CHAPTER 8 Hemoglobin, an Allosteric Protein

Mike Ames Doug Balmer

Loreen Holstein

Pre-survey

Hemoglobin is an allosteric protein.

What does the prefix “allo” mean?

A. In B. Out C. Same D. Different E. Soothing

Pre-survey

Hemoglobin is an allosteric protein.

What does the suffix “steric” mean?

A.  repulsion B.  geometry/shape C.  clean D.  regulator E.  inhibitor

Pre-survey Hemoglobin is an allosteric protein.

Put together, allosteric means that a hemoglobin changes its activity based on a

“difference in shape”

Pre-survey

What element is at the center of the heme group? Enter the symbol

?

Pre-survey

What charge does iron have when O2 is not attached (deoxyhemoglobin)?

Which protein structure is myoglobin missing?

A)  1º

B)  2º

C)  3º

D)  4º

What is the highest protein structure for hemoglobin?

A)  1º

B)  2º

C)  3º

D)  4º

The pO2 in the lungs is 100 torr. Which would be better at picking up oxygen in the lungs?

A

Hemoglobin

B

The pO2 in tissues is 20 torr. Which would be most likely to release oxygen?

A

Hemoglobin

B

Myoglobin has a much greater affinity for O2 at the tissues

Myoglobin picks up O2 from

hemoglobin at the capillaries and

transfers the O2 to the tissues that

need it.

If deoxyhemoglobin starts with Fe2+, what charge will the iron have in

oxyhemoglobin?

Fe2+ vs. Fe3+ Which is Smaller?

Electron Configurations

A) Fe2+ : 4s0 3d5 B) Fe3+ : 4s0 3d4

Proximal Histidine

A histidine ring is attached to the iron ion. As the iron moves into the protoporphyrin ring, the histidine as well as the attached α-helix shift. This changes the 4º structure of hemoglobin.

Besides the 15º twist, use one word to describe a difference between the two conformations.

Allosteric Regulator

BPG fits in the deoxyhemoglobin pocket, making deoxyhemoglobin more stable.

BPG pocket

Allosteric Regulator How does BPG affect the

affinity of hemoglobin for O2?

A)  Increases O2 affinity in the lungs

B) Decreases O2 affinity in the lungs

C)  Increases O2 affinity in the tissue

D) Decreases O2 affinity in the tissue

When pH drops, what happens

to hemoglobin’s

affinity for oxygen?

A)  It increases

B)  It decreases

C)  Stays the same