Structures and Functions in Living Organisms · 9 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 16% of your exam marks.
Enzymes in digestion and the role of digestive structures appear regularly across both papers.
Enzymes are also used in industry to speed up reactions outside the body. A common trick is to immobilise the enzyme so it can be reused.
The enzyme is trapped inside small beads (typically beads of alginate, a jelly-like substance). The beads are then packed into a column. A liquid containing the substrate is poured through the column. The substrate diffuses into the beads, meets the enzyme, gets converted into product, and the product flows out of the bottom of the column.
The enzyme stays inside the beads and can be used again and again, instead of being washed away with the product.
Many adults cannot digest lactose, the sugar in milk, because they no longer make the enzyme lactase. Without lactase, lactose sits undigested in the gut and causes bloating, cramps and diarrhoea (this is lactose intolerance).
Lactose-free milk is made by passing ordinary milk through a column packed with immobilised lactase. The lactase in the beads splits the lactose into glucose and galactose, both of which can be absorbed easily. The milk that comes out the bottom tastes slightly sweeter (because glucose is sweeter than lactose) and is safe for lactose-intolerant people to drink.
The same trick is used to make many other industrial products, including high-fructose corn syrup (using glucose isomerase) and some medicines.