Ch 2.4 LESSON Reactions and Enzymes

Chemical Reactions and Enzymes

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.

Labelling

Label the equation

Drag labels to their correct position on the image

reactants

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

Multiple Choice

Which reaction would be more likely to occur spontaneously?

Multiple Choice

Why might this reaction occur spontaneously?

• Energy is released.

  Products have less energy than reactants.

• Energy is released.

  Reactants have less energy than products.

• Energy is absorbed.

  Reactants have less energy than products.

• Energy is absorbed.

  Products have less energy than reactants.

Multiple Choice

To start a reaction, it requires ______ energy.

• reactant

• activation

• product

• enzyme

Enzymes

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

Multiple Select

What two effects do enzymes have on a reaction?

• raise activation energy

• lower activation energy

• speed up the reaction

• slow down the reaction

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.

Multiple Choice

Enzymes speed up chemical reactions in living things.

Which type of macromolecule are enzymes?

• carbohydrate

• protein

• nucleic acid

• lipid

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.

Multiple Select

Which TWO are true of the active site on an enzyme?

• it's shape is determined by the folding of amino acids

• it's shape will conform to any substrate

• it's shape is specific to fit only certain molecules

• it's shape is determined by the folding of sugars

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.

Multiple Choice

What is a substrate?

• the background fluid in a chemical reaction

• product of a chemical reaction with an enzyme

• reactant that uses an enzyme in a chemical reaction

• molecule that provides the activation energy

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

The Enzyme-Substrate Complex

Match

Put the following steps in order

• substrates bind to an enzyme

• enzyme-substrate complex is created

• substrates are converted into products

• products are released

Step 1

Step 2

Step 3

Step 4

• Step 1

• Step 2

• Step 3

• Step 4