Option D.2 – Antacids
D.2.1 – State and explain how excess acidity in the stomach can be reduced by the use of different bases
The human stomach has a pH of approximately 1.5 to allow for the effective functioning of the enzyme pepsin. The gastric juices secreted by the gastric glands in the stomach contain hydrochloric acid to maintain this acidic environment. To protect the cells that line the wall of the stomach from these conditions, they also secrete protective mucous. However, if too much acid is produced, this could damage the lining of the stomach.
Sometimes, there may be excess acid in the stomach, which can be caused by a number of factors including smoking, overeating, alcohol, anxiety, certain foods and anti-inflammatory drugs. Indigestion is when there is excess acid, creating discomfort for the person. If the lining of the stomach is damaged, there may be tissue loss and inflammation, called an ulcer.
Indigestion can be overcome by taking antacids to reduce the amount of acid. These antacids are typically weak bases, like hydroxides, carbonates, metal oxides or hydrogencarbonates. They undergo an acid-base reaction to neutralise some of the acid in the stomach and relieve the symptoms.
Sodium hydrocarbonate:
Calcium carbonate
Magnesium oxide (Magnesium hydroxide is also used)
Aluminium hydroxide:
Some antacids are made up of combinations of these compounds to be more effective.
These reactions happen as the antacids enter the stomach, mixed with alginates that float near the top of the stomach, and produce a neutralised layer preventing acid in the stomach from rising into the oesophagus. If this acid enters the oesophagus, it is called heartburn. Along with alginates, many antacids will also come with anti-foaming agents such as dimethicone, preventing flatulence.
Side Effects
Antacids made of magnesium compounds are known to cause diarrhoea when consumed in larger quantities. Aluminium compounds can cause constipation, and interfere with the absorption of phosphate. This can lead to bone problems if taken frequently taken in high doses. Sodium hydrogen carbonate reacts in the body to form CO2 gas, leading to bloating and belching, so antifoaming agents will often be added to prevent this.