HL Chemistry D.4: pH Regulation of the stomach

Stomach Acid

• pH: 1-2

• HCl produced by gastric glands

What protects stomach cells from acid?

• Mucus

What does stomach acid do?

• Chemical digestion

• Kills pathogens

• good pH for catalytic activity (e.g. pepsin)

Major cause of stomach lining irritation

• Excess acid via: too much alcohol, large/fatty meals, smoking, stress

• Reduction of mucus: aspirin reduces amount of mucus produced

Results of acid attacking stomach lining

• Indigestion

• Heartburn/acid reflux

• Peptic Ulcers

Can be resolved with antacids

Indigestion

• Irritation of stomach lining leading to pain/discomfort in abdomen

• Causes nausea

Heartburn/Acid Reflux

• Stomach acid starts going up into esophagus

Peptic Ulcer

• Erosion of mucosal layer causing internal bleeding

Antacids

• Weakly basic compounds

  • Neutralize stomach acid

  • relieve pain

  • allow stomach lining to repair

• Metal hydroxides: Mg(OH)2, Al(OH)3

• Metal carbonates: CaCO3, NaHCO3

• Non-specific

• anti-foaming agents added to reduce flatuence b/c of CO2 production

Why are Mg(OH)2 and Al(OH)3 mixed?

• Mg(OH)2 works quickly

• Al(OH)3 long-lasting: reduces number of doses

• Mg(OH)2 laxative effect offset by Al(OH)3

Peptic Ulcer treatments

• Parietial cells produce stomach acid

• Treatment regulates lvls of stomach acid

  • Stopping acid production

  • Preventing acid release

Drugs used to treat peptic ulcers

• Ranitidine/Zantac

• Omeprazole and esomeprazole

Omeprazole and esomeprazole

• Proton-pump inhibitors

• Weak bases

• Prevent release of acid

• Antagonist

• Active metabolites

• Irreversible for long time (until cell makes more proton pumps)

• Non-polar —> lipid-soluble

  • Can pass through phospholipid bilayer of cells

• Active when in cell cytoplasm

• Inactive at blood pH (7.35-7.45)

Ranitidine/Zantac

• Prevent acid production

• Antagonist

• Binds to H2 receptors (preventing release of histamine)

• Histamine acts as messenger to produce acid