Enzymes And Metabolism

Front 1

What are enzymes?

Back 1

Proteins that allow biological reactions to occur faster by reducing the energy of activation required for the reaction to take place between a substrate and a product.

Front 2

What is the structure of enzymes?

Back 2

globular proteins that can take a variety of shapes

Front 3

active site of enzyme

Back 3

key structural aspect of an enzyme is the active site, a unique region which binds the substrate

Front 4

allosteric site

Back 4

a region removed from the active site which allows molecules to bind and affects enzyme function.

Front 5

change in G (free energy) and enzyme

Back 5

changes in a reaction with (lower) and without (higher) an enzyme.

Front 6

What is the induced fit hypothesis

Back 6

describes the interaction between an enzyme and a substrate. After which, a conformational change occurs bringing together the various components of the enzyme allowing for the enzyme to catalyze the reaction via a stabilized transition state. For example, sucrose which catalyzes the hydrolysis of sucrose into glucose and fructose

Front 7

five modulators of enzyme activity

Back 7

Environmental conditions
Cofactors
Inhibition
Allosteric regulation
Cooperativity

Front 8

What are two environmental conditions which affect enzyme activity?

Back 8

Temperature

Most enzymes work at body temperatures (35C to 40C), but some bacterial enzymes (e.g. thermophiles in hot springs) can work at higher temperatures. In fact, the DNA polymerase isolated from thermophiles is used in PCR reactions.
pH
Enzymes change their shapes depending on the pH. For example, pepsin works best at a pH of 2 while trypsin works at a pH of 8.

Front 9

What are...




Cofactors?

Back 9

Non-protein molecules which allow enzymes to be active, e.g. vitamins.




These molecules typically bind by weak bonds. In the event that the bond is strong, these cofactors are called prosthetic groups.

Front 10

Apoenzymes?

Back 10

An enzyme that does not have its cofactor and is inactive.

Front 11

Holoenzymes?

Back 11

An enzyme that has its cofactor and is active.

Front 12

What are three forms of inhibition?

Back 12

feedback, irreversible, reversible inhibition

Front 13

Feedback inhibition:

Back 13

when the product of a reaction can bind to the enzyme in the pathway and inhibit it (this is a form of allosteric inhibition, see below).

Front 14

Irreversible inhibition:

Back 14

when a molecule interacts with an enzyme using covalent bonds or damages the enzyme's structure and permanently inhibits it.

Front 15

Reversible inhibition:

Back 15

when a molecule interacts with an enzyme using noncovalent bonds and decreases the enzyme's activity

2 types: competitive and non-competitive inhibition

Competitive inhibition whereby an inhibitor competes with the substrate for the enzyme's active site.
Noncompetitive inhibition whereby an inhibitor binds to an enzyme away from the active site, i.e. an allosteric site.