GI - Pt 4 Digestion

Question 1

T/F

Gastrin is a great digestive enzyme

Answer 1

False

Gastrin does not digest anything. It is an endocrine hormone.

Question 2

Histological Enterocyte function

• Contains Folds of []
• [] - which are longest in the dueodenum and shortest in the ileum
• Structure
  
  • [] Cells
  • [] cells produce mucus
  • Apical surface contains [] brush b order

Answer 2

• Contains Folds of Kerkring
• Villi - which are longest in the dueodenum and shortest in the ileum
• Structure
  
  • Columnar Cells
  • Goblet cells produce mucus
  • Apical surface contains microvilli brush border

Question 3

The tips of enterocytes are borderline [] and are easily [] off.

Answer 3

The tips of enterocytes are borderline ischemic and are easily abraided off.

Question 4

T/F

Gastrectomy has a greater effect on gastric stomach digestion than on intestinal digestion/absorption

Answer 4

False

gastrectomy often has a greater indirect effect by causing defective intestinal digestion and absorption.

Question 5

The most absorption occurs in the [] []

Answer 5

small intestine

Question 6

Usually the principle source of calories in the diet = []

Answer 6

carbohydrates

Question 7

[] and [] are indigestible due to [] glycosidic linkages

Answer 7

Fiber and Cellulose are indigestible due to B-1,4 glycosidic linkages

Question 8

The greatest amount of carbohydrate ingested is in the form of [].

Answer 8

starch

Question 9

• [] are long, unbranched chains of glucose with à-1,4 linkages
• [] have multiple à-1,4 linkages with branches at []

Answer 9

• Amylose are long, unbranched chains of glucose with à-1,4 linkages
• Amylopectin have multiple à-1,4 linkages with branches at à-1,6

Question 10

T/F

We need à-amylase for digestion?

Answer 10

False

It is not essential, for digestion.

Question 11

Salivary à-amylase

• Secreted by the [] gland
• converts starch to [] and []
• not required, but ends up being [] of carbohydrate digestion
• Continues to work in somach fundus until []

Answer 11

• Secreted by the parotid gland
• converts starch to maltose and oligosaccharides
• not required, but ends up being 50% of carbohydrate digestion
• Continues to work in stomach fundus until acidified

Question 12

Pancreatic à-amylase

• Identical to [] amylase
• Completes activity within 10 minuyutes after chyme enters the []

Intestinal amylase - identical to [] amylase

Answer 12

• Identical to salivary amylase
• Completes activity within 10 minutes after chyme enters the duodenum

Intestinal amylase - identical to salivary amylase

Question 13

à-Amylase

• hydrolyzes [] linkages
• Spares [] linkages and terminal [] linkages

Answer 13

• hydrolyzes à 1-4 linkages
• Spares à 1-6 linkages and terminal à 1-4 linkages

Question 14

• Digestion by à-Amylase results in [], [] and []-[]

Answer 14

Digestion by à-Amylase results in maltose, maltotriose and à-limit-dextrans

Question 15

Many brush border enzymes have []-[] [] - indicating that they may hve more than one giestive activity.

Answer 15

Cross Over Activity

Question 16

[] (or []) on the brush border only goes after à 1-6 linkages

Answer 16

Isomaltase (or à-dextrinase) on the brush border only goes after à 1-6 linkages

Question 17

Sucrase converts Sucrose into [] and []

Answer 17

Sucrase converts Sucrose into glucose and Fructose

Question 18

Isomaltase (à-Dextrinase) - converts [] and other branch point residues to Glucose by acting on [] glycosidic linkages…highest activity is in the [] and []

Answer 18

Isomaltase (à-Dextrinase) - converts Isomaltose and other branch point residues to Glucose by acting on à-1,6 glycosidic linkages…..highest activity is in the jejunum and ileum

Question 19

Any enzyme that produce free glucose is considered to have [] activity

Answer 19

Maltase

Question 20

• Maltase converts [] or [] to glucose by actin on [] glycosidic linkages
• Maltotriase converts [] to glucose by acting on (terminal) [] glycosidic linkages

Answer 20

• Maltase converts maltose or maltotriose to glucose by actin on à-1,4 glycosidic linkages
• Maltotriase converts maltotriose to glucose by acting on (terminal) à-1,4 glycosidic linkages

Question 21

Maltase-Glucoamylase Complex

• Primarily an [] enzyme
• 2 different enzymes
  
  • Digest either [] or [] linkages
• Exhibits [] activity
• Highest activity in the []
• Considered to be an [] (acts on terminal 1-4 linkages)

Answer 21

• Primarily an à-Glucosidase enzyme
• 2 different enzymes
  
  • Digest either à 1-4 or à 1-6 linkages
• Exhibits Maltase activity
• Highest activity in the ileum
• Considered to be an exoglucosidase (acts on terminal 1-4 linkages)

Question 22

B-Galactosidase (or []) acts on [] linkages, converting [] to [] and []

Answer 22

B-Galactosidase (or lactase) acts on B-1-4 linkages, converting lactose to glucose and galactose

Question 23

1. Only monosaccharides may be absorbed [] (minor component)
2. Most monosaccharide absorption occurs via [] [] Trnasport mechanisms coupled thorugh the movements of []

Answer 23

1. Only monosaccharides may be absorbed passively (minor component)
2. Most monosaccharide absorption occurs via Secondary Active Trnasport mechanisms coupled through the movements of Na⁺

Question 24

Monosaccharide Absorption

• [] and [] compete for the same active uptake system
• []/[] carriers bring in Na+ and Glucose from the lumen into the enterocyte.
  
  • 2 Na⁺/[] cross the apical membrane
• [] transporter moves glucose across the basolateral membrane

Answer 24

• Glucose and galactose compete for the same active uptake system
• SGLT-1/2 carriers bring in Na+ and Glucose from the lumen into the enterocyte.
  
  • 2 Na⁺/glucose cross the apical membrane
• Glut-2 transporter moves glucose across the basolateral membrane

Question 25

Fructose uses the [] carrier protein to cross the apical membrane of an enterocyte

Answer 25

GLUT-5

Question 26

Exopeptidases remove one [] [] at a time from the C-terminal end

Answer 26

amino acid

Question 27

* Pepsin is an [] * hydrolyzes [] peptide bonds

Answer 27

* Pepsin is an **endopeptidase** * hydrolyzes **interior** peptide bonds

Question 28

Pancreatic Proteases * released from pancrease as inactive [] precursor * Trypsinogen is converted to [] by [] in the brush border * Trypsin then converts the following * Chymotrypsinogen --\> [] * Proelastase --\> [] * Procarboxypeptidase --\> [] * proteases [] each other as their route of inactivation

Answer 28

* released from pancrease as inactive **zymogen** precursor * Trypsinogen is converted to **trypsin** by **enteropeptidase** in the brush border * Trypsin then converts the following * Chymotrypsinogen --\> **chymotrypsin** * Proelastase --\> **Elastase** * Procarboxypeptidase --\> **Carboxypeptidase** * proteases **digest** each other as their route of inactivation

Question 29

Trypsin, Chymotrypsin, and Elastase are all []

Answer 29

endopeptidases

Question 30

What are the 3 exopeptidase pancreatic enzymes?

Answer 30

Aminopeptidase Carboxypeptidase A Carboxypeptidase B

Question 31

How are all amino acids absorbed through the basolateral membrane of an enterocyte?

Answer 31

Through some unknown carrier protein

Question 32

What structure/mechanism breaks down amino acids even further once they cross the apical membrane into the enterocyte?

Answer 32

Lysozymes as Cytoplasmic Peptidases

Question 33

1. How many amino acid transporters do we find on the apical membrane of enterocytes, that need require specific "types" of amino acids? 1. What molecule is coupled with amino acids for transport? 2. What are the different "types" of transporters?

Answer 33

1. 4 1. Na⁺ 2. Basic Amino Acids, Neutral Amino acids, acidic amino acids, Imino Acids

Question 34

* Non specific amino acids transport, located on the apical membrane of enterocytes, are coupled with [] for transport

Answer 34

Na⁺ ​

Question 35

Di and Tri peptides croos the enterocyte apical membrane through the [] transporter

Answer 35

Pep T1

Question 36

[] is a proton and amino acid transporter located on the [] membrane of eneterocytes

Answer 36

**hPAT-1** is a proton and amino acid transporter located on the **apical** membrane of eneterocytes

Question 37

Duodenal receptors respond to _fat_ by activating release of[] and neural reflex slows [] []

Answer 37

Duodenal receptors respond to fat by activating release of **CCK** and a neural reflex that slows **gastric emptying**

Question 38

* 10% of fats within the stomach are hydrolyzed by [] [] * Its optimum pH is around [] +/- 1

Answer 38

* 10% of fats within the stomach are hydrolyzed by **Lingual lipase** * Its optimum pH is around **5** +/- 1

Question 39

Bile [] fats and lipid within the intestine

Answer 39

emulsifies

Question 40

* Pancreatic Secretions act as detergents and enzymes in fat digestion * [] - acts in intestine and cells * [] & [] [] - water soluble * Pancreatic Co-Lipase - has []activity with Pancreatic Lipase

Answer 40

* Pancreatic Secretions act as **detergents** and **enzymes** in fat digestion * **Phospholipase A₂** - acts in intestine and cells * **Pancreatic & Intestinal Lipase** - water soluble * Pancreatic Co-Lipase - has **potentiation** activity with Pancreatic Lipase

Question 41

Micelles * surface covered with [] [] * Fuse with lipid bilayer of enterocyte and [] their contents into cell cytoplasma

Answer 41

* surface covered with **bile salt** * Fuse with lipid bilayer of enterocyte and **release** their contents into cell cytoplasma

Question 42

* Bile Salts are [] reabsorbed in the Proximal intestine * Bile Salts are [] reabsorbed in the distal intestine

Answer 42

* Bile Salts are **passively** reabsorbed in the Proximal intestine * Bile Salts are **actively** reabsorbed in the distal intestine

Question 43

Steatorrhea * Causes: * [] deficiency - leading to a failure to emulsify fats * Absence of pancreatic secretions like [] * [] disease

Answer 43

Steatorrhea * Causes: * **Bile** deficiency - leading to a failure to emulsify fats * Absence of pancreatic secretions like **lipase** * **Whipples** disease