Science Double-Award 2012 questions

[aalmuhannadi]

Hi,

So first of all, can someone please explain to me the difference between different variant papers (e.g. 31/32/33) and their significance? Do you get an advantage if you do one over the other? Do you get to choose? Are they of the different difficulty levels, or do they just contain different material of the same difficulty?

Alright, and second of all. This question is related to the Double-Award Science 2012 syllabus, on the final page of the chemistry section, "Organic Chemistry":
The final bullet point in the extended section: State that proteins can be hydrolised to amino acids under acidic or alkaline conditions...
I've 3 chemistry books, and none of them talk about hydrolising proteins using alkalis, they all mention the use of warming proteins with hydrochloric acid in order to return the water molecules at each amide link, to revert the proteins into amino acids. But can someone provide any advice on where I can find info on hydrolising proteins under "alkiline conditions"?

Oh and one last thing, what is the difference between an alkaline and an alkali? Some examples would be appreciated.

Thank you,

 

[princesszahra]

Hi,

So first of all, can someone please explain to me the difference between different variant papers (e.g. 31/32/33) and their significance? Do you get an advantage if you do one over the other? Do you get to choose? Are they of the different difficulty levels, or do they just contain different material of the same difficulty?

Alright, and second of all. This question is related to the Double-Award Science 2012 syllabus, on the final page of the chemistry section, "Organic Chemistry":
The final bullet point in the extended section: State that proteins can be hydrolised to amino acids under acidic or alkaline conditions...
I've 3 chemistry books, and none of them talk about hydrolising proteins using alkalis, they all mention the use of warming proteins with hydrochloric acid in order to return the water molecules at each amide link, to revert the proteins into amino acids. But can someone provide any advice on where I can find info on hydrolising proteins under "alkiline conditions"?

Oh and one last thing, what is the difference between an alkaline and an alkali? Some examples would be appreciated.

Thank you,

Different varients will have different questions but with the same level of difficulty!its significane is to avoid paper leaking due to time difference!

abt the oraganic chem ques--- its true that u can use alkaline conditions as well
u can use LiAl3H4 or NaOH!

Acid Hydrolysis of Protein:
1 mL of 3M p-toluenesulphonic acid, containing 0.2% tryptamine (0.2% 3-[2-aminoethyl] indole) is added to the protein dried in a Pyrex glass tube (1.2 x 6 cm or similar, in which a constriction has been made by heating in an oxygen/gas flame).
The solution is sealed under vacuum and heated in an oven for 24 to 72 hours at 110 Celcius degree.
Altematively, you can use 3M mercaptoethanesulfonic acid as p-toluenesulphonic acid replacing, The sample is hydrolyzed for a similar time and temperature.
The tube is allowed to cool and cracked open with a heated glass rod held against a horizontal scratch made in the side of the tube.
The acid is taken to near neutrality by carefully adding 2 mililiters of 1M sodium hydroxide.
After this hydrolysis you can continue carrying out to quantitatively analyze certain amino acids, such as tryptophan.

Alkaline Hydrolysis Protein:
0.5 mL of 3M sodium hydroxide is added to the protein dried in a Pyrex glass tube.
The solution is sealed under vacuum and heated in an oven for 4 to 8 hours at 100 Celcius degree.
After cooling and cracking open, the alkali is neutralized carefully with an equivalent amount of 1M HC1.