Lecture 27 blood

Question 1

Blood plasma

Answer 1

water + electrolytes (Na+, Cl-, K+, HCO3-, Ca2+), plasma proteins, glucose, urea, etc.

Question 2

Formed Elements

Answer 2

erythrocytes (RBCs) - 5,000,000/uL
leukocytes (WBCs) - 5,000-10,000/uL
platelets

Question 3

RBCs

Answer 3

are anucleated cells, filled with hemoglobin

blood cells are produced in red bone marrow from hematopoietic stem cells

Question 4

hematocrit

Answer 4

= % by volume of RBCs (normally 45%)

Question 5

erythropoietin

Answer 5

hormone produced by kidneys, stimulates production and differentiation of RBCs

Question 6

polycythemia

Answer 6

high RBC count (high hematocrit)

Question 7

anemia

Answer 7

low O2 carrying capacity of blood (low hemoglobin concentration)

Question 8

Hemoglobin structure and function

Answer 8

protein composed of 4 polypeptide (globin) subunits (2 a, 2B)
each subunit contains a heme group with iron (Fe2+) at the center
each heme reversibly binds O2 (-> 4 O2 binding sites)

Question 9

Oxygen transported by blood

Answer 9

1. O2 dissolved in plasma
2. O2 carried by hemoglobin
3. oxygen-hemoglobin dissociation curve
4. factors that affect O2 affinity of hemoglobin

Question 10

O2 dissolved in Plasma

Answer 10

low solubility of O2 in plasma
at Po2 = 100 mm Hg, plasma: 3 mL O2 / L blood
whole blood: 200 mL O2 / L blood

Question 11

O2 carried by hemoglobin

Answer 11

99% of O2 in blood is carried by hemoglobin

O2 carrying capacity of blood depends on hemoglobin concentration

Question 12

Hemoglobin-O2 binding

Answer 12

deoxyhemoglobin (Hb) + O2 -><- oxyhemoglobin (Hb O2)

Question 13

Binding and release of O2 depends on:

Answer 13

1. PO2 of the blood

2. affinity of hemoglobin for O2

Question 14

Oxygen Hemoglobin Dissociation Curve

Answer 14

relationship between Po2 of blood and percent O2 saturation of hemoglobin
S-shaped curve results from interactions among hemoglobin subunits -> promotes loading of O2 in the lungs and unloading of O2 in the tissues

Question 15

Normal Values (curve) (resting, sea level)

Answer 15

arterial Po2 = 100 mm Hg, 98% O2 saturation

venous Po2 = 40 mm Hg, 75% O2 saturation

Question 16

In lungs

Answer 16

Po2 = 100 mmHg

flat part of curve -> nearly 100% saturated

Question 17

In tissues

Answer 17

Po2 < 60 mm Hg -> rapid unloading of oxygen as Po2 decreases

Question 18

During exercise

Answer 18

tissues Po2 decreases -> more O2 released from Hb -> O2 sat. of venous blood

Question 19

Pulmonary disease

Answer 19

Pulmonary disease -> decrease arterial Po2 -> decrease O2 saturation (hypoxemia)

Question 20

At high altitude

Answer 20

decrease in arterial Po2 -> decrease O2 saturation

Question 21

Factors that affect O2 affinity of hemoglobin

Answer 21

1. increase temp -> decreases affinity (rightward shift of O2 dissociation curve)
2. decrease pH (increase [H+]) -> decreases affinity - (bohr shift)
3. increase PCO2 -> decrease affinity
4. increae 2, 3-DPG -> decreased affinity

Question 22

rightward shift

Answer 22

means more O2 will be unloaded from Hb at a given Po2

Question 23

in active tissues

Answer 23

increase temp, decrease pH and increase Pco2 promote unloading of O2

Question 24

Carbon Dioxide transport by blood

Answer 24

1. dissolved Co2 plasma (10%)
2. bicarbonate (70%)
3. carbamino hemoglobin (20%)

Question 25

Bicarbonate

Answer 25

Co2 + H20 -><- H+ + HCO3-
in tissues high PCO2 drives reaction forward to form HCO3-
in lungs, lower PCO2 pull reactions in reverse, HCO3- is converted back into CO2

Question 26

carbonic anhydrase

Answer 26

in RBC catalyzes conversion of CO2 to carbonic acid
CO2 is a major source of H+ in the body
increase PCO2 -> decrease pH

Question 27

Buffer

Answer 27

hemoglobin acts as a buffer of H+ formed by the reaction

Question 28

HCO3-

Answer 28

is transported from RBC out to plasma in exchange for Cl-

Question 29

carbamino hemoglobin

Answer 29

binding of Co2 to amino end of hemoglobin chains