Prelim Biology: Enzymes: How to define them, and any biological concept in an exam.

8 Mins Read | Written by Simon Tang

Key Points Summary

  • When defining concepts, use this FALE-safe approach. What is its Function, Appearance, Limitations and Examples?
  • Enzymes are biological catalysts that speed up chemical reactions.
  • They are small proteins, made up of long chains of amino acids
  • They are temperature, pH and substrate specific.
  • Examples include lactase.



Picture this. After many late nights preparing for your upcoming biology exam, you sit in the exam hall, the paper sitting right in front of you. With the exam invigilator calling the start of the exam, you speed through the multiple choice, only to see this question at the very start of the short answer section:

What are enzymes??

This blog will go through everything you need to know about enzymes, and also some tips and tricks to answer ‘define’ questions to maximise your marks. Let’s go!

What is an enzyme?

When asked to define a concept or object, many students fall into the trap of simply giving an example instead of describing its qualities. See example below:

What is an adaptation? [4 Marks]

An adaptation is like a tiger’s sharp teeth, or a chameleon’s camouflaging skin. ✖

To help you best define enzymes (or any concept really), go with the tried and true FALE-safe approach. What is its Function, Appearance, Limitations and Examples?

  1. Function: What do enzymes do?

Enzymes speed up chemical reactions in the body (they are catalysts). They do this by bringing the substances that go into a chemical reaction (substrates) together and make it easier for them to react (lowering the activation energy of the reaction). They do not get used up during the reaction, and can speed up (catalyse) many reactions after doing one. 

  1. Appearance: What do enzymes look like?

Enzymes are microscopic proteins. They are made up of a long chain of amino acids, which fold together due to attractive forces between the acids (kind of like magnets!). 

  1. Limitations: What are the limitations of enzymes?

As mentioned before, enzymes are made up of proteins, which are then made up of a carefully folded chain of amino acids. Because of these delicate structures, enzymes only work in very specific environments. If they are put into environments other than their optimal environments, these three-dimensional structures can break down. We call this denaturation. 

They are temperature, pH and substrate specific. This is explained more in the example below.

  1. Examples: What types of enzymes are there? What is an example of an enzyme?

There are two main types: catabolic and anabolic enzymes. Catabolic enzymes break down a substrate, while anabolic enzymes build substrates. 

Anabolic Enzyme Function:

Catabolic Enzyme Function:

One way of remembering which one is which is that some bodybuilders take anabolic steroids to build muscle (don’t do this though!).

A specific example of an enzyme is lactase. Lactase is a catabolic enzyme found in the small intestine of the body, breaking down lactose into simple sugars. Let’s have a look at its specificity.

  • Since the internal human body temperature is 37C, they work best in temperatures ranging between 35 and 40C. 
  • Because the small intestine ranges between a pH of 6 to 7.4, studies have shown that lactase works best in a pH environment of 6. 
  • Finally, the lactase enzyme is substrate specific because it will not break down anything other than lactase – it just won’t fit in the enzyme!


With all that information, here is something that you might write in response to the question in the introduction.

  1. Define enzymes. [4 Marks]

Enzymes are small proteins that act as biological catalysts. They speed up chemical reactions in the body by lowering their activation energy, and are not expended in the reaction itself. Due to the denaturation of proteins, enzymes are temperature, pH and substrate specific, meaning that they work optimally at a set temperature, pH and substrate concentration. An example of an enzyme is lactase, a catabolic enzyme that speeds up lactase breaking down into simple sugars. 

So there you have it! Enzymes defined using the FALE-safe approach. If you liked this blog and want to know more about how we teach biology at Dymocks Tutoring, give us a ring at (02) 8774 2610 or book a free trial with us!

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