Enzymes and Catalysis Study Guide

Flashcards about Enzymes and Catalysis

Catalyst

A chemical that increases the rate of reaction without changing the nature of the reaction or being changed by the reaction

Enzyme

A protein catalyst that increases the rate of specific chemical reaction

How Enzymes Catalyze

Enzymes lower the activation energy required for a reaction to proceed, allowing a larger portion of reactants to participate, increasing reaction rate.

Enzyme Structure

Large proteins with complex 3D shapes, with ridges, grooves, and pockets lined with specific amino acids; shape allows substrates to fit into the active site.

Mechanism of Enzyme Action

Substrates fit into active sites, enzyme-substrate complex forms, reaction occurs, products dissociate, enzyme is unaltered

-ase

A suffix used in naming almost all enzymes (with some exceptions).

Phosphatases

Catalyze the removal of phosphate groups.

Synthases and Synthetases

Catalyze dehydration synthesis reactions.

Dehydrogenases

Remove hydrogen atoms from substrates.

Kinases

Add phosphate groups to a particular molecule.

Isomerases

Rearrange atoms within their substrate molecules to form structural isomers.

Factors Affecting Enzyme Activity

Rate depends on enzyme concentration, pH, and temperature; Extreme temperature can denature it.

Inactive Enzymes

Many enzymes are produced in an inactive form but become active by phosphorylation and inactivated by dephosphorylation .

Cofactors

Ions or small organic molecules needed for the activity of specific enzymes; Aids in temporary bonding between enzyme and substates

Coenzymes

Organic molecules, derived from vitamins, that are needed for the function of particular enzymes. Act as 'taxi cabs'.

Law of Mass Action

The principle that reversible reactions will be driven from the side of the equation where the concentration is higher to the side where the concentration is lower

Metabolic Pathway

Sequences of enzymatic reactions that begin with an initial substrate, progress through intermediates, and end with a final product.

End-Product Inhibition

Occurs when a product in a divergent pathway inhibits the activity of the branch-point enzyme.

Inborn Error of Metabolism

An inherited defect in a gene that codes for a polypeptide.

Endergonic Reactions

Require an input of energy to proceed; products contain more free energy than reactants.

Exergonic Reactions

Release energy as the process occurs; products contain less free energy than reactants.

Oxidation and Reduction

When an atom or a molecule gains electrons, it is said to become reduced. When it loses electrons it is said to become oxidized.

NAD and FAD

Coenzymes that function as hydrogen carriers.

Reduction

If a molecule gains electrons

Oxidation

If molecule loses electrons

Mechanisms of Controlling Enzyme Activity

Phosphorylation, allosteric modulators, end-product inhibition, and competitive inhibition.

Competitive inhibition

Binds to active site on enzyme or binding site on receptor and inhibits activity