Chemical and Phvsical Processes of Digestion OBJECTIVES
MATEBIALS
1. To lisi the digestive system enzymes involved inthedigesiion of prcteins, tuts, and carbohydrates; io siate their site of origin; and to sumrnarize the environmental conditions prcmoiing their optimal funct oning.
Part l: Enzyme Action
2. To recognizethe variation beiween differenttypes of enzyme assays.
! ! !
L-j
Boilng chips Testiubes andtesttube rack
3. To name ihe end producls of protein, fat, and cafbohydraie digestion, 4. To perform the appropr aie cherficaltests io determine if digestion of a particular foodstuff has occurred,
Waier balh set at 37'C ( I not avai able, ncubat€ ai roorn temperature and
5. To clte ihe funciion(s) of bile in the digestve process.
Charl on chalkboard lof recofding class
Actiti9
! !
1:
Statch Diqestiah
Dropper bortl€
oldisr
led water
6. To discussthe possible role of temperature and pH in the regulaiion of enzyme activlty.
1. fo define enzyme, catalyst, cantrol, substrate, and hydtalase. L To explain why swallowing is both a voluntary and a rcflex activity. L To discuss the role ofihe tongue, arynx, and gasircesophageal sphincter in swallowing. 10. To compare and contrast segmentation and peristalsis as mechanisms
Dropper boltles ol the lo lowing:
1% alpha-amylase so ut on' 1% bo ed starch solution,lreshly 1% ma iose solution
1.
Adivny 2: Pratein Digestiah
I
qurz
PRE"LAA
Lugo 's odne sollilon (lK) Bened ct's so 0tion
2.
Dbpper botl es of i% trypsi. and
C rclethe coffeci term. Enzymes are caialvsts / substrates that increase ihe €te of chemical reactions withoui becoming a part ofthe product.
A(n)_
is a specimen or standard against which al
expe mental samples are compared.
0.01% BAPNA solli on _Thc
alpha-anylasc must be a low maltose
3.
p.epdatior fbr good results. 'Prepa.e by addinS
l g sttuch to l00ml distilled \r.ter: boil.nd coolr add a plnch ofsalt (NaCl). Prepare tcsh daily. tui mtinu?s.nnut
pa!?.
c. substrate d.
Vial
One enzyme thai you will be sludying today, produced by lhe sal vary glands and secreted into the mouth. hvdrolvzes slarch to matose. lt is
CircleTrue or False. When you use iodine io test fof starch, a coor change to blue-back indcates a positive starch iest, preciptate, 5. lf Benedicl's test in the starch assay produces then yourtesi willbe recorded as posiiivefor maltose. a. blue io black b. grcen to orangec. white 6. The , produced bylhe pancreas, is responsible for breaking down proteins, a. b- kinase d. trypsin
a
enzyme amylase
i4aitefln9A&P Access prcctice quizes and narc in the study Aea at ||wwmsteingaandp.cam,
Ths lab cotresponds lo PhysoEx Exerc se 8,
7.
Circle the correct term- The enzyme @lateAiliqlipasc/pcpgir hydrclyzes
rc tralfatsioiieir componelt monoglycerides ard hdy acids. 8. Circle True of False. Boih smooth and skeleial rnuscles are involved in ihe physical prccesses of d gesiion. 9. movements are local contractions that mix ioodstuffs with digestivejuices and increase the rate of absorption. a. Deqluiition b. Elimination c. Peristaltic d. Segmental
598
Exerc se 39
Activity 3: Bile Action ahd Fat Digestion
Part ll: Physical Processss
!
Activily 5: ObseNing Agestion
Drcpper botlles ol I % pancreal n solut on, litmus cream (n€sh croam to whlch powdered itmus s add€d lo a.h eve a deep bue color),0.1 A' HC
L.] Biesalts
-
(sodium iaurocholate) Paraf m (smal squares lo covorthe tesl
!
Teevsior and VCR ior nd€pendent v ewing of v
! ! !
deocassefl€ by
srld€.l
/nielactivePhysiolosyq Disestive
Disposable alloclave bag waich, clock, oriimer
ecause nutrients can be absorbed only when broken doqn ro rheif mono ner.. f^od dige.||ol r' J prcrcqlisite to food absorytion. You have already studied nechanisns of passive and active absorption in Exercise 5 and/or 58. Before proceeding, review that material.
Ghemical Digestion of Foodstuffs: Enzymatic Action Enzymes are large protcin molecules produced by body cells. They de bioLogical catalysts, meaning that they incrcase the rate of a chemical reaction without themselves becoming pan of the product. The digestive enzymes are hydrolydc en zymes, or hydrolases. Their substrates, or the molecules on which they act, are organic food molec ies which ihey break down by adding warer to the moleculd bonds, thus cleaving the bonds between the subunits or monomers.
The various hydrolytic enzymes are highly specific in their action. Each elzynre hydrolyzes only one or a small group of snbsirate molecules. and specific environmental conditions are necessary lbr ii to function optimally- Since digestive enzymes actualy function outside the body cells in the digestive tract, their hy&olytic activity can also be stud ied In d rer rube. SJch Jn in \ irro rrJJ provide. a conrenierl laboraiory environment fof investigating the effect of such variations on enzynatic activityFigure 39. I is a flowchart of the progressive digestion of carbohydrates, proteins, fats, and nucleic acids. It sulnmarizes the specific enzynes involved. thei sire of fornation, and their site of action. Acquaint yourself with the flowchaft before beginning this experinent. and refer to ii as necessary during the laboratory session.
General lnstructions for Activities 1-3 work in groups of four. with each grcup taking responsibjlity for sefting up and conducti.g one of lhe fbllowing expen nenis. tn each of the djgeslive procedures being studied lstarch. prorein, and fat digeslion) rnd in the amylase assay, you are directedto boil the contenis of one of moretestlubes. To do ihis, obtain a 250-ml beaker. boilirg chips, and a hot plaic from the general supply area. Place a few boiling chips i.to lhe beaker. add about 125 m I of s,ater and bring to a boil. Place the test tube for each specimen in the water fbr the num_ ber of minutes specified in fie directions. You will also be using a 37'C and .tn icc {,aler bath for parts ofthese experiments. You will need to use your lime very efficiently in order to set up and perlbrm each test properly.
Upon completion of lhe experiments, each group should communicate irs resulrs io the resi of rhe class by recording them in a chart on the chalkboard. AI members of the class should observe the controls (the specimens or standards against which experinental samples are compared) as wel as lhe positive and negative examples of all experimental results. Additionaliy. all members of the class should be able to explain lhe tests used and the results observed and anticipated lbr each experiment. Note that water baths and hot plates are at the general supply area.
Assessing Starch Digestion by Salivary Amylase
L
Fron the general supply area. obtain a test tube rack, 10 test tubes, and a wax marking pencil. From fieActivity I supply area, obtain a dropper bottle of distilled water and dropper bottles of maltose. amylase. and starch solutions.
2.
In this experiment you wil investigate the hy&o]ysis of starch to maltose by saliyary amylase (the enzyme produced by ihe salivary glands and secreted into the Inouth). so you will need to be able to identify the presence of starch and maltose to detemine !o what extent the enzymatic activity has occuffed. Thus controls must be prepared to pfovide a known standitrd igainst which comparisons can be made. Starch decreases and sugarincreases as digestion occurs, xc cording 1() the fbllowing fbrmula:
Two students should Fepare the controis (tubes 1A ro 3A) while ihe other two Fepare the e)tperimenial sanples (tubes
. M!*
each tube with a wax pencil and load ihe lubes as indicrted in the Salivary Amylase chart on page 600, using 3 dlops (gu) of each indicated substance.
. Place all tubes in a rack in the 37'C water bath lbr ap proximalely t hour. Shake the rack gently from time to time to keep the contents evenly mixed.
.
At the end of the hour, perform tbe amylase assay de'
.
While these tubes are incubating. proceed to Physical of Food Propulsion and Mjxing (page603). Be sure to nonitor the time so as to complete this
kocesses: Mechanisms
Chem cal and Physical Processes oi Digestion
Enzyme(s) and source
@
ffi ffi
I[ffiW
ffiwr ffim
ffi
W FIGURE 3S.1 Flowchad of digestion and absorption of foodstuff s. Amylase Assay I . After one hour obtain a spol plate lnd dropper bottles of Lugol's solution (fbr the lKI, or iodine. resi) and Benedict s solulion hom lhe Aciivily I supply area. Set up your boiling
water balh using a hot plate, boiling chips. and a 250 ml beaker oblained hom the general supply area.
2.
While the water is heating, mark six deprcssions of the 6A (A lbr amylase) lbr sxmple identificarion.
spot plare 1A
Exerclse 39
600
Salivary Amylase Digestion ot Starch 2A
(3 glt ea)
H
H
ul
ul
IU
37"C
37"C
37"C
rmyrase
|
=
sra.n !:
t'.r"
tose
ll
0"c
= water
3.
Pour about a drop of the sample from each of the tubes 1A 6A into the appropri elv numbered spot lnto each sam ple aropr"r. prace aarop ot Lugol ' lKt'olur;on A hlLe blacl iolo'indicare' rhe pre*nce "r 'Larch and ' relened Io d5 nixture \rill Dositiye starch test lf starch is not presenl, ihe starch test' rs a negative to is refened ;ot tum blue. which in rhe for negative) (+ positive your for results Record
i
SalivaryAnylase chart and on the chalkboard-
4.
Into the remaining mixture in each 1ube. ptace 3 drops ofBenedicr's solution. Pul each tube into the beaker ofboilins water for about 5 minules lf a green-to orange prectplt€st' taie forms. maltose is presentr this is a pditive srgar
A negatile sugar l("1
i'
eeroio l our re.ulrs ir rhe
chalkboard.
I
b)
no colo" change SJI;' dD A n) l"e 'hJn and on ne in,lcared
Tr)Tsin, an enzyme Foduced bv the pancreas, hvdrolvzes .."'r nagmenr' 'oloreo'e' pep''ne' rd pepp-o.ii ^ 'o ude5r. BAP\A 1V-alpha benz"yl-r irginine p-ninoanil;del is a .) nrhelic rO ot:n .ub.rrale
"n
imino
t
on5i'ri
rC
cleaves the dye molecule ftom the xmino acid' caustng the so lution to chanqe from colorless to bright yelo\r. Since the co valent bond b;Neen the dve molecule and the amino acid is
ihe same as the peptide bonds that link amino acids together lhe aoDearance ;f a vellow color indicates the presence and activiw ol an enzyne that is capable of peptide bond hydro' lysis. ihe colorchange from clear to velow is directevidence ;fhv{trolvsis. so additional tests are notrequtedwhen deter minins trypsin activity using BAPNA
Assessing Protein Digestion by Trypsin
1.
ftom the general supply area, obtain five test tubes and a ind from the Activitv 2 supplv area get a drop'
test tube mck.
per bottle of trypsin and one of BAPNA and bring them ro
Protein Digestion bY TryPsin
nn.nA ro
37"C
37"C
(-)
nesative
!:
H
of
a
dye co\ alenll)
rcirl ftlpsrn h)drcl)crs 'J
BAPNq
2.
Two students should prepare the controls (tubes 1T and 2T) white the orher two pr€pare ihe experimental sanples (tubes 3T to 5T).
Chemical and Phvsical Processes of Dlgestion
601
Trypsln Digestion ol Protein 4T
1T
(3 gtr ea)
37"C
37'C
l: .
rrypsin
ffi:
eaere
37"Q
37.C
fl:w.t.r
Mark each tube with it wax pencil and load the tubes
indicated in the Ttypsin chart, using 3 drops (gtt) of each
as
n-
.
lir. Fats/ojls
Place all tubes in a rack in the apFopriate water bath for approximately I hour' ShrLe the rack occasionallv to keep the
Then:
contents well mixed.
Fai/oil droplets
.
At the end of the hout examine the
of the
tlpsin
0'c
tubes for the res lts
assay (detailed below)
.
While these hrbes are incubating. prcceed to Phvsical Processes: Mechanisms of Food Propulsion and Mixing (page 603).
Trypsin Assay Since BAPNA is a synthetic colorigenlc (color-prod cing) \ubiuare. lhe presence ol )elrou color IndicJre' J Po\ifve hldroly\i! iesi: lhe dle molecu e hr' Deen cled\ed f-om rhe amino acid- If the sample mixnrre remains clear. a negaove hvdrolvsis test has occuned
Record the results in the Ttl'psin chart and on the chalkboard.
G*#:ri"d '
cl$"d
minute fadoil &oplets
and fattv acids
'monoglvcerides The telm pancreatrn describes tlle enzymatic product of the Dancreas. which includes enzvmes that digest protens, caf bohvdrates. nucleic acids, and fats lt is used here to investigate rhe propenje" or pancreati( lipase. $hn h h)drol)/e' lars 0nJ rrl. ro their comporenl mologllceri,le' and'\o tur') rciJ' (and occasionally to glycercl and thrce fattv acids). The fact that some of the end products of fat digestion (fatty acidt ate orsanic acids thal dedease the pH provides an er.) $a) Lo recogni/e lha, Jigenion i' olgoing or com ? to Dleted. You will be using a pH indicator called l,,,Ls pink as the test blue ro from it changes chan.ses; these iollow
'l
tube contents become acid.
I
Pancreatic Lipase Digestion of Fats and the Action of Bile The teatment that fats and oils go though during digestion in rhe sma intestlne is a bit more complicated ihan that of {arbohydrale' or ororeir'- pretreJlmenl $irh brle lo ph)'i
cdrl)
erul.iI rhi :n .
required Hence 'w^ 'er' ol re'c'
Demonstrating the Emulsification Action of Bite and Assessing Fat Digestion by Lipase
1.
From the general supply area. obtain nine test tubes and a lesi tube rack, plus one dropper bottle of each of the solu' rions in theActivity 3 supply area
2.
Altbo sh b/la a seclEtory Foduct ofthe livet isnotanenzyme, it is i;ponant to fat digestion because oI its emulsifving
Exercise 39
602
Pancreatic Lipase Digesllon or Fats 2L
3L
4L
5L
4B
5B
H
(5 grt ea)
tffil 37'C
ripase ffi = rir.,"
ffi:
37.C
37"C
37.Q
surface area for enzymatic activity. To demonstrdie the action of bile on fats. pepare two test tubes and mark th€m 1E md 2E (,E lor emulsi
fied fats).
.
To tube 2E, add 10 drops of water, 2 drops of vegeiable oi], and a pinch of bile salts. Cover each tube with a small square of Panfilm. shake vigorously, and alow rhe tubes to stand at room iemperanre. 10
to
15 minutes. observe both tubes.
has not occurred, the oil
will
If enulsification
be floating or the surface of the
water If emulsification has occurred, the fat droplets will be suspended throughout ihe water. fomring an emulsion. In which tube has emulsification occuned?
3. Two students should prep:re &e controls (lL and 2L, , for lipase). while th€ other tlvo students in the group set up $e erperimentrl samples (3L io 5L, for bile)
.
as
,1B, and
58. where B is
illustrated in the Pancreatic Lipase chat.
Mafk each tube with
a
wax pencil and load the tubes us
ing 5 drops (gh) ofeach indicated solution.
.
. .
To tube lE, add 10 drops of water and 2 drops of vegerable oil.
After
o"c
Shake the test tube rack from iime to time to keep lhe conren,' well mrred
action (the physical breakdown of lafger paticles into smaler
.
37'C
: "'... [ water 2\ = Pinch bire sarts
onet on fats. Emulsified lats provide a larger
.
0"c
ofbile salts in tubes 48 and 58. Cover each tube with a small square of Parafilm. and
At the end of the hour. pedorn dle lipase assay (below).
While these tubes are incubating proceed to Physical Processes: Mechadsms of Food Propulsion and Mixing (p. 603). Be sufe to nonitor the time so as to complete ihis activity when needed.
Lrpase Assay Thebasis oftbis assay is apHchange thatis detected by a litmus powder indicator Alkaline or neutal solutions contain ing litmus are blue bxt will tum reddish in the presence of acid. Since lats are digested to fatty acids (organic acidt durlng hydrolysis, they lower the pH of the sample they are in. Litmus cream (fresh cream providing the fat subslrate to which litmus powder was added) will tum from blue to pink if the solution is acid. Because the effect ofhydrolysjs is dircctly seen. additional assay reagents are not necessary.
1.
To prepare a color cortrol. add 0.1 N HCl drop by drop lL and 2L (covenng the tubes with a square of Parafilm after each addition and shaking to mix) until the
to tubes
2.
Record the color of the |ubes in the Pancreadc Lipase cha( and on the chalkboard. I
Place apinch
shake to mix rhe contenls of the tube.
Reporting Results and Conclusions
Remove the Parafilm, and place all tubes in a rack 'n the appropr;ate water bath for approximately I hour.
Share your results wiih rhe class as directed in the ceneral lnstructions on Dase 598.
1.
Chenrical and Physical Processes of Digestion
Epi9lorris
O
upper esopnageat sprrincrer s conrracred. DLrinq th6 blccal phase, the longue presses agairsrrhe hard paate iorcing lhe lood bo us nlolhe oropharynx where lhe nvolunlary
@ rhe
Orhe
uvula and larynx rse lo
constriclor musc es ol tlre pharynx conract, forc ng food irro the esophagLs ni€rony.The upper esophageal sphincter cof tracts
prevert lood ircm enler ng respiEtory passageways. The longue b ocks oil the ftouth.The upper esophageal sphircter relaxes, allow ng lood to
FIGUBE 39.2 Swallowing.
The process of swallowing consisis oi vo untary (bucca) (stepO) and involuntary(pharynseafesophaseal) phases (stepsO{O).
Fr lJ
2.
Suggest additional expenments. and carry out experiments if tine permits.
3.
Prepare a lab repoft fof the experiments on digesiion. See Geuing Stafied on page rv.
I
Observing Movements and Sounds of Digestion
l.
Obiain a pitcher of water, a stethoscope, a paper cup. an alcohol swab, and an autoclitye bag in preparation for naking
Physical Processes: Mechanisms of Food Propulsion and Mixing
the following observations.
2.
White swallowing
a
mouthful of waier, consciously nore
the movementofyour tongue dudng theprocess. Record your
Although enzyme rctivity js
a very impofant part of the overall digestion process, foods must also be processed physically (by chewing and chuming) and novedby nechanical neans along the tracr if digesiion and abso.ption arc to be completed. Just about any time organs exhibit mobility, muscles are in!o1ved, and movements of and in the gastrointestinal tract arc no exception. Althoughwetend io thinL only ofsmooth mus cles when visceral activities are involved, both skeletal and smooth muscles lre involved in digestion. This fact is amply demon,rr.,red b) ,he ,imfle dcr'\ ie, lhr. follo$.
Deglutition (Swallowing) Swallowing, or deglutition, which is largely the resuh of skeletal muscle activity, occuN in two phases:raccdi (nouth) and pharynqeal-esophaseal. The inirial phase the buccal (Figure 39.2 step (D)-is voluntarily controlled and initi ated by thetongue. Once begun.lhe process continues invol untarily in thepharynx andesophagus. through peristalsis, re-
sulting
in lhe delivery of the swallowed conten$ to €) O).
stonach (Figure 39.2 steps
the
3.
Repeat the swallowing Focess while yoxr labomtory
partner watches the externally visible movenenrs of your lar ynx. (This novement is more obvious in a male, since males have a largerAdam's apple.) Record your observations.
wl
t
do thele mo\ ements accornpli\hr
I 604
{
Exercise 39
Before donning the stethoscope' your lab partner should clean the earpieces with an alcohol swab Then. be or she your ab should place ihe diaphragm of the steihoscope ovef the (l belo$ inch) crn donini wal1. apDr;ximatelv 25 I^r li'ten to Io 'erI 'ound' J' xiDhord nroce*;nd 'lignd)
4.
r
*"i"
'he
q drer'
rhJee'v allos' of
',j. "r.'*.sounds --one when the waler ;e tw; audible
Thcre'hoLlJ
splashes aga;nst rhe pel rhe rhe gan.oe'ophageal 'phinffr an,l 'e(ond-$hen rne lhe:phrn'rer q1 e\ ar rhe e.ophrgJ\ arri\ ,'r11;. .r16
'rr
.phrncler oper.. dloq;nC ua,er Io gurgle Inlo rhe Jnr.]rcn inrervJl beIieLermine. a' accurarel) a' po\sible rh( timc tween these two sounds and record it below.
Tnterval between anival of water at the sphincter and the opening of the sphincter:
This interval eives
a
I I I I
I
I
I
{
I
fair indication of the time it iales for the
Deri.ulric q ;ve ro rra\ e ,lo$n rhe 25 . m I l0 irLhe'r ol rhe e,oohaeu.. rqcruallr Ine -rime irrenrl ; 'lighrl) le\\ rhan i' p'"'.,'. . ause' rhe sphinLrer Io rela\ berore
I
I
'".;.,;..,,'. the peristaltic wave reacbes lt.l I
Dispose of the used paper cup in rhe ,tutoclaYe bag
!
l
Segmentation and Peristalsis Although several types of movemenis occur in the digestive llact or;ans. Densdsis and segmentalion are most important as
nixing
and propulsive mechanisns
(Figue 39 3)
Prr;taltia movements are the major means of proL"enliall) Dellrnq lood rf ougn nosl of rhe Jrgeni\e vr'cerJ
of."nnrcr'on lollo$ed b) $d\ et of rela\d'ion rhdi.quee/e lood.rufl ' rhroJPh Ihe alimen rr) canal andrhev ffe superimposed on setsrnental molementl Seemental moremints nreroc!l con'uicrron' ^r rhe "l to nix ean wJl ttrat occur rhyttrmicallv. Thev serve mainlv the mte of juices increase and ro ft; foodstuffs with dis;sdve ponron' of rhe ddlerenr conrin;dlr) b\ ab5omron 'no\rng cnrmeo'eri,liacenr regi"r' ol rhe Inre{;rrl url' Ho$e\er' rher a"r qa' et
(b)
and segmental movemenG nerghbo'irg Pe'ista'sis: ofthe digestive tract. {a) and -e'aY conlract alternately i4testine t1e seoments ol s nqle -o'v'nq fooO "'ong rt'e t'act {b) Segmenlation: rela* ard seqmenLs o''nteslne arte'nate'y cortrdct Be;ause lnactive segments exist beiween active segments' {ood mlxing occurs to a greai€r degree than lood movement. Peristalsis is superimposed on segmentaron during digestion
FIGUBE 39'3 Peristaltic
propulslon
segmenration is also an importiint means of food in ile snall inrestine. an
Viewing Segmental and Peristaltic Movements If a videotape showing
some of the propulsjve moYements is
rfe a\airrble, ro to z \;e$ ing '!3rion lo \ ies rr oclbre lea! n! Ph";otnP'" the lr!'rc'ttw u\e Ahemari\el). laDurdlon inodule o; the Disestjve Syslem to observe gl]t
notilitv
l
NA]\4E
LAB TIIVE/DATE
Ghemical and Physical Processes of Digestion Chemical Digestion of Foodstuffs: Enzymatic Action 1. Match the following definirions with the proper choices
(e)r a.
2. List
3.
tuom the key.
catalyst
l.
substance on which a catalyst
2.
biologic catalysc protein in naiure
3.
incrcases the rate of a chemical reaction .rJithout beconing pan of the product
4.
provides
a
wo*s
standard of comparison for resi results
the three characteristics of enzymes.
The enzymes ol the digestive system are classified as hydrotases. Whai does thjs mean?
4. Fill in ihe following
chart about the various digestive system enzynes encountered in this exercise.
Organ producing it
Enzyme
Site of action
Sallvary amylase Trypsin Lipase (pancreauc)
5. Nane
the end products of digestion for the following types of foods.
Substrate(s)
Optimal pH
Review Sheet 39
-
You used several indicators or tests in fie laboratory to detendne the pesence or absence of certain substances. Choose the colrect test or ildicator from the key lo cofespond 10 the condition described below-
retr .t.
b.
Lugol's iodine (lKI)
d,
Benedict's solution
BAPNA
I -
F
l.
used to test for protein hydrolysis, which was indicated by a yellow color
2.
used to test for the presence of starch, which was indicated by a blue black color
3.
used ro test for the Fesence of fatty acids, which was evidenced by a color change from blue to pink
4.
used to lest fbr the presence of reducing sugars (maltose. sucrose, glucose) as indicated by a blue ro green or orange color change
7. Wlar conclusions can you draw when an experimental sample gives botb a positive siarch test and a positive maltose test
a,
r
Why was 37"C the optimal incubation temperature?
Why did very little, if any, starch digestion occur in lest tube 4A?
= incubated lvith amylase at 0"C, did yor see any starch digestion?
Why or why not?
E Assume you have made the statement to a group of your peers that amylase is capable of starch hy&olysis to malrose. If you had not done control tube 1A, what objection to your siatement could be
raised?-
= C
L what if you had not done tube 2A
?
8. In the exercise conceming trypsh tunction . why was an enzyme assay like Benedici's orLugol's ence of
a
IKI (which
test for the pres
reaction Producr) not necellrry7
Why was tube lTnecessary?
I t L L
Why was |ube 2T necessary /
Trypsin is a protease similar to pepsin, the protein digesting enzyme in the stonach Would trypsin work well in rhe
\-
whv? 9. In the procedure concerning pancreatic lipase digestion of fats and the action of bile salis, how did dre appearance of tubes 1E and 2E
differ?
Explain the reason for lhe difference.
e. =
F
r.
Review Sheei 39
why did
why
rhe
lituus indicator
change from blue to
607
pinl during fat hydrolysisl
is bjlenor considered an enzyme'
How oro rhe rube' Lonrdin.np bile compare \\
lh
lhose noL conrrining
bilel
What role does bile play in fat digestion?
st ciure of a functional proiein is altered by intense heat or nonphysiological pH even though pep tide bonds may not break- Such inactivation is called denaturation, and denatued enzymes arc nonfunctional. Explain why.
10, The thre€ dimensional
What specific experimental conditions resul€d in denatured enzymes?
and intestinal e'zymes operate opiimally at a pH that is slightly alkaline, yet the chyme entering the duodenum from the stomach is very acid. How is the Foper pH for fte functionins of the pancreatic-intestinal enzymes ensured?
11. Pancreatic
12. Assume you have becn chewing
a piece of bread tbr 5 or 6 ninutes. How would you expect its taste to change during this
why? 13. Noie the mechanism of absorption ipassive or active tansport) of the following food breakdown products. and indicate by check mark (lacteals). a
(/)
whether the absorption would result in their movement into the blood capillaries or tbe lymph capillaries
Substance
Mechanism of absorption
Blood
Fatty acids and glycerol
Na*, Cl , Ca'z*
14. People on a strict diet to lose weisht besin to metabolize stored fats at an accelerated rate. How blood pH?
does this condition affect
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f
Review Sheei 39
f :
15. Using a flowcharr, tace the pathway of a ham sandwich (ham potein and fat; head = starch) from the mouth to the site of absorprion ofits breakdown products, noting where digestion occurs and what specific enzymes are involved.
I.
a
\ \ 16. Some of the digestive organs have groups of secretory cells that liberate hornones into dle blood. These exed
an effect on rhe digestive process by acting on other cells or structures and causing ihem to release digestive enzynes, expel bile, or in crcase the moriliiy of the digestive tract- For each hormone below, note the organ producing the homone and its effecis on the digestive process. Include the tffget organs affected.
Target organ(s) and effects
\ \ \
\ c I
Secretin Gastrin
I
I
Cholecystokinin
I
Physical Processes: Mechanisms of Food Propulsion and Mixing
I
17. Complete the following staiements.
T
2
phases-the and Swallowing, or -L, occurs in f"vo On€ of these phases, the lL pbase, is voluntary. During the volun tfiy phase, the *L is used to push the fbod inlo the back of the throai. Dwing swalowing. the -lL rises io ensure that its passageway is covered by the epiglottis so that the ingested substances don'tenter the respiratory passageways.lt is possible to swallow water while standing on your head because the water is canied aiong the esophagus involuntarily by the process of -L. The pres sphincGr causes it to open, sure exened by the foodstuffs on the allowing the foodstuffs to enter the stomach The two major types ofpropulsive movements that occur in One of tbese movements, the small intestine are L and -11L. acts to continually mix the loods and to increase the absorption rate by moving difterent parts ofthe chyme mass over the in iestinal mucosa, but it has less ofa rcle in moving foods along the digestive tract.
rL
lL,
-L.
1.
I
i 3.
I
4.
I
5.
I
I
I 1.
I
I
10. I l_
