Polar amino acids: Difference between revisions

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'''&nbsp;Polar amino acids'''<br><ref>Berg J., Tymoczko J and Stryer L, (2007) Biochemisty, 6th edition, New York: WH freeman.</ref>There are twenty amino acids, five of which are polar but uncharged. Two of which contain a hydroxyl group (-OH) attached to aliphatic side chain that is ''serine ''and ''threonine''. As for the ''aspargaine ''and glutamine they contain a terminal carboxamide in place of carboxylic acid. The fifth polar amino acid is ''cysteine'' that is structurally similar to serine but contain a sulfhydryl, or thiol (-SH), instead of the hydroxyl (-OH) group. <references />}
'''Polar Amino Acids''' There are twenty [[Amino acids|amino acids]] that occur naturally, these amino acids can be separated into two groups; [[Non-polar|non-polar]] amino acids and [[Polar_amino_acids|polar]] amino acids. The polar group consist of 10 amino acids, two are negatively charged - [[Aspartic_acid|aspartic acid ]]and&nbsp;[[Glutamic_acid|glutamic acid]], 3 have a positive charge - [[Arginine|arginine]], [[Lysine|lysine ]]and&nbsp;[[Histidine|histidine]], and 5 are uncharged&nbsp;- [[Asparagine|asparagine]], [[Glutamine|glutamine]], [[serine|serine]], [[Threonine|threonine ]]and [[Tyrosine|tyrosine]].<ref>Alberts B., Johnson A., Lewis J., Raff M., Roberts K. and Walter P. (2008) Molecular Biology of the cell, 5th edition, New York: Garland Science. (Pg 127)</ref> The properties of the amino acid are due to the properties of the side chain or R-group. These properties are extremely important when it comes to forming protein structure as different R-groups allow different [[Non-covalent bonds|non-covalent bonds]] to form between amino acids in the polypeptide chain. For example only amino acids with charged R-groups can form [[Ionic bonds|ionic bonds]] with each other or with other charged molecules&nbsp;<ref>Gupta P.K. (2009) Cell and Molecular Biology, 2nd edition, New Delhi: Rastogi Publications, p. 43</ref>.<br>All polar amino acids have either an OH or NH2 group (when in aqueous environment), and can therefore make [[Hydrogen bonds|hydrogen bonds]] with other suitable groups&nbsp;<ref>Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science, p. 125 - 129</ref>.


'''Polar amino acids'''
[[Polarity|Polarity]] of the amino acids affects the overall structure of a protein. Polar amino acid residues have a tendency to be on the outside of a protein, due to the hydrophilic properties of the side chain&nbsp;<ref>Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science, p. 125 - 129</ref>.<br>A mutation which causes an amino acid substitution can have a great affect on protein structure and therefore protein function. For example the point mutation which substitutes [[Valine|valine]] for the polar amino acid [[Glutamate|glutamate]] causes [[Haemoglobin|haemoglobin]] to change its shape, due to the new hydrophilic region, leading to the condition known as [[Sickle cell anaemia|sickle cell anaemia]]&nbsp;<ref>Chen, Harold (2006) Atlas of genetic diagnosis and counseling, Totowa, N.J. : Humana Press</ref>


{| width="200" border="1" cellpadding="1" cellspacing="1"
=== References  ===
|-
 
| Serine
<references />
| Ser
| S
|-
| Cysteine
| Cys
| C
|-
| Threonine
| Thr
| T
|-
| Glutamine
| Gln
| Q
|-
| Asparagine
| Asn
| N
|}

Latest revision as of 15:18, 20 October 2014

Polar Amino Acids There are twenty amino acids that occur naturally, these amino acids can be separated into two groups; non-polar amino acids and polar amino acids. The polar group consist of 10 amino acids, two are negatively charged - aspartic acid and glutamic acid, 3 have a positive charge - arginine, lysine and histidine, and 5 are uncharged - asparagine, glutamine, serine, threonine and tyrosine.[1] The properties of the amino acid are due to the properties of the side chain or R-group. These properties are extremely important when it comes to forming protein structure as different R-groups allow different non-covalent bonds to form between amino acids in the polypeptide chain. For example only amino acids with charged R-groups can form ionic bonds with each other or with other charged molecules [2].
All polar amino acids have either an OH or NH2 group (when in aqueous environment), and can therefore make hydrogen bonds with other suitable groups [3].

Polarity of the amino acids affects the overall structure of a protein. Polar amino acid residues have a tendency to be on the outside of a protein, due to the hydrophilic properties of the side chain [4].
A mutation which causes an amino acid substitution can have a great affect on protein structure and therefore protein function. For example the point mutation which substitutes valine for the polar amino acid glutamate causes haemoglobin to change its shape, due to the new hydrophilic region, leading to the condition known as sickle cell anaemia [5]

References

  1. ↑ Alberts B., Johnson A., Lewis J., Raff M., Roberts K. and Walter P. (2008) Molecular Biology of the cell, 5th edition, New York: Garland Science. (Pg 127)
  2. ↑ Gupta P.K. (2009) Cell and Molecular Biology, 2nd edition, New Delhi: Rastogi Publications, p. 43
  3. ↑ Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science, p. 125 - 129
  4. ↑ Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science, p. 125 - 129
  5. ↑ Chen, Harold (2006) Atlas of genetic diagnosis and counseling, Totowa, N.J. : Humana Press
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