O2 and CO2 transport ; acid/base regulation

partial pressure of any gas =

total pressure of a gas x concentration of specific gas

P_gas =

ambient pressure x fraction of the gas

atmospheric O₂ at sea level

159 mmHg

atmospheric CO₂ at sea level

.3 mmHg

atmospheric N₂ at sea level

600 mmHg

dalton’s law

total pressure = partial pressure of all gases in a mixture

P_B

760 mmHg at sea level

henry’s law

gases diffuse from high to low pressure

• passive process

• depends on pressure differential and solubility of gas in the fluid

solubility

CO₂ is 20x more soluble/diffusible than O₂

normal PO₂

100

normal PCO₂

40

transport of O₂ in the blood

1. dissolved in plasma

2. combined with hemoglobin

O₂ dissolved in plasma

• establishes the PO₂ of the blood

• determines loading of hemoglobin

• regulates breathing when P_aO₂ falls below 60 mmHg

O₂ combined with hemoglobin

each of the 4 iron atoms associated with hemoglobin combines with one O₂ molecule

O₂ carrying capacity of hemoglobin

1g combines with 1.34 mL O₂

combining with hemoglobin vs dissolving in plasma

98.5% with hemoglobin and 1.5% dissolved in plasma

reduces O₂ carrying capacity

iron deficiency anemia, sickle cell, EPOO deficiency, and CO poisoning

A-_vO₂ difference

can increase 3 times the resting value during exercise

• arterial levels don’t normally change

bohr effect

• moves to left and right

• right shift:

increased PCO₂, increased temp, increased 2-3,-DPG, decreased pH

2,3 diphosphoglycerate

• byproduct of glycolysis

• helps deliver O₂ to tissues

RBC contain no mitochondria, rely on glycolysis

• increases with intense exercise

P₅₀ normal curve

27

myoglobin

• skeletal muscle can hold a single O molecule

• iron-containing globular protein in skeletal and cardiac muscle

• only 1 iron atom

→ not as efficient as hemoglobin

hyperbaric chamber

increases P_B to 2 atm

CO₂ transport

1. dissolved in plasma

2. bound to carbamino compounds

3. plasma bicarbonate

CO₂ dissolved in plasma

~5% os transported CO₂ reduces O₂ carrying capacity

• establishes PCO₂ gradient of the blood

CO₂ bound to carbamino compounds

• different site than O₂ on hemoglobin

• CO₂ reacts directly with amino acids to form carbamino compounds

• aids in releasing CO₂ in the lungs

haldane effect

hemoglobin’s interaction with O₂ reduces its ability to combine with CO₂

CO₂ and plasma bicarbonate

• CO₂ in solution combines with water to form carbonic acid

• primary

carbonic anhydrase

speeds things up more than 100,000 times

buffering

acids dissociate in solution and release H⁺

• bases accept H+ to form OH- ions

buffers

minimizes changes in pH

normal blood pH

7.35-7.45

alkalosis

higher than 7.4

acidosis

lower than 7.4