Lecture 17: The rest

Question 1

What is 2,3-Bisphosphoglycerate (BPG) essential for?

Answer 1

The formation of the T state of Hb

Question 2

What happens if there is no 2,3-Bisphosphate present?

Answer 2

Hemoglobin doesn’t adopt the T state

Question 3

What would the oxygen binding curve of Hb look like without BPG present?

Answer 3

It would be hyperbolic

Question 4

What is the charge of BPG?

Answer 4

It carries a strong negative charge

Question 5

What kind of effector is BPG?

Answer 5

It is a negative allosteric effector

Question 6

What does BPG do to hemoglobin?

Answer 6

It decreases Hb’s affinity for O2

Question 7

What state does BPG bind to?

Answer 7

The T-state

Question 8

How many BPG binding sites are there for each Hb?

Answer 8

There is one BPG binding site for each Hb

Question 9

What is the BPG binding sites found between?

Answer 9

Between the subunits of the hemoglobin quaternary structure

Question 10

What cavity does BPG bind in?

Answer 10

The central cavity of deoxyhemoglobin

Question 11

What do the negative charges on BPG interact with?

Answer 11

Positively charged groups on the protein that are directed into the central cavity

Question 12

What positively charged groups interact with BPG?

Answer 12

• 4 Lysine
• 2 Lysine
• 2 N-terminal residues

Question 13

What is the size of the central cavity of the hemoglobin in the T state and in the R state?

Answer 13

In the T state the cavity is larger

Question 14

Which direction would a negative allosteric inhibitor shift a hemoglobin binding curve?

Answer 14

It would shift the curve right

Question 15

What ions does Metabolism generate?

Answer 15

Protons

Question 16

Through what reactions does BPG increase protons (lower pH)?

Answer 16

• ATP + H2O ➡️ ADP + P + H+

* CO2 + H2O ➡️ HCO3- + H+

Question 17

How does lowering the pH affect the side chains of Hb functional groups?

Answer 17

It causes protonation
•His + H+ ➡️ His+
•-NH2 + H+ ➡️ NH3+

Question 18

What happens when groups associated with BPG binding become protonated because of low pH?

Answer 18

They Enhance BPG binding and reduce O2 binding

Question 19

What happens to carbon dioxide when it appears in the blood stream?

Answer 19

It is converted to carbonic acid which lowers the pH in the blood stream

Question 20

How is the subunit interface in hemoglobin affected by lower pH?

Answer 20

New electrostatic interactions form

Question 21

What is the Bohr effect?

Answer 21

• Enhance binding of BPG and reduced binding of O2 associated with increased protons
• Hemoglobin subunit interface forming new electrostatic interactions

Question 22

What is the difference in pH between the blood in the lungs and in skeletal muscle?

Answer 22

•The pH of blood in the lungs is 7.6
•The pH of blood in skeletal muscle is 7.2
Blood in skeletal muscle is more acidic

Question 23

How is oxygen binding affected by an increase in proton concentration?

Answer 23

There will be a decrease in oxygen binding behavior

Question 24

How is oxygen binding affected by an decrease in proton concentration?

Answer 24

There will be increased oxygen binding

Question 25

What does the proportion of molecules that are in either the T or the R state depend on?

Answer 25

The presence of BPG, [H+] ions and the PO2

Question 26

What are the characteristics pH and partial pressure of O2 in the lungs?

Answer 26

The lungs have a high PO2 and a high pH

Question 27

What hemoglobin state is favored in the lungs?

Answer 27

The R state

Question 28

What are the characteristics pH and partial pressure of O2 in the the peripheral tissues?

Answer 28

They have a low pH and a low PP of O2