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Chymosin is an enzyme that causes milk to curdle - Edexcel - GCSE Biology Combined Science - Question 5 - 2021 - Paper 1
Question 5
Chymosin is an enzyme that causes milk to curdle. When milk curdles the proteins in the milk clump together and become solid. (a) As part of an investigation, milk ... show full transcript
Worked Solution & Example Answer:Chymosin is an enzyme that causes milk to curdle - Edexcel - GCSE Biology Combined Science - Question 5 - 2021 - Paper 1
Step 1
Which variables need to be kept constant in this investigation?
Answer
In this investigation, it is essential to keep the temperature and the concentration of chymosin constant to ensure that any observed changes in curdling time are due to temperature variations alone. Therefore, the correct choice is D.
Step 2
Explain why the time taken for the milk to curdle decreases from 30 °C to 40 °C.
Answer
The decrease in the time taken for milk to curdle from 30 °C to 40 °C is due to the increasing activity of the chymosin enzyme as the temperature rises. Enzymes, including chymosin, typically have an optimal temperature range where their activity is maximized. As the temperature increases, the kinetic energy of the molecules also increases, leading to a higher frequency of effective collisions between the enzyme and the substrate (milk proteins), resulting in a faster reaction time.
Step 3
Explain what the expected result would be if two drops of chymosin were added to the milk at 70 °C in the test tube.
Answer
At 70 °C, it is expected that the chymosin enzyme would be denatured due to the high temperature. Denaturation alters the enzyme's active site shape, making it ineffective in catalyzing the curdling of milk. Therefore, the expected result would be that the milk does not curdle, or it takes significantly longer than at optimal temperatures.
Step 4
State why these test tubes containing only milk were used.
Answer
The test tubes containing only milk served as controls in the experiment. This allows for a comparison to determine the effect of adding chymosin, ensuring that any changes in curdling time can be attributed directly to the enzyme's activity rather than other variables.
Step 5
Describe two improvements that could be made to the method of this investigation so that the optimum temperature for chymosin can be found.
Answer
One improvement could be to use a broader range of temperature increments when heating the milk to identify where the optimum activity occurs with greater precision. A second improvement could be to replicate each temperature condition multiple times to ensure that the results are consistent and reliable, thereby reducing the impact of any anomalies in the data.
Step 6
Explain how to genetically modify a bacterial cell to produce chymosin.
Answer
To genetically modify a bacterial cell to produce chymosin, one would begin by isolating the gene responsible for chymosin production from a source organism. This gene can then be inserted into a plasmid vector, which is a small circular DNA molecule. The plasmid is introduced into the bacterial cells through a process known as transformation. Once inside the bacteria, the presence of the chymosin gene enables the bacterial machinery to transcribe and translate the gene into the chymosin enzyme. This modified bacterial strain can then be cultured to produce chymosin for use in various applications.