Chapter 9

Question 1

hemoglib

Answer 1

6

Question 2

myoglobin

Answer 2

10

Question 3

heme

Answer 3

5

Question 4

protoporphyrin

Answer 4

7

Question 5

proxumal histidine

Answer 5

9

Question 6

2,3-biphosphoglycerate

Answer 6

3

Question 7

sickle-cell anemia

Answer 7

4

Question 8

bohr effect

Answer 8

2

Question 9

carbonic anhydrase

Answer 9

1

Question 10

carbamate

Answer 10

8

Question 11

5. what is the physiological significance of the cooperative binding of oxygen by hemoglobin

Answer 11

cooperativity allows hemoglobin to become saturated in the lungs where oxygen pressure is high. when hemoglobin moves to tissues, the lower oxygen pressure induces it to release oxygen and thus deliver oxygen where it is needed. thus cooperative release favors more complete unloading of oxygen in tissues

Question 12

when crystals of deoxyhemoglobin are exposed to oxygen, the crystals shatter. why

Answer 12

deoxyhemoglobin is in T state. prescence of oxygen disrupts T/R equilibrium in favor or R state. structural changes are significant enough to cause the crystal to come apart

Question 13

the oxygen binding behavior of hemoglobin displays aspects of both the sequential model and the concerted model. explain

Answer 13

hemoglobin with oxygen bound to only one of four sites remains primarily in T state quaternary structure, an observation consistent with sequential model. hemoglobin behavior is concerted in that hemogobin with 3 sites occupied by oxygen is almost in almost always quaternary structure associated with R state

Question 14

8. what accounts for the fact that fetal hemoglobin has a higher oxygen affinity than maternal hemoglobin?

Answer 14

fetal hemoglobin does not bind 2,3 BPG as well as maternal hemoglobin does. right binding of 2,3 BPG by hemoglobin reduces oxygen affinity of hemoglobin

Question 15

how does hemoglobin S cause tissue damage?

Answer 15

Hemoglobin S molecules bind together to form large fibrous aggregates that extend across cell and giving shape. small blood vessels are blocked because of deformed cells, creating local region of low oxygen concentration. more hemoglobin changes into deoxy form and so more cells undergo sickling.

Question 16

hemoglobin A inhibits formation of long fibers of hemoglob S and subsequent sickling of red cell on deoxygenation. why does hemoglobin A have this effect?

Answer 16

deoxyhemoglobin A contains complementary site and so it can add to fiber of deoxyhemoglobin S. fiber cannot grow further because terminal deoxy Hb A lacks sticky patch.

Question 17

first protein to have its structure determined was myoglobin from sperm whales. propose explanation for observation that sperm whale muscle is rich source of protein.

Answer 17

whale swims long distances between breath. high concentration of myoglobin in whale muscle maintains ready supply of oxygen for muscle between breathing episodes

Question 18

describe role of 2,3 bisphosphoglycerate in funcation of hemoglobin

Answer 18

presence of 2,3 BPG shifts equilibrium toward T state. 2,3 BPG binds only to center cavity of deoxyhemoglobin (T state)
size of center cavity decreases on change to R form expelling 2,3 BPG and forming R state

Question 19

15. what is the bohr effect and what is its chemical basis?

Answer 19

regulation of hemoglobin oxygen binding by hydrogen ions and carbon dioxide. deoxyhemoglobin stabilized by ionic bonds that stabilize T state