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SingaporeBiology

Biological Molecules and Enzymes

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What are the main food molecules made of, and what are they used for?

Describe the elements, building blocks and roles of carbohydrates, fats and proteins
A focused answer to the O-Level Biology outcome on biological molecules. The elements and building blocks of carbohydrates, fats and proteins, and the role each plays in the body.
8 min answer →

What are enzymes, and how do they speed up reactions in living things?

Explain that enzymes are biological catalysts and describe their action using the lock and key model
A focused answer to the O-Level Biology outcome on enzymes. What a biological catalyst is, the lock and key model, the meaning of substrate, active site and specificity, and why enzymes matter in the body.
8 min answer →

How do temperature and pH change how fast an enzyme works?

Describe and explain the effects of temperature and pH on the rate of enzyme-controlled reactions
A focused answer to the O-Level Biology outcome on enzyme activity. The effect of temperature and pH on the rate of reaction, the meaning of the optimum, and what denaturing does to an enzyme's active site.
8 min answer →

How can we test a food sample to find out what nutrients it contains?

Carry out and interpret the standard food tests for starch, reducing sugar, protein and fat
A focused answer to the O-Level Biology practical outcome on food tests. The reagent, method and colour change for starch, reducing sugar, protein and fat, and how to write up a result for full marks.
8 min answer →