Myoglobin and Hemoglobin Review

These flashcards cover key concepts pertaining to myoglobin and hemoglobin structure, function, and binding mechanisms.

What is myoglobin primarily responsible for in muscle tissue?

Myoglobin is primarily responsible for oxygen storage in muscle tissue.

What type of protein is hemoglobin and its primary function?

Hemoglobin is a tetrameric protein responsible for transporting oxygen in the bloodstream.

What structural feature of the heme group enables oxygen binding?

The heme group contains a bound iron atom in its ferrous (Fe2+) state which facilitates oxygen binding.

How does carbon monoxide (CO) compare to oxygen in terms of binding affinity to heme?

CO binds over 20,000 times better to heme than oxygen due to its ability to donate a lone electron pair to iron.

What is the significance of the distal histidine (His E7) in myoglobin?

The distal histidine forms a hydrogen bond with bound O2, stabilizing the Fe-O2 complex and increasing heme's affinity for oxygen.

What is the effect of ligand binding on protein conformational changes?

Ligand binding can induce structural changes in proteins, altering their function and stability.

How many heme groups are present in hemoglobin?

Hemoglobin contains four heme groups, one in each globin subunit.

What is Kd in the context of ligand binding?

Kd, or the dissociation constant, measures the affinity of a ligand for a protein; a smaller Kd indicates higher affinity.

What does a higher Ka indicate when comparing two proteins' binding affinities for a ligand?

A higher Ka indicates a higher affinity of the ligand for the protein.

How does hemoglobin's structure differ from that of myoglobin?

Hemoglobin is tetrameric (four polypeptide chains) while myoglobin is monomeric (one polypeptide chain).

What are the main functions of the different types of globins found in humans?

Myoglobin facilitates O2 diffusion in muscle tissue, hemoglobin transports O2 in the blood, neuroglobin protects neurons from low O2, and cytoglobin regulates nitric oxide levels.

Define the term 'quaternary structure' as it pertains to hemoglobin.

Quaternary structure refers to the arrangement and interactions between the multiple subunits of a protein, such as the α and β chains in hemoglobin.

What role do proximal and distal histidines play in oxygen binding in hemoglobin?

The proximal histidine coordinates the iron of heme, while the distal histidine stabilizes the bound O2, facilitating reversible binding.

What is the significance of the cooperative binding mechanism of hemoglobin?

Cooperative binding allows hemoglobin to increase its oxygen affinity as more O2 molecules bind, enhancing its efficiency in oxygen transport.

Describe the changes in hemoglobin structure upon oxygen binding.

Oxygen binding to hemoglobin alters its quaternary structure, transitioning from a deoxy (T state) to an oxy (R state) form.