Enzymes! (What are they good for?)

Essential Questions:What is an enzyme?

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

How do they maintain homeostasis for the body?

What do YOU know about enzymes?

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.

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.

What are Enzymes?• 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?

• 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?

Wait, What is a Chemical Reaction?

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?

Wait, What is activation energy?• Activation energy is the

amount of energy needed to start a chemical reaction.

Ok, so How do Enzymes Work?

Enzymes are the instigators!

Ok, so How do Enzymes Work?

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.

How do enzymes speed up reactions?

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

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.

Enzyme Animation:http://www.youtube.com/watch?v=V4OPO6JQLOE

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)

Enzyme Animation:http://www.youtube.com/watch?v=V4OPO6JQLOE

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”.

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?

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!

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!

Induce Fit Hypothesis

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

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.

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

Where can we find enzymes?

• http://www.novozymes.com/en/MainStructure/Discover+bioinnovation/Used+everywhere/How+enzymes+work+for+you/

Phenolase (ase = enzyme)

Found in…• Salicilic acid (plant hormone)• Cannabis• Wintergreen• Western poison oak (to

discourage animals from eating them)

• …and apples!

Your Turn! Phenolase in apples

Your Turn! Phenolase in applesQuestion/Problem: What are the effects of pH on

enzymatic activity?

Observations/Control: What initial observations can you make about the effect of phenolase in an apple (without lemon juice)?

Your Turn! Phenolase in applesQuestion/Problem: What are the effects of pH on

enzymatic activity?

Observations/Control: What initial observations can you make about the effect of phenolase in an apple (without lemon juice)?

Hypothesis: 1. What do you expect to see on the apple with lemon juice?

2. What effect do you think that the lemon juice will have on the action of phenolase in apples? What is the pH of lemon juice? How does this affect enzymatic activity?

Results and Conclusions

Experiment: Cut an apple in half. Leave one half alone as a (-) control. Add lemon juice to the other half and let it sit.

Results: What happened to the apple with the lemon juice on it?

Results and Conclusions

Experiment: Cut an apple in half. Leave one half alone as a (-) control. Add lemon juice to the other half and let it sit.

Results: What happened to the apple with the lemon juice on it?

Conclusions: 1. Do the results support your hypothesis?

2. What do you think happened to phenolase in such an acidic environment?