Amino Acids (AQA GCSE Chemistry)

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Amino Acids

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  • Amino acids are small molecules containing the amino, NH2, and carboxylic acid, COOH, functional groups
  • The NH2 group is basic and behaves in a similar way to ammonia
  • The COOH group is acidic and is called a carboxyl group
  • There are twenty naturally occurring amino acids and they all have the same general structure

Amino Acid - General Formula, IGCSE & GCSE Biology & Chemistry revision notes

The structure of naturally occurring amino acids have an amino group on the second carbon along from the carboxyl group. The R represents a varying side group.

  • Polypeptides are condensation polymers which are formed from amino acid monomers joined together by peptide links
  • In polypeptides the amino group on one amino acid links to the acid group of an adjacent amino acid

Peptide-Link, IGCSE & GCSE Chemistry revision notes

Diagram showing a peptide link which holds proteins together

  • This pattern continues to form the polymer chain with one water molecule being lost per peptide link
  • Proteins are one or more long-chains of polypeptides
  • Most proteins contain at least 20 different amino acids
  • Polypeptides and proteins can contain different amino acids in their chains. The order of the amino acids determines the proteins structure and properties

Forming-a-Protein, IGCSE & GCSE Chemistry revision notes

Diagram showing condensation polymerisation to produce a protein

Exam Tip

When drawing biological polymers it is important that you show the peptide link clearly in your sketch.

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Stewart

Author: Stewart

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.