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101 terms

Lab 8 Chemical Digestion

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nutrients can only be absorbed when broken down
to their monomers
enzymes
large protein molecule produced by body cells. biological catalysts that increase the rate of a chemical reaction without themselves become part of the product
the digestive enzymes are what type of enzymes?
hydrolases
hydrolases
break down organic food molecules by adding water to the molecular bonds, cleaving the bonds between the subunits or the monomers
the various hydrolytic enzymes are
highly specific in their action
each enzyme hydrolyses only
1 or a small group of substrate molecules and specific environmental conditions are necessary for it to function optimally
digestive enzymes actually function where?
outside the body cells in the digestive tract, so their hydrolytic activity can also be studied in a test tube - in vitro
carbohydrate digestion:

what is the enzyme that breaks down STARCH and what site of action does it take place in?
enzyme / source = salivary amylase
site of action = mouth
when starch is broken down by salivary amylase, what is it broken down to?
dextrin + disaccharides
carbohydrate digestion:

what is the enzyme that breaks down dextrin + disaccharides and what site of action does it take place in?
enzyme / source = pancreatic amylase
site of action = small intestine
when dextrin + disaccharides is broken down by pancreatic amylase, what is it broken down to?
disaccharides
the 3 enzymes of the small intestine (maltase, lactase and sucrase) break the disaccharides down to what 3 things?
lactose
maltose
sucrose
lactose is broken down to what 2 substances?
galactose
glucose
maltose is broken down to what substance?
glucose
sucrose is broken down to what 2 substances?
fructrose
glucose
galactose, glucose, and fructose are considered
monosaccarides
the monosaccharides are absorbed into the intestinal vili and transported via the
hepatic portal vein in the liver
Salivary Amylase
the enzyme produced by salivary glands and secreted into the mouth
Experiment A. Starch DIgestion by Salivary Amylase
we investigated the hydrolysis of starch to maltose by salivary amylase to determine to what extent the enzymatic activity occurred.
what does the following equation suggest?

starch + water + amylase --->
maltose (units) + amylase
starch decreases and sugar increases as digestion occurs
Experiment A. Starch DIgestion by Salivary Amylase

procedure - IKI TEST
added 3 drops of each indicated substance and placed the tubes in a water bath for 1 hour. then we marked a spot plate A for amylase and made 6 depressions

added a drop of the sample from each of the tubes with a drop of IKI solution
what color would indicate a positive starch test? (indicating the presence of starch) - IKI TEST
a blue black color
what color would indicate a NEGATIVE starch test? (indicating that starch is not present) - IKI TEST
the mixture will not turn blue
Experiment A. Starch DIgestion by Salivary Amylase

procedure - Benedict's Test
into the remaining mixture in each tube, we placed 3 drops of benedict's solution and put each tube into a beaker of boiling water for 5 minutes.
what color would indicate a POSITIVE sugar test? (indicating that maltose is present) - Benedict's Test
green-to-orange precipitate
what color would indicate a NEGATIVE sugar test? (indicating that maltose is not present) - Benedict's Test
no color change
protein digestion by
Trypsin
protein digestion:

what is the enzyme that breaks down PROTEIN and what site of action does it take place in?
enzyme = pepsin in the presence of HCl

site of action = stomach
what does the breakdown of protein lead to?
proteases and peptones
protein digestion:

what is the enzyme that breaks down proteases & peptones
and what site of action does it take place in?
enzyme = pancreatic enzymes (trypsin, chymotrypsin and carboxypeptidase)

site of action = small intestine
what does the breakdown of proteases & peptones lead to?
small peptides
protein digestion:

what is the enzyme that breaks down small peptides
and what site of action does it take place in?
enzyme = small intestine enzymes (aminopeptidases and dipeptidases)

sit of action = small intestine
amino acids are absorbed into the intestinal vili and transported via
the hepatic portal vein in the liver
trypsin, an enzyme is produced by what digestive organ?
pancreas
what does trypsin do?
it hydrolyzes proteins to small fragments (proteases, peptones and peptides).
BAPNA
used to test for protein hydrolysis, which was indicated by a yellow color
the appearance of yellow color indicates what with the BAPNA dye?
the presence and activity of an enzyme that is capable of peptide bond hydrolysis
Experiment B: Protein DIgestion by Trypsin

procedure
5 test tubes, and added 3 drops of trypsin and 3 drops of BAPNA, placed the tubes in a 1 hour water bath and observed the color results
what color indicates a positive hydrolysis test?
yellow
the dye molecule has been cleaved from the amino acid
what happens when no detectable hydrolysis has occurred?
the sample mixture remains clear
fat digestion:

what are the 2 enzyme that break down unemulsified fats?

and what site of action does it take place in?
enzymes = emulsified by bile salts from liver, stored in the gall bladder

& pancreatic lipases

site of action = small intestine
what 2 substances does the breakdown of unemulsified fats lead to?
1. monoglycerides & fatty acids
2. glycerol & fatty acids
lipids are absorbed mainly by what?
lacteals in the villi and into lymphatic circulation, eventually into circulation
the treatment that fats and oils go through during digestion in the small intestine is a bit more complicated than carbs and proteins, why is this so?
because pre-treatment with bile to physically emulsify the fats is required.
what 2 reactions occur in fat digestion?
First - fats and oils are emulsified in the presence of bile salts to produce minute droplets.

Second - the minute fat/oil droplets are digested by lipase to free fatty acids and glycerides
pancreatin shows what?
used to describe the enzymatic product of the pancreas, which includes :
- protein
- carbohydrates
- nucleic acids
- fat digesting enzymes
pancreatin is used in the lab to investigate what?
the properties of pancreatic lipase
pancreatic lipase
hydrolyzes fats and oils to their component monoglycerides and 2 fatty acids
(and occasionally to glycerol and 3 fatty acids)
the benefit of the end products of fat digestion are being (fatty acids) that are organic acids that decrease the pH is that
they provide an easy way to recognize that digestion is ongoing to completed
what is the name of the pH indicator that can help you follow these changes?
litmus blue
what colors does litmus blue change from and to as the test tube contents become acid
blue to pink
Experiment C: Pancreatic Lipase DIgestion of Fats and the Action of Bile

to demonstrate the action of bile on fats

procedure
2 test tubes
10 drops of water with 2 drops of veggie oil in one tube

10 drops of water with 2 drops of veggie oil and pinch of bile salts in the 2nd tube

cover each tube, shake, allow tubes to stand at room temp
bile is a secretory product of the liver but it is not what?

why is it important to fat digestion
an enzyme

because of its emulsifying action (the physical breakdown of larger particles into smaller ones)
on fats.
emulsified fats provide a
larger surface area for enzymatic activity
Experiment C test results:

what happens if emulsification has not occurred?
the oil will be floating on the surface of the water
Experiment C test results:

what happens if emulsification has occurred?
the fat droplets will be suspended throughout the water, forming an emulsion
Lipid Digestion by Lipase experiment, how many drops did you add?
5 drops
lipase assay - what is the basis of this assay?
a pH change that is detected by a litmus powder indicator
what color will alkaline or neutral solutions containing litmus (which are blue) turn into in the presence of acid?
reddish
since fats are digested to fatty acids (organic acids) during hydrolysis, they do what to the pH of the sample they're in?
lower the pH
Litmus cream (fresh cream providing the fat substrate to which litmus powder was added) will turn from what color to what color if the solution is acid?
bluish color to pink
how did you prepare a color control?
added 0.1 N HCl drop by drop to tubes 1L and 2L until the cream turns pink
Mechanisms of Food Propulsion & Mixing

just about any time organs exhibit mobility, what are involved?
muscles and movements of the GI tract
what 2 types of muscle are involved in digestion?
skeletal and smooth muscle
swallowing aka
deglutition
swallowing aka deglutition is largely the result of what type of muscle activity?
skeletal muscle activity
swallowing occurs in what 2 phases?
1. buccal (mouth)
2. pharyngeal-esophageal
1. buccal (mouth) phase is voluntary or involuntary??
voluntary controlled and initiated by the tongue
2. pharyngeal-esophageal phase is voluntary or involuntary??
involuntary in the pharynx and esophagus

through peristalsis

resulting in the delivery of swallowed contents to the stomach
peristalsis
wave like muscular contractions that squeeze food through the esophagus into the stomach
Activity D - food propulsion and mixing

procedure
place stethoscope 1 inch below the xiphoid process and slightly to the left

listen to sounds as the partner consumed 2 or 3 swallows of water

determine time interval between two sounds
how many audible sounds should you have heard?
two sounds:

1 when the water splashes against the gastroesophageal sphincter

2. when the peristaltic wave of the esophagus arrives at the sphincter and the sphincter opens, allowing water to gurgle into the stomach
what does the time interval give an indication of?
the time it takes for the peristaltic wave to travel down the 10 inch esophagus
catalyst
increases the rate of a chemical reaction without becoming part of the product
control
provides a standard of comparison for test results
enzyme
biologic catalyst - protein in nature
substrate
substance on which a catalyst works
list at least 3 characteristics of enzymes
1. not used up in the reaction / does not change shape

2. used to speed up a reaction

3. will bind to a molecule if the enzyme-substrate complex can form
the enzymes of the digestive system are classified as hydrolases, what does this mean?
catalyze digestive hydrolysis reactions
1. organ that produces it
2. site of action
3. substrate

salivary amylase
1. salivary glands
2. mouth
3. starch
1. organ that produces it
2. site of action
3. substrate

trypsin
1. pancreas
2. small intestine
3. proteins
1. organ that produces it
2. site of action
3. substrate

lipase (pancreatic)
1. pancreas
2. small intestine
3. fats
name the end products of digestion for protein
amino acids
name the end products of digestion for carbohydrates
simple sugars
name the end products of digestion for fats
fatty acids and glycerol
why was 37 degrees the optimal incubation temperature?
because the body's enzymes work at their optimum temperature.
what happened to the tube in starch digestion that was incubated at 0 degrees rather than 37 degrees?
no starch digestion occurred
in the exercise concerning Trypsin function in the BAPNA test, why was an enzyme assay like Benedicts or IKI (which tests for the presence of a reaction product) not necessary?
because the color change from clear to yellow is direct evidence of hydrolysis, additional tests are not required when using BAPNA
what did you do to tube 1T
added water, trypsin and incubated at 37 degrees
trypsin is a protease similar to what?
pepsin
pepsin is
the protein digesting enzyme in the stomach
would trypsin work well in the stomach, why or why not?
no, the stomach is highly acidic while trypsin works well in the neutral/basic environment of the small intestine
int he procedure concerning pancreatic lipase digestion of fats, why did the litmus indicator change from blue to pink during fat hydrolysis
because the change of blue to pink indicates the presence of acids as is the case when fats is broken down into glycerol and fatty acids
BAPNA is used to test for?
protein hydrolysis
what color was the BAPNA test for protein hydrolysis indicated by?
yellow
Litmus is used to test for?
presence of fatty acids
what color change was Litmus test presence of fatty acids evidenced by?
blue to pink
IKI was used to test for the presence of what?
starch
what color was indicated by the IKI test presence of starch?
blue-black color
Benedict's solution was used to test for
presence of reducing sugars (maltose, sucrose, glucose)
Benedict's solution that was used to detect the presence of reducing sugars (maltose, sucrose, glucose) was indicated by what color?
a colored precipitate