Lecture 23: Hemoglobin and O2 transport

Question 1

what is meant by the saturation of hemoglobin

Answer 1

How many of the Hb binding sites of O2 are occupied

Question 2

dissolved oxygen (O2 in solution) is directly proportional to what

Answer 2

PO2
*only dissolved oxygen has a partial pressure and is available to tissues

Question 3

what does polypeptide (globin) bind

Answer 3

CO2 and H+

Question 4

what is meant by the concentration of oxygen in blood

Answer 4

the volume of gas dissolved in a volume of blood (usually a deciliter)

Question 5

how is oxygen transported in the blood

Answer 5

• dissolved in plasma
  -carried by Hb in RBCs

Question 6

O2 diffuses from alveoli to blood along its_____?

Answer 6

partial pressure gradient

Question 7

what is the strength of the bond b/w O2 and Hb

Answer 7

weak ish, O2 molecules dissociate easily from Hb when dissolved levels of O2 drop

Question 8

What is the effect of Hb on blood transport?

Answer 8

it increases blood transport by 50x

Question 9

Blood O2 concentration is a function of O2 ______?

Answer 9

partial pressure

Question 11

explain cooperativity of O2 and Hb

Answer 11

once one O2 binds, it increases the affinity for others to bind

Question 12

the binding of what molecules causes a change in the structure of Hb and decreases its affinity for O2

Answer 12

CO2 and H+

Question 13

at what PO2 is Hb 100% saturated

Answer 13

PO2’s above 100mmHg

Question 14

what is oxygen carriage directly dependent on

Answer 14

Hb content

Question 15

what does Erythropoietin do

Answer 15

stimulates RBC production (erythropoiesis) in bone marrow

Question 16

what stimulates the release of Erythropoietin

Answer 16

hypoxia and androgens

Question 17

what / where is erythropoietin produced

Answer 17

produced by interstitial cells in the capillary bed of the renal cortex

Question 18

At the level of tissues, what does metabolism cause an increase in and what is the result of these factors increasing

Answer 18

temperature
CO2 production
H+

these factors lower the affinity of Hb for O2 (promotes unloading of O2 at tissues = BOHR effect)

Question 19

what is the BOHR effect

Answer 19

increased CO2 levels lower blood pH, reducing the affinity of Hb for O2, causing Hb to unload more O2 at tissues

Question 20

what direction does the Hb sat. curve shift under carbon monoxide poisoning

Answer 20

left shift

Question 21

what conditions cause a right shift in the Hb saturation curve

Answer 21

increased 2,3 BPG
CO2, H+ (decreased pH)

Question 22

what causes an increase in the concentration of 2,3 BPG

Answer 22

hypoxia in peripheral tissues

Question 23

what is the effect of increased levels of 2,3 BPG

Answer 23

Hb saturation curve shifts right
increases the ability of RBCs to release oxygen (more O2 gets unloaded at tissues)

Question 24

what is the consequence of 2,3 BPGs effects not being reversed at the lungs

Answer 24

O2 loading may be inhibited

Question 25

effect of 2,3 BPG on Hb

Answer 25

causes an allosteric conformational change in Hb, reducing its affinity for O2

Question 26

what is hypoxia

Answer 26

insufficient O2 at the cellular level

Question 27

what is hypoxic hypoxia

Answer 27

PaO2, SaO2 and CaO2 all low
ex: high altitude, suffocating atmospheres

Question 28

what is anemic hypoxia

Answer 28

reducing carrying capacity of blood
CaO2 is low

Question 29

what is circulatory hypoxia

Answer 29

not enough oxygenated blood reaches the tissues
ex: heart failure, shock

Question 30

what is histotoxic hypoxia

Answer 30

O2 delivery is fine but cells are not able to use the oxygen
ex: cyanide poisoning

Question 31

why does PO2 remain high during carbon monoxide poisoning

Answer 31

b/c the tissues are not able to uptake O2

Question 32

how do nitrites affect Hb O2 saturation?

Answer 32

elevated levels of nitrite cause oxidation of Hb = methemoglobinemia

methemoglobin cannot bind O2 = functional anemia

Question 33

what enzyme converts methemoglobin back into hemoglobin

Answer 33

methemoglobin reductase

Question 34

what is the initial effect of altitude on animals

Answer 34

increased ventilation in order to increase tissue PO2
- this lowers PCO2 and raises pH

increased 2,3 BPG shifts curve right, increasing unloading of O2 at tissues

Question 35

what is the long-term effect of altitude on animals

Answer 35

an increased hematocrit raises blood O2 carrying capacity

increased capillary density increases tissue O2 delivery

Question 36

what is a potential negative side effect of an increased hematocrit?

Answer 36

increasing risk if heart attack or stroke caused by increased viscosity