TEST 4

What percentage of HCl is produced in the cephalic phase

40%.

What triggers the cephalic phase of HCl secretion

Sight, smell, taste, or thought of food activating vagus nerve.

What percentage of HCl is produced in the gastric phase

50%.

What triggers the gastric phase of HCl secretion

Stomach stretch and peptides.

What percentage of HCl is produced in the intestinal phase

10%.

What triggers the intestinal phase of HCl secretion

Food entering the duodenum.

What hormone from D cells inhibits HCl secretion

Somatostatin.

What triggers somatostatin release

Stomach pH < 3.

What is the effect of somatostatin on parietal cells

Inhibits HCl secretion.

What secretes prostaglandin E2

Surface epithelial cells.

What is the effect of PGE2 on parietal cells

Inhibits HCl via EP3 receptor.

How does H. pylori affect D cells

Inhibits somatostatin → increases HCl.

What do surface epithelial cells produce

Mucus and HCO3−.

What receptors stimulate mucus production

EP3 and mAChR.

What receptors stimulate HCO3− production

EP3 and mAChR.

What is the function of trefoil factor

Cytoprotection after mucosal injury.

What do mucus neck cells do

Produce mucus and act as stem cells.

What is the turnover time of mucus neck cells

1–3 days.

What do mucus neck cells differentiate into

All gastric cell types.

What do parietal cells secrete

HCl and intrinsic factor.

What is the function of intrinsic factor

Protects B12 and allows ileal absorption.

Where is vitamin B12 absorbed

Ileum.

What do chief cells secrete

Pepsinogen.

What activates pepsinogen

HCl.

What does pepsin do

Breaks proteins into peptides.

What enzyme digests casein in infants

Rennin.

What do ECL cells secrete

Histamine and serotonin.

What receptor does serotonin bind in gut

5‑HT3 receptor.

What is serotonin’s effect on motility

Increases motility.

What organism produces serotonin‑like toxin

Enterotoxigenic E.coli (ETEC).

What is the effect of ETEC toxin

Activates 5‑HT3 → diarrhea.

What hormone do I cells release

CCK.

What stimulates CCK release

Fat and protein in duodenum.

What receptor does CCK bind

CCK‑1 receptor.

Where is CCK‑1 receptor for enzyme secretion

Pancreatic acinar cells.

What is CCK’s effect on acinar cells

Releases digestive enzymes.

What effect does CCK have on gallbladder

Contracts it.

What effect does CCK have on sphincter of Oddi

Relaxes it.

What hormone do S cells release

Secretin.

What stimulates secretin release

Acidic chyme in duodenum.

What receptor does secretin bind

Secretin receptor.

Where is secretin receptor located

Pancreatic ductal cells.

What is secretin’s effect on ductal cells

Increases HCO3− secretion.

What is the purpose of pancreatic bicarbonate

Neutralize gastric acid.

What stimulates pancreatic secretion via vagus nerve

Acetylcholine.

What receptor does ACh act on in pancreas

mAChR.

What are zymogens

Inactive enzyme precursors.

How are zymogens identified

“Pro‑” or “‑gen.”

What activates trypsinogen

Enteropeptidase.

What does trypsinogen become

Trypsin.

What enzymes does trypsin activate

Chymotrypsinogen, pro‑elastase, pro‑carboxypeptidase, pro‑aminopeptidase.

What do active proteases produce

Amino acids.

Where is enteropeptidase located

Brush border of duodenum.

What is the function of HCO3− in pancreatic juice

Neutralizes acid.

What are the main components of dietary fat

Triglycerides, cholesterol, phospholipids, fat‑soluble vitamins.

What converts pro‑colipase to co‑lipase

Trypsin.

What is the function of co‑lipase

Helps lipase bind fat droplets.

Why is co‑lipase needed

Bile salts inhibit lipase.

What does pancreatic lipase do

Breaks triglycerides into monoglycerides + FFAs.

What begins cholesterol synthesis

Acetyl‑CoA + aceto‑acetyl‑CoA.

What enzyme forms HMG‑CoA

HMG synthase.

What enzyme converts HMG‑CoA to mevalonate

HMG‑CoA reductase.

What cofactor does HMG‑CoA reductase require

NADPH.

What is the rate‑limiting step of cholesterol synthesis

HMG‑CoA → mevalonate.

What drug class inhibits HMG‑CoA reductase

Statins.

How do statins work

Competitive inhibition.

What molecule forms after mevalonate

Squalene.

What forms after squalene

Lanosterol.

What forms after lanosterol

Cholesterol.

What activates SREBP2

Low intracellular cholesterol.

Where does active SREBP2 go

Nucleus.

What does SREBP2 bind

SRE on LDL receptor gene.

What is the effect of SREBP2 activation

Increases LDL receptors.

What is the effect of increased LDL receptors

More LDL uptake → lower blood cholesterol.

What is one structural function of cholesterol

Maintains membrane fluidity.

What hormones are made from cholesterol

Cortisol, aldosterone, testosterone, estrogen, progesterone.

What organ synthesizes bile salts

Liver.

What enzyme converts cholesterol to 7‑α‑hydroxycholesterol

7‑α‑hydroxylase.

What are primary bile acids

Cholic acid, chenodeoxycholic acid.

What amino acids conjugate bile acids

Glycine, taurine.

What are conjugated bile salts examples

Glycocholic, taurocholic, glycochenodeoxycholic, taurochenodeoxycholic.

Why are conjugated bile salts hydrophilic

Water‑soluble.

Why are unconjugated bile salts hydrophobic

Fat‑soluble.

What is the bile micelle ratio

10 bile salts : 3 phosphatidylcholine : 1 cholesterol.

What creates micelle hydrophobic surface

Bile salts.

What creates micelle hydrophilic core

Phosphatidylcholine.

What causes cholesterol gallstones

Excess cholesterol.

What causes pigment stones

Calcium + bilirubin.

What is the consequence of blocked bile flow

Pale stool, fat malabsorption.

What fills micelle core in duodenum

Monoglycerides, FFAs, cholesterol, vitamins A/D/E/K.

What transporter absorbs free cholesterol

NPC1L1.

What drug inhibits NPC1L1

Ezetimibe.

What does ACAT do

Converts cholesterol → cholesterol ester.

What does DGAT do

Converts monoglycerides + FFAs → triglycerides.

What protein forms chylomicrons

ApoB48.

What protein loads lipids onto ApoB48

MTP.

Where are chylomicrons formed

Enterocytes.

How do chylomicrons exit enterocytes

Exocytosis.

Where do chylomicrons go first

Lacteals.

Why do chylomicrons enter lacteals

Too large for blood capillaries.