BIOCH 200 (February 10, 2014)
o Composed of more than one polypeptide chain where each one is referred
to as a subunit
2 = dimer; 3 = trimer; 4 = tetramer
*If the subunits are the same, it is called a homo___mer
*If the subunits are different, it is called a hetero___mer
o Is the quaternary structure:
*Like tertiary structure, it is MAINLY stabilized by hydrophobic
interactions. H-bonding and ion interactions help make strengthen
The Structure and Function of Myoglobin and Hemoglobin
• Myoglobin is a monomer
• *Hemoglobin is a oligomer (more specifically, a tetramer)
• *Remember that the function of a protein is determined 100% by its
o *3-D structure dependent on the primary structure
• *Hemoglobin binds to oxygen in the lungs and carriers it to the tissues where it
releases the oxygen for myoglobin to pick up.
o Think of it like a baton pass: Lungs with oxygen pass it to hemoglobin
which runs to the destination (tissue) and passes it on to myoglobin.
• Red blood cells = erythrocytes
• Myoglobin Function:
o Facillitate oxygen diffusion through muscle tissue
o *Acts as O 2torage for muscles
Allows for efficient diffusion of oxygen to muscles
o Store O 2n aquatic animals as well. • *The function of proteins depends a lot on its ability to bind to other molecules
called ligands IN A REVERSIBLE WAY!
o *The greater the affinity, the higher the [protein-ligand complex] is
compared to the [protein] and [ligand] individually
o *If you kept adding ligands to a solution of proteins, it would eventually
reach a saturation point this is when the total allowable protein-ligand
bonds have been created.
o *If there are two ligands that a protein can bind to, the one that the protein
has the highest affinity for will have a higher saturation rate and therefore
will reach 100% saturation first.
• The structure of myoglobin
o *8 α