enzyme protocol

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Enzymes Help Us Digest Foodi

Introduction to Sugars and EnzymesThe food you eat contains many dierent types of molecules, including two typesof sugar molecules: monosaccharides and disaccharides.

Three types of monosaccharides are:

Two types of disaccharides are:

1.Each disaccharide is made up of two __________________________ .

Monosaccharides from the food you eat are absorbed from your gut into your bloodand carried to all the cells in your body where they are used for energy. Eachdisaccharide molecule must be broken down or digestedinto its monosaccharide

components before it can be absorbed into the blood.

2.When a sucrose molecule is digested, which monosaccharides are produced

The digestion of the disaccharide lactose to the monosaccharides glucose andgalactose occurs !ery !ery slowly unless there is an enzyme to speed up theprocess. The en"yme that speeds up the digestion of lactose is called lactase.#actase and most other en"ymes are proteins.

Each en"yme has an active sitewhere a substrate molecule binds. $ore%ample, the substrate lactose binds to the acti!e site of the en"yme lactase.&otice that the name of the en"yme lactase was created by adding the su'% aseto part of the name of the substrate lactose.

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.(ircle the acti!e site in the lactase en"yme in the )gure.*n en"yme speeds up a chemical reaction which con!erts a substrate moleculeor molecules to a product molecule or molecules. The products are releasedfrom the en"yme and the en"yme returns to its original state, so the en"yme isready to act on another substrate molecule. Thus, an en"yme molecule can bereused o!er and o!er. $or e%ample, a single molecule of the en"yme lactasecan speed up the digestion of many many molecules of lactose.

!.The following e+uation shows the digestion of lactose.

"actase"actose #lucose $ #alactose

se E to indicate the en"yme, - to indicate the substrate, and to indicate theproducts. (ircle the molecule that is a protein, and use asterisks to indicate themolecules that are sugars.

E%periment 1 & 'an the sugar lactose be digested (ithoutany enzyme)

To test whether the en"yme lactase is needed to digest the sugar lactose, youwill test whether lactose breaks down to glucose and galactose in two dierentconditions:

/01 with no en"yme and/21 when the en"yme lactase is present.

*. $irst, predict what you think will happen3 for each column, circle thee+uation that describes what you think will happen.

+rediction (ith ,o Enzyme +rediction (ith the Enzyme"actase

&o En"yme#actose 4lucose 54alactose

6r&o En"yme

#actose #actose/no glucose

produced1

#actase#actose 4lucose 54alactose

6r #actase

#actose #actose /no glucose

produced1

To test whether your predictions are correct, you will use glucose test stripsto test whether glucose has been produced.

+rocedure 6ne member of your group /e%perimenter 01 should label test tube 0 and

add 07 m# of lactose solution.

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*nother member of your group /e%perimenter 21 should label test tube 2and add 07 m# of lactose solution and 0 m# of lactase solution. ut on aglo!e, put your thumb on the top of the tube and turn the tube upside downse!eral times to mi% the two solutions.

Wait 8 minutes to allow time for lactose to break down to glucose andgalactose.

While you are waiting, e%perimenter 0 and 2 should each get a test strip.9ecord the original color of your test strip. ______________________________ nthe ne%t step, if your test strip changes color, this will indicate that glucoseis present.

*fter the 8 minute wait, each e%perimenter should use a glucose test strip totest for glucose in the solution in his or her test tube. ;our teacher will gi!eyou the instructions for using your glucose test strip.

9ecord your results in the table in +uestion < below. (lean your test tubes.

-esults

. 9ecord your results in this table./ube 1 & 10 m" olactose solution

/ube 2 & 10 m" olactose solution $ 1 m" olactase solution

Test strip colorafter 8 min.wait

Was there any

change in thecolorof the teststrip

(onclusion___ no glucose produced___ some glucose produced

___ no glucose produced___ some glucose produced

Interpretation. Was lactose digested without any en"yme ___ yes ___ no

3. Was lactose digested when the en"yme lactase was present ___ yes ___

no

4. =o your results match your predictions ___ yes ___ nof yes, what conclusion do your results support f no, what do you think is thereason for the dierence between your predictions and results

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10a. n Tube 2, there were o!er >777 lactose molecules for each lactasemolecule. ?ow can a single lactase molecule break down many many lactosemolecules /?int: -ee the top of page 2.1

10b.* catalyst is de)ned as a substance that increases the rate of a chemicalreaction without itself undergoing any permanent chemical change. s theen"yme lactase a catalystE%plain why or why not.

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E%periment 2 & 'an the same enzyme digest lactose and sucrose)To test whether the same en"yme can digest lactose and sucrose, you will testwhether the en"yme lactase can digest the disaccharide sucrose.

11a. Write the procedures for your e%periment to test whether lactase can digestsucrose. ;ou will ha!e a!ailable the same supplies as you used in E%periment 0plus a sucrose solution.

11b. (reate a data table to record the results of your e%periment.

*fter your teacher has checked your procedures and data table, carry out youre%periment and record your results.

Interpretation12. =id lactase break down sucrose ?ow do you know

1. =oes the same en"yme digest lactose and sucrose ___ yes ___ no

;our results illustrate a general principle called enzyme speci5city. Each en"ymeacts only on a single substrate or se!eral chemically similar substrates.

1!. Which part of an en"yme do you think is responsible for this en"ymespeci)city E%plain your reasoning. /?int: -ee the bottom of page 0.1

@ecause of en"yme speci)city, our bodies need lots of dierent en"ymes to digestdierent types of food molecules. $or e%ample, our small intestine has the en"ymelactase to digest lactose and a dierent en"yme to digest sucrose.

1*. What do you think is the name of the en"yme that digests sucrose /?int: -eethe bottom of page 0.1

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1. (omplete the following e+uation to show the digestion of sucrose. nclude theen"yme and the products.

Sucrose

E%periment 6 Does the enzyme lactase digest the sugar in mil7)

1. -uppose you ha!e mi%ed 07 m# of milk with 0 m# of lactase solution, waited 8

minutes, then tested for glucose and found that your mi%ture of milk and lactasecontained glucose. What are two possible interpretations of this result /?int: Thinkabout the possibility that, before digestion, milk contains eithera disaccharide oramonosaccharide.1

13. =esign an e%periment to test whether lactase is needed to digest the sugar inmilk. $or this e%periment, you will ha!e a!ailable the same supplies you used inE%periment 0 and milk. Write your procedures and create a data table.

*fter your teacher has checked your procedures and data table, carry out youre%periment and record your results.

Interpretation14.s lactase needed to digest the sugar in milk ___ yes ___ no ?ow doyou know

20. Which sugar does milk contain ___ glucose ___ lactose ___sucrose ?ow doyou know

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/he Digestive System and "actose Intolerance

Molecules like sugars and protein en"ymes are much much smaller than a wholeperson. $or e%ample, a person is roughly a billion times longer than a proteinmolecule like an en"yme. -o where are these tiny molecules located in our bodies

This diagram shows a simpli)ed outlineof the human digestive system,including the small intestinewhereen"ymes like lactase and sucrase breakdown food molecules into smallermolecules. Most digestion occurs in thesmall intestine.

21.n this diagram, use = with arrows toshow how disaccharides like lactose andsucrose get from food to the smallintestine.

A se E to indicate the location of theen"ymes, lactase and sucrase.A se M to indicate wheremonosaccharides like glucose areproduced from disaccharides.

=igesti!e -ystem

22. -uppose that the cells in a personBs digesti!e system do not make lactase.What do you think would happen to the lactose molecules in the milk that persondrinks

?uman babies and the babies of all other mammals depend on milk for theirnutrition. *lmost all babies produce the en"yme lactase to digest lactose, which isthe main sugar in milk.

n contrast, many adults produce !ery little lactase, so they can only digest a littlebit of lactose at a time. When a person who produces !ery little lactase consumeslarge amounts of lactose in a short time period, most of the lactose is not digestedin the small intestine and lactose reaches the large intestine where it is digestedby bacteria. This can result in symptoms such as diarrhea, Catulence, and

discomfort. This condition is calledlactose intolerance

.2a. * person who is lactose intolerant can drink lactoseAfree milk to gain thebene)ts of the protein, calcium and !itamin = that milk pro!ides. E%plain how amanufacturer can use lactase to make lactoseAfree milk.

2b. =o you think lactoseAfree milk contains glucose ___ yes ___ no

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f yes, where did the glucose come from

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8hat happens to the digested ood molecules)

The digesti!e system and the circulatory systemwork together to pro!ide nutrients to cells in allparts of your body. =igested food molecules areabsorbed from the small intestine into the blood.The heart pumps the blood through the blood!essels to carry the digested food molecules toall the cells in your body.

;our cells use the digested food molecules fortwo basic purposes:

to pro!ide the building blocks forsynthesi"ing needed molecules

to pro!ide the energy for cellular acti!itiessuch as muscle contraction andsynthesi"ing needed molecules.

The circulatory system

includes the heart, blood!essels and blood.

2!. =escribe the steps by which disaccharides in your food end up asmonosaccharides in cells throughout your body. Write se!eral sentences andDoradd arrows and labels to these diagrams. nclude the words blood, en"ymes,heart and small intestine in your e%planation.

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