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It is important to note that bases on the DNA (and mRNA) are read in separate sets of 3s along a DNA/(mRNA) stand (this is called a triplet code in DNA, or the codon in mRNA). So, if a base is deleted, the whole sequence undergoes a frame shift in which the base after the deleted one is read with the original group (E.g. AT
TGCAC --> ATGCAC). This means that the triplet code (the set of 3 bases) is different. Note above how both triplet codes have been altered by this. This will happen to ALL the sequences following the deletion, so all those triplet codes will be altered and incorrect.
As the codon on the mRNA is transcribed from this altered DNA sequence, it will also have a different codon. The codon on the mRNA is translated into a polypeptide, with each codon of 3 bases coding to 1 specific amino acid. Hence, if the codon is wrong, the amino acid is wrong, so the polypeptide is wrong.
Polypeptides are long chains of amino acids strung together, and are folded into specific 3D shapes (the tertiary structure) to form a protein. They do this by forming hydrogen, ionic and/or disulphate bonds with the specific amino acids in the chain. If these amino acids aren’t there because a different one has been coded for by the mRNA due to the deletion in the DNA, then these bonds cannot form. Hence, the 3D shape will not be formed so the protein is not formed correctly, hence mutating it.see more
A surd is an irrational number which cannot be expressed as a fraction or a recurring number. E.g. root 2 = 1.4142135…. and it continues (but it does NOT repeat like a recurring fraction though). E.g. pi would actually be a surd too, because it cannot be accurately presented as a simple number like a fraction or recurring decimal. 1.4.... or 32/9 are not surds for that matter.
If you were to round 1.4142135… to 1.414, and then square it when trying to get back to 2, you will in fact get 1.999396. This is because rounding is a type of approximation, so you will not get the exact figure for 2 but for a number close to it. This would be the same with all surds. Root 2 would be the only fully accurate representation of the number.
Hence (root 2)2 would be 2. To help understand this, imagine it was root 16.
Root 16= 4.
42 = 16.
Hence, (root 16)2 = 16.
In the same way, any rooted surd multiplied by itself = the number inside the surd.
And in terms of multiplying different surds…
Root 9 x Root 4 = Root 36
We can prove this is because
Root (9x4) = Root 36 = 6 and root 9 x root 4 = 3 x 2 = 6. Therefore, this is correct!
Hence, with any surd, the inside number of the surds can be multiplied to make a new surd. (e.g. root 3 x root 5 = root 15 ) :)see more
MgCO3 +2HCl --> MgCl2 + H2O +CO2
For this kind of question, I would always try to convert what I can into moles because that is the link between the solid (the grams of the MgCO3) and the liquid (the HCL and NaOH). Here is my process:
Since mol=conc x vol, the mol of HCl initially added to the impure MgCO3 is 0.5moldm-3 x 75x10-3 dm3 = 0.0375 moles.
The mol of NaOH that reacted with the excess HCl moldm3-3 is 0.5 x 21.6x10-3 dm3 = 0.0108 moles.
Because the NaOH and HCL are in a 1 to 1 molar ratio: (1NaOH + 1HCl --> NaCl +H2O), the mole of excess HCl is also 0.0108.
(All in moles) Total HCl initially added to MgCO3 sample – HCl that actually reacted with (the pure) MgCO3 = Excess HCl (which was reacted with the NaOH).
So, 0.0375 - HCl that actually reacted with (the pure) MgCO3 = 0.0108.
HENCE, HCl that actually reacted with (the pure) MgCO3 = 0.0375 – 0.0108 = 0.0267 moles.
As the (pure)MgCO3 and HCl reacted in a 1:2 ratio (see equation above) the mol of MgCO3 is 0.0267/2 = 0.01335
The molecular mass (Mr) of (pure) MgCO3 is 84.3 (worked out from the periodic table)
So as the mass(of pure MgCO3) = mol x Mr, the mass = 0.01335 mol x 84.3 = 1.125g
Since the mass of impure MgCO3 is 1.25g, the percentage mass of pure MgCO3 is 1.125/1.25 x100% = 90%see more