grade 12 enzyme lab

8/19/2019 grade 12 Enzyme Lab

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LAB #:

Title: Enzymes

Aim: To investigate the effects of limiting factors on enzyme-catalyzed reactions

Factors affecting Enzyme Activity• The activity of an Enzyme is affected by its environmental conditions. Changing these

alter the rate of reaction caused by the enzyme. In nature, organisms adjust the

conditions of their enzymes to produce an Otimum rate of reaction, where necessary,

or they may have enzymes which are adated to function !ell in e"treme conditions where they live.

Temerature

• ncreasing temerature increases the $inetic Energy that molecules possess. In afluid, this means that there are more random collisions between molecules per unit time.

• Since enzymes catalyse reactions by randomly colliding with %u&strate molecules,

increasing temerature increases the rate of reaction, forming more product.

• However, increasing temerature also increases the 'i&rational Energy that

molecules have, specifically in this case enzyme molecules, which puts strain on the

&onds that hold them together.

• As temperature increases, more &onds, especially the !ea(er )ydrogen and onic

bonds, will &rea( as a result of this strain. rea!ing bonds within the enzyme will causethe Active %ite to change shae.

• This change in shae means that the Active %ite is less *omlementary to the shae of

the %u&strate, so that it is less li(ely to catalyse the reaction. "ventually, the enzyme

will become +enatured and will no longer function.

• As temerature increases, more enzymes, molecules, Active %ites, shaes will be less

*omlementary to the shae of their %u&strate, and more enzymes will be +enatured.

This will decrease the rate of reaction.

• In summary, as temerature increases, initially the rate of reaction will increase, because of increased $inetic Energy. However, the effect of &ond &rea(ing will become greater and greater, and the rate of reaction will begin to decrease.


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• The temperature at which the ma"imum rate of reaction occurs is called the enzyme#s

Otimum Temerature. This is different for different enzymes. Most enzymes in the

human body have an Optimum Temperature of around 37.0 °C.

) - Acidity and Basicity

• ) measures the Acidity and Basicity of a solution. It is a measure of the )ydrogen on

$)% concentration, and therefore a good indicator of the )ydro"ide on $O)-%concentration. It ranges from ). to )./. Lo!er ) values mean higher )

concentrations and lo!er O)- concentrations.

• Acid solutions have pH values &elo! 0, and Basic solutions $al!alis are bases% have pH

values a&ove 0. +eionised !ater is )0, which is termed #neutral#.

•

H

&

and 'H

(

Ions are charged and therefore interfere with )ydrogen and onic bondsthat hold together an enzyme, since they will be attracted or reelled by the charges

created by the bonds. This interference causes a change in shae of the enzyme, and

importantly, its Active %ite.

• +ifferent enzymes have different Otimum ) values. This is the pH value at which

the bonds within them are influenced by H& and 'H( Ions in such a way that the shae oftheir Active %ite is the most *omlementary to the shae of their %u&strate. At the

'ptimum pH, the rate of reaction is at an optimum.

• Any change in ) a&ove or &elo! the Otimum will 1uic(ly cause a decrease in the

rate of reaction, since more of the enzyme molecules will have Active %ites whoseshaes are not $or at least are less% *omlementary to the shae of their %u&strate.


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• %mall changes in ) above or below the Otimum do not cause a ermanent change

to the enzyme, since the &onds can be reformed. However, e"treme changes in ) can

cause enzymes to +enature and ermanently loose their function.

• "nzymes in different locations have different Otimum ) values since their

environmental conditions may be different. For example the enzyme !epsin fun"tionsbest at around p#$ and is found in the stoma"h %hi"h "ontains #ydro"hlori" &"id

'p#$(.

*oncentration

• Changing the Enzyme and %u&strate concentrations affect the rate of reaction of an

enzyme(catalysed reaction. *ontrolling these factors in a cell is one way that an

organism regulates its enzyme activity and so its 2eta&olism.

• Changing the concentration of a su&stance only affects the rate of reaction if it is the

limiting factor) that is, it the factor that is stoing a reaction from preceding at a

higher rate.

• If it is the limiting factor, increasing concentration will increase the rate of reaction

up to a oint, after which any increase will not affect the rate of reaction. This is

because it will no longer be the limiting factor and another factor will be limiting the

ma"imum rate of reaction.

• As a reaction roceeds, the rate of reaction will decrease, since the %u&strate will getused u. The highest rate of reaction, !nown as the nitial 3eaction 3ate is the

ma"imum reaction rate for an enzyme in an e"erimental situation.

%u&strate *oncentration


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• ncreasing %u&strate *oncentration increases the rate of reaction. This is because

more su&strate molecules will be colliding with enzyme molecules, so more roduct

will be formed.

• However, after a certain concentration, any increase will have no effect on the rate of

reaction, since Substrate Concentration will no longer be the limiting factor. Theenzymes will effectively become saturated, and will be wor!ing at their ma"imumossi&le rate.

Enzyme *oncentration

• ncreasing Enzyme *oncentration will increase the rate of reaction, as more enzymes

will be colliding with su&strate molecules.

• However, this too will only have an effect up to a certain concentration, where the

"nzyme Concentration is no longer the limiting factor.


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4B5 6%E T)E ABO'E 7EB%TE TO 8ET T)E 3E%T OF T)E FOLLO748:


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Cues:

Questions:

ENZYMES – noteEnzymes - are proteins made of amino acids

- are catalysts- they speed up chemical reactions &lower the activation energy

- are reusable- they remain unchanged after thereaction

- are specic- there is a perfect enzyme for a certain

substrate- have a 3D shape which can be destroyeddenatured

we!treme changes in p" & temperature

- have active sites # places where substrate $food &waste% molecules attachDraw the enzyme with an active site a substrate:

http://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Enzyme


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"g., % Catalase brea!s down hydrogen pero0ide $waste produced in

cells% into /H/'/ ((((1 /H/' & '/ 'actase brea(s down lactose in mil()rotease brea(s down proteins

'ipase

brea(s down lipids

"ow *nzymes +or(,• ctive sites on enzymes # places to which a specic

substrate binds• *nzyme-substrate comple!es form $when substrates

attach to active sites on the enzymes% to brea(apart or put together substances at a fast rate

.here are two models of enzyme action/0 lock & key model substrate & the enzyme t

together perfectly10 induced-ft model enzymes change shape slightly to

accommodate the substrate

2actors aecting enzyme action/0 Temperature 4 enzymes wor( best at certain

temperatures5 – 37oC is best or human enzymes inthe body

10 pH 4 enzymes wor( best at certain p"6 basic5

neutral5 andor acidic environmentseg0% mylase in saliva at p" 75 )epsin in the stomach

at p" 1-35 & .rypsin in the intestines at p" 8

30 9ubstrate & enzyme concentrations 4 how fastreactions ta(e place depends on how much of thesubstrate & enzyme is available0

0 Coenzymes 4 helpers such as vitamins & minerals

9ummary

http://plantphys.info/Plant_Physiology/enzymefactors.htmlhttp://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/proteinstructure.htmlhttp://plantphys.info/Plant_Physiology/enzymefactors.htmlhttp://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/proteinstructure.html


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ENZYMES – book questions Answer the following questions in complete sentences./0 +hat are enzymes,10 re enzymes proteins,30 +hat are coenzymes,

0 +hat are the functions of enzymes,;0 +hat are the elements found in enzymes,0 +hat are the factors that aect how enzymes wor(,//0 Classify the following substances as carbohydrate5 lipid5 protein5 or

nucleic acid: maltose5 chlorophyll5 D?5 vegetable oil5 fructose5 @?5wa!5 glycogen5 insulin5 and albumin0

O&serving the enzyme *ATALA%E

N!"#$%&!#N' wh(t woul) h(ppen to your cells if they m()e (poisonous chemic(l* You might think th(t they woul) )ie. n f(ct+

your cells (re (lw(ys m(king poisonous chemic(ls. !hey )o not )iebec(use your cells use enzymes to bre(k )own these poisonouschemic(ls into h(rmless subst(nces. Enzymes (re proteins th(tspee) up the r(te of re(ctions th(t woul) otherwise h(ppen moreslowly. !he enzyme is not (ltere) by the re(ction. You h(,e hun)re)sof )i-erent enzymes in e(ch of your cells. E(ch of these enzymes isresponsible for one p(rticul(r re(ction th(t occurs in the cell.

n this l(b+ you will stu)y (n enzyme th(t is foun) in the cells ofm(ny li,ing tissues. !he n(me of the enzyme is c(t(l(se /A!0uh01AYSS23 it spee)s up ( re(ction which bre(ks )own hy)rogenpero4i)e+ ( to4ic chemic(l+ into 5 h(rmless subst(nces00w(ter (n)o4ygen. !he re(ction is (s follows'

565#5 00007 565# 8 #5

!his re(ction is import(nt to cells bec(use hy)rogen pero4i)e 65#52is pro)uce) (s ( bypro)uct of m(ny norm(l cellul(r re(ctions. f thecells )i) not bre(k )own the hy)rogen pero4i)e+ they woul) bepoisone) (n) )ie.


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9"E1A: "E;E-ml Fraduated cylinder 9traight-edged razorblade3 bea(ers for water baths9cissors and 2orceps$tweezers%

/molar "Cl solution $in droppebottle%/molar ?a" solution $in dropbottle%> ml 3E "ydrogen pero!idesolution

2resh liver5 chic(en meat5 ppand )otato


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93O*E+63E% A4+ A4AL%% ;6E%TO4%

9art < 93O*E+63E -- 4ormal *atalase Activity 'T") e sure to clean your stirring rod $and test tubes% between steps.

-. 2lace = ml of the 34 hydrogen pero0ide solution into a clean test tube

/. Add a small piece of liver to one test tube. 'bserve the bubbles5 what gas is being

released6

Throu)hout this investi)ation you %ill estimate the rate of the rea"tion 'ho% rapidly the solution bubbles( on a s"ale of 0*+ '0,no rea"tion -,slo%.... +, very fast(. Assume that

the reaction in step / proceeded at a rate of 77 and record the speed in +ATA TABLE .,

and +ATA TABLE = as the rate at room temperature.

3. 8ecall that a reaction that absorbs heat is endothermic5 a reaction that gives off heat is

e"othermic. ow, feel the temperature of the test tube with your hand.

Has it gotten warmer or colder6 Is the reaction endothermic or e0othermic6

s *atalase 3eusa&le>

. 2our off the li9uid into a second clean test tube. Assuming the reaction is complete.

:hat is this li9uid composed of6 :hat do you thin! would happen if you added more

liver to this li9uid6 :hy6

;. Add another = ml of hydrogen pero0ide to the liver remaining in the first test tube.

Can you observe a reaction6 :hat do you thin! would happen if you poured off this

li9uid and added more hydrogen pero0ide to the remaining liver6

Are enzymes reusable6

Occurrence of *atalase

Catalase is present in many !inds of living tissues. (;%

for each tube in TABLE ..:hich tissues contained catalase6


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9art < 93O*E+63E -- Effect of Temerature on *atalase Activity

?. 2ut a piece of liver into the bottom of a clean test tube and cover it with a small amount

of distilled water. 2lace this test tube in a boiling water bath for ; minutes. :hat will

boiling do to an enzyme6

@. 8emove the test tube from the hot water bath, allow it to air cool, then pour out the water.

Add = ml of hydrogen pero0ide. *A6TO4: se a test(tube holder when handling the

hot test tubes. :hat is happening in the test tube6 8ecord the reaction rate $>(;% in

+ATA TABLE =.

B. 2ut e9ual 9uantities of liver into / clean test tubes and . ml H/'/ into / other test tubes.

2ut one test tube of liver and one of H/'/ into each of the following water baths) Ice

bath $> deg.C% and :arm water bath $3? deg.C%

->. After ? minutes, pour each tube of H/'/ into the corresponding tube of liver andobserve the reaction. 8ecord the reaction rates $>(;% in +ATA TABLE =. deg.C6

:hy did the reaction not proceed at all at ->> deg.C6

9art < 93O*E+63E -- Effect of ) on *atalase Activity

-/. Add = ml hydrogen pero0ide to each of 3 clean test tubes. Treat each tube as follows)

Tube -((add a drop of -molar HCl $acid% at a time until pH 3.

Tube /((add a drop of -molar a'H $base% at a time until pH ->.Tube 3((adust the pH to ? by adding single drops of either -molar HCl or -molar a'H

as needed.

*A6TO4: Do not let acids or bases contact your s!in or clothing. Swirl each test tube

after adding each drop and measure the pH of each solution with pH paper. To do this,remove a drop or two of solution from a test tube using a clean glass stirring rod. 8inse

your stirring rod and wipe dry before you dip it into each test tube. 2lace the drop on pH paper. 8ecord the pH of each solution in +ATA TABLE ?.

-3. e0t, add a small piece of liver to each test tube. "stimate the reaction rates $>(;% andrecord in +ATA TABLE ?.

-. Does there appear to be a pH 7optimum76 At what pH6


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:hat is the effect of low or high pH on enzyme activity6

TABLE .: Occurrence of *atalase

%amle 3ate of Enzyme Activity

Eiver

2otato

Chic!en

Apple

TABLE =: Temerature effect on Liver *atalase Activity

Temerature 3ate of Enzyme Activity

FFF oC Greezing Temp.

FFF oC 8oom Temp.

FFF oC ody Temp.

FFF oC oiling Temp.


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TABLE ?: ) effect on *atalase Liver Activity

) 3ate of Enzyme Activity

3

?

->


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6nderstanding the enzyme *ATALA%E < La& #

9"E1A: "E;E. i)entify tissues th(t h(,e the enzyme c(t(l(se5. stu)y the enzyme c(t(l(se (cti,ity. e4plore f(ctors th(t (-ect enzyme (ction p6+ !emper(ture+ etc.2B. un)erst(n) th(t enzymes (re speciCc (n) reus(ble

9re01(b Duestions

/0 .he reaction is

10 +hy is this reaction necessary in the body,

30 .he enzyme is GGGGGGGGGGGGGGGG & the substrate is GGGGGGGGGGGGGGGGGGG $"11%0

0 .he reactants are GGGGGGGGGGGGGGGGGGGGGGG & the products are GGGGGGGGGGGGGGGG

;0 )rotein Denaturation is GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG0


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"nzyme lab

grade 12 enzyme lab

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