EnzymesEssential Questions:What is an enzyme?

How do enzymes work?What are the properties of enzymes?

How do they maintain homeostasis for the body?

What happens to the food we eat?

It gets broken down!

Many substances have lactose in it. Why can we not accept lactose the way it is?

It is too big! Our body cannot process it.

So we have enzymes to break it down.

What happens to the food we eat?

What are Enzymes?• Enzymes are proteins which act as biological

catalysts.– A catalyst is a substance

that starts or speeds up a chemical reaction.

– It lowers the activation energy required for the reaction to take place.

• Enzymes are used by cells to trigger and control chemical reactions.

• Without enzymes, several reactions in cells would never occur or happen too slowly to be useful.

Wait, What is a Chemical Reaction?

• The process of changing one set of chemicals (reactants) into another set of chemicals (products) by rearranging the atoms.

• The bonds joining the reactants are broken and new bonds are formed in the products.

• All life processes are driven by chemical reactions

2H2 + O2 → 2H2O

Wait, What is activation energy?

• Activation energy is the amount of energy needed to start a chemical reaction.

How do enzymes speed up reactions?• Enzymes lower activation energy

How do Enzymes Work?

• Enzymes catalyze (speed up) chemical reactions between reactants (substrates) that form new products.

• After the reaction, enzymes are unchanged and ready to catalyze the next reaction.

What is a substrate?• Enzymes bind to molecules called substrate(s).• The(se) substrate(s) are the reactants in the

chemical reaction that is catalyzed by the enzyme.

• Example: Typically something we ingest that needs to be broken down further for use by the body like Lactose from Cow’s milk. (Done by Lactase)

What enzyme breaks down lactose?

What are Enzymes?

LactaseWhat is the function of Lactase?

Lactase breaks lactose into the smaller sugars glucose and galactose

• Proteins!

• What is the monomer of an enzyme (or any protein)?

• What does the function of an enzyme depend on?

• What do nucleic acids (DNA) have to do with enzymes?

What are Enzymes?

Enzyme Activity: Locks & Keys• Enzymes provide an area where

reactants can be brought together to react.

• The site on the enzyme where the substrates bind is called the active site.

• The substrate(s) enters the active site which becomes the enzyme-substrate complex.

• The shape of an enzyme is so specific that generally only one enzyme will work for one substrate(s).

The fit is so exact that the active site and substrates are compared to a “lock and key”.

Enzyme Activity: Catch & Release• After undergoing a

reaction in the enzyme-substrate complex, the changed substrate is released as a product to be used by the body.

• Since only the substrate changes during the reaction, the enzyme can be reused again and again.

The fit is so exact that the active site and substrates are compared to a “lock and key”.

Induced Fit Hypothesis

• Enzymes can change shape slightly to fit the substrate a little better (like a hand in a glove).

The Enzyme Catalyzed Reaction

E + S ESC E + P

Enzyme + Substrate yields Enzyme Substrate Complex yields Enzyme + Product

So many enzymes!

• Recall: Based on what you know about proteins, what is it about enzymes that allows each one to be specific to a single substrate? (ie: how are there so many different enzymes to fit all of the different substrates in our bodies?)

• Recall: What is it each amino acids that makeseach one different?

Because of the different combination of the 20 essential amino acids!

The R-group!

What factors affect enzyme function?1. Enzymes work best at specific temperatures and pH.

– Extreme temperature and pH can change the shape of the enzyme, affecting the binding “active” site.

– Recall: What is the term for destroying an enzymes (or any protein)?

– Enzymes in our body work best at 37°C (98.6°F) and at a pH between 6.5 to 7.5.

2. Cells contain proteins that turn enzymes on or off during critical stages of development.

Enzyme Characteristics: Review• Enzymes are catalytic proteins.

Enzymes…

1. …speed up reaction rate. They do not change the reaction.

2. …are very specific.

3. …work like locks & keys.

4. …are unchanged by the reaction.

5. …function depends on structure (shape)

6. …are sensitive to changes in temperature and pH.

The suffix –ase means it is an enzyme.– Example: lactase, phenolase, sucrase