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Proteins The hydrophobic effect helps some proteins to maintain their structure. When
globular proteins are in solution, their hydrophobic groups points outwards,
- build from amino acids away from the water.
- contains C H O N (carbon, hydrogen, oxygen and nitrogen)
- some contain S P (sulphur and phosphate) Quaternary Structure:
In a quaternary protein structure there are two or more tertiary level
The basic building block of a protein is an amino acid. polypeptide chains involved.
There are also non-peptide groups involve this structure.
Haemoglobin. This is made up from four polypeptide chains with a haem
group in the centre.
Classification of Proteins:
There are two main types of proteins.
Amino acids carboxyl group - Fibrous. Structural function, insoluble, strong and long chains
containing many cross linkages.
There are twenty different R groups and so twenty different amino acids each
with different properties.
A peptide bond is formed between the amino acid group of one amino acid
(peptide) and the carboxyl group of the next.
A dipeptide bond is formed by two peptides and a number of amino acids
joined together producing a polypeptide.
The sequence of amino acids in a polypeptide is called the Primary Protein
The polypeptide that adopts a Secondary Protein Structure. There are two
main types, -helix and the -sheet.
The polypeptide chain is then pulled into the tertiary protein structure.
The helix is than bent and twisted into a more complex structure.
More bonds are created.
Bonds in the Tertiary Structure:
- Hydrogen bonds. Between hydrogen atoms and some oxygen atoms
in a polypeptide chain.
- Ionic Bonds. Between any charged groups that aren't joined by
- Globular. Enzymes, antibodies and hormones. They are soluble and
are globular or spherical in shape.
- Disulphate Bonds. Between sulphur atoms of amino acids that are
close together. They are very strong and contribute to the strength of
structural proteins such as keratin and collagen.