代做BIOSCI 203 Laboratory 1 hand in sheet代写Java编程

日期：2024-07-30 04:47

BIOSCI 203

Laboratory 1 hand in sheet

Part 1:

1. What shape is the curve in the first graph?

[1 mark]

2. Why is it sensible to blank the spectrophotometer using tube #11 instead of tube #1?

[2 marks]

3. Insert the graphs you have drawn into your report, with appropriate brief figure legends. 

[6 marks]

4. Use your graphs to determine the pKa of the ionization of the tyrosine sidechain. Show your workings.

[2 marks]

5. Using the Henderson-Hasselbalch equation, calculate the % ionization of a tyrosine side-chain in the cell. Use the value you determined in Question 4, and assume that the cytosol is buffered at pH 7.35. Show your working.

[2 marks]

6. What consequence does this ionisation state have for the role of tyrosine residues in proteins?

[2 marks]

Part 2:

7. How many α-helices are there in the protein?

[1 mark]

8. How many β-strands make up the β-sheet?

[1 mark]

9. Is the topology of the β-sheet parallel, anti-parallel or mixed?

[1 mark]

Use the Henderson-Hasselbalch equation to answer Questions 10 and 11. Show your workings for both questions.

10. The pK_a of the –SH group of free cysteine is 8.35. The cytosol of human cells is normally pH 7.35 What would be the % ionization of the –SH group of free cysteine in the cytosol?

[2 marks]

11. The pK_a of the active site cysteine in a 1-Cys Prx enzyme has been measured at 6.2. What would be the % ionization of the –SH group of the Prx active site cysteine in the cytosol?

[2 marks]

12.  Give the name and residue number for each of the amino acid residues that have side chains within 4Å of the sulfur atom in Cys47.

[1 mark]

13. What feature of the local environment around Cys47 might stabilize the existence of a thiolate ion?

[2 marks]