- large biological molecules which catalyse chemical reactions in living organisms
- responsible for the metabolic processes which sustain life
- enzymes can be proteins or ribonucleic acid (RNA)
Properties of enzymes:
- lower the minimum amount of energy needed to start a reaction (activation energy)
- has active site of specific shape, which is complementary to its substrate
- does not alter properties of end products of reaction
- highly efficient in small amounts
- denatured easily due to high heat
How do enzymes work?
- After an effective collision between a substrate and an enzyme (where the substrate binds to the active site of the enzyme), an enzyme-substrate complex is formed.
- The substrate molecule is held in the active site by interactions such as hydrogen and ionic bonds between the R groups of the amino acids and the substrate molecule.
- Enzyme catalyses conversion of substrate to the end product.
- The alteration of chemical conformation results in the product being released from the active site since it is no longer complementary to the structure of the active site.
- The active site is then available for other substrates to bind to it.
"Lock and Key" Hypothesis
- there is an exact fit between the substrate and the active site of the enzyme
- the enzyme (lock) has a unique shape complementary to the substrate (key)
- enzymes are very specific; only substrates that are exactly complementary to its active site are able to bind with it
image taken from: http://katysstudynotes.files.wordpress.com/2010/11/enzymes.png
Induced Fit model
- active site of enzyme is flexible
- active site is able to mould itself around the substrate to make the fit better
- active site returns to original shape after the products are released
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| Illustration of the induced fit model |
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