Globular and Fibrous proteins

[akira88]

In my Heinemann textbook, I don't believe that they go in depth about globular and fibrous proteins! I only realised I didn't know the actual properties of each properly until I came across a question in Checkpoints: "Describe a distinctive property of a fibrous protein and explain how this property is due to the arrangement of its polypeptides."

Any help?

[stonecold]

damn, i don't know the answer either

i do know though that globular proteins are water soluble and are involved in chemical reactions (enzymes, hormones etc.), whereas fibrous proteins are insoluble in water and serve structural purposes, such as keratin in hair and nails, or collagen in skin.

[akira88]

Yeah! I stated that fibrous proteins are insoluble but I don't know how the arrangement makes it like that! Hmmm..

[stonecold]

what is the answer?  maybe all the hydrogen bonds come together and face inwards or something, so the hydrophobic regions are facing outwards, making them insoluble...

[TrueLight]

wiki is your friend
They form long protein filaments, rod- or wire-like shapes. They are usually inert structural or storage proteins. They are generally water-insoluble and are found as an aggregate due to hydrophobic R groups that stick out of the molecule. The amino acid sequences they are made from often have limited residues with repeats. These can form unusual secondary structures, e.g. collagen triple helix. The structures often contain 'cross-links' between chains, for example cys-cys disulfide bonds between keratin chains.

Globular proteins tend to denature more easily than fibrous proteins.


google is your friend more copy and paste lol...


Fibrous proteins also gain strength due to interactions between the side chains of the residues. The alpha-keratin polypeptides , for example, have a large number of cystine residues, which can form disulfide bonds .


Coils such as those found in alpha-keratin are not the only structural motifs present in fibrous proteins. Silk, for example, is largely composed of fibrous proteins whose structures resemble interleaved sheets.



Coils such as those found in alpha-keratin are not the only structural motifs present in fibrous proteins. Silk, for example, is largely composed of fibrous proteins whose structures resemble interleaved sheets.

http://www.answers.com/topic/fibrous-protein

google!

[akira88]

Hmm @ TrueLight, I'm not sure if they want the answer to be that in depth, unless you've done biology and know that that depth is required? The information is kind of confusing!
@stonecold, I don't have the answers as it is a photocopied version of Checkpoints and it's not from the 2009 one (which I have). How frustating!

[TrueLight]

http://74.125.153.132/search?q=cache:n1KXoztGT_8J:www.kscience.co.uk/resources/ks5/as/biomolecules/proteins/globular_and_fibrous_proteins.doc+fibrous+vs+globular+proteins&cd=5&hl=en&ct=clnk&gl=au

i dunno i guess that says it pretty simple
although im not sure if this type of question is asked on ur bio exam, it seems like an in depth question and to explain the specific folds and stuff .. i dunno i would just skip it! is this stuff in ur study check list thing...

[stonecold]

@ akira...not 100% sure on this, but when i did checkpoints last year, they would always put the year of the question in the corner next to it?  maybe we can check the examiners report then?

and yeah, i don't think they want a really complicated answer, hopefully for our sake something nice and simple

[akira88]

That's a great idea! Didn't think of that... oh but wait.....
the question number is cut off so I don't know what question number it is NOR what year it's from. Shattered And it's the only question where it's question number is cut off.

Let me say, incredibly frustrating.

EDIT: I said "question number" quite a lot there ^

[akira88]

I went through all the Biology Exam 1 from '06-'08 and did a search of the word "fibrous" and came up with "No matches found". I guess it was a question not from the exam

[stonecold]

rofl i am exactly the same.  i post something, and then read it back to myself and it'll be like, man that sounds really bad, no wonder i stink at english lol.

but i will ask my teacher about this one.  she will be bound to know it

[akira88]

OH what is this. I search "globular" and it comes up, and right under it there is the word fibrous. Why didn't the search pick it up... :|
But yes I will ask my teacher as well
I stink at English even more

[stonecold]

Answer, direct from vcaa's big ugly mouth:

Property
•strength
•flexibility

Explanation
•due to the arrangement of the polypeptides which enabled them to be stretched and return to the original shape
•parallel arrangement of protein fibres for support

[akira88]

Thanks for that, I read it on the assessment report as well
Surely being insoluble is also a distinctive property? Hmm lol "vcaa's big ugly mouth"