In this A-Level Biology Lesson “A Summary of Basic Enzyme Properties" we'll build directly on what you already know from GCSE and re-cap the important features of Enzymes. You'll probably remember that Enzymes are Specific and that the Active Site of an Enzyme is its Catalytic Centre. You'll see diagrammatically how the The Enzyme-Substrate-Complex (ESC) forms. Here we can take the opportunity to re-enforce that enzymes are proteins and that the Primary sequence of amino acids determines the 3D conformational shape of the enzyme. This is very important to know (and apply). For example, factors affect enzyme structure and function - and you'll have to know this! You'll also be expected to apply your knowledge of basic enzyme properties by understanding that If the substrate and active site are not complementary NO Enzyme-Substrate-Complex can form. Finally we'll quickly summarise this lesson and once you're happy with all this you'll be ready to move on to the lock and Key V's Induced fit models of enzyme action.

When you've watched this lesson and you're confident with the topic covered you’ll be ready to download the knowledge check PDF and test your knowledge regarding the basic properties of enzymes. When you’ve answered all the questions, compare your answers to the ones I’ve written in the back of the work booklet - and of course here you can see exactly how to write answers in a way that gains maximum marks in the exams.

Enzymes are biological catalysts. There are approximately 40,000 different enzymes in human cells, each controlling a different chemical reaction. Enzymes increase the rate of reactions allowing the chemical reactions that make life possible to take place at optimal temperatures and pH levels. Enzymes were discovered in fermenting yeast in 1900 by Buchner, and the name enzyme actually means "in yeast". In addition to catalysing all the metabolic reactions of cells (such as respiration, photosynthesis and digestion), Enzymes also play roles as ‘motors’, ‘membrane pumps’ and ‘receptors’.

You already know by now that Enzymes are Proteins, and as proteins, their function is determined by their complex 3D structure.

Enzymes catalyse reactions which take place in a small part of the enzyme known as the active site.

The amino acids around the active site attach to the substrate molecule and hold it in position while the reaction takes place. This makes the enzyme specific for one reaction only, since other molecules are not complementary to its active site.

Many enzymes may also need cofactors (or coenzymes) to work properly. 

Coenzymes can be metal ions (such as Fe2+, Mg2+, Cu2+) or organic molecules (such as haem, FAD, NAD or coenzyme A). Many coenzyme are derived from dietary vitamins, which is why vitamins are such important in our diet! Also, just in case you come across this terminology:

A complete active enzyme with its cofactor is called a holoenzyme.

Whilst,  just the protein part of the enzyme without its cofactor is called the apoenzyme.

So, How do enzymes work?

There are 3 ways to think about enzyme as catalysis. They all describe the same process, but in different ways (you must know each of them).

Reaction (forming the Enzyme-Substrate-Complex).

Geometry (Lock and key / Induced Fit Models of Enzyme Action).

Energy Changes (Enzymes Lower Activation Energy (EA).