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ALL CIE CHEMISTRY DOUBTS HERE !!
tmisterr:
--- Quote from: Nera_egypt on February 20, 2011, 07:58:14 am ---I have a question in the application booklet related to Biochemistry
In section 1.3 – Genetic information. I couldn't solve SAQ 11 part c on page 41 :( .
I would be really glad if someone helps me work it out :)
P.S: I attached the question
--- End quote ---
from the peptide fragment, we see -Ala-Ala-: two same amino acids one after another. so we would expect that we see two same codons following each other on the fragment of mRNA. the first time this happens is -GCU-GCU- so we can say that the codon for Ala is GCU. we can confirm this by skipping the next two codons (-GAA-GGA-), which we can suspect to be for the -Glu-Gly- section of the peptide and we see that the next codon is again -GCU- confirming that GCU is the codon for Ala since is coincides with the polypeptide chain, that it two Ala, followed by two other amino acids then Ala again. once you know this, you can easily get the rest ;)
(ii) deciphering gives the codon for tyrosine as UAC. this is for the mRNA so the DNA triplet code from which it was transcribed from is ATG (I hope you know how the bases match). since mRNA is always synthesised from the 5' end to the 3'end the direction of this codon is 5'-ATG-3'
well then, I hope this helps
tmisterr:
i'd also like to emphasize that there is no need to memorize codons, you will be given the genetic code which has all the codons if you are needed to use it in exams so no need to stress yourself on that. just understand how transcription and translation work and you'll be fine
Nera_egypt:
--- Quote from: tmisterr on February 20, 2011, 04:39:03 pm ---from the peptide fragment, we see -Ala-Ala-: two same amino acids one after another. so we would expect that we see two same codons following each other on the fragment of mRNA. the first time this happens is -GCU-GCU- so we can say that the codon for Ala is GCU. we can confirm this by skipping the next two codons (-GAA-GGA-), which we can suspect to be for the -Glu-Gly- section of the peptide and we see that the next codon is again -GCU- confirming that GCU is the codon for Ala since is coincides with the polypeptide chain, that it two Ala, followed by two other amino acids then Ala again. once you know this, you can easily get the rest ;)
(ii) deciphering gives the codon for tyrosine as UAC. this is for the mRNA so the DNA triplet code from which it was transcribed from is ATG (I hope you know how the bases match). since mRNA is always synthesised from the 5' end to the 3'end the direction of this codon is 5'-ATG-3'
well then, I hope this helps
--- End quote ---
Thanks alot, this was the best explanation given to me :)
narnia:
--- Quote from: Amelia on February 19, 2011, 04:57:00 pm ---Silicon dioxide is a giant molecule (macromolecular structure due to extensive network of covalent bonds in the crystalline lattice structure that extends to infinity). since the solubility of a substance is related to the similarity in bond strength in the solvent (water in this case) AND the solute (silicon dioxide in this case), and the extensive network of covalent bonds is much stronger than the water-water interactions (i.e. hydrogen bonds), therefore silicon dioxide CANNOT be hydrated by water molecules (i.e. water cannot break down the giant crystal lattice structure of the macromolecule SiO2) to form aqueous ions and therefore it remains insoluble in water. (silicon dioxide only dissolves by heating with strong alkali. in this case water is not alkaline enough to hydrolyse silion dioxide to give sillicate ions).
Also Silicon dioxide is an acidic compound.
In one line, Silicon dioxide doesn't react with water, because of the difficulty of breaking up the giant covalent structure.
http://www.thestudentroom.co.uk/wiki/Revision:Acid-Base_Character_of_Group_4_Oxides
--- End quote ---
Thanks tons!
EMO123:
What are the Friedel-Crafts Catalyst?
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