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structural differences between fibrous and globular proteins.

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Introduction

Question: Explain with examples, the structural differences between fibrous and globular proteins. A globular protein has a fixed specific sequence of amino acids that are non-repetitive while a fibrous protein has a repetitive regular sequence of amino acid. For example, haemoglobin, a globular protein is made up of 4 polypeptide chains to form a tetramer (?2?2), composed of two identical alpha-beta (??) dimers. Collagen, a fibrous protein, has a primary structure characterized by a repeating tripeptide sequence of Glycine - X - Y. ...read more.

Middle

chains and 2? chains. These four subunits are packed to form an overall spherically shaped molecule. However, collagen, a fibrous protein, is formed with three polypeptide chains lie parallel and wind round one another, forming a tropocollagen. The tropocollagen molecules lie side by side and are linked to each other giving a collagen fibril. A globular protein has its length of polypeptide always identical in two examples of the same globular protein where else a fibrous protein has its length of polypeptide chain varying in two examples of the same fibrous protein. ...read more.

Conclusion

Y rotates around hydroxyproline and hydroxylysine so the length of polypeptide chains differ. A globular protein is held primarily by numerous intra- and inter-molecular non-convalent bonds, such as hydrogen, ionic bonds while a fibrous proteins are held due to numerous intra- and inter- molecular hydrogen and disulphide bonds. For example, haemoglobin, a globular protein, is basically held together by interchain hydrophobic interatctions, with hydrogen and ionic bonds occurring. On the other hand, collagen, a fibrous protein, has its triple helix held together by extensive network of hydrogen bonds. Tropocollagen of collagen is also held by covalent cross-links to give the collagen fibre strength and rigidity. ?? ?? ?? ?? ...read more.

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Here's what a star student thought of this essay

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Response to the question

Good overall response to the question. The answer is rather short but provides a perfect example of what an A level candidate should be aiming for in terms of length and segregation of the different parts, going for comparison rather ...

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Response to the question

Good overall response to the question. The answer is rather short but provides a perfect example of what an A level candidate should be aiming for in terms of length and segregation of the different parts, going for comparison rather than describing each protein separately which is good in this instance. The response to the question is clear and concise.

Level of analysis

The analysis of the proteins is quite deep, but to improve their grade the candidate could have presented the information in a tabular format which would have made the information easier to read and mark. The candidate could have used more example to explain the differences between the two different proteins, for example going beyond the question and relating the structural differences to how the protein actually functions. Scientific terms used show a high level of understanding.

Quality of writing

Grammar, spelling and punctuation are all correct.


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Reviewed by skatealexia 12/04/2012

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