Chemical digestion

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Chemical digestion
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• Eat anything good lately?
• Do you know what happens to all that yummy food
  after it's swallowed?

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Carbohydrate hydrolysis

• Basic storage molecule of carbohydrate is starch
  amylase and amylopectin.
• Both can be hydrolyzed by the same enzyme
  amylase
• In salivary gland salivary amylase
• In small intestine pancreatic amylase

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Carbohydrate hydrolysis tests

• Iodine test for starch breakdown
• Add Lugols iodine (IKI)
• If starch present purple color
• If starch absent no reaction
• Benedicts test for the presence of reducing
  sugars (glucose, maltose and fructose)
• Reduced sugars presence results in red
  precipitate
• Small amounts result in green color

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Protein hydrolysis

• Proteins long chains of amino acids
• The enzyme pepsin secreted by the chief cells in
  the stomach, begins the process of protein
  digestion by breaking the proteins to shorter
  chains
• Most protein digestion occur in the small
  intestine with the help of pancreatic enzymes

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Protein hydrolysis tests

• Biurets solution contains NaOH and copper
  sulfate.
• In the presence of proteins the copper sulfate
  reacts with the peptide bonds and the mixture
  turn to deep violet color
• No proteins no color

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Lipids hydrolysis

• Primary lipids in the diet are triglycerides.
• Very small and insignificant amount of lipids are
  digested in the mouth my lingual lipase and in
  the stomach by gastric lipase
• Fat digestion occur in the small intestine by
  water soluble enzymes.
• Bile from the liver serve as emulsifier by
  physically separation of lipids to small pieces.
  By that, it increases the surface area of the
  lipids and allow lipase to work
• Bile salts form aggregations of 20-40 molecules
  micelles in which the hydrophobic units turn
  inside and hydrophilic to the outside
• The products of lipid hydrolysis are being
  dissolved into the micelles and being carried to
  the brush border of the small intestine

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Lipids hydrolysis tests

• Some of the products of lipids hydrolysis are
  organic acids (fatty acids)
• These products decrease pH
• That provide a way to identify lipid digestion

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Experiments - carbohydrates

• p. 613 B. Iodine test for starch breakdown
• What is the purpose of this test?
• p. 614 C. Benedicts test
• What is the purpose of this test?

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Experiments - carbohydrates

• P 614 D. Experiment
• Tube 1 10 drops of starch 10 drops of water
• Tube 2 10 drops of starch 10 drops of saliva
• Place tubes in 370C for 30 min (why?)
• Take drop from each tube and add iodine.
• What do you expect will happen?

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Experiments - proteins

• P 615 B. Biurets test
• What is the purpose of this test?
• C. Experiment
• Tube 1 10 drops of protein 10 drops of water
  pH 8 (why?)
• Tube 2 - 10 drops of protein 10 drops of
  pancreatin
• Place tubes in 370C for 30 min
• What do you expect will happen?

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Experiments - lipids

• p. 615 B. experiment
• Tube 1 2 ml cream, 2 ml water (pH 8), bile
  salts, 15 drops of litmus solution (or use litmus
  paper)
• Tube 2 - 2 ml cream, 2 ml pancreatin (pH 8), bile
  salts, 15 drops of litmus solution (or use litmus
  paper)
• Tube 3 - 2 ml cream, 2 pancreatin, 15 drops of
  litmus solution (or use litmus paper)
• Place tubes in 370C for 30 min
• What do you expect will happen?

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Lab report

• Introduction explain shortly the chemical
  digestive processes and where do they occur.
  State the objectives of the experiments
• Materials and methods describe exactly how did
  you performed the experiments include list of
  solutions and equipment and than describe the
  procedure
• Results give detailed results for each
  experiment (use tables to show results)
• Discussion explain your results and explain how
  does these experiment demonstrate the chemical
  digestion processes