Protein Structure

Chemicals composed of C, H, O, N, and S.

Primary structure: order of amino acids.

Secondary structure: alpha helix or beta sheet.

Tertiary structure: globular arrangement of protein in space.

Quaternary structure: chains of polypeptides.

Enzymes

Metabolism: all the chemical reactions going on in a cell.

Catabolism: taking apart of molecules to make molecules.

Anabolism: putting together of molecules to make new molecules.

Active site: specific area of the enzyme which works on the substrate.

Substrate: molecule on which the enzyme works.

Enzymes are usually named according to the substrate on which they work.

Example: sucrose --> sucrase

Enzyme Properties

A protein catalyst (lowers activation energy of reactions to speed the reaction).

Made by ribosomes and found throughout the cell.

Unchanged by the chemical reaction it catalyzes.

Reusable in other reactions.

May use helper molecules:

Coenzymes: organic molecules formed from vitamins.

Cofactors: inorganic molecules formed from minerals.

Enzymes are specific: chemically structured so that they usually catalyze only one reaction.

Enzyme Reaction Rates

Concentration of enzyme or substrate

Temperature

pH: each enzyme has an optimum range.

Enzymes can be denatured if the temperature or pH is extreme.

Enzyme Action: Catabolism

Lock and Key Hypothesis

Enzyme and substrate fit together like a key fits a lock.

No change occurs in the enzyme.

Substrate changes.

Induced Fit Model

Enzyme’s active site changes slightly to fit the substrate.

Substrate’s surface changes slightly to fit the enzyme.

Enzyme leaves reaction as it entered.

Substrate is changed during reaction.

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