Question

طلاطلالتط[
@ if coz and O2 present with some amount in blood then write
you result with the combination of Hemoglobin​

Answer 1

Answer:

The protein hemoglobin is a molecule which is responsible for carrying almost all of the oxygen in the blood. It is composed of four subunits, each with a heme group plus a globin chain. The heme group is composed of a porphyrin ring which contains an iron (Fe) atom in its center. Normally, the Fe is in the +2 redox state (ferrous) and can reversibly bind oxygen. There are at least six genes that control globin synthesis in humans, resulting in the formation of six structurally different polypeptide chains that are designated α, β, γ, δ, ξ, and ς chains. All normal and most abnormal hemoglobin molecules are tetramers consisting of two different pairs of polypeptide chains, each chain forming a monomeric subunit.

The blood of a normal adult human contains at least six different species of hemoglobin molecules, all of which have the same principal structure and function. Hemoglobin A (A for adult) makes up 92% of the total hemoglobin concentration in a normal adult human. To date, approximately 200 structurally different human hemoglobin variants have been reported. These abnormal hemoglobins (relative to hemoglobin A) often have different oxygen-binding properties.

Hemoglobin A (HbA) is composed of two α chains and two β chains, symbolically written as α2 β2. Its molecular weight is 64,400 Da. Each a chain has 141 amino acids, and each β chain has 146. The concentration of Hb inside red blood cells is 330 g/l (= 33 g%). At a hematocrit of 45%, this yields a blood [Hb] of 150 g/1 or 15 g%. The structure of the Hb molecule has been elucidated by the x-ray crystallographic work of Perutz and his co-workers [14,30]. The α and β chains are arranged in αβ pairs, and any conformational change in one polypeptide chain is transmitted to the others in the molecule. There are two different arrangements of the subunits within the tetramer that are much more stable than all others. One of these two quaternary conformations predominates when the iron atoms are saturated with oxygen (oxy structure), and the other predominates when these binding sites are vacant (deoxy structure). The deoxy structure is characterized by the presence of inter- and intrasubunit salt bridges which give it a constrained or taut (T) configuration. The oxy conformation is obtained when the salt bonds are broken so as to give the tetramer a relaxed (R) quaternary structure.

When the iron atom in the heme group becomes oxidized (loses an electron), its valence state changes from +2 (ferrous) to +3 (ferric). The hemoglobin is then called methemoglobin (metHb) or ferrihemoglobin (Fe+3 will not bind oxygen). Ordinarily, about 1% of the hemoglobin in a red blood cell is in this form. The level of metHb is maintained at this low level primarily by the enzyme NADH-methemoglobin reductase. It is important that the level of metHb be kept low since it will not reversibly bind oxygen and thus cannot carry oxygen.

Explanation:

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