ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: sam0001 on May 18, 2012, 09:46:14 pm

Title: A bit of help
Post by: sam0001 on May 18, 2012, 09:46:14 pm

Prolyl, leucyl, glycinamide. How many different tripeptides could be formed using the three amino acids?

Title: Re: A bit of help
Post by: Mao on May 18, 2012, 10:20:13 pm

6. PLG, PGL, LPG, LGP, GLP, GPL.

Title: Re: A bit of help
Post by: jadams on May 18, 2012, 10:45:16 pm

For finding the number of different combinations for a polypeptide chain, use factorials.
ie for finding the number of unique combinations for a chain of 5 amino acids:

the answer would be 5!
which is equal to 5x4x3x2x1   
= 120 unique chain combinations!

Title: Re: A bit of help
Post by: AllAboutTheLGs on May 18, 2012, 11:59:58 pm

Yeah factorials are a really good way to remember them. Just be careful if there are 2 of the same amino acid though

Title: Re: A bit of help
Post by: pi on May 19, 2012, 12:14:05 am

Just on the side for those who may become confused, this method will NOT work for finding the number of isomers of a particular molecular formula (especially in relation to alkanes).

A good tip (this is getting random lol) for alkanes (non-cyclic) is that if you half the number of Cs in the alkane and round up, that is the number of possible isomers :)

Title: Re: A bit of help
Post by: charmanderp on May 19, 2012, 01:45:02 pm

When given a molecular formula I always just try to draw as many different structural isomers as possible, and then name them all to make sure that I haven't doubled up.