Enzymes

Chemical Reactions in CellsThe molecule you start with is called

the SUBSTRATE (also known as the reactant).

The molecule you end up with is called the PRODUCT.

SUBSTRATE PRODUCT

Chemical Reactions in CellsGlycogen Glucose + Glucose +

Glucose

Amino Acid + Amino Acid Protein

Substrate Products

Substrates Product

Enzymes – Made of PROTEINEnzymes are :

catalysts in living organismsA catalyst is a molecule which speeds up chemical reactions.

SubstrateProducts Enzyme makes it happen more quickly

Enzyme

Shoulder partner examples

In order to speed up reactions, the substrate must fit PERFECTLY into a place on the enzyme known as the ACTIVE SITE.

The active site and substrate fit together like a lock and a key.

Products

Products

The enzymes bind the substrates, and force them into a position which makes it easier for bonds to be broken so they can be converted into products.

Enzyme activity can be affected by several factors

Enzymes are proteinsEach protein

has its own unique shape that is perfect for its function.

Protein structure is very delicate.

Protein structure can be:

Denatured (destroyed) by high temperatures

Denatured by changes in pH

When an enzyme is denatured, the shape of its active site is changed, so the active site (lock) no longer matches the substrate (key).

Effect of temperature on enzyme activity

Low temp. – molecules move slowly

As temperature increases to optimum temperature, molecules move faster and reaction rate increases

At very high temp. – enzyme structure is denatured

Effect of pH on enzyme activity

Enzymes have an optimum pH, which is the pH at which they work best

At other pH’s, enzymes are denatured

Competitive inhibitors of enzymes

•Competitive inhibitor competes with the substrate for the active site.•Therefore, the substrate is sometimes prevented from binding to active site.

Many chemical reactions occur in living organisms

Examples:Break down starch into many glucose molecules

Link amino acids together to build proteins

Effect of competitive inhibitors on enzyme activity

Normal activity

Increasing substrate concentration →

Effect of amount of substrate on enzyme activity

concentrationIncreasing substrate

Effect of amount of enzyme on enzyme activity

Increasing enzyme concentration →

Essential points to understandEnzyme activity is affected by:

TemperaturepHSubstrate concentrationEnzyme concentrationCompetitive inhibitors