CH 9 - Hemoglobin

Flashcards about Hemoglobin

What is Hemoglobin?

A red blood cell protein that carries oxygen from the lungs to the tissues.

What is Myoglobin?

Stores oxygen in muscle cells.

How is Oxygen binding measured?

Measured as a function of the partial pressure of oxygen (pO2).

What is the structure of Myoglobin?

A single polypeptide chain consisting mainly of α helices arranged to form a globular structure.

What is a heme?

A bound prosthetic group in both myoglobin and hemoglobin that binds oxygen.

What is protoporphyrin?

An organic component of heme.

What is ferrous iron (Fe2+)?

The form of iron found in the heme group.

What binds at the fifth coordination site of iron?

Binds the proximal histidine.

What binds at the sixth coordination site of iron?

Binds oxygen.

What is the structure of Hemoglobin?

A tetramer consisting of two α subunits and two β subunits, each with a bound heme.

How is the quaternary structure of Hemoglobin best described?

A pair of identical αβ dimers (α1β1 and α2β2).

What state does Deoxyhemoglobin correspond to?

Corresponds to the T state of allosteric enzymes.

What state does Oxyhemoglobin correspond to?

Corresponds to the R state.

When does the transition from deoxyhemoglobin (T state) to oxyhemoglobin (R state) occur?

Occurs upon oxygen binding.

What is the function of 2,3-Bisphosphoglycerate (2,3-BPG)?

Stabilizes the T state of hemoglobin and thus facilitates the release of oxygen.

Where does 2,3-BPG bind?

Binds to a pocket in the hemoglobin tetramer that exists only when hemoglobin is in the T state.

Do you predict that fetal α2γ2 hemoglobin binds 2,3-BPG better or worse than adult/maternal hemoglobin?

It would bind worse than adult/maternal hemoglobin.

How do Carbon dioxide and H+ affect oxygen release?

Enhance oxygen release by hemoglobin.

What are Carbon dioxide and H+ in relation to oxygen binding?

Heterotropic regulators of oxygen binding by hemoglobin.

What is the Bohr effect?

The stimulation of oxygen release by carbon dioxide and H+.

How does Low pH affect the oxygen affinity of hemoglobin?

Allows the formation of ionic interactions that stabilize the T state of hemoglobin, enhancing oxygen release.

What happens when CO2 reacts with terminal amino groups of both α and β subunits?

Forming negatively charged carbamate groups.

What disease is caused by a mutation resulting in a glutamine being replaced by valine at position 6 of the β chains?

Sickle-cell anemia.

What happens in Sickle-cell hemoglobin (HbS)?

The substituted valine is exposed in deoxyhemoglobin and can interact with other deoxy HbS to form aggregates that deform the red blood cells.

What is bicarbonate?

Much of the carbon dioxide in the blood is transported to the lungs as this.