Lab 6

BY: WAN ISKANDAR FIRDAUS B SHAHARIMAN

MUHAMMAD IZWAN BIN NORMAN

ANTHONEO JAY AUGUSTINE

LAB 6: DIGESTION OF STARCH, PROTEIN, AND FATS IN HUMAN

THE HUMAN DIGESTIVE SYSTEM

DIGESTION OF STARCH

WHERE DOES THE DIGESTION OF STARCH

OCCUR?

ORGANS THAT SECRETES ENZYME AMYLASE

Starch Digestion by AmylaseStarch is a polymer composed or repeating units of glucose.

Amylase breaks starch into smaller subunits such as maltose.

Maltose

20cm3 of uncontaminate

d saliva was collected in a

measuring cylinder

Transfer one quarter of the saliva into a test tube and place this test tube in boiling

water for 15 minutes

Transfer a further

quarter of the saliva

into another test tube

Add four drops of

hydrochloric acid, mix well and

leave for at least 15 minutes

Set up six

pairs of test tubes

Leave the test tubes for at least

10 minutes

METHODS

Sugar only Starch onlyStarch

+ untreat

ed saliva

Starch + pre-

heated saliva

Starch + acidified

saliva

Untreated saliva only

TESTS

Iodine test Benedict’s test

Pair

Contents Test with iodine solution

Test with benedict’s reagent

A Sugar only No change Turns brick red color

B Starch only

Turns dark blue No change

C Untreated saliva only

No change No change

D Starch + untreated saliva

No change Turns brick red color

E Starch + pre-heated saliva

Turns dark blue No change

F Starch + acidified saliva

Turns dark blue No change

RESULTS

LAB 6: DIGESTIO

N OF PROTEIN

IN HUMAN

DIGESTION OF PROTEIN

Amino acid

Peptide

Poly peptide

Protein

MATERIALS USED

4 test tubesTest tube rack2 syringes or

pipettes (10 ml)2 syringes or

pipettes (1 ml)Label

pH paperIncubator (37’c)

1% pepsin solution

1% trypsin solution

0.1 M HCL0.2 M sodium

carbonateEgg white

METHOD

The 4 test tubes are labeled; P2, P9, T2, T9Test tubes are set up as follows;

Test tubes are shaken as to mix the content

.

Test tube Contents

P2(PEPSIN AT pH 2.0)

5cm³ pepsin and 0.5cm³ HCl

P9(PEPSIN AT pH 9.0)

5cm³ pepsin and 0.5cm³ sodium carbonate

T2(TRYPSIN AT pH 2.0)

5cm³ pepsin and 0.5cm³ HCl

T9(TRYPSIN AT pH 9.0)

5cm³ pepsin and 0.5cm³ sodium carbonate

A small strip of egg white is added to each of the test tube

Then, test tubes are placed in an incubator at 37°C and then leave for 2

hoursThe contents are examined and the appearance of the egg white and it’s

surrounding is observed.Results are recorded.

THEORY……

Simply said, pepsin react best at a low pH value white trypsin react

best at high pH value.

So, protein is best digested via this

respective enzyme at their suitable pH.

RESULT- FOR PEPSIN VIA BIURET TEST

TEST OBSERVATION INFERENCE

POSITIVE The solution turns from blue to violet( purple)

Presence of peptide bonds in protein

NEGATIVE No change /The solution remains blue

No presence of peptide bonds in protein

RESULT- FOR TRYPSIN VIA MILLION’S TEST

TEST OBSERVATION INFERENCE

POSITIVE The solution turns from blue to pink

Presence of the amino acid tyrosine

NEGATIVE No change /The solution remains blue

No presence of the amino acid tyrosine

IF POSITIVE….

DIGESTION OF FATS

METHOD

1)The first 3 test tubes are labeled and marked at 3cm and 6 cm levels. 1% to 2%

pancreatic solutions is added to test tube 1-3 to the 3cm mark. 4 test tubes are

preparedTest tube 1:

1% bile (until 6cm mark) + 2/3 drops phenolphthalein + 0.2% NaOH drop by drop until pink

+ 3 drops vegetable oilShake and incubate at 37°C for

1 hour

Test tube 2:Distilled water (until 6cm

mark) + 2/3 drops phenolpthalein + 0.2%

NaOH drop by drop until pink + 3 drops of oil

Shake and incubate at 37°C for 1 hour

Test tube 3:1% bile (until 6cm mark) + 2/3 drops phenolphthalein

+ 0.2% NaOH drop by drop until pink + 3 drops of oilShake and allow to remain at room temp. for 1 hour

Test tube 1:PinkColourless

Fats are emulsified and digestedTest tube 2:

Pink remainsFats are not emulsified

Test tube 3:Pink remains

Condition not suitableLow temperature

RESULT

» Fats are made of carbon, hydrogen, and oxygen.

FATS

» Fats supply your body with: Energy Form your cells Maintain body temperature Protect your nerves

»Unsaturated Fats have at least one unsaturated bond in a place where hydrogen can be added to the molecule.

UNSATURATED FATS

»Unsaturated fats are usually liquid at room temperature.

»Unsaturated fats are classified as either monounsaturated fats or polyunsaturated fats.

» Fats that have all the hydrogen the carbon atoms can hold are called saturated fats.

SATURATED FATS

» Saturated fats are usually solid at room temperature.

» Too much saturated fat in your diet can lead to heart disease.

» Fats are digested by mixing the fat with the digestive enzyme lipase (from pancreatic juice), which enters the duodenum from the pancreas - the main source of enzymes for digesting fats and proteins. 

» Lipase chops up lipid molecules into fatty acid and glycerol.

» Fat does not dissolve in water.» To overcome this problem the digestive

system uses a substance called bile, produced in the liver but stored in the gallbladder, which enters the duodenum via the bile duct.

» Bile emulsifies fats - meaning, it disperses them into small droplets which then become suspended in the watery contents of the digestive tract. 

» Emulsification allows lipase to gain easier access to the fat molecules and thus accelerates their breakdown and digestion.

FAT BREAKDOWN IN THE SMALL INTESTINE

+Water soluble

Emulsifica

tion

Fatty acids

Hydrolys

is

» Absorption of fat into the body occurs in the villi - the millions of finger-like projections which cover the walls of the small intestine.

» Inside each villus is a series of lymph vessels (lacteals) and blood vessels (capillaries).

» The lacteals absorb the fatty acids and glycerol into the lymphatic system which eventually drains into the bloodstream.

» The fatty acids are transported via the bloodstream to the membranes of adipose cells or muscle cells, where they are stored or oxidized for energy.

» Fats are only converted to glucose for energy supply during extreme condition.

» The glycerol part is absorbed by the liver and is either converted into glucose (gluconeogenesis), and/or used to help breakdown glucose into energy (glycolysis).HOW FAT IS ABSORBED INTO THE

BLOODSTREAM

BILE

• Produced in liver, stored in gallbladder– Except horse

• Alkaline solution composed of:– Bile salts– Cholesterol– Lecithin– Bilirubin

• Responsible for fat emulsification– Detergent action

Fatty acid + glycerol

Lacteal

Lymph