Enzymes

Enzyme Digestion


An enzyme is a biological catalyst. It increases the rate of a biochemical reaction and remains unchanged. Enzymes affect the rate of digestive breakdown. Most enzymes are proteins. This assignment will explore enzyme digestion in each area of the digestive system.
There is only one enzyme in the mouth, produced by saliva, which is amylase. The amylase begins the breakdown of starch into maltose and lactose, which are disachharide (double) sugars. The teeth physically breakdown food, which mixes with saliva to ease swallowing.
Gastric juice is secreted by gastric pits in the stomach lining when the food enters. The gastric juice contains hydrochloric acid which gives the stomach its pH of 2.0, the optimum pH for proteases. The hydrochloric acid kills any bacteria which the food may contain, it also activates the enzyme pepsinogen. Once activated the pepsinogen forms pepsin. If it were to be activated when released then the pepsin would digest the stomach wall as the stomach is protein. Pepsin hydrolyses, breaks down, protein into smaller polypeptides. The part-digested contents from the stomach is known as chime.
The small intestine consists of two main parts, the duodenum and the ileum. Although the ileum is mainly concerned with absorption. There are 3 juices which operate in the small intestine these are bile, pancreatic juice and intestinal juice. Bile is made in the liver and stored in the gall bladder before being released into the duodenum. Bile doesn’t contain any enzymes but is very important in digestion. It contains salts which emulsify lipids. This means breaking them down into smaller droplets, this is a physical change rather than chemical. Emulsifying the lipids gives them a larger surface area for the enzymes to work on.
Pancreatic juice contains many enzymes as well as alkalis to neutralise the stomach acid. Trypsinogen is found in the juices. This becomes activated by enterokinase, a non-digestive enzyme produced by... [continues]

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