Proteins and Enzymes

Proteins have many different functions in the body

Structure – proteins help provide structure and support, make up muscles and bones

Protein Function

Transport – some proteins help to carry things around the body or into and out of cells

Protein Function

Hormones – messenger proteins that carry signals throughout your body

Enzymes – proteins that help with chemical reactions

Antibodies – proteins that help protect the body from infection

Protein Function

Proteins can have up to 4 levels of organization◦ Primary◦ Secondary◦ Tertiary◦ Quaternary

Proteins

Primary protein organization = the initial chain of amino acids

Peptide bond – the bond between amino acids to form the long chain we call a protein

Primary Level

Secondary structure consists of two shapes◦Alpha helix◦Beta sheets

Caused by hydrogen bonding

Secondary Level

Three dimensional structure of a single protein molecule

Caused by hydrophobic interactions

Tertiary Level

3D structure with multiple protein subunits Held together by disulfide bonds

Quaternary Structure

Some proteins help to control reactions and cell processes

Enzyme – Specific proteins that can speed up reactions

Enzymes

Energy can be either released or absorbed whenever chemical bonds form or are broken

Living things carry out chemical reactions that require energy

Organisms need a source of energy◦ Plants have the sun◦ Animals eat food

Energy in Reactions

Activation energy – the energy needed to start a chemical reaction

Energy in Reactions

Remember! Some reactions give off energy…and some

absorb energy!

Energy in Reactions

Chemical reactions that release energy often occur spontaneously

Chemical reactions that absorb energy won’t happen without an input of energy

Spontaneous Reactions

Draw two energy reaction graphs in your notes!

Catalyst –a substance that speeds up the rate of a reaction

Catalysts lower activation energy

Enzymes are biological catalysts! They help speed up chemical reactions in your body!

Catalyst

Enzymes are very specific!

A single enzyme usually only works with one type of reaction

HINT: The name of an enzyme usually has something to do with reaction it works with

Enzymes almost always end with –ase!!!

Enzymes Action

Each enzyme will combine with only a specific molecule

Substrate – the molecule an enzyme binds to in a reaction

We call this the “lock and key model”

Why are enzymes so specific?

Like a key in a lock…each enzyme fits only one substrate molecule

Lock and Key Model

Lock and Key Model

Enzymes are picky…they only like to work under certain conditions

Each enzyme is designed to work in a certain temperature range

Enzymes in your body work best at 37 ºC

Temperature and pH

pH also plays a role on enzyme activity

Enzymes in your stomach work best at a pH of around 2

Each enzyme works best at a specific pH level◦ Most around 7.4 …Why?

Temperature and pH

What type of molecule are enzymes?

Proteins

Proteins are made up of what type of molecules?

Amino acids

Quick Review

The amino acids that make up proteins and enzymes are held together by which type of bond?

Peptide bond

Quick Review

How do enzymes help speed up a chemical reaction?

Lower the reactions activation energy

What are two things that can change how well an enzyme works?

Temperature and pH

Quick Review

Each enzyme works on one particular substrate

“Lock and Key Model”

Quick Review

Enzymes aren’t used up!

Once the reaction is done, the enzyme is left unchanged and can continue its job

So enzymes are reusable!

A few more things about enzymes…

pH and Temperature have an effect on enzyme activity

Denature – when a protein loses its shape and can no longer work

http://www.sumanasinc.com/webcontent/animations/content/proteinstructure.html

Stopping an Enzyme