Transport of O2 and CO2 in blood

Question 1

In blood, what generates the partial pressure to drive diffusion?

Answer 1

DISSOLVED GAS only!

Question 2

How much O2 content in blood is dissolved?

Answer 2

.3%

Its there to provide O2 when needed

Question 3

How much O2 in blood is conjugated to Hb?

Answer 3

99.7%

Question 4

What is the composition of Hb?

Answer 4

2 alpha, 2 beta chains,
each chain bound to a heme group
Each heme group can bind 1 O2 molecule using Fe2+
Meaning adult Hb can bind 4 O2 molecules

Question 5

What is Methemoglobin?

Answer 5

when iron is Fe3+ rather than Fe2+
DOES NOT BIND O2!
This oxidation happens due to Nitrates and sulfonamides OR a deficiency in methemoglobin reductase

Question 6

What is different about Fetal Hb (HbF)?

Answer 6

Two beta chains, two gamma chains
Higher affinity for binding O2 than Hemoglobin A
l

Question 7

What is Hemoglobin S?

Answer 7

Causes sickle cell disease
Alpha subunits normal, BETA subunits abnormal
Lower affinity for O2 than HbA and can change shape

Question 8

What is O2 binding capacity?

Answer 8

The maximum O2 volume that can combine with Hb
1.34 mLO2/gHb
Blood Hb concentration = 15g/dL
1.34x15=20.1 mLO2/dL
All this depends on Hb concentration and binding properties

Question 9

What is O2 content mean?

Answer 9

The ACTUAL amount of O2 per volume of blood

O2 content=O2 binding capacityxSaO2+Dissolved O2

Question 10

How do you calculate O2 delivery?

Answer 10

O2 delivery = Cardiac Output x O2 Content

Question 11

What are the axes for the Hb dissociation curve?

Answer 11

Hemoglobin saturation (y) and PO2 (x)

Question 12

Why is the top of the Hb dissociation curve flat?

Answer 12

ensures a relatively contant oxyhemoglobin saturation despite changes in PO2
Starts at about 40 mmHg

Question 13

Why is the bottom of the Hb dissociation curve steep?

Answer 13

At decreased amount of PO2, O2 gets dumped from the Hb.
In tissues this is important
15-40mmHg

Question 14

Under normal conditions, How much O2 is transported from the lungs to the tissues per 100mL blood flow?

Answer 14

5 mL
PO2 is about 40 mmHg
Hb saturation is about 75

Question 15

What is the upper limit that Hb sets on tissue PO2?

Answer 15

40mmHg
divides flat upper from steep lower
below this point O2 is automatically delivered to the tissues

Question 16

What is the P50 of O2-Hb dissociation curve?

Answer 16

The PO2 when Hb is 50% saturated with O2
Normal value is 27mmHg
Used as an indicator for affinity of Hb for O2
Value changes depending on location in teh body

Question 17

What does increased P50 value mean?

Answer 17

Weaker affinity of Hb for O2

HbO2 releases O2 more easily

Question 18

What does decreased P50 mean?

Answer 18

Higher affinity of Hb for O2

HbO2 less ready to release O2

Question 19

How does temperature affect the Hb dissociation curve?

Answer 19

Increased temperature (fever) shifts the curve to the right = weaker affinity
Decreased temperature (hypothermia) shifts curve to the left = higher affinity, preserve O2

Question 20

How does pH affect the Hb dissociation curve?

Answer 20

Decreased pH = shift right
increased pH = shift left
Exercise = increased lactic acid production
also hypoxemia, kidney failure, ketoacidosis dec pH

Question 21

How does the PCO2 level affect the Hb dissociation curve?

CO2 Bohr effect

Answer 21

Increased CO2 levels = shift right
Think of anything that happens in the tissues shifts the curve to the right = release of O2
CO2 binds with higher affinity to Hb and kicks it off

Question 22

How does 2/3-DPG levels affect Hb dissociation curve?

Answer 22

Increased levels = shift right, less affinity

Question 23

What is 2/3-DPG?

Answer 23

an end product of RBC metabolism
Increased in Chronic hypoxia, anemia, high altitude
DECREAsED IN STORED BLOOD

Question 24

What are the toxic effects of Carbon monoxide?

Answer 24

CO binds Hb at the same point on the molecule as O2, but with 250x the affinity
The PaO2 will remain about normal even though O2 content is low.
The Hb that hasnt been bound by CO will bind O2 much more tightly
Tx: hyperbaric chamber

Question 25

How is CO2 transported from the tissues to lungs?

Answer 25

Secreted by tissues to plasma - 7% remains dissolved here
Rest diffuses into the RBC
70% combines with water to form bicarb and H+ = Dec pH
23% binds to HHb to form Carbaminohemaglobin

Question 26

How much of the RBC CO2 gets converted to bicarb?

Answer 26

70%

Question 27

How much of the RBC CO2 gets converted to Carbaminohemaglobin?

Answer 27

23%

Question 28

How Much CO2 remains dissolved in teh PLasma?

Answer 28

7%

Question 29

What is the Haldane effect?

Answer 29

A higher PO2 will shift the CO2 equilibration curve downward and to the right
This allows more CO2 to be loaded in the tissues and unloaded in the lungs