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Gas Exchange

-Pathway for O2 flow
-Passive diffusion of gases
-enhancing diffusion
-Air vs. water O2 levels





Gas exchange with environment

-exchange CO2 and O2 via gas exchange structures




Gas molecules move from an area of ____ to ___ PARTIAL PRESSURE

P(atm) x % of air

P (O2) (N)

surface area x diffuse gradient/thickness

Diffusion Rate

Material properties

influence diffusion rates of gases (ex. dry vs moist skin)

Enhancing Diffusion 1

-Increased surface area (ex. aveoli in mammals)

Enhancing diffusion 2

-Decreased thickness of gas exchange membranes
-thin walls of aveoli
-thin walls of capillaries
-thin skin (amphibian)

Enhancing diffusion 3

-Increase diffusion gradient (PUMPS to move fluid)


O2 in water is variable; water holds less ________ than air

Gas molecules

___ ___ in air must dissolve in liquid (water)

Factors that affect gas solubility

-Properties of the gas: CO2>>O2>>N2
-Partial Pressure in air
-Temperature of water: solubility inversely related
-Dissolves solutes in water: solubility inversely related


Most O2 in blood bound to _______ in red blood cells (98.15%)


O2 solubility ____ in plasma (1.5%)

4 Oxygen

Hb can bind up to ___ ____ Molecules (saturated)

Blood pH

buildup and elimination of CO2 affects ___ ___

Decreased pH

affinity of Hb for O2 decreased with ______

O2 Uptake


O2 exchange


Carbon Dioxide transport

CO2 combines w/ H20 to form carbonic acid (H2CO3)

Carbon Dioxide Transport

reaction catalyzed by carbonic anhydrase

Carbon dioxide transport

H2CO3 dissociates into (H+) and bicarbonate (HCO3-)

Carbon dioxide transport

HCO3- released into plasma--->buffers H+ ions

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