Proteins and mutations

Question 1

What are all proteins made out of?

Answer 1

Long chains of amino acids joined together.

Question 2

What are the functions of different proteins?

Answer 2

• Structural proteins used to build cells and tissues, e.g. collagen.
• Hormones, which carry messages to control a reaction, e.g. insulin controls blood sugar levels.
• Carrier proteins, e.g. haemoglobin which carries oxygen.
• Enzymes.

Each protein has its own number and order of amino acids. This makes each type of protein molecule a different shape and give it a different function.

Question 3

What do enzymes do?

Answer 3

• Enzymes speed up reactions in the body and so are called biological catalysts.
• They catalyse chemical reactions occuring in respiration, photosynthesis and protein synthesis of living cells.

Question 4

What do enzymes do to substrate molecules?

Answer 4

• The substrate molecule fits into the active site of the enzyme like a key fitting into a lock.
• This is why enzymes are described as working according to the ‘lock and key mechanism’.
• It also explains why each enzyme can only work was on particular substrates. This is called specificity and it happens because the substrate has to be the right shape.

Question 6

What is the optimum?

Answer 6

Enzymes all work best at a particular temperature and pH. This is called the optimum. Any change away from the optimum will slow down the reaction.

Question 7

How is enzyme activity affected by pH and temperature?

Answer 7

• At low temperatures molecules are moving more slowly and so the enzyme and substrate are less likely to collide
• At very high or low pH values and at a high temperature the enzyme’s active site changes shape. This is called denaturing. The substrate cannot fit, so cannot react so quickly.

Question 8

How can you work out how temperature alters the rate the reaction?

Answer 8

By calculating the temperature coefficient, called Q_10. This is done for a 10 °C temperature change, using: Q₁₀ = rate at higher temperature/rate at lower temperature.

Question 9

When do mutations occur?

Answer 9

Mutations may occut spontaneously but can be made to occur more often by radiation or chemicals.

Question 10

When they occur, mutations:

Answer 10

• May lead to the production of different proteins.
• Are often harmful but may have no effect.
• Occasionally they might give the individual an advantage.

Question 11

Why are some proteins not made in cells?

Answer 11

• Although every cell in the body has the same genes it does not mean that the all the same proteins are made. This is because different genes are switched off in different cells. This allows different cells to perform different functions.

Question 12

What do gene mutations do to protein manufacturing?

Answer 12

Gene mutations alter or prevent the production of the protein that is normally made, because they change the base code of DNA, and so change the order of amino acids in the protein.