Which one of the given proteins transports oxygen in the blood stream?

Options

A. collagen
B. Insulin
C. albumin
D. haemoglobin

Answer

C

Explanation

Albumins are a group of soluble globular proteins occurring in many animals tissues and fluids: e.g. egg-white (egg albumin), milk (lactalbumin), and blood (serumalbumin).
Insulin is the hormone which maintains the level of sugar in blood. It possesses 51 amino acid residues in two polypeptide chains which are cross-linked by two disulphide bonds. Note that the medicine which is prescribed to a diabetic patient suffering from hyperglycaemia is insulin. Collagen, a fibrous protein is the major protein component of connective tissues such as tendon, skin and cartilage. It contains a high proportion of proline residues. Collagen consists of three are wound about each other (as in braid) in a right - handed super helix. Upon boiling with water, collagen is the most abundant protein present in mammalian body. As we grow older. the number of cross-links in collagen increases. Consequently collagen fibres become more rigid and brittle, making tendons (connective tissues) more easily injured. Simple proteins consist only of `A A's` while conjugated proteins also contains a nonamino acid unit (or non-peptide proteins) called a prosthetic group. The prosthetic group is intimately concerned with the specific biological action of the protein.
For example, the prosthetic group of haemoglobin (a conjugated protein) is heme. It contains Fe bound to the pyrrole system known as porphin. It is formation of a reversible oxygen-heme complex that enables haemoglobin to carry `O_(2)` from the lungs to the tissues. `CO` forms a similar but more stable, complex, it thus ties up haemoglobin, prevents oxygen transport, and causes death. Heme is held to the peptide portion (globin) of the protein by a combination of forces: coordination of iron by histidine `N` of the protein, hydrogen bonding, and van der Waals forces between hydrophobic parts of the two molecules.