Digestive Enzymes

Question 1

3 major areas of chemical digestion

Answer 1

mouth, stomach, sm. intestine

Question 2

what is the pH of saliva?

Answer 2

6.0-7.0

Question 3

What is the major digestive factor in the stomach

Answer 3

gastric acid

Question 4

What are the functions of gastric acid?

Answer 4

aids in denaturing dietary proteins
stimulates the action of pepsin
kills m.o.

Question 5

What happens to people who suffer from lack of gastric acid?

Answer 5

an increased rush of intestinal infections

Question 6

total gastrectomy leads to

Answer 6

protein and fat digestion problems, increased risk of bacterial infection, need for vitamin B12 supplementation (loss of intrinsic factor)

Question 7

Where are some digestive enzymes anchored to in the small intestine?

Answer 7

surface of microvilli

Question 8

What is sucrose

Answer 8

Sucrose (table sugar) (alpha-D-glucopyranosyl-(1↔2)-Beta-D-fructofuranose)

Question 9

What is Lactose?

Answer 9

Lactose (milk sugar) (B-D-galactopyranosyl-(1→4)-B-D-glucopyranose)

Question 10

What is Maltose?

Answer 10

Maltose (grain sugar) (a-D-glucopyranosyl-(1→4)-a-D-glucopyranose)

Question 11

Name 2 polysaccharides and their structure?

Answer 11

1. 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
2. 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

Question 12

What is the linkage for amylose?

Answer 12

linear polymer of glucose linked by a(1→4)

glycosidic bonds

Question 13

What is the linkage for amylopectin?

Answer 13

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

Question 14

Name two enzymes in the mouth that breakdown starch and glycogen

Answer 14

Salivary a-amylase

lysozyme

Question 15

Where does salivary a- amylase cleave?

Answer 15

its an endoglycosidase (cleaves internal glycosidic bonds) at a(1-4)

Question 16

What does Pepsin cleave?

Answer 16

Endopeptidase but also cleaves terminal peptide bonds

specifically cleaves amino side of hydrophobic amino acid

Question 17

What kind of protease is pepsin?

Answer 17

aspartate protease

Question 18

What does trypsin cleave?

Answer 18

endopeptidase

cleaves peptide bonds on the carboxyl side of lysine, arginine except when followed by proline

Question 19

What kind of protease is trypsin?

Answer 19

Serine protease

Question 20

What does chymotrypsin cleave?

Answer 20

endopeptidase

cleaves peptide bonds on the carboxyl side of hydrophobic amino acids

Question 21

What kind of protease is chymotrypsin?

Answer 21

serine protease

Question 22

What does Elastase cleave?

Answer 22

endopeptidase

cleaves peptide bonds on the carboxyl side of small aa

Question 23

What kind of protease is elastase?

Answer 23

Serine protease

Question 24

What does carboxypeptidases cleave

Answer 24

exopeptidase: cleaves one aa at a time from the c-terminus

Question 25

Differentiate btwn carboxypeptidase A and carboxypeptidase B?

Answer 25

Carboxypeptidase A: cleaves off C-terminal hydrophobic aa | Carboxypeptidase B: cleaves off C-terminal basic aa

Question 26

What kind of protease is Carboxypeptidase?

Answer 26

Zn2+ metalloprotease

Question 27

What are the brush border enzymes used for protein?

Answer 27

Aminopeptidases | Dipeptidases

Question 28

What does aminopeptidase cleave?

Answer 28

exopeptidase | cleave off one amino acid at a time from the N- Terminus

Question 29

What does dipeptidase cleave?

Answer 29

exopeptidase | cleaves the peptide bond in dipeptides, liberating the two amino acids

Question 30

Fat is prepared for chemical digestion in the ___ and ___?

Answer 30

mouth and stomach

Question 31

Fat begins to be emulsified during______

Answer 31

mastication

Question 32

What does emulsification do?

Answer 32

reduces the attraction between fat molecules so that can be more widely dispersed. Emulsification does not break covalent bonds

Question 33

What does lingual lipase cleave?

Answer 33

a small percentage of dietary fat into mono, diglycerides and free FA

Question 34

What does gastric Lipase cleave?

Answer 34

triglycerides into fatty acids, monoglycerides and diglycerides

Question 35

Where does chemical digestion of lipids occur?

Answer 35

small intestine

Question 36

What aids fat emulsification in the mouth and stomach?

Answer 36

dietary phospholipids and proteins

Question 37

As the large fat emulsion globules enter the small intestine what are they coated with?

Answer 37

bile salts which leads to greater emulsification of the fat

Question 38

The addition of bile salts to the large fat globules makes___.

Answer 38

mixed micelles | and increases the number of triglycerides exposed to the action of pancreatic lipase

Question 39

Bile salts are also necessary for the absorption of ____

Answer 39

other dietary lipids, such as cholesterol and fat soluble vitamins

Question 40

What is the function of pancreatic lipase?

Answer 40

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

Question 41

Where is Colipase produced, secreted and activated by?

Answer 41

pancreas, pancreas, trypsin

Question 42

What is the function of collapse?

Answer 42

a co-enzyme that functions to maintain the activity of pancreatic lipase in the presence of bile salts

Question 43

Fat malabsorption can result from ____.

Answer 43

pancreatic failure, lack of bile salts (from biliary obstruction) or extensive intestinal diseases, steatorrhea (fatty stool)

Question 44

Where does chemical distention of nucleic acids occur?

Answer 44

small intestine

Question 45

What do pancreatic nucleases consist of?

Answer 45

DNases, RNases, exonucleases, endonucleases

Question 46

What is the function of pancreatic nucleases?

Answer 46

Break down of nucleic acid into monomeric nucleotides DNA--> deoxy-ATP, deoxy-GTP, TTP, deoxy-CTP RNA--> ATP, UTP, CTP, GTP

Question 47

Name two brush border enzymes used for nucleic acid digestion.

Answer 47

Phosphatases and nucleosidases

Question 48

What is the function of phosphatase?

Answer 48

breaks down nucleic acids into nucleotides (phosphate group + nucleosides)

Question 49

What is the function of nucleosidases?

Answer 49

breaks down nucleic acids into ribose/deoxyribose + nitrogenous bases

Question 50

What is dietary fiber?

Answer 50

plant polymers that are resistant to human digestive enzymes

Question 51

How is dietary fiber beneficial?

Answer 51

helps move food along the GI tract by providing bulk

Question 52

Dietary fiber can be broken down by colonic bacteria to produce………..

Answer 52

a flammable gas and acids

Question 53

Name two dietary fibers which are found in beans/peas that are broken down by colonic bacteria.

Answer 53

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.