Question

What is the iron-containing portion of hemoglobin (Hint: think blood) and myoglobin (Hint: think muscle) molecules called? _______In which specific types of cells in the body will you find these two iron-containing portions?___________ and _____________cells

Answer 1

ANSWER :

The iron containing portion of the Hemoglobin and the myoglobin is Heme.

In the human body ,roughly 80% of heme is present in Red blood cells,15% is synthesized and present in liver,and the rest is distributed in other tissues.

Hemoglobin is a heterotetrameric oxygen transport protein found in Red blood cells (Erythrocytes),whereas Myoglobin is a monomeric protein found mainly in muscle tissue where it serves as an intracellular storage site for oxygen.

EXPLANATION :

HEMOGLOBIN :

Hemoglobin is the heme protein molecules found in red blood cells, carrying oxygen from the lungs to the body’s tissue and returns carbon dioxide from the tissue back to the lungs.

Hemoglobin has less affinity for binding oxygen and its concentration is higher in RBC (red blood cells). So when oxygen binds to the first subunit of hemoglobin, it changes into the quaternary structure of the protein and thus making easier for other molecules to bind.

Structure of Hemoglobin

Hemoglobin contains a heme group which is a protein and held noncovalently. The difference lies in the globin part that has the different arrangement of amino acids in different animals.

‘Heme‘ is the central iron, hook up with four pyrrole rings. The iron is in the form of a ferric ion, while the pyrrole rings are attached by methylene bridges.

Globin– the protein part, is a dimer of heterodimer (alpha-beta) which means four proteins molecules are connected in which two alpha globulin and other two can be beta, delta, gamma or epsilon-globulin chains can be present which depends on the type of hemoglobin. This globulin chain contains ‘porphyrin’ compound which contains iron.

Hemoglobin (humans) consist of two alpha and two beta subunits where each alpha subunit has 144 residues and beta-subunit has 146 residues. It helps in transportation of oxygen throughout the body.

MYOGLOBIN :

Myoglobin is a kind of heme proteins, serving as an intracellular storage site for oxygen. During the deprivation of oxygen, the bound oxygen called as oxymyoglobin is released from its bound form and further used for other metabolic purposes.

As myoglobin has tertiary structure, which is easily soluble in water, in which its characters which are exposed on the surface of the molecules are hydrophilic while those molecules which are packed into the interior of the molecule are hydrophobic in nature. It is a monomeric protein having a molecular weight of 16,700, which is one-fourth to that of haemoglobin.

Structure of myoglobin

It consists of non-helical regions, from A through H which is right-handed alpha helices, and 8 in number. Though the structure of myoglobin is similar to that of haemoglobin.

Myoglobin also has the protein called heme, which contains iron and gives red and brown colour to the proteins. It exists in the secondary structure of protein having a linear chain of amino acids. It contains one subunit of alpha helices, and beta sheets and presence of hydrogen bond marked its stabilization.

Myoglobin helps in transportation and in storing of oxygen in muscles cells, which helps during the working of muscles by providing energy. The binding of oxygen is more tightly with myoglobin because venous blood combines more firmly than haemoglobin.