1. Gastric Juice Part1 What is gastric juice? Part2 How does stomach acid form? Part3 What happens when the concentration of HCl acid is excessively high in the stomach? Part4 How can we solve the problem that the concentration of HCl acid is excessively high in the stomach? (stomach juice)

2. Part1 Gastric juice Gastric juice is a thin,acidic digestive 助消化的 fluid secreted 分秘 by glands 腺 in the mucous 黏液的 membrane 隔膜 that is the inner wall of stomach. Hydrochloric acid = 0.03M pH = 1.5

3. What ’ s the use of gastric juice in the stomach? digest 消化 food activate 刺激 digestive enzymes 酶

4. Part2 How is stomach acid formed in the stomach? Two reactions taking place in the blood moving in mucosa 黏膜 : CO 2(g) + H 2 O (l) ⇔ H 2 CO 3(aq) H 2 CO 3(aq) ⇔ H + (aq) + HCO 3 - (aq) Mucosa 黏膜 Membrane 隔膜 Stomach inside Simplified diagram of stomach : H+ @H+ @ Cl - @ @

5. Most of ions are prevented from going back into the blood by membranes. If hydrogen ions go back to the blood, it will cause hemorrhages 出血.

6. Part3 what happens when the concentration of HCl acid is excessive high in the stomach? When the concentration of HCl acid is excessively high, hydrogen ions will go back to the blood. hemorrhage pain, inflammation 炎症 and bleeding 出血 in the stomach.

7. Part4 How can we solve the problem the concentration of HCl acid is excessively high in the stomach? One way is to reduce the concentration of hydrogen ions in the stomach. How can the hydrogen ion concentration is reduced in the stomach? The way is to take the antacid 抗酸剂.

8. What is the antacid ? The antacid is a kind of base that can neutralize stomach acid.

9. Some Common Commercial Antacids Commercial Name Active Ingredients Alka-2 Calcium carbonate Alka-Seltzer Aspirin, Sodium bicarbonate, citric acid Bufferin Aspirin, Magnesium carbonate, aluminum glycinate 氨基乙酸盐 Milk of magnesia Magnesium hydroxide Rolaids Dihydroxy 二羟基 aluminum sodium carbonate

10. The major function of antacids: neutralize excessive hydrochloric acid in gastric juice.

11. Reactions between stomach acid and some common antacids : NaHCO 3 (aq) + HCl (aq) → NaCl (aq) + H 2 O (l) + CO 2(g) CaCO 3(s) +2HCl (aq) → CaCl 2(aq) +H 2 O (l) +CO 2(g) MgCO 3(s) +2HCl (aq) → MgCl 2(aq) +H 2 O (l) +CO 2(g) Mg(OH) 2(s) +2HCl (aq) → MgCl 2(aq) +2H 2 O (l) Al(OH) 2 NaCO 3(s) +4HCl (aq) → AlCl 3(aq) +NaCl (aq) +3H 2 O (l) + CO 2(g) @ @

12. Aspirin Acetylsalicylic acid 乙酰水杨酸 It can ionize into hydrogen ion and acetylsalicylate ion. A characteristic of the membrane : The membrane allows neutral molecules to pass in and out of the stomach. Aspirin has the ability to penetrate membrane.

13. Water pocket ( a trap ) in the membrane The large amount of ions in water pocket weakens the structure of the membrane and causes bleeding. In general, about 2 ml of blood are lost for every aspirin tablet 药片 taken. The action of aspirin can result in serious bleeding in some individuals.

14. Alcohol Alcohol can make aspirin more soluble in the membrane. It promotes the bleeding. Therefore, we can ’ t drink wines when taking aspirin. back to topic back to topic

15. When a person takes some antacids, it ’ s possible to cause the person to belch 打嗝. End End

16. Active transport Eating stimulates hydrogen ion secretion. Maintain electrical balance