reversible binding

[superduper12]

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what does it mean when it says that the oxygen in the blood binds reversibly with the protein hemoglobin in the erythrocytes to make oxyhemoglobin.

also EK says that "cosubstrates reversibly bind to a specific enzyme, and transfer some chemical group to another substrate."

can anyone clarify reversible binding?

 

[RPedigo]

what does it mean when it says that the oxygen in the blood binds reversibly with the protein hemoglobin in the erythrocytes to make oxyhemoglobin.

also EK says that "cosubstrates reversibly bind to a specific enzyme, and transfer some chemical group to another substrate."

can anyone clarify reversible binding?

It's reversible because it can unbind, which is a good thing. If it wasn't reversible, the oxygen would bind to the heme group and then it could never unbind it to deliver it to your cells. So it's just saying that it can bind (at the lungs) and then unbind (where it needs to go).

 

[superduper12]

so the molecule that reversibly binds is unaltered?...like oxygen does not change.

 

[Lukkie]

what does "binding" mean? things join together.

hemoglobin is not an enzyme. it BINDS oxygen to CARRY it through the body. its reversible so when it gets to a muscle cell for example it can release the oxygen.

enzymes BIND substrate and catalyze a REACTION. if the enzyme is doing its job, yes the molecule would be altered.

 

[sleepy425]

what does "binding" mean? things join together.

hemoglobin is not an enzyme. it BINDS oxygen to CARRY it through the body. its reversible so when it gets to a muscle cell for example it can release the oxygen.

enzymes BIND substrate and catalyze a REACTION. if the enzyme is doing its job, yes the molecule would be altered.

actually typical substrate binding to an enzyme is reversible as well, and the substrate can dissociate unaltered. however, in an enzyme, it's also possible for the product to be altered, and this reaction is also reversible (usually). finally, a product can reversibly bind to the enzyme. so in other words, pretty much every interaction with proteins, as well as every transformation, is reversible. hemoglobin has no significant catalytic ability so oxygen binding is reversible but there's no significant possibility of a forward reaction so what dissociates is oxygen, unaltered.

 

[dannySera]

what is the reversible binding of oxygen in heme? hydrophobic interaction? or van der waals force ? or hydrophilic interaction?

 

[chemist16]

The answer to this question is basically the crux of catalysis. When you have a catalyst (or enzymes in biological systems), a molecule/ligand can coordinate it and dissociate from it. The forward and reverse rates determine the kinetics of the reaction. Now, this is only if the ligation is reversible. If it's not, then that step is the rate-determining step and the ligand cannot dissociate. The kinetics for these reactions are very different.

Now, as someone said above, hemoglobin isn't catalyzing anything here. All it's doing is binding oxygen and transporting it somewhere else. Think of it as a train. Oxygen gets on the train at some point in your body and gets off at another point. It would be a really bad train if oxygen could get on, but not get off, right?

 

[Quinoline]

what is the reversible binding of oxygen in heme? hydrophobic interaction? or van der waals force ? or hydrophilic interaction?

It is called a coordination bond, oxygen donates 2 electrons to Fe2+ to fill its shell.

 

[chemist16]

what is the reversible binding of oxygen in heme? hydrophobic interaction? or van der waals force ? or hydrophilic interaction?

It is called a coordination bond, oxygen donates 2 electrons to Fe2+ to fill its shell.

I wouldn't even go so far as to call it a bond. If you're interested, take a look at transition metal chemistry or inorganic chemistry for a more in-depth explanation. By convention, we treat oxygen as a Lewis base so it "donates" an electron pair to iron. However, if you look at an electronegativity table, transition metals are not electronegative at all. So in reality, the electrons stay a lot closer to the ligand and so the nature of the bond is almost ionic. A good example is olefin coordination. The metal isn't really "bonding" with the olefin but rather coordinating (very weak interaction compared to a covalent bond) in a sigma fashion with the pi bond.