Globin and Protein Function Model

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What is the primary function of oxygen transport systems in large animals?

To allow for the transport of dissolved gas alone

To enable the circulation of respiratory molecules

To facilitate the pickup and release of oxygen at different locations (correct)

To provide respiratory molecules and cells for transport and storage

What is the key prosthetic group that allows globin proteins to bind oxygen?

The distal histidine residue

The ferrous (Fe2+) oxidation state of the iron atom

The porphyrin ring with a central metal atom (correct)

The proximal histidine residue

How does the iron atom in the heme group interact with oxygen?

The iron atom temporarily accepts an electron from oxygen, forming a superoxide radical (correct)

The iron atom is oxidized to the ferric (Fe3+) state, which prevents oxygen binding

The iron atom binds oxygen directly, forming a stable complex

The distal histidine residue forms a hydrogen bond with the oxygen molecule

What is the role of the proximal and distal histidine residues in the heme pocket?

The proximal histidine binds the iron atom, while the distal histidine stabilizes the oxygen binding Signup and view all the answers

What is the significance of the Bohr effect in the regulation of hemoglobin?

It decreases the affinity of hemoglobin for oxygen at low pH Signup and view all the answers

How does fetal hemoglobin differ from adult hemoglobin in its oxygen-binding properties?

Fetal hemoglobin has a higher affinity for oxygen, allowing it to obtain oxygen from the mother's bloodstream Signup and view all the answers

What is the role of distal histidine in hemoglobin?

It inhibits methemoglobin formation. Signup and view all the answers

How does hemoglobin enhance selectivity for oxygen?

By preventing the release of toxic superoxide. Signup and view all the answers

How do myoglobin (Mb) and hemoglobin (Hb) differ?

Hb is a monomer, while Mb is a tetramer. Signup and view all the answers

What effect does oxygen binding have on the magnetic properties of iron in hemoglobin?

The iron becomes paramagnetic upon O2 binding. Signup and view all the answers

What happens to the Fe ion when oxygen binds to hemoglobin?

Fe ion increases its oxidation state. Signup and view all the answers

In a simple binding reaction, what determines the equilibrium between P + L and PL?

[P], [L], rate constants, and temperature. Signup and view all the answers

What structural change occurs in hemoglobin when oxygen binds?

The alpha helix shifts slightly, altering the alpha-beta interface Signup and view all the answers

Why is the affinity of hemoglobin for oxygen lower in red blood cells compared to in vitro conditions?

The presence of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells Signup and view all the answers

What is the primary function of 2,3-bisphosphoglycerate (2,3-BPG) in regulating hemoglobin activity?

It stabilizes the T (tense) state of hemoglobin, decreasing oxygen affinity Signup and view all the answers

How does fetal hemoglobin differ from adult hemoglobin?

It consists of alpha and gamma globin chains instead of alpha and beta Signup and view all the answers

What is the significant change in fetal hemoglobin that affects its interaction with 2,3-BPG?

The histidine at position 143 is replaced by serine Signup and view all the answers

What is the Bohr effect in relation to hemoglobin?

The decrease in hemoglobin's affinity for oxygen at lower pH Signup and view all the answers