Animal Physiology: Respiratory Pigments
chlorocruorin found in . . .
- 4 families of marine annelids
myoglobin
- a different type of hemoglobin - chemical structure differs - single subunit protein - holds oxygen tighter than hemoglobin - gives muscles their red coloration
chlorocruorins
- always extracellular, dissolved in plasma - iron porphyrin ground bound to protein, different from hemoglobin - bind one oxygen per iron porphyrin group
respiratory pigment
- any molecule that increases the oxygen-carrying capacity of the blood
oxygenated hemocyanin
- blue color
deoxygenated hemerythrin
- colorless
hemoglobin
- comprised of four subunits, each containing one polypeptide chain and one heme group - consists of alpha and beta globin - heme group is the part of hemoglobin that can bind oxygen - each heme contains one iron atom at the center of a porphyrin ring that binds oxygen - each hemoglobin can bind a total of 4 oxygen molecules
oxygenated chlorocruorins
- darker green
characteristics of respiratory pigments
- has a highly specific binding sites - conformation change occurs when pigment binds its ligand - allosteric sites exist for binding molecules other than the primary ligand, thus affecting the binding for the primary ligand - if pigments have multiple subunits, binding sites demonstrate cooperativity
which respiratory pigments contain the metal copper
- hemocyanins
which respiratory pigments contain the metal iron
- hemoglobin - chlorocruorins - hemerythrins
hemoglobin affinity
- hemoglobins that have high oxygen affinities are saturated at low partial pressure of oxygen - hemoglobins with low oxygen affinities are completely saturated only at relatively high partial pressures of oxygen
methemoglobin
- inactive form of hemoglobin - band in high amounts - can be caused by environmental poisons or dugs such as amyl nitrate and nitroglycerin
state of iron in hemoglobin
- iron in ferrous state, oxygen binds to hemoglobin - iron in ferric state, oxygen binds to hemoglobin but it cannot release the oxygen due to its increased in binding affinity *oxidize ferrous to ferric iron
deoxygenated chlorocruorins
- light green
hemerythrin is found in . . .
- marine annelids - sipunculid worms - branchiopods - priapulida
hemocyanin is found in . . .
- molluscs - arthropods
molecules that inactive ferrous hemoglobin to ferric methemoglobin
- nitrates, which greatly increase the rate of oxidation of ferrous to ferric iron (i.e. Blue Baby syndrome) - carbon monoxide inactivates the oxygen carrying ability of hemoglobin
hemerythrins
- no heme group - two iron atoms bound directly to the protein - 8 oxygen binding sites
oxyhemoglobin
- oxygen bound to hemoglobin - bright red
deoxyhemoglobin
- oxygen is not bound to hemoglobin - dark, maroon-red
oxygenated hemerythrin
- reddish violet
methemoglobin reductase
- reduces ferric methemoglobin to the functional ferrous hemoglobin
hemocyanin
- second most common class of respiratory pigments - binds oxygen when the partial pressure of oxygen is high, and releases it when the partial pressure is low - only about 1/4 the efficiency of hemoglobin - copper as metal ion - one oxygen molecule per two copper atoms - it is not contained in cells, but it is dissolved in blood plasma
How does cooperativity work?
- the binding of oxygen by the iron atom causes it to be moved slightly - this causes the histidine attached to it to slightly change position, which causes all other amino acids in the subunits to slightly change position - the change in shape results in the protein gaining affinity for oxygen as more oxygen is bound
deoxygenated hemocyanin
- transparent
types of respiratory pigments
1. hemoglobins 2. chlorocruocins 3. hemerythrins 4. hemocyanins
reason for anucleate RBCs
allow for: - greater flexibility in maneuvering small vessels such as capillaries - more hemoglobin to be contained within the cell, so more oxygen to be transported around the body
