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Proteins and Amino Acids - The Basics

Updated on February 2, 2013

What Are Amino Acids?

  • Amino acids are simple organic compounds and are the monomers of all proteins.
  • They all have the same basic structure.
  • The 20 different naturally occurring amino acids that are involved in protein synthesis only differ because of the R-Group that is bonded to the central carbon.
  • The R-group in different amino acid molecules differ in charge (positive or negative), size (some are larger than others) and polarity.
  • All amino acids have an amino group at one end of the molecule, an carboxyl group at the other end and a carbon in between.
  • Amino acids join end-to-end to create a 'repeating backbone'.

What Are Proteins?

  • Proteins make up about 50% of the organic matter of a cell.
  • Proteins are large molecules that are made out of carbon, nitrogen, hydrogen and oxygen.
  • Their functions include:
  • They provide structure - for muscles and bone.
  • They can be protein carriers and channels in cell membranes.
  • Many hormones are proteins.
  • All enzymes are proteins.
  • Antibodies are proteins.

8-10 of the essential amino acids that we need are found in meat.
8-10 of the essential amino acids that we need are found in meat.

Amino Acids - Animals vs Plants

  • Plants are able to make their own amino acids that they need to live - providing they can obtain a sufficient amount of nitrate from the soil.
  • They convert the nitrate into amino groups which then bond to organic groups which are the product of photosynthesis.
  • Animals however cannot manufacture 8-10 of the amino acids that they need (essential amino acids) and therefore must eat protein (in the form of meat) which is then digested into amino acids.
  • Animals cannot store excess amino acids, the amino group makes them toxic if too much is present.
  • The amino group is removed in a process called deamination - this takes place in the liver in animals.
  • The removed amino groups form urea and is removed in the urine.

Joining Amino Acids

  • All amino acids join together in the same way no matter what kind of R-Group they may contain!
  • A condensation reaction (where a water molecule is removed) between the acid group of one amino acid and the carboxyl group of the other forms a covalent bond between the two amino acids.
  • The bond formed is called a peptide bond and the molecule produced is called a dipeptide.
  • The peptide bond can be broken by adding water, this is called a hydrolysis reaction and is basically the opposite of a condensation reaction.
  • Making and breaking peptide bonds is essential for building proteins in organisms, for example the breaking down of proteins into amino acids during digestion.
  • Lots of dipeptide molecules can join (in a hydrolysis reaction) to form polypeptide molecules.


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      biochemi 4 years ago

      Amino acids are of two types based on the optical isomerism except for glycine. These isomers are called as L-amino acids and the next one is D-amino acids. In animals and plants only L-amino acids are used in the formation of proteins while D-amino acids are used to form cell wall of some bacteria, and therefore D-amino acids are not used in animals or plants.

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      morgan 4 years ago

      for all your protein and amino acid needs with a great range of selection from all the top retailers with all the top brands visit