Zusammenfassung der Ressource
Th1L03 Amino acids
- Building block of proteins
- Structure
- Central carbon atom (alpha-carbon) linked to an amino group, a
carboxylic group, a hydrogen atom and a R group (variable group)
- Chiral
- Can exist in two
mirror-image forms
- L and D isomers
- L isomer has amino
group on left side
- Only L amino groups are constituents
of proteins probably because are more
soluble
- D isomer has amino
group on right side
- Dipolar ions or zwitterions
- Amino acids at neutral pH
- Amino group is
protonated (-NH3+)
- Carboxyl group (-COO-)
is deprotonated
- Ionisation sates of
an amino acid
depends on pH
- In acidic solution
- amino acid group(-NH3+)
- carboxyl group (-COO-) is deprotonated
- In basic solution
- carboxyl group tends
to be the first group
to give up its proton
as it has a low pKa
(approx . 2)
- The dipolar form persists until pH
= 9 where the protonated amino
group loses a proton
- Functional groups
- include alcohols, thios, thioesters,
carboxylic acids, carboxamides and
various basic groups
- Most are chemically
reactive and account for
protein function
- Size, shape, charge, hydrogen bonding
capacity, hydrophobic character,
chemical reactivity
- Reactive properties of functional groups
are essential to enzymes
- Proteins can interact with one another and
with their biological macromolecules which
have more complex functions
- Proteins differ in their rigidity/ flexibility and this plays
a role into function (think cytoskeleton vs. connective
tissue)