Do Now• Take out weekend homework. • Take out a sheet of paper for today’s

notes and answer the following questions: •What is a chemical reaction? •What is activation energy? • Describe what a saltine cracker tastes like. •What macromolecule composes saltines?

Saltine

• Chew the saltine in front of you for 2 minutes.

• What does it taste like? • How does it get to this point?

ENZYMES

Catalyst

Activation Energy

II. Chemical Reactions• Chemical reaction: the process of

making or breaking the chemical bonds that join atoms together

• Do chemical reactions take place in your cells? Yes!!! All the time.

• Metabolism: all the thousands of chemical reactions occurring together in a cell

III. Product/Reactant• The material at the beginning of a chemical

reaction is called the reactant(s)• The material produced at the end of a

chemical reaction is called the product(s).• 2H2 + O2 2H2O

Reactants Product

ADITL of an MIT freshman

• http://tech.mit.edu/V127/N36/sodiumdrop/video.htm

Activation Energy

• The energy needed to get a reaction started.

TAPE DEMO

Definition

• CATALYST- a substance that helps speed up the speed of the reaction

Practice

• Think of another example of a catalyst.

• Tell it to your partner and be prepared to share out your neighbor’s answer!

Biological Catalyst = Enzyme

• An enzyme is a protein, or protein complex, that catalyzes a chemical reaction

Enzyme Vocabulary• Catalyze (Verb): to begin or speed up a process• Catalyst (noun): something that speeds up the chemical

reaction. • Using these terms, how would you change the definition of

an enzyme?

An enzyme is a protein that speeds up a chemical reaction

Substrates = the reactants that the enzyme binds to in order to catalyze the reaction. Without the enzyme they would still react but much slower

How do enzymes work?An enzyme catalyzes a chemical reaction by binding lowering the activation energy of the reactionEnzymes are SUBSTRATE- SPECIFIC

That means the enzymes only work with certain reactants because each active site only fits certain reactants (substrates)If the substrate don’t fit, it ain’t legit.

Explanation in a diagram

Enzyme’s active site Reactants

It is like a lock and a key. Just like only one kind of key fits in each lock, only one set of reactants fits inside the enzyme

how it works continuedWhen the right substrates get together with the right enzymes (it all fits), how does the enzyme catalyze (speed up) the reaction?The enzyme helps break chemical bonds and form new ones

Why?? Your thoughts? All the reactions required for life would not be possible without enzymes

Practice

• What is a enzyme? • How does it relate to a catalyst? • What is a substrate?• What does a lock and key have to do with

this?

Practice• You end up taking a fall during soccer

practice and eating a faceful of grass. Grass contains cellulose. In your mouth, you have amylase, which digests amylose.

• Cellulose and amylose are both sugars, and they look pretty similar. Can the amylase in your mouth digest the handful of cellulose you just ate? Why or why not?

Step 1: Enzyme getting ready to bind to a substrate

Step 2: Substrate bound to enzyme

Step 3: Substrate changing while attached to enzyme

Step 4: Products being released

• THAT’S ALL FOLKS!

Do Now• Put the cracker in front of

you in your mouth for 2 minutes. Try and see what happens to the taste.

Factors that Effect Enzymes

The Energy DiagramEnzymes lower the activation

energy!

Think-Pair-Share

• Turn to your partner(s) and come up with an analogy for how enzymes work together

Check for understanding

Will a reaction take place without the enzyme? In other words, will the reactants become the product when there is no enzyme?YES! it will just happen much much much slower but it will eventually happen. Enzymes just speed it up

Conditions for Enzymes

What can affect an enzyme? Change the temperature (hot or cold) Change the pH (add an acid or base)

Enzymes have optimal (just right) temperatures and pH where they work the best.

Check for understanding

What will happen to the enzymes if we change its conditions?

The reaction rate will DECREASE because there is no enzyme to speed it up.

What will happen if the enzyme gets too hot?

It will unfold

Conditions for the Enzyme

Just like a plastic tape dispenser can’t work when it is melted, enzymes can’t work if they get too hot and are “melted”

Denatured = what happens when the enzyme literally gets bent out of shape due to change in temperature. The amino acids fold and the substrates don’t fit anymore! Happens if

Too hot

III. Protein Review• Chains of amino acids are folded

and joined together to give each protein a specific three dimensional shape.

• A protein’s function (job) depends on its structure (3-D shape)

• Proteins are sensitive to changes in temperature and pH, which may cause the protein to lose its specific shape. If a protein loses its structure (shape), it may no longer be able to function properly.

Quiz type question