GI Secretion and Digestion

Question 1

The _____________ uses more energy than any other process in the body.

Answer 1

secretion of acid

Question 2

What are the functions of stomach acid?

Answer 2

• Denatures protein, which prepares them for digestion

- Kills bacteria

Question 3

How does the stomach protect itself from acid?

Answer 3

Mucus layer
Tight junctions between epithelial cells
High turnover of epithelial cells

Question 4

____________ increase mucus production.

Answer 4

Prostaglandins

Question 5

The ______________ have branches.

Answer 5

gastric pits

Question 6

Prior to binding intrinsic factor, cobalamin binds to _____________.

Answer 6

salivary R protein, which then gets cleaved by gastric proteases

Question 7

Intrinsic factor, coupled to cobalamin, gets taken up by _________________.

Answer 7

receptors in the terminal ileum

Question 8

What three molecules stimulate gastric secretion?

Answer 8

Histamine
Gastrin
Acetylcholine

Question 9

What is the alkaline tide?

Answer 9

When you eat a big meal, the gastric parietal cells secrete more protons, which pumps more bicarb into the blood.

Question 10

True or false: sodium passes through a pore in the intestines.

Answer 10

False. Chloride passes through CFTR, but sodium passes between cells.

Question 11

The surface area of the villi is _______ that of the crypts.

Answer 11

greater

Question 12

The main difference between carbohydrate digestion and protein digestion is that ______________.

Answer 12

carbohydrates have to be broken down to monomeric subunits, while proteins do not

Question 13

Sodium binding to the SGLT1 receptor induces ____________.

Answer 13

absorption into the cell

Question 14

Explain how the apical H+/K+-ATPase drives the secretion of Cl- and H2O into the stomach.

Answer 14

The creation of protons inside the cell also creates bicarb, because the reaction is catalyzed by carbonic anhydrase. The excess intracellular bicarb exits the cell via the basolateral Cl-/HCO3- exchanger. Chloride then builds up inside the cell and is transported out of the apical membrane down its concentration gradient. Water follows this chloride.

Question 15

Gastrin and acetylcholine work by _______________, while histamine works by ______________.

Answer 15

raising intracellular calcium; raising cAMP, which starts a cascade that ultimately phosphorylates the H+/K+-ATPase

Question 16

What are ECL cells?

Answer 16

Enterochromaffin-like, they secrete histamine and gastrin in response to PNS stimulation (via Ach) or local gastrin

Question 17

True or false: the stomach is always secreting acid.

Answer 17

False. Between meals the pH of the stomach can be as high as 7.

Question 18

The gastric phase and intestinal phase are mediated by ____________ effects.

Answer 18

local (distension and partially digested proteins in the stomach and partially digested amino acids in the small intestine)

Question 19

Oxyntic cells are _____________.

Answer 19

parietal cells

Question 20

Basal acid secretion is highest in the _____________.

Answer 20

evening

Question 21

What are canaliculi?

Answer 21

Little pillars of tissue that give parietal cells more surface area to secrete acid through

Question 22

Which sugar does not need sodium as a co-transporter to be absorbed by the small intestine?

Answer 22

Fructose (absorbed by the GLUT 5 receptor)

Question 23

The sugar-absorbing receptors of the small intestine are inducible. What does this mean?

Answer 23

It means that the more sugar you eat, the more your body will express sugar-absorbing receptors in the small intestine.