2021TrialShort answer

Q29

3 marks

Question

The coiled-coil was one of the earliest tertiary protein structures described and first discovered in the two-stranded coiled-coil protein (CC) alpha-keratin. Coiled-coils consist of two or more alpha-helices winding around each other.
Figure 1: Coiled-coil
Such proteins are involved in a wide variety of structural and mechanical processes in cells. Long-CC (LCC) includes long coiled-coils with a minimum stretch of 70 amino acids in one coiled coil and a minimum stretch of 50 amino acids in the other.
A study was carried out to compare the presence of CC and LCC proteins in species from different kingdoms. The graph below represents the estimated percentages of CC proteins, LCC proteins and superlong CC per genome for 22 different species.
Figure 2: % coiled-coil proteins per genome for 22 species. A: Archaea; B: Gram positive bacteria; C: Gram negative bacteria; D: Fungi; E: Animals; F: Plants

“Animals are more closely related to plants than other kingdoms”. Analyse the data provided and assess whether this statement is supported.

Uncropped source page 24 for question 29; requires human review and cropping — Reviewed visual · source page 24

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Solution

Criteria	Marks
• Assesses the data and states agreement or disagreement.<br>• Supports or disproves the assessment with relevant numerical data from the graph.<br>• Identifies limitations.	3
• Any TWO of the above.	2
• Any ONE of the above.	1

Sample answer:

The percentage of CC total per genome lies between the rage of 1-7.5 for animals whereas Archaea is from 1-2.5, Gram negative bacteria is from 1-4 whereas plants have a closer relation of cc total with a range of 1-6. Similarly, Long CC also show a close relation between animals and plants with a range of 1.4-1.8 and plants with a range from 1.3-3. But the data is limited as only 2 species of plants and 4 species of animals were used to compare CC and Long CC where as 4 species of animals , 7 of Gram negative and 3 of gram negative species were used for comparison.

Supplied marking guidance · human reviewed

Compare this with your working, not only your final sentence.

Syllabus alignment

Module 5 · Heredity

DNA and Polypeptide SynthesisInvestigate protein structure and function in living things.

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