AA, Proteins and Protein Synthesis 07/10/19
- Proteins are one of the 4 categories of biomolecules (proteins, fats, carbs and nucleic acids)
- Proteins = over 50% of the dry mass of most cells
- Functions include: structural support/storage/transport/antibodies and more
There are several types of proteins in living organisms, all with specific functions and role
- There are 20 standard amino acids that make up all known proteins – ranges from bacteria to
humans
- The way said acids are assembled determines the function of the protein therefore
accounting for the diversity of proteins
- At pH 7, carboxyl = conj. base form and amino = conj. acid
form
- Central C12 is chiral. Shape = tetrahedral and exist as
enantiomers (optical isomers so rotate plane polarized light)
- – L or D enantiomer (e.g. L-Alanine or D-Alanine). Only L –
amino acids = present in proteins.
- Racemization (where one enantiomer becomes equal
proportion of both forming racemic mixture)
- This can be bad as one enantiomer of a certain amino acid in
a medicine can be effective, but one can cause problems –
e.g. birth defects
- AA can be split into 4 groups:
Non-Polar side chains (hydrophobic) Polar side chains (hydrophilic)
Acidic (net charge = -ve) Basic (net charge = +ve)
- AA have important biological roles in addition to their role of protein construction.
- For example, arginine is the precursor of NO
- Tyrosine is the precursor of dopamine neurotransmitter
AA form peptides via peptide bonds formed by the condensation reaction between an OH from the
carboxyl group of one AA and the H from the amino group of another AA.
- In the AA cystine, a highly reactive sulfhydryl bond forms (SH).
- Reversible oxidisation of this forms a disulphide bridge/bond.
- Proteins are one of the 4 categories of biomolecules (proteins, fats, carbs and nucleic acids)
- Proteins = over 50% of the dry mass of most cells
- Functions include: structural support/storage/transport/antibodies and more
There are several types of proteins in living organisms, all with specific functions and role
- There are 20 standard amino acids that make up all known proteins – ranges from bacteria to
humans
- The way said acids are assembled determines the function of the protein therefore
accounting for the diversity of proteins
- At pH 7, carboxyl = conj. base form and amino = conj. acid
form
- Central C12 is chiral. Shape = tetrahedral and exist as
enantiomers (optical isomers so rotate plane polarized light)
- – L or D enantiomer (e.g. L-Alanine or D-Alanine). Only L –
amino acids = present in proteins.
- Racemization (where one enantiomer becomes equal
proportion of both forming racemic mixture)
- This can be bad as one enantiomer of a certain amino acid in
a medicine can be effective, but one can cause problems –
e.g. birth defects
- AA can be split into 4 groups:
Non-Polar side chains (hydrophobic) Polar side chains (hydrophilic)
Acidic (net charge = -ve) Basic (net charge = +ve)
- AA have important biological roles in addition to their role of protein construction.
- For example, arginine is the precursor of NO
- Tyrosine is the precursor of dopamine neurotransmitter
AA form peptides via peptide bonds formed by the condensation reaction between an OH from the
carboxyl group of one AA and the H from the amino group of another AA.
- In the AA cystine, a highly reactive sulfhydryl bond forms (SH).
- Reversible oxidisation of this forms a disulphide bridge/bond.
