This is my mind map: '1.6 Proteins'. Its is based on the AQA A-Level Biology specification, and it is also based on the AQA Biology A -Level 2nd edition textbook. Find my matching 'Proteins' Flashcards on my profile, or follow the link here: https://www.goconqr.com/en-GB/p/4819880
Occur in all living organisms -
evidence for evolution
Constituents:
- Variable R group
- Central C atom
- Amino Group (NH2)
- Carboxylic Acid
Group (COOH)
Amino Acid Monomers
combine to make
dipeptides!
Condensation Reaction
Water molecule made from -OH of
carboxylic acid group and -H from amino
group of another amino acid
The monomers are joined by a PEPTIDE BOND between the
carbon atom of one amino acid and the nitrogen atom of
the other
Can be broken through a Hydrolysis reaction
If many join together
to make long chains,
it is called
POLYMERISATION.
This makes a
polypeptide
Protein Structure
Primary
- A specific sequence of amino acids
- A single polypeptide chain
Secondary
Hydrogen Bonds form between different amino acids
Polypeptide chain twisted into 3D structure
Alpha Helix
Beta Pleated Sheet
Tertiary
The Helix/Beta pleated sheet is
now folded even more. This
means a more complex, yet
SPECIFIC shape.
Disulphide Bridges - Fairly strong
Hydrogen Bonds - Weak but there are many
Ionic - Formed between any carboxyl and amino acid groups
that ARE NOT involved forming peptide bonds. Weaker than
disulphide bonds and easily broken by changes in pH
Quarternary
Has a combination of
MORE THAN ONE
polypeptide chain
Can be associated
with non-protein
(prosthetic)
groups into large,
complex protein
molecules such as
heamoglobin
Test for Proteins
Biuret Test
Detects Peptide Bonds
Add sodium hydroxide solution to
solution that is to be tested
Add a few drops of very dilute Copper (II) Sulphate solution and mix
Goes purple = peptide bonds present = protein!
Fibrous Proteins
Long chains that run parallel
Chains linked by cross-bridges
Secondary structure is
very tightly wound
Teritary
structure
is wound
into helix
Quaternary is made of many
of these, which are tightly
wound into a 'rope'