This document is designed to help students with enzymes topics as enzymes are a very ticky topic and there is mostly always a question in the exam paper of them so it is better to learn the key points. And it has exam-style questions too.
Proteins are made of long chains of amino acids. Each protein has its own
number and sequence and number of amino acids, which results in differently
shaped molecules, which have different functions.
The function of proteins includes:
- Structural – used to build cells and tissues (limited to collagen)
- Hormones – carry messages to control a reaction (limited to insulin)
- Carrier Molecules – self explanatory (limited to haemoglobin which
carries oxygen)
- Enzymes
Enzymes:
Describe enzymes as:
- Biological catalysts (speed up reactions in the body)
- Catalysing chemical reactions occurring in living cells: respiration,
photosynthesis, protein synthesis
- Having a high specificity for their substrate.
The substrate molecule fits into the active site like a key into a lock:
- This is why enzymes are described as working in a ‘lock and key
mechanism’
- It also explains why each enzyme can only work with a certain substrate.
This is called specificity and happens because the substrate must be the
right shape to fit into the active site
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, Proteins and Mutations – Revision Pack
Enzymes work best at a particular temperature and pH. This is called optimum
and any change away from either optimum will slow the reaction down.
When explaining how enzyme activity is affected by pH and temperature,
include:
- lower collision rates at low temperatures
- denaturing at extremes of pH and high temperatures
- denaturing as an irreversible change inhibiting enzyme function
- denaturing changing the shape of the active site
It’s possible to work out how temperature affects the rate of reaction by
calculating the temperature coefficient, called Q 10. This is done for a 10oC change
in temperature using:
Q10 = rate at higher temperature
Rate at lower temperature
Mutations:
Gene mutations may lead to the production of different proteins. Mutation may
occur spontaneously but can be made to occur more often by radiation or
chemicals. Mutations are often harmful but may be beneficial or have no effect.
Only some of the full set of genes is used in any one cell; some genes are
switched off. The genes switched on determine the functions of a cell.
Changes to genes alter, or prevent the production of the protein which is
normally made, this is because they change to base code of DNA, and so change
the order of amino acids in the protein.
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