Chemical Reactions and Enzymes

Factors affecting reaction rates

• Substrate concentration

• Enzyme concentration

• pH, temperature, and ion concentrations

Learning Objectives

▪ Explain what happens to chemical bonds during chemical reactions.
▪ Investigate how energy changes affect whether a chemical reaction will

occur.

▪ Explain the role enzymes play in living things and what affects their

function.

Chemical Reactions

A chemical reaction changes one set of chemicals into another.
The elements or compounds that engage in a chemical reaction
are known as reactants.
The elements or compounds produced by a chemical reaction are
known as products.

Energy in Reactions

Chemical reactions that release energy often occur spontaneously.

Chemical reactions that absorb energy require a source of energy.

Which reaction can occur spontaneously?

Activation Energy

Activation Energy

Enzymes

Enzymes lower activation energy and speed up chemical reactions in cells.

Enzymes are Biological Catalysts

• They are proteins

• Catalysts speed up chemical reactions

• Structure = Function: Enzymes are specific to their Substrate (reactants). Active site of the enzymes fits together with the substrate(s)

• Different reactions require different enzymes

The Enzyme-Substrate Complex

Remember an enzyme
speeds up a chemical
reaction by lowering the
activation energy.

Enzymes are proteins.
Proteins are polymers
made of amino acid
monomers.

The Enzyme-Substrate Complex

There are over 20 amino
acids that can arrange to
form proteins. The order
of the amino acids
affects how the protein
folds which affects its
function.

Enzymes have an active
site, its shape is specific
to certain molecules.

The Enzyme-Substrate Complex

This enzyme is specific
for carbon dioxide and
water.

The reactants in a
reaction are called
substrates when they
are acted on by an
enzyme.

While attached to the
enzyme, the substrates
(reactants) are converted into products and
released.

The Enzyme-Substrate Complex