A dipeptide is formed when 2 amino acids are joined together by a peptide linkage.
Each amino acid molecule contains an amino group ( -NH₂) and a carboxyl ( -COOH) group. During peptide formation, a carboxyl group of one amino acid reacts with amino group of the other , resulting in the formation of a linkage known as "peptide linkage". A water molecule is also eliminated in this reaction.
A general peptide formation reaction can be written as
In the above reaction, we can see a peptide linkage ( -CONH-) getting formed between 2 amino acid molecules.
In the given molecule the peptide linkage is shown by drawing a box around it. Please refer to the attached image.
If we want to know the amino acid molecules from which this peptide is formed, we will simply break the CO-NH bond.
We will add -OH group to CO part and -H to NH part to get 2 amino acid molecules as shown in the picture.
The two amino acids thus formed are Serine & Cysteine.
Serine is designated as "Ser" and Cysteine is designated as "Cys"
Therefore the given dipeptide is designated as "Ser-Cys"
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1070 hours.
1 mole of iron-59 would mass 59 grams, so 0.133 picograms would be 0.133x10^-12 / 59 = 2.25x10^-15 moles of iron-59. Multiplying by Avogadro's number, we can determine the number of atoms of iron-59 we have, so: 2.25x10^-15 * 6.02214x10^23 = 1.35x10^9
Since we have 242 decays over a period of 1 second, we can divide the
number of atoms left by the original number of atoms
(1350000000 - 242)/1350000000
= 1349999758/1350000000
= 0.999999820740741
And calculate the logarithm to base 2 of that quotient.
ln(0.999999820740741)/ln(2)
= -1.79259275281191x10^-7/0.693147180559945
= -2.58616467481524x10^-7
The reciprocal of this number will be the half life in seconds. So
-1/2.58616467481524x10^-7
= -3866729.79388461
And dividing by 3600 (number of seconds in an hour) will give the half-life in
hours.
-3866729.79388461 / 3600 = -1074.091609
So the half life in hours to 3 significant figures is 1070 hours.
Dividing that figure by 24 gives a half life of 44.58 days which is in pretty close agreement to the official half-life of 44.495 days for iron-59.
