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STRUCTURE OF AMINO ACIDS
Amino acids are molecules containing an amine group and a carboxylic acid group. Naturally
occurring amino acids have the following general formula:
There is a central carbon atom attached to a hydrogen, a carboxylic acid group, an amine group
and an alkyl group. Amino acids are thus all chiral except for glycine, in which the R is another
H atom.
Amino acids occur widely in nature and have a number of uses in the human body.…read more

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In high pH, therefore, amino acids exist in anionic form:
ii) reaction with acids
Amino acids react with strong acids such as hydrochloric acid:
In low pH, therefore, amino acids exist in cationic form:
iii) reaction with itself
Since amino acids have a proton donating group and a proton accepting group on the same
molecule, it follows that each molecule can undergo an acidbase reaction with itself:
The double ion that is formed as a result of this reaction is called a Zwitterion.…read more

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In the solid state, therefore, amino acids are ionic. This explains why they are solids with a high
melting point.
iv) summary
Amino acids can exist in molecular form, in cationic form, in anionic form or in Zwitterion form
depending on the environment:
in neutral solution in alkaline solution in acidic solution in the solid state
Since amino acids can react with acids and alkalis, they make very effective buffer solutions.…read more

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The resulting molecule is called a dipeptide.
Dipeptides can also be formed by the condensation of two different amino acids. In this case
two different molecules can be formed:
or
Since the resulting dipeptides also have both amine groups and carboxylic acid groups, they can
undergo further condensation reactions, eventually forming polymers:
This reaction is carried out alongside DNA molecules in the bodies of living organisms.…read more

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PROTEINS
Proteins are naturally occurring polyamides formed by the condensation of many amino acid
molecules under carefully controlled conditions around the DNA backbone.
i) structure
The sequence of amino acids in a protein is known as the primary structure of the protein. It
varies from protein to protein, depending on the function that the protein needs to perform.…read more

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The peptide link in proteins is the same as the peptide link in Nsubstituted amides. As a result it
can be broken by heating in strong acid or strong alkali.
Proteins can thus be broken down into their constituent amino acids by heating in strong acid or
strong alkali in practice 6 moldm3 HCl is generally used.
This reaction is an example of a hydrolysis reaction.…read more

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Type of reaction Mechanism
1. acidbase reactions of amino acids
a) with acids
reagents: HCl
conditions: room temperature
equation: RCH(NH2)COOH + HCl RCH(NH3+Cl)COOH
b) with alkalis
reagents: NaOH
conditions: room temperature
equation: RCH(NH2)COOH + NaOH RCH(NH2)COONa+ + H2O
2. condensation reactions of amino acids
conditions: DNA
equation: n RCH(NH2)COOH H(NHCRHCO)nOH + (n1) H2O Nucleophilic
additioneliminati
3.…read more

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