Chapter 7

Question 1

Why are oxygen transport proteins necessary?

Answer 1

The diffusion of O2 and CO2 is insufficient for larger animals. O2 has a low solubility in plasma, and oxygen transport proteins can also serve to store oxygen.

Question 2

Describe the differences between myoglobin and hemoglobin

Answer 2

Myoglobin is a single polypeptide chain folded about heme, while hemoglobin is a tetrameric protein that binds 4 heme groups.

Question 3

What is an apoprotein and a holoprotein

Answer 3

An apoprotein is the polypeptide portion of a protein, while the holoprotein includes all prosthetic groups.

Question 4

Where does heme bind ?

Answer 4

A hydrophobic crevice

Question 5

How many coordinating groups can Iron have?

Answer 5

6

Question 6

Describe the coordinating groups of iron while it is bound to heme

Answer 6

the 4 nitrogen molecules of the porphryin occupy 4 of them, while the F8 histidine occupies the 5th.

Question 7

What increases the stability of oxygen binding heme?

Answer 7

the hydrogen bond between the distal histidine E7 and the o2.

Question 8

What purpose does the hydrophobic pocket serve in heme?

Answer 8

prevents the acid catalyzed oxidation of Fe(II) to Fe(III).

Question 9

What is metmyoglobin?

Answer 9

Fe3+ myoglobin

Question 10

How is oxidized heme corrected?

Answer 10

Erythrocytes contain reducing enzymes.

Question 11

Nitric oxide inhibits ______ ______. And is released by macrophages to destroy _____ _____.

Answer 11

Respiratory proteins. Invading organisms.

Question 12

What is henery’s law?

Answer 12

The concentration of gas diolved in fluid is proportional to partial pressure of gas above fluid.

Question 13

The R-State is also known as?

Answer 13

Oxyhemoglobin

Question 14

The T-sate is also known as?

Answer 14

Deoxyhemoglobin

Question 15

What tertiary feature stabalizes the t-state?

Answer 15

salt bridges

Question 16

What is the equation for the change in gibs free energy for bonding

Answer 16

-RTln(kd)

Question 17

what is the equation for theta?

Answer 17

L/(kd+L) or Po2/(p50+po2)

Question 18

What are the features of the Perutz mechanism?

Answer 18

In the deoxy state, heme has a dome shape, binding of o2 pulls the iron into the heme plane flattening the heme and causing strain. A shift in the orientation of his f8 relieves the strain, partly because val fg5 is pushed to the right.

Question 19

T and R are in equilibrium regardless of___?

Answer 19

whether or not o2 is present.

Question 20

When does sigmoidal binding arise?

Answer 20

When a low affinity binding, hyperbolic state switches to a high affinity, also hyperbolic binding state.

Question 21

Where is the p50 for hill plot?

Answer 21

the zero line

Question 22

What is the hill number?

Answer 22

The number of effectively interacting units.

Question 23

Describe the Bohr effect

Answer 23

O2 and H+ bind Hb in an inverse manner, HB releases O2 upon binding protons, and releases protons upon binding of o2. Increased proton concentration decreases O2 affinity and stabilizes the the T state.

Question 24

Do protons bind at the same site as o2? If not what are they called?

Answer 24

no, they are allosteric effectors

Question 25

Where is waste co2 carried by hemoglobin? What effect does co2 binding have on o2 affinity?

Answer 25

It is bound by amino group at n-term of the four chains to form carbamido-Hb. Decreases the affinity for o2.

Question 26

What is the mechanism of t state stabilization that co2 binding acts through?

Answer 26

creating a new salt bridge.

Question 27

Does myoglobin show a bohr effect?

Answer 27

No, because it is only a single subunit.

Question 28

What role does 2,3-Bisphosphate glycerate play?

Answer 28

HbBPG + O2 <> HBO2 +BPG. BPG Raises the p50.

Question 29

Describe fetal erythrocyte hemoglobin

Answer 29

Higher O2 affinity than HbA, alpha 2 gama 2

Question 30

In sickle cell anemia a point mutation in the gene is translated to____?

Answer 30

an amino acid change glu 6 to valine