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DIGESTION OF FOODGROUP 6 - DAD

+OBJECTIVES1. TO BE ABLE TO SHOW THE

DIGESTION OF A CARBOHYDRATE BY SALIVA AND PANCREATIC JUICE.

2. TO SHOW THE EFFECT OF THE GASTRIC AND PANCREATIC PROTEASES ON PROTEINS.

3. TO SHOW THE EFFECT OF PANCREATIC ENZYMES ON FAT.

+DISCUSSIONThe process of digestion involves a series of hydrolytic process. The changes on the food intakes are due to the catalytic activity of the various enzymes in the saliva, in the gastric and pancreatic juices.

Dietary carbohydrates include starch, sucrose, lactose and indigestible fiber. These carbohydrates are digested into simpler forms mostly glucose but galactose and fructose maybe are produced. The principal sites of dietary carbohydrate digestion are the mouth and intestinal lumen. This digestion is rapid and involves several enzymes.

+DISCUSSIONProteins are digested into amino acids which are absorbed through the intestinal epithelial cells and enter the blood. Protein digestion is due to digestive proteases usually produced and secreted in its inactive forms. The process begins in the stomach up to the small intestines.

The major dietary is triacylglycerol which is obtained from the fat stores of the plants and animals in the food supply. These are water insoluble must be emulsified by bile salts and digested in the small intestine to fatty acids.

+CARBOHYDRATE DIGESTION

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MATERIALS Cooked Starch Lugol’s Iodine solution Litmus paper Benedict’s solution Na2CO3

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PROCEDUREACTION OF SALIVA ON STARCH

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1. 1. Put a drop of cooked starch mixture on a water glass and add a drop of Lugol’s iodine solution. Observe and record results.

2. 2. Collect 10ml of saliva in a test tube & filter it into another test tube. Test filtered saliva with red and blue litmus paper. Observe and record results.

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PROCEDUREACTION OF SALIVA ON STARCH

3. To 10ml of filtered saliva in a test tube adds 5ml of cooked starch solution. Immerse the tube containing the mixture in a beaker of H2O, keeping the H2O warm at 37°C-40°C for about 30 minutes. At 5 minute intervals, remove a drop of mixture and place it on a watch glass and test with iodine solution.

4. Transfer remaining cooked starch and saliva mixture in a test and add 4ml of Benedict’s solution. Heat the tube gently to boling.

+RESULTSLugol’s

Iodine TestBenedict’s Test

COOKED STARCH

The concentrated starch in the middle became dark purple while the fluids became yellow green

The concentrated starch and fluid became baby blue

COOKED STARCH +

SALIVA

YELLOW BLUE

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PROTEIN DIGESTIONACTION OF THE GASTRIC PROTEASE ON PROTEIN

Materials• Commercial Pepsin•Concentrated HCl

•NaOH•CuSO4 solution•O.5% Na2CO3

+PROTEIN DIGESTION(Action of Gastric Protease on Protein)

1. Label 3 test tubes into A, B, C. Then fill half of each tube with warm H2O

2. Into each tube put a small amount of grated white of hard boiled egg.

3. To the first tube, add a pinch of commercial pepsin and 2 drops of concentrated HCl.

4. To the second test tube, add only a pinch of pepsin, add nothing to the H2O-egg-white mixture in the third tube.

5. Place these tubes in a warm H2O bath kept at body temperature for at least 1 hour.

6. Filter the contents of each tube and test the filtrate with NaOh and CuSO4 solution. Observe and record the results.

+ RESULTS

A

B

C

TEST TUBE BIURET TEST

A Lavender in color, clear

B Blue in color, small amt. of precipitate

C Sky blue in color, w/ greater

precipitate

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RESULTS

A B C

+POST LABORATORY QUESTIONS

+What are the enzymes used in carbohyrdate digestion? Lipid digestion? Protein digestion? Carbohydrate Digestion : Amylase, Pepsin

Lipid Digestion : Lipase, Pancreatic Proteases (Pancreatin)

Protein Digestion : Trypsin, Pepsin, Pancreatic Proteases

+What are the similarities and differences of these enzymes?

They are alike in the way that these enzymes break down macromolecules into their builiding blocks. They are found in the digestive tract of both humans and animals where they aid in the digestion of food.

However they differ in function and are classified by their substrates.

Proteases and peptidases split proteins into amino acids,Lipases split fat into three fatty acids and glycerol, Carbohydrases split carbohydrates such as starch into sugars,

+What are the factors that would bring about carbohydrate digestion? Lipid digestion? Protein digestion? CARBOHYDRATE DIGESTION : Salivary amylase, Pepsin, Lactase LIPID DIGESTION : Bile acids, Pancreatic Lipase PROTEIN DIGESTION : Trypsin, Pancreatic Proteases

+Trace the pathway of carbohydrate digestion, lipid digestion and protein digestion.CARBOHYDRATE DIGESTION : Mouth breaks down polysaccharides through amylase. The stomach, however, because of its high acid content stops the process and is continued in the duodenum (small intestine). The pH changes dramatically from a strong acid to an alkaline content. The pancreas secrete a bicarbonate to neutralize while in the duodenum thus finishes the breaking down of chyme to simple sugars.

+ LIPID DIGESTION:Triglycerides and other dietary facts are relatively unaffected by conditions in the stomach and enter the duodenum in the form of large lipid drops. Bile salts emulsify them into tiny droplets the pancreatic lipase could attack. The enzymes breaks the triglycerides apart and lipids released interact with bile salts to form the small complexes called micelles. When a micelle contacts the intestinal epithelium , the enclosed lipids diffuse across the cell membrane and enter the cytoplasm. The intestinal cells use the arriving lipids to manufacture new triglycerides that are then coated with proteins.

+PROTEIN DIGESTION :In the mouth, initial physical breakdown of protein begins. The stomach continues physical breakdown and begins chemical breakdown by secreting pepsinogenic which is converted into an enzyme called pepsin. Pepsin breaks down protein into amino acids. The food is then moved to the duodenum. It works with the pancreas to complete the physical and chemical breakdown of protein into single amino acid molecules with the help of trypsin. The small intestine absorbs the amino acid molecule allowing them to pass into the bloodstream.

+What tests are used to the completeness of carbohydrate digestion? Lipid digestion? Protein digestion? CARBOHYDRATE DIGESTION : Iodine test, Benedict’s test, Barfoed’s test, Seliwanoff’s test, Bials test LIPID DIGESTION : Sudan red test, Grease spot test PROTEIN DIGESTION : Biuret’s test

+What are the factors affecting carbohydrate digestion? Lipid digestion? Protein digestion? CARBOHYDRATE DIGESTION : Botanical source of carbo., main classes and subclasses of carbo., physical and chemical structure, calcium, cooking and addition to formulated foodLIPID DIGESTION : Insolubility in waterPROTEIN DIGESTION : Concentration of enzyme, amount of protein food needed, acidity of food, time, presence of any digestive inhibitors

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