Question

1. A. Describe all interactions that form the tertiary structure protein. B. Compare and contrast between hemoglobin and myoglobin.

Answer 1

The overall three-dimensional structure of a polypeptide is called tertiary structure.

The tertiary structure is primarily due to interactions between the R groups of the amino acids that make up the protein.

We can observe interactions that are covalent means where pairs of electrons are shared between atoms.

non-covalent means where pairs of electrons are not shared between atoms.

The following are the main interactions that make up the tertiary structures of proteins.

hydrophobic interactions, in which amino acids with nonpolar, hydrophobic R groups cluster together on the inside of the protein

Disulfide Bridges

These are very strong covalent bonds found between cysteine residues that are in close proximity in space. The bonds form between the sulfur groups on the different cysteine residues

Ionic Bonds

If an amino acid with a positive charge comes close enough to an amino acid that carries a negative charge, they can from a bond that helps to stabilize the protein molecule.

Hydrogen Bonds

Hydrogen bonds occur between polar side chains and help in stabilizing the tertiary structure.

B)

Similarities Between Hemoglobin and Myoglobin

• Both haemoglobin and myoglobin are oxygen-binding globular proteins.
• Both of them contain the oxygen-binding haem as their prosthetic group.
• Both hemoglobin and myoglobin give the red color to the blood and muscles respectively.

Differences Between Hemoglobin and Myoglobin.

Hemoglobin	Myoglobin
Hemoglobin is a red protein which is responsible for transporting oxygen in the blood of vertebrates.	Myoglobin is a red protein with haem which carries and stores oxygen in the muscle cells.
The molecular weight of hemoglobin is 64 kDa.	The molecular weight of hemoglobin is 16.7 kDa.
Hemoglobin is composed of four polypeptide chains.	Myoglobin is composed of a single polypeptide chain.
Hemoglobin is a tetramer composed of two alpha and two beta subunits.	Myoglobin is a monomer. Therefore, it lacks a quaternary structure
Hemoglobin binds with four oxygen molecules.	Myoglobin only binds with a single oxygen molecule
hemoglobin is a tetramer, it exhibits cooperative binding with oxygen.	myoglobin is a monomer, it does not exhibit cooperative binding.
Hemoglobin has a low affinity to bind with oxygen.	Myoglobin has a high affinity to bind with oxygen, which does not depend on the oxygen concentration.
Hemoglobin is found in the bloodstream.	Myoglobin is found inside muscles.
Hemoglobin A, hemoglobin A2 and hemoglobin F are the types of hemoglobin in humans.	A single type of myoglobin is found in all cells.
Hemoglobin takes oxygen from lungs and transports to the rest of the body.	Myoglobin stores oxygen in the muscle cells and releases when needed.