Enzymes Flashcards

Flashcards about Enzymes

Enzymes

Biological catalysts, mostly proteins (some RNAs), that increase reaction rates by 10^9 to 10^20 times.

Ways Enzymes Facilitate Reactions

Bringing substrates together, orienting substrates, stabilizing the transition state, and eliminating translational and vibrational motion

General Properties of Enzymes

High reaction rates, Milder reaction conditions, Greater reaction specificity, Capacity for regulation

Functions of Agricultural Enzymes

Increase crop production, soil fertility, and food protection.

Agricultural enzymes

Help increase crop production, soil fertility, and food protection.

Phosphatases

Hydrolytic soil enzymes essential in the phosphorus cycle.

Dehydrogenase

Enzymes that cause the biological oxidation of soil.

Urease

Enzyme that breaks down urea-based fertilizers in the soil.

Oxidoreductases

Catalyze redox reactions.

Transferases

Transfer a group from one molecule to another.

Hydrolases

Cleave bonds by adding water.

Lyases

Catalyze removal of groups to form double bonds or the reverse break double bonds.

Isomerases

Catalyze intramolecular rearrangements.

Ligases

Catalyze a reaction in which a C-C, C-S, C-O, or C-N bond is made or broken

Substrate

The compound or compounds whose reaction an enzyme catalyzes.

Active site

The specific portion of the enzyme to which a substrate binds during reaction.

Ordered Mechanism

Substrates have to bind to the enzyme in a specific order.

Random Mechanism

Substrates can bind to the enzyme in any order.

Ping-pong Mechanism

Substrate binds to the enzyme and releases a product before the second substrate binds to the enzyme.

Catalytic Mechanisms

Acid-base catalysis, Covalent catalysis, Metal ion catalysis, Proximity and orientation effects, Preferential binding of the transition state complex

Lock and Key Enzyme Model

Enzyme is assumed to be the lock and the substrate the key; fails to take into account protein's conformational changes.

Induced Fit Enzyme Model

Assumes the enzyme active site is a flexible pocket whose conformation changes to accommodate the substrate molecule.

Enzyme Specificity

The ability of an enzyme to bind only one, or a very few, substrates.

Absolute Enzyme Specificity

Enzyme reacts with only one substrate.

Group Enzyme Specificity

Enzyme catalyzes reaction involving any molecules with the same functional group.

Linkage Enzyme Specificity

Enzyme catalyzes the formation or break up of only certain category or type of bond.

Stereochemical Enzyme Specificity

Enzyme recognizes only one of two enantiomers.

Active enzyme / Holoenzyme

Polypeptide portion of enzyme (apoenzyme) and Nonprotein prosthetic group (co-factor).

Coenzymes

An organic molecule bound to the enzyme by weak interactions / Hydrogen bonds.

Environmental Effects on Enzymes

The environment surrounding an enzyme can have a direct effect on enzyme function.

Allosteric Enzymes

Effector molecules change the activity of an enzyme by binding at a second site.

Allosteric Effector

Substrate, inhibitor, or activator that binds to an allosteric enzyme and affects its activity.

Homotropic Effects

Allosteric effects that occur when several identical molecules are bound to a protein.

Heterotropic Effects

Allosteric effects that occur when different substances are bound to a protein

Feedback Inhibition

A product late in a series of enzyme-catalyzed reactions serves as an inhibitor for a previous allosteric enzyme earlier in the series.

Proenzymes

Enzyme made in an inactive form that is converted to its active form by proteolysis when needed at the active site in the cell.

Protein Modification

Chemical group is covalently added to or removed from the protein.

Irreversible Inhibitors

Bind tightly to the enzyme and thereby prevent formation of the E-S complex.

Reversible Competitive Inhibitors

Often structurally resemble the substrate and bind at the normal active site.

Proteolytic Enzymes

Cleave the peptide bond in proteins.