Chapter 9 - Hemoglobin

Question 1

`Why does hemoglobin release only part of the bound oxygen?

Answer 1

Allosteric regulators from tissues can enhance further oxygen release on demand

Question 2

What does the ability of myoglobin and hemoglobin to bind oxygen depend on?

Answer 2

The presence of a heme group

Question 3

The Fe2+ in myoglobin and hemoglobin creates two binding sites. What are these binding sites occupied by?

Answer 3

The first is occupied by the imidazole ring of a histidine residue
The second is kept empty and is the place where oxygen can bind

Question 4

The quarternary structure of hemoglobin changes when binding oxygen. Explain what happens, using R and T state, BPG and oxygen affinity.

Answer 4

Deoxyhemoglobin is in the T-state

Hemoglobin is in the R-state

Question 5

How can tissues signal the need of oxygen?

Answer 5

They release the signal molecules hydrogen ions and carbon dioxide when actively metabolizing. These signals enhance oxygen release.

Question 6

How do CO2 and pH changes affect hemoglobin?

Answer 6

A decreased pH, decreases oxygen affinity. If CO2 is released, it is converted to carbonic acid, which lowers the pH inside the blood cell. CO2 can also bind to hemoglobin stabilizing deoxyhemoglobin

Question 7

What are two disease related to hemoglobin you can name? What happens in these diseases?

Answer 7

In Sickle-cell anemia, hemoglobin is mutated, forming a hydrophobic patch of deoxyhemoglobin, forming fibrous polymers. These fibers distort red blood cells.
In thalassemia, there is a reduced production of the alpha or beta chain, making hemoglobin tetramers with only one type of hemoglobin chain.