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Proteins and Mutations – Revision Pack (B3)
Types of Proteins:
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:
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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 (B3)
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 Q10. 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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Proteins and Mutations – Revision Pack (B3)
PPQ(1):
OCR Gateway B1 B2 B3 January 2012
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Proteins and Mutations – Revision Pack (B3)
PPQ(2):
OCR Gateway B1 B2 B3 January 2013
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Proteins and Mutations – Revision Pack (B3)
PPQ(3):
OCR Gateway B1 B2 B3 June 2012
PPQ(4):
OCR Gateway B1 B2 B3 June 2013
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Proteins and Mutations – Revision Pack (B3)
PPQ(5):
OCR Gateway B3 C3 P3 January 2013
PPQ(6):
OCR Gateway B3 C3 P3 June 2013
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Proteins and Mutations – Revision Pack (B3)
PPQ(7):
OCR Gateway B3 C3 P3 June 2012
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Proteins and Mutations – Revision Pack (B3)
Mark Schemes:
PPQ(1):
PPQ(2):
PPQ(3):
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Proteins and Mutations – Revision Pack (B3)
PPQ(4):
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Proteins and Mutations – Revision Pack (B3)
PPQ(7):
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