chem final enzyme

enzymes

Enzymes are specialized, water-soluble globular proteins that act as biological catalysts, speeding up chemical reactions by lowering their activation energy. They are essential for virtually all cellular processes, enabling reactions to occur rapidly and efficiently under normal body conditions. Without enzymes, processes like digestion would take decades. They function both in body fluids and when attached to cell membranes, directing and catalyzing nearly every activity within the cell.

what makes enzymes remarkable

▪ increase reaction rates from 109 to 1020 times

▪ they are very specific

what the specificity of enzymes means

• each enzyme catalyzes one reaction or a certain type of reaction

• they are also stereospecific – can catalyze an L-amino acid but not a D-amino acid

enzyme activity

measure of how many times the reaction reate is increased

what factors affect enzyme activity

▪ enzyme-substrate concentration

▪ temperature

▪ pH

▪ solvents

Enzyme-substrate concentration

➢ The substrate must first bind to the enzyme to form the enzyme- substrate complex

➢ If the enzyme concentration is kept constant, increasing the substrate concentration increases the rate until the substrate saturates the enzyme. At this point the rate reaches its maximum and cannot increase.

temperature

➢ At low temp, most enzymes show little activity because there is not sufficient energy for the reaction to take place.

➢ At higher temp, enzyme activity increases because the moleculesare moving faster and having more collisions.

➢ Enzymes are most reactive at body temp. 37oC. Above 50oC, the shape of most proteins is destroyed.

pH

➢ Most active at their optimum pH of about 7.4.

➢ A pH which is above or below the optimum, causes a change in the three-dimensional structure, disrupting the active site.

➢ Enzymes cannot bond effectively to the substrate.

➢ If small changes in pH are corrected, an enzyme can regain its structure and activity

State the model of enzyme action:

E + S ----> ES* -- E + P

enzyme + substrate→ enzyme substrate complex = Enzyme + product

enzyme-substrate complex

➢ Enzyme must first bind to the substrate in a way that favors catalysis.

➢ There is a region called the active site where the enzyme binds to the substrate and catalyzes the reaction.

➢ The proper alignment of a substrate within the active site forms the enzyme-substrate complex

lock and key medoel of enzyme action

➢ The active site is considered to have a rigid, nonflexible shape.

➢ Only substrates with shapes that fit exactly into the active site are able to bond with that enzyme.

➢ Shape of the enzyme is compared to a lock, and the substrate is the key that fits into the lock.

Induced Fit Model

➢ Interaction between both the enzyme and the substrate.

➢ The active site adjusts to fit the shape of the substrate more closely.

➢ At the same time, the substrate adjusts its shape to better fit into the active site

cofactor

the additional chemical groups appearing in enzymes that are conjugate proteins they must consist of metal ions or complex organic molecules

apoenzyme

the protein part of the enzyme molecule

coenzyme

a cofactor which is a complex organic molecule other than a protein

substrate

chemical substance or substances upon which the enzyme acts

activation

any process that intiates or increases the action of an enzyme

inhibition

any process that makes an active enzyme less active or inactive

competitive inhibitors

bind to the active site of the enzyme surface which prevents the binding of a substrate

noncompetitive inhibitiors

bind to some other portion of the enzyme surface which alters the teritary structure of the enzymes so that its catalytic effectiveness is reduced