2.5 Enzymes: Enzymes control the metabolism of the cell.

Nature of science: Experimental design—accurate, quantitative measurements in enzyme experiments require replicates to ensure reliability.

Understandings:•Enzymes have an active site to which specific substrates bind.•Enzyme catalysis involves molecular motion and the collision of substrates with the active site.•Temperature, pH and substrate concentration affect the rate of activity of enzymes.•Enzymes can be denatured.

Applications and skills:Application: Methods of production of lactose-free milk and its advantages. Lactase can be immobilized in alginate beads and experiments can then be carried out in which the lactose in milk is hydrolysed.

PRACTICALDesign of experiments to test the effect of temperature, pH and substrate concentration on the activity of enzymes. Students should be able to sketch graphs to show the expected effects of temperature, pH and substrate concentration on the activity of enzymes. They should be able to explain the patterns or trends apparent in these graphs.

Theory of knowledge: Development of some techniques benefits particular human populations more than others. For example, the development of lactose-free milk available in Europe and North America would have greater benefit in Africa/Asia where lactose intolerance is more prevalent. The development of techniques requires financial investment. Should knowledge be shared when techniques developed in one part of the world are more applicable in another?

Topic 2: Molecular biology (21 hours)

Biology Journal 9/19/2014

What is a rate? What is the rate we are measuring in this lab?

Biology Journal 9/18/2014

a. What does a broken toothpick represent?

b. What represents the enzyme?

c. You need 3 to 5 people in your group. What does each one do?

Describe the lock and key model of enzyme function.

Enzymes are specific to one (although sometimes multiple) substrate. How?1. Structurally: the 3D shape of the active site matches the substrate2. Chemically: the polar / nonpolar parts of the active match the substrate

Biology Journal 9/22/2014

Some Jobs for this Experiment:

1. Enzyme: person who breaks the toothpicks

2. Organizer: person who sets up the trial3. Cleaner: makes sure all materials are

returned / disposed of after each trial4. Timer: keeps track of and announces

time5. Counter: keeps track of number of

broken toothpicks during trial6. Recorder: writes down data

There are 3 Trials in this Experiment…

A. Rate and time1. Start with 100 toothpicks2. Lasts 180 seconds (3 minutes) 3. Count number of toothpicks broken at 10, 20, 30, 60,

120, 180 seconds

B. Rate and concentration1. Start with different numbers of toothpicks (10, 20, 30,

40, 50, 60, 70, 80, 90, 100) and 100 paperclips.2. Lasts 20 seconds only3. Count number of toothpicks broken at end

C. Rate and temperature1. Start with 10 toothpicks2. Time is now dependent variable (you measure how long

it takes the enzyme to break all 10 toothpicks)

Biology Journal 9/17/2014

a. What kind of reaction is shown?

b. Write out the reaction as words:

fructose + _______ → ________ + _______

c. Which are the reactants?

d. Which are the products?

+ +→ H2O

Biology Journal 9/5/2013

a. What kind of reaction? Anabolic Condensation

b. Write out the reaction as words: below

c. Which are the reactants? fructose, glucose

d. Which are the products? sucrose, water

+ +→ H2O

fructose + glucose → sucrose + water

Today we will learn how Today we will learn how enzymes make this happen!enzymes make this happen!

Biology Journal 9/17/2014

What is a genome?What is a proteome?

Do you think all humans have mostly the same genome, or naw?

Do you think all humans have mostly the same proteome, or naw?

Where could be some places that our biological differences come from?

Humans share over 99% the same DNA. DNA codes for proteins, so our proteins are over 99% identical as well.

Our differences come from 2 things: mutations, and the recombination of genes during every sexual reproduction!

What is a catalyst?What is a catalyst?

Catalysts speed up chemical reactions (and they’re not used up by the reaction)

Review!Review!

2.5 Enzymes

Hair is a protein called Keratin Enzymes speed things up.

Enzymes: Specially shaped proteins that are catalysts. Enzymes are specific, like a lock and key.

Enzymes make reactions fast! (but they usually don’t blow up; that’d be bad for a living thing)

TIME

Ene

rgy

in R

eact

ants

/Pro

duct

s

Start(reactants)

Intermediaries

Reaction Complete(products)

Activation Energy

Withoutenzyme With

enzyme

Energy-Time Graph for a Chemical Reaction

Activation energy is the energy which must be put into reactants to break some bonds to get a reaction started

Enzymes lower activation energy, making reactions happen faster.

These reactants (TNT) really want to be the products (a bunch of gasses). It just needs the activation energy to do the reaction….

Where does the activation energy come from?

An Explosive Example…

SubstrateSubstrate: the reactant that goes into the enzymeActive siteActive site: where the substrate bonds on the enzymeProdProductsucts: what the substrate turns into

Enzymes do not run out. They keep making the product over and over.

How is this chemical reaction different from the previous one?

Enzymes are specific

• Each enzyme acts on only one (or a limited number) of substrates• Each enzyme will only act on substrates that will fit into its active site

Enzyme

Active site

Substrate: shape is complementary to shape of active site

• Each enzyme catalyses very few reactions

Active site fits around substrate Active site no longer fits round substrate

Treat with high temperature…

… or strong acid/alkali

Like any protein, an enzyme can denature (lose its shape and thus stop working).

Enzymes end in “-ase” (almost always)

What do you think these enzymes What do you think these enzymes do?do?

ProteaseProteaseLactaseLactaseLipaseLipaseCellulose synthaseCellulose synthaseGlucose phosphotransferaseGlucose phosphotransferase

Sketch this picture into your journal and label the parts.

Describe what kind of reaction is occurring in as much detail as you can.

A = SubstrateB = EnzymeC = Active siteD = Enzyme-substrate complexE = Products

This is the enzyme-catalyzed decomposition of A into E’s.

Read the entire toothpickase lab. Re-read until you understand the directions completely!

Do all of the parts of the lab in your graph notebook through “Data: lab group data”. Specifically:

1.Write the title2.Do the pre-lab questions3.Write the first heading4.Write the “Procedure” for this part5.Write “Data: class data” and prepare a data

table that you will have ready to fill in tomorrow!

Your Assignment:

Enzymes are an example of a kind of molecule Enzymes are an example of a kind of molecule called a called a proteinprotein. Tissues like hair, muscle, and . Tissues like hair, muscle, and skin are also made out of this polymer; the skin are also made out of this polymer; the polymer is composed of monomers called polymer is composed of monomers called amino acidsamino acids..

Enzymes are an example of a kind of molecule Enzymes are an example of a kind of molecule called a ______. Tissues like hair, muscle, and called a ______. Tissues like hair, muscle, and skin are also made out of this polymer; the skin are also made out of this polymer; the polymer is composed of monomers called polymer is composed of monomers called ___________.___________.

Enzymes Enzymes (almost)(almost) always end in what always end in what 33 letters? letters?

ASEASE

Do all enzymes catalyze (speed up) decomposition reactions?

No! What kind of reaction is this?No! What kind of reaction is this?

Are enzymes consumed in a chemical reaction?

What happens to the enzyme in this picture?What happens to the enzyme in this picture?What happens to the product?What happens to the product?

Describe the lock and key model of enzyme function.

Enzymes are specific to one (although sometimes multiple) substrate. How?1. Structurally: the 3D shape of the active site matches the substrate2. Chemically: the polar / nonpolar parts of the active match the substrate

Define what it means for a protein to denature.

All enzymes have an optimal temperature and pH.

TIME

Ene

rgy

in R

eact

ants

/Pro

duct

s

Start(reactants)

Intermediaries

Reaction Complete(products)

Activation Energy

Withoutenzyme

Withenzyme

What is activation energy?How does an enzyme “catalyse” a reaction?

What is lactose intolerance?What is lactose intolerance?

A person with lactose intolerance is not producing the enzyme lactase.

Lactase is the enzyme that catalyzes the catabolic hydrolysis of lactose into galactose and glucose.

Percentage of Population with Lactose Intolerance

Where are you from? The chances of having lactose intolerance are genetically tied to cultural and historical uses of animal milk as a food source. For example, in Northern European culture cow milk was used as a food source for many centuries; in South America, it was not.

Aspergillus niger is also known as black mold. You’ve most likely seen it before.

To cope with lactose intolerance…1.Take a lactase supplement, made by a genetically engineered fungus.

2.Drink lactose-free milk.

Lactose-free milk can be made by:1. Adding lactase to milk.2. Running milk through an apparatus with immobilized lactase.

Scientific Method

What is the dependent and independent variables in What is the dependent and independent variables in this experiment? What could be controls?this experiment? What could be controls?

• Independent Variable: The “cause” that is more directly controlled or measured. Graphed on x axis.

• Dependent Variable: The “effect” you measure. Graphed on y axis.

• “Independent causes Dependent”• “The dependent variable depends on the

independent variable”• Controls: Anything that could effect the outcome

of the dependent variable. • Some controls can be “controlled” (purposely kept

constant), but some can only be acknowledged as variables impacting the data.

Independent Variable