprotein molecules permanently attached to enzymes that assist in their function

inorganic cofactors

metal ions, copper and zinc which binds to certain enzymes - not always permanent

coenzymes

organic molecules that temporarily associate with enzymes and assist in catalysis, often derived from vitamins.

saturation

the point at which an enzyme is working at maximum efficiency, with all active sites occupied by substrates.