Digestive Enzymes Flashcards
3 major areas of chemical digestion
mouth, stomach, sm. intestine
what is the pH of saliva?
6.0-7.0
What is the major digestive factor in the stomach
gastric acid
What are the functions of gastric acid?
aids in denaturing dietary proteins
stimulates the action of pepsin
kills m.o.
What happens to people who suffer from lack of gastric acid?
an increased rush of intestinal infections
total gastrectomy leads to
protein and fat digestion problems, increased risk of bacterial infection, need for vitamin B12 supplementation (loss of intrinsic factor)
Where are some digestive enzymes anchored to in the small intestine?
surface of microvilli
What is sucrose
Sucrose (table sugar) (alpha-D-glucopyranosyl-(1↔2)-Beta-D-fructofuranose)
What is Lactose?
Lactose (milk sugar) (B-D-galactopyranosyl-(1→4)-B-D-glucopyranose)
What is Maltose?
Maltose (grain sugar) (a-D-glucopyranosyl-(1→4)-a-D-glucopyranose)
Name 2 polysaccharides and their structure?
- Glycogen (animal storage form)
-Linear polymer of glucose linked by a(1→4) glycosidic bonds containing branches ~ every 8-12 residues that are joined to the main chain by a(1→6) glycosidic bonds - Starch (plant storage form)—most digestible carbohydrates are in this form
- Exists in two forms
o Amylose—linear polymer of glucose linked by a(1→4)
glycosidic bonds
o Amylopectin—linear polymer of glucose linked by
a(1→4) glycosidic bonds containing branches ~ every 24- 30 residues that are joined to the main chain by a(1→6) glycosidic bonds
What is the linkage for amylose?
linear polymer of glucose linked by a(1→4)
glycosidic bonds
What is the linkage for amylopectin?
linear polymer of glucose linked by
a(1→4) glycosidic bonds containing branches ~ every 24- 30 residues that are joined to the main chain by a(1→6) glycosidic bonds
Name two enzymes in the mouth that breakdown starch and glycogen
Salivary a-amylase
lysozyme
Where does salivary a- amylase cleave?
its an endoglycosidase (cleaves internal glycosidic bonds) at a(1-4)
What does Pepsin cleave?
Endopeptidase but also cleaves terminal peptide bonds
specifically cleaves amino side of hydrophobic amino acid
What kind of protease is pepsin?
aspartate protease
What does trypsin cleave?
endopeptidase
cleaves peptide bonds on the carboxyl side of lysine, arginine except when followed by proline
What kind of protease is trypsin?
Serine protease
What does chymotrypsin cleave?
endopeptidase
cleaves peptide bonds on the carboxyl side of hydrophobic amino acids
What kind of protease is chymotrypsin?
serine protease
What does Elastase cleave?
endopeptidase
cleaves peptide bonds on the carboxyl side of small aa
What kind of protease is elastase?
Serine protease
What does carboxypeptidases cleave
exopeptidase: cleaves one aa at a time from the c-terminus
Differentiate btwn carboxypeptidase A and carboxypeptidase B?
Carboxypeptidase A: cleaves off C-terminal hydrophobic aa
Carboxypeptidase B: cleaves off C-terminal basic aa
What kind of protease is Carboxypeptidase?
Zn2+ metalloprotease
What are the brush border enzymes used for protein?
Aminopeptidases
Dipeptidases
What does aminopeptidase cleave?
exopeptidase
cleave off one amino acid at a time from the N- Terminus
What does dipeptidase cleave?
exopeptidase
cleaves the peptide bond in dipeptides, liberating the two amino acids
Fat is prepared for chemical digestion in the ___ and ___?
mouth and stomach
Fat begins to be emulsified during______
mastication
What does emulsification do?
reduces the attraction between fat molecules so that can be more widely dispersed. Emulsification does not break covalent bonds
What does lingual lipase cleave?
a small percentage of dietary fat into mono, diglycerides and free FA
What does gastric Lipase cleave?
triglycerides into fatty acids, monoglycerides and diglycerides
Where does chemical digestion of lipids occur?
small intestine
What aids fat emulsification in the mouth and stomach?
dietary phospholipids and proteins
As the large fat emulsion globules enter the small intestine what are they coated with?
bile salts which leads to greater emulsification of the fat
The addition of bile salts to the large fat globules makes___.
mixed micelles
and increases the number of triglycerides exposed to the action of pancreatic lipase
Bile salts are also necessary for the absorption of ____
other dietary lipids, such as cholesterol and fat soluble vitamins
What is the function of pancreatic lipase?
In the sm. intestine lumen, it binds to the surface of fat emulsion droplets and cleaves triglycerides into 2 FA anions and one 2-monoacylglycerol molecules
Where is Colipase produced, secreted and activated by?
pancreas, pancreas, trypsin
What is the function of collapse?
a co-enzyme that functions to maintain the activity of pancreatic lipase in the presence of bile salts
Fat malabsorption can result from ____.
pancreatic failure, lack of bile salts (from biliary obstruction) or extensive intestinal diseases, steatorrhea (fatty stool)
Where does chemical distention of nucleic acids occur?
small intestine
What do pancreatic nucleases consist of?
DNases, RNases, exonucleases, endonucleases
What is the function of pancreatic nucleases?
Break down of nucleic acid into monomeric nucleotides
DNA–> deoxy-ATP, deoxy-GTP, TTP, deoxy-CTP
RNA–> ATP, UTP, CTP, GTP
Name two brush border enzymes used for nucleic acid digestion.
Phosphatases and nucleosidases
What is the function of phosphatase?
breaks down nucleic acids into nucleotides (phosphate group + nucleosides)
What is the function of nucleosidases?
breaks down nucleic acids into ribose/deoxyribose + nitrogenous bases
What is dietary fiber?
plant polymers that are resistant to human digestive enzymes
How is dietary fiber beneficial?
helps move food along the GI tract by providing bulk
Dietary fiber can be broken down by colonic bacteria to produce………..
a flammable gas and acids
Name two dietary fibers which are found in beans/peas that are broken down by colonic bacteria.
Raffinose and stachyose and are alpha 1-6 galactosides
which can cause flatulence from the produced gas, abdominal discomfort from the produced acids and diarrhea from their osmotic activity.
