Flashcards in Chapter 7 Terms Deck (38):
The ability of myoglobin and hemoglobin to bind oxygen depends on the presence of this bound prosthetic group. It consists of an organic component and a central iron atom.
Is made up of 4 pyrrole rings linked by methine bridges to form a tetrapyrrole ring.
In myoglobin, the fifth coordination site is occupied by the imidazole ring of a histidine residue from the protein, which is referred to as the __________ histidine.
One of the most powerful methods for examining brain function. This noninvasive technique identifies areas of the brain that process sensory information.
Functional magnetic resonance imaging (fMRI)
When released, the effects are reactive and damaging; also, it would leave the ferric ion, which is not oxygen binding.
Does not bind oxygen.
Is what keeps the O2 bound to the heme; it donates an H+ bond to the O2.
A set of alpha helicies that make up both myoglobin and hemoglobin.
A set of beta linkages that make up both myoglobin and hemoglobin.
Hemoglobin subunit that contains alpha helicies that are identical to the helicies of myoglobin.
Dimers that associate to form the tertramer, hemoglobin.
A plot of the fractional saturation versus the concentration of oxygen. It is used to determine the oxygen-binding properties of myoglobin and hemoglobin.
Is defined as the fraction of possible binding sites that contain bound oxygen. The values can range from 0 (all sites empty) to 1 (all sites filled).
The concentration of oxygen in a oxygen-binding curve is most conveniently measured by its ______ _______.
Plotted curves that resemble an "S".
The binding reactions at individual sites in each hemoglobin molecule are not independent of one another. The binding of O2 at one site in the hemoglobin tetramer influences the O2 binding properties at the other sites.
The quaternary structure observed in the deoxy form of hemoglobin, deoxyhemoglobin, is often referred to as the _____ state, because it's quite constrained by subunit-subunit interactions.
T state; Tense state
The quaternary structure of the fully oxygenated form of hemoglobin, oxyhemoglobin, is referred to as the _____ state, because it's less constrained.
R state; Relaxed state
The binding model that states the overall assembly can exist in only 2 forms: the T state and the R state. The binding of ligands simply shifts the equilibrium between these two states.
Concerted model (MWC model)
The binding model that states the binding of a ligand to one site in an assembly increases the binding affinity of neighboring sites without inducing a full conversion from the T into the R state.
Lowers the O2 affinity of hemoglobin; keeps hemoglobin from binding O2 tightly; is necessary for hemoglobin for releasing O2 in designated tissues.
Tetramers include two alpha chains and two gamma chains. The O2 affinity of hemoglobin is higher in infants than in adults. The gamma chain is 72% identical to the beta chain, the difference being a substitution in the 2,3-BPG binding site which as a result reduces the affinity of 2,3-BPG.
Is a colorless, odorless gas that binds to hemoglobin at the same site as oxygen. Is very dangerous.
A complex formed when CO binds to hemoglobin at the oxygen binding site.
The regulation of oxygen binding by hydrogen ions and CO2 is called the _____ effect.
An enzyme abundant in red blood cells that accelerates the reaction between CO2 and H2o to form carbonic acid, H2CO3.
When carbon dioxide reacts with the terminal amino groups of deoxyhemoglobin, it forms this negatively charged group.
A blood disease; hemoglobin molecules form large fibrous aggregates; poor circulation; impaired blood flow; clogging of small capillaries.
The mutated form of hemoglobin where a substitution has occurred in the beta chain: glutamate residue replaced with a valine residue.
A disease caused by a parasite, Plasmodium falciparum, that lives within red blood cells at one stage in its life cycle.
A blood disease; caused by the loss or substantial reduction of asingle hemoglobin chain. The result is low levels of functional hemoglobin and a decreased production of red blood cells, which may lead to anemia.
These hemoglobin tetramers lack a sufficient amount of alpha chains, and thus bind oxygen with high affinity and no cooperation, resulting in poor oxygen release in tissues.
The most severe form of beta-thalassemia is called _____ ______.
Thalassemia major (Cooley anemia)
This protein forms a soluble complex specifically with newly synthesized alpha chain monomers. The protein binds to the same face of alpha-hemoglobin as does beta-hemoglobin, and in both the oxygenated and deoxygenated forms. It serves to bind and ensure the proper folding of alpha-hemoglobin as it is produced.
alpha-hemoglobin stabilizing protein (AHSP)
Is expressed primarily in the brain and at especially high levels in the retina. It may play a role in protecting neural tissues from hypoxia (insufficient oxygen).
Is expressed more widely throughout the body. In both this and neuroglobin, the proximal and the distal histidines are coordinated to the iron atom in the deoxy form. Oxygen binding displaces the distal histidine.
A useful way of quantitatively describing cooperative binding processes such as that for hemoglobin.