Transcript Respiration Part 3 - Diffusion of gases

Respiration: Part 3
How does gas exchange happen?
 Substances diffuse from high concentrations to low
concentrations
 Example: Scent molecules move across a room
How does gas move into / out
of the blood?
 In the lungs:
 O2 moves from HIGH concentration in the alveoli to LOW
concentration in the blood
 CO2 moves from HIGH concentration in the blood to
LOW concentration in the alveoli
External Respiration
 Remember, this is the exchange between gases in the
AIR and the BLOOD
 It takes place in the lungs through alveoli and capillary
walls (each only one cell thick!)
How do you diffuse the most
O2 into the blood?
Lung Capillary
Alveolus
Hemoglobin
O2
O2
O2
O2
O2
O2 O2
O2
O2
O2
=
O2
O2
O2
O2
O2
O2
O2
O2
O2
O2
HIGH Concentration
LOW Concentration
What just happened?
 Breathe in and there is more O2 in the alveoli than in
the blood
 O2 moves from HIGH to LOW concentration
 Alveoli and blood are at the same concentration
 Hemoglobin took up four more O2
 Alveoli had more O2 than the blood again
 O2 moves from HIGH to LOW concentration
Result: We get MORE oxygen diffusing into the blood!
Helpful Hemoglobin!
 Hemoglobin contains iron
 There are 200 million per
red blood cell
O2
 4 O2 molecules can attach
to each Hb molecule
O2
 Increases carrying capacity
of O2 by 60 times
Internal
Respiration
 Exchange of O2 and CO2
between the BLOOD and
the TISSUES
 Cells have a LOW
concentration of O2
 Blood has a HIGH
concentration of O2
How does the O2 get from the
blood to the cells?
Body Cell
Body Capillary
Hemoglobin
O2
O2
O2
O2
O2
LOW Concentration
=
O2
O2
O2
O2
O2
O2
O2
O2
O2
O2
HIGH Concentration
What happened this time?
 Blood arrives with a HIGH concentration of O2
 Cells have a LOW concentration of O2
 O2 diffuses out of the blood into the cells (HIGH 
LOW)
 Hb gives up its four O2
 There is more O2 in the blood again
 More O2 diffuses out of the blood into the cells
Result: We get MORE oxygen diffusing into the cells!
O2
 Consider this reaction:
Hb + O2
(hemoglobin + O2)

O2
HbO2
(oxyhemoglobin)
Why will this help you to diffuse more oxygen into the blood?
When there is lots of O2 the reaction shifts this way:
Hb + O2  HbO2
Happens in LUNGS
When there is lots of HbO2 the reaction shifts this way:
Hb + O2

HbO2
Happens in TISSUES
How do we maximize the
transfer of O2 using Hb?
 Effect of temperature:
 Hb gives up O2 better at higher temperatures
 Hb attaches to O2 better at lower temperatures
 Effect of pH:
 At higher or neutral pH, Hb attaches to O2 better
 At lower pH, Hb gives up O2 better
What are the best conditions?
 For TAKING UP O2?
 pH = High pH (Basic)
 Temperature = Low Temperature (Cool)
Lungs
 This occurs in the _________________.
 For GIVING AWAY O2?
 pH = Low pH (Acid)
 Temperature = High Temperature (Hot)
Tissues
 This occurs in the _________________.
What happens with CO2?
 CO2 also diffuses from HIGH to LOW concentration
 In the lungs:
 Blood is HIGH in CO2  Alveolus is LOW in CO2
 In the tissues:
 Cells are HIGH in CO2  Blood is LOW in CO2
 Some CO2 changes into carbonic acid (H2CO3) in the
blood
 This lets more CO2 diffuse in from the cells
ALVEOLAR SPACE IN LUNG
CO2
CO2 produced
INTERSTITIAL
FLUID
CO2
CO2
BLOOD
PLASMA
WITHIN
CAPILLARY
CO2
Capillary
wall
CO2
CO2
CO2
H2O
H2O
RED
BLOOD
CELL
Hemoglobin
picks up
CO2 and H+
H2CO3
HCO3–
HCO3–
+
H+
Hemoglobin
releases
CO2 and H+
H2CO3
HCO3–
HCO3–
+
H+
Why is carbon monoxide poisonous?
CO + Hb   HbCO
Carbon monoxide + hemoglobin
carboxyhemoglobin
 Hb has an affinity for carbon monoxide 230 times
greater than its affinity for O2
 Hemoglobin can’t carry oxygen because it is
taken up with carbon monoxide