GI Digestion and Absorption

Question 1

About ______ percent of proteins are digested by gastric pepsin.

Answer 1

15

Question 2

Luminal peptidases and brush-border enzymes break down _______________.

Answer 2

proteins into dipeptides, tripeptides, and amino acids

Question 3

Intracellular peptidases within enterocytes break down ____________. This prevents the need for basolateral polypeptide transporters.

Answer 3

dipeptides and tripeptides to amino acids

Question 4

The major uptake route for amino acids is ______________.

Answer 4

sodium cotransport (from the Na/K ATP pump gradient)

Question 5

Infants utilize ____________ to absorb proteins.

Answer 5

pinocytosis

Question 6

Protons help ____________ get absorbed via cotransport.

Answer 6

dipeptides and tripeptides

Question 7

The body can make all necessary lipids except _____________.

Answer 7

linoleic acid (omega-6 fatty acid) –which gets converted to arachidonic acid –and alpha-linoleic acid (omega-3 fatty acid)

Question 8

What is steatorrhea?

Answer 8

Excessively greasy stool

Question 9

The substance in lacteals is called ______________.

Answer 9

chyle

Question 10

Most GI secretion occurs in the ___________, while most absorption occurs in the ____________.

Answer 10

stomach; jejunum

Question 11

Potassium is absorbed ____________ in the jejunum and ______________ in the colon.

Answer 11

paracellularly; transcellularly

Question 12

Vitamin D is first hydroxylated in the __________ and then again in the ______________.

Answer 12

liver; kidney

Question 13

Iron can be absorbed as ___________.

Answer 13

Fe2+ or heme

Question 14

Water absorption ___________ as you proceed from the small intestine to the large intestine.

Answer 14

decreases (because paracellular permeability decreases in the colon); in the distal colon, water absorption must be coupled to ion movement

Question 15

Chloride channels are dependent on _____________.

Answer 15

cAMP

Question 16

True or false: loperamide can treat cholera diarrhea.

Answer 16

False. Loperamide does not affect the diarrheal mechanism of cholera.

Question 17

Maltose is __________.

Answer 17

a disaccharide of glucose

Question 18

Elastase breaks down ______________.

Answer 18

neutral, aliphatic amino acids

Question 19

True or false: fatty acids require co-transport to be absorbed.

Answer 19

False. They pass through the membrane.

Question 20

What activates pepsinogen?

Answer 20

Low pH (1-3)

Question 21

How are the pancreatic proteases terminated?

Answer 21

They digest themselves.

Question 22

Cysteinuria is usually accompanied by __________.

Answer 22

loss of lysine, arginine, and ornithine (COAL); this results from loss of the Na-amino acid transporter, resulting in inability to absorb or excrete these molecules

Question 23

Chylomicrons contain what three things?

Answer 23

Triglycerides, cholesterol, and phospholipids

Question 24

Lipase and colipase form what?

Answer 24

Micelles that are passively absorbed

Question 25

Water rapidly crosses the intestinal epithelium, so chyme ____________.

Answer 25

quickly becomes isotonic with the blood

Question 26

By what receptors are proteins absorbed?

Answer 26

• Sodium cotransport
• Proton cotransport for di- and tripeptides
• Pinocytosis of peptides (only in infants)
• Sodium independent transport

Question 27

What does lipase do?

Answer 27

It hydrolyzes triglycerides to free fatty acids.

Question 28

Chylomicrons are synthesized in _________________.

Answer 28

intestinal epithelium

Question 29

About _______ liters of fluid are secreted into the gut each day. All but about 100-200 mLs is reabsorbed.

Answer 29

9

Question 30

In which part of the GI tract does sodium enter via ENaC?

Answer 30

The colon