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Two enzymes, P and Q, are proteins with quaternary structure which catalyse the same reaction, but they have different amino acid sequences - AQA - A-Level Biology - Question 5 - 2022 - Paper 1
Question 5
Two enzymes, P and Q, are proteins with quaternary structure which catalyse the same reaction, but they have different amino acid sequences. 1. Define the quaternar... show full transcript
Worked Solution & Example Answer:Two enzymes, P and Q, are proteins with quaternary structure which catalyse the same reaction, but they have different amino acid sequences - AQA - A-Level Biology - Question 5 - 2022 - Paper 1
Step 1
Define the quaternary structure of a protein.
Answer
The quaternary structure of a protein refers to the arrangement and interaction of multiple polypeptide chains, or subunits, in a protein complex. These subunits come together through various interactions including hydrogen bonds, ionic bonds, and hydrophobic interactions.
Step 2
Explain how two enzymes with different amino acid sequences can catalyse the same reaction.
Answer
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Both enzymes (P and Q) have active sites that are structurally similar or identical, enabling them to bind the same substrate effectively.
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Despite differences in their amino acid sequences, the enzymes can form enzyme-substrate complexes with the same substrate due to their functional similarities.
Step 3
Describe what the scientists should place in the control tubes in this investigation.
Answer
- Same volume of buffer solution at both pH 8.4 and pH 7.5.
- Same concentration/mass of substrate at the start.
- Same concentration/mass of denatured enzyme, or buffer with substrate but with no enzyme.
Step 4
Give three conclusions you can make from Figure 8.
Answer
- Both enzymes P and Q are active at pH 8.4, but enzyme Q shows reduced activity at pH 7.5.
- The reaction rate drops for enzyme P at lower pH compared to pH 8.4 but not as significantly as enzyme Q.
- The substrate concentration is not fully utilized in reactions at pH 7.5 for enzyme Q, indicating suboptimal conditions.