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Biology- A level AQA
Biological Molecules
1.4 Proteins
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Cards (15)
Amino acid structure
-4 chemical groups
arranged around a
central carbon
atom
Amino acid
-20
different amino acids that make proteins
-R
group differs for each amino acid
-2 bonded amino acids=
dipeptide
-more than 2=
polypeptide
Dipeptide
Two amino acids bonded together
primary structure
The
specific sequence
of
amino acids
that make up a
protein
Secondary structure
Coiling
and
pleating
of parts of the
polypeptide
molecule
Alpha
helix and
beta
pleated sheets
Alpha helix
-right
hand
coil
-as it coils,
hydrogen
bonds form
-stabilises
the protein
Beta pleated sheets
-Amino acid
chain folds up on itself
-hydrogen
bonds form across sheets
-stabilises
the protein
Tertiary structure
-overall 3D structure of a protein molecule
-Held in place by:
-polar
interactions
-disulphide
bonds
-Ionic
interactions
-covalent
bonds
quatenary structure
more than one
polypeptide chain
Polar interactions
-Hydrophobic
R
groups cluster to
interior
of protein molecule
- forms
hydrophobic
interactions
-stabalises
protein
-Hydrophilic R groups on
outside
of proteins
- water soluable
Disulphide bonds/ bridges/ linkages
-covalent
bonds
-will bond as soon as two
R
groups with
sulphur
are close
Ionic interactions
-Carboxyl
and
amino groups
form
charges
in solutions
-Opposite
charges come together
3D proteins shapes
-Fibrous
-Globular
Fibrous
-Structural
functions
-repetitive
amino
acid sequences
-usually
insoluable
Globular
-metabolic
functions
-formed through
hydrophobic
and
hydrophillic
interactions
-water
soluable