Transcript Chemical digestion

Eat anything good lately?
Do you know what happens to all that yummy
food after it's swallowed?
Organ
Enzymes Present
mouth
amylase (in saliva)
esophagus
none
stomach
pepsin
gastric juice
hydrochloric acid (HCl )*
small intestine
pancreatic juice
intestinal juice
bile*
large intestine
none
rectum
anus
none
none
What Happens Here
mechanical digestion of all food (teeth
chewing & grinding)
chemical digestion of carbohydrates begins
food passes from mouth through the
esophagus to the stomach
mechanical digestion of food (churning of
stomach walls)
chemical digestion of proteins begins
chemical digestion of carbohydrates, proteins,
& lipids continues & is completed
the small, soluble nutrients (sugars, amino
acids, fatty acids) are absorbed
water is absorbed from unusable, indigestible
wastes (feces)
feces are temporarily stored
feces are eliminated (egested) from
Accessory Organ What it does
tongue
helps mix food with saliva, assists in swallowing
produces saliva (which contain the enzymes amylase)
salivary glands
amylase chemically digests carbohydrates
produces bile
liver
bile EMULSIFIES fats (lipids)
gall bladder
stores bile, then releases into small intestine
produces pancreatic juice, which is a mixture of digestive
enzymes
pancreas
pancreatic juice ends up in the small intestine where it assists in
completing the digestion of proteins, lipids, & carbohydrates
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
Carbohydrate hydrolysis tests
• Iodine test for starch breakdown
• Add Lugol’s iodine (IKI)
• If starch present – purple color
• If starch absent – no reaction
• Benedict’s test for the presence of reducing sugars
(glucose, maltose and fructose)
• Reduced sugars presence results in red precipitate
• Small amounts – result in green color
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
Protein hydrolysis tests
• Biuret’s 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
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
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
Experiments - carbohydrates
p. 613 B. Iodine test for starch breakdown:
What is the purpose of this test?
p. 614 C. Benedict’s test
What is the purpose of this test?
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?
Experiments - proteins
P 615 B. Biuret’s 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?
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?
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