Zusammenfassung der Ressource
1.6 Proteins
- Amino Acids
- 20 Different A.A's in Protein
- 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'
- Glycine helps close package of lots of A.A
- Collagen
- STRUCTURAL FUNCTIONS
- Insoluble
- Globular Proteins
- METABOLIC FUNCTIONS
- Enzymes
- Heamoglobin
- Folded Structure
- Soluble