Organismal Physiology Lecture No. 16: Oxygen Transport & Respiratory Pigments
Tuesday November 6 , 2012
The Transport Of Oxygen – Respiratory Pigments:
-Blood must be thicker than water. The solubility of O in2water (especially warm salty water) is not
enough to provide O to active tissues. Many organisms use respiratory pigments that bind O and
transport it to tissues. Respiratory pigments can be in solution or enclosed in pigments. A hematocrit is
a process where you centrifuge whole blood and measure the proportion of ‘solids’ (cells). It is a pretty
good measure of blood oxygen carrying capacity in vertebrates.
The Real Advantage Behind Respiratory Pigments:
-In humans, blood picks up oxygen from the lungs and holds 200mL of O per lit2e of blood in chemical
combination as opposed to holding 4mL of O per l2tre in solution. This 50-fold increase in oxygen
demonstrates the fact that without hemoglobin, the heart would need to pump 50 litres for every single
litre it pumps now. A respiratory pigment is a that combines reversibly with oxygen. Many animals
possess these pigments and all of them are metalloproteins (proteins that contain a metal atom), which
is the reason for their colour. Respiratory pigments like hemoglobin are not only effective at sucking O 2
out of water, but can transport a lot per unit volume as well.
Components Of A Respiratory Pigment:
-In hemoglobin, the protein contains four subunits (tetrameric) and a metal-containing “Heme” group
that is the site of oxygen binding. By looking at the general distribution of hemoglobin on a phylogeny, it
is pretty well dispersed throughout the animal kingdom.
Chlorocruorins, Hemerythrins & Hemocyanins: