Question

describe the actuve location (S) of hemoglobin and myoglobin. How does the former function to transport 0₂ from the lungs to the cells where it is used?

Answer 1

The active location (S) of hemoglobin and myoglobin is actually a non-protein group called heme. The heme consists of a flat organic ring surrounding an iron atom. The organic part is a porphyrin ring based on porphin (a tetrapyrrole ring), and is the basis of a number of other important biological molecules, such as chlorophyll and cytochrome. The ring contains a large number of conjugated double bonds, which allows the molecule to absorb light in the visible part of the spectrum. The iron atom and the attached protein chain modify the wavelength of the absorption and gives hemoglobin its characteristic colour. Oxygenated hemoglobin (found in blood from arteries) is bright red, but without oxygen present (as in blood from veins), hemoglobin turns a darker red. Venous blood is often depicted as blue in colour in medical diagrams, and veins sometimes look blue when seen through the skin. The appearance of blood as dark blue is a wavelength phenomenon of light, having to do with the reflection of blue light away from the outside of venous tissue if the vein is ~0.02 inches deep or more.

Hemoglobin consists of 4 myoglobin units joined together, and its action with respect to uptake of oxygen is similar, but more complex. When we breathe, oxygen in the lungs passes through the thin-walled blood vessels and into the red blood cells, where it binds to the hemoglobin, turning it into the bright red oxy-hemoglobin. The blood then passes around the body until it reaches cells and tissues which require oxygen to sustain their processes. These cells are rich in CO₂, which is a waste product of these processes. The CO₂ displaces the weakly-bound O₂ and forms carbaminohemoglobin, which then travels in the bloodstream back around to the lungs where it is again displaced by oxygen.