CAS BI 315 Chapter Notes - Chapter 9: Cardiac Output, Pebble Bed Modular Reactor, Sodium Hydroxide

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Lab 9: Digestive Enzymes
I. Carbohydrates linked by dehydration reactions; broken down by hydrolysis reactions
A. Usually large polysaccharides called starches
B. Digestion begins in mouth but most of it happens in the SI
C. Salivary amylase hydrolyzes starches into maltose (disaccharide) → only for 3-
5% of starches though → works best at pH 6-7 (stops in stomach where pH
drops)
D. Resumes in SI via pancreatic amylase and rest of starch goes to maltose
E. Maltose, sucrose, lactose (all disaccharides) → monosaccharides via intestinal
brush border enzymes (maltase, sucrase, and lactase)
II. Fats → triglycerides = three FA and one glycerol → lipase hydrolyze using two water
molecules to give us three FA’s
A. Some digestion from lipases in the mouth and stomach, but mostly in the SI
(lipases secreted from pancreas into the SI)
B. Neutral fats are insoluble in water so must be broken down from large globules
→ emulsification (begins from physical effects of stomach and SI)
C. Emulsification is completed by bile (made by liver, stored and released from gall
bladder in response to CCK hormone secreted by SI during a meal)
D. Biles have bile salts → polar carboxyl end and nonpolar sterol end → sterol end
faces surface of fat globules and keep them coalescing again → water-soluble
lipases attack surface of fats hydrolyzing fats to FA and monoglycerides → either
absorbed into intestinal epithelium or made into triglycerides which are turned
chylomicrons and released into lacteals (lymphatic vessels that absorb fats) of
the villi
III. Proteins formed from AA bound by peptide linkages (dehydration reactions)
A. Happens in stomach and SI
B. Stomach → pepsin (optimal pH 2-3; inactive at pH > 5) → HCl secreted in
stomach to lower pH and activate pepsin → proteins go to smaller polypeptides
C. SI → digested to dipeptides and AA via pancreatic enzymes (see three below)
and brush border aminopeptidases (hydrolyze N-terminal end of proteins)
C.1. Trypsin → cleaves carboxyl of lysine and arginine (except if
followed by another arginine)
C.2. Chymotrypsin → cleave carboxylic side of phenylalanine,
tryptophan, and tyrosine
C.3. Carboxypeptidases → hydrolyzes C-terminal
IV. Benedict’s Test: Detection of Reducing Sugars
A. Positive = green, yellow, orange, red (with red being the most amount of
sugars/oligosaccharides present)
B. Negative = blue (no sugars are present)
V. Lugol’s Test: Effectiveness of Salivary Amylase on Starch Digestion
A. Positive = black (unhydrolyzed starch; intensity of black depends on starch
concentrations)
B. Negative = clear or amber (no starch is present)
VI. Biuret Test: presence of peptide linkages
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Document Summary

Carbohydrates linked by dehydration reactions; broken down by hydrolysis reactions: usually large polysaccharides called starches, digestion begins in mouth but most of it happens in the si, salivary amylase hydrolyzes starches into maltose (disaccharide) only for 3- Trypsin cleaves carboxyl of lysine and arginine (except if followed by another arginine) Chymotrypsin cleave carboxylic side of phenylalanine, tryptophan, and tyrosine. Benedict"s test: detection of reducing sugars: positive = green, yellow, orange, red (with red being the most amount of sugars/oligosaccharides present, negative = blue (no sugars are present) Lugol"s test: effectiveness of salivary amylase on starch digestion: positive = black (unhydrolyzed starch; intensity of black depends on starch concentrations, negative = clear or amber (no starch is present) Biuret test: presence of peptide linkages: positive = purple (lots of peptide linkages, middle = pink (some digestion has occurred, negative = blue (completely hydrolyzed; only single aa) Litmus test: presence of fatty acid products from fat digestion.

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