Quaternary structure of proteins
This structure contains more than one polypeptide and simply means how different polypeptides are arranged together. In general, the same types of interactions that contribute to tertiary structure (mostly weak interactions, such as hydrogen bonding and London dispersion forces) also hold the subunits together to give quaternary
structure.
Quaternary structures of proteins can be conjugated or non-conjugated
Non-conjugated
Conjugated
Quaternary structure of proteins Conjugated
Conjugated proteins have one or more non-polypeptide subunits in proteins
addition to their polypeptides. Hemoglobin is an oxygen carrying protein consisting of 4 polypeptides. Each subunit contains one iron atom (prosthetic group) and can carry one molecule of oxygen.
https://en.wikipedia.org/wiki/Hemoglobin
Haemoglobin
Quaternary structure of proteins
Non-conjugated
Non conjugated proteins are composed only of polypeptides. The
together using the same interactions as in the tertiary structure.
structure is formed by linking several polypeptide chains
Insulin Collagen
Form and function in globular & fibrous proteins
The function of a protein depends on its form. This is also shown when considering fibrous and globular proteinns. Look at the examples below and discuss how any why these molecules are adapted to the function they carry out.
Form and function in globular & fibrous proteins
Compare the two types of tertiary structures for proteins in the table below to understand how the form relates to the function of proteins:
Form and function in globular & fibrous proteins
Compare the two types of tertiary structures for proteins in the table below to understand how the form relates to the function of proteins:
Fibrous proteins
Globular proteins
Shape
Long and narrow
Often only alpha helices in the secondary structure
Rounded/spherical
Alpha helices and beta-pleated sheets in secondary structure
Role
Structural (strength and support)
Functional (catalytic, transport etc)
Solubility
(Generally) insoluble in water
(Generally) soluble in water
Stability
Repetitive amino acid sequence
Irregular amino acid sequence
Sequence
Less sensitive to changes in pH and temp
More sensitive to changes in pH and temp
Examples
Collagen, myosin, fibrin, actin, keratin, elastin
Catalase, hemoglobin, insulin, immunoglobulins