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What does heme mean?
Iron
What is hemoglobin?
An iron containing respiratory protein found within red blood cells (RBC)
What is the ratio of RBC to hemoglobin?
There are about 200-250 million hemoglobin molecules per RBC
What does hemoglobin do?
Increases the oxygen carrying capacity of the blood by 60-70%
What is the structure of hemoglobin?
It is composed on 4 polypeptide chains (tetramer, quaternary structure) connected to 4 heme groups (which contain iron)
How many oxygens bond to one hemoglobin?
The oxygen forms a loose association with the iron portion in hemoglobin
One hemoglobin can carry 4 O2’s
When does hemoglobin take oxygen up?
It takes up O2 in increasing amounts as the pressure of O2 increases
What conditions allow Hb to take up O2 more readily?
In low temperatures and basic pH (lungs 37º, 7.4 pH)
What conditions allow Hb to give up O2 more readily?
At higher temperatures and acidic pH (body tissues, 38º, 7.3 pH)
What is external respiration?
Gas exchange between the lungs (alveoli) and the blood
What does the concentration of oxygen and carbon dioxide in the alveoli?
Oxygen concentration is high (20% of air) and carbon dioxide is low (0.5% of air)
What does the concentration of oxygen and carbon dioxide in the the blood?
Oxygen concentration is low and carbon dioxide concentration is high
Why is oxygen concentration in the blood low?
Many oxygen molecules have been used to make ATP
Why is carbon dioxide concentration in the blood high?
It is a byproduct of cellular respiration in the tissues
Where do the gases diffuse?
From [H] to [L]
Between the alveoli/bloodstream, which gases diffuse where?
Oxygen diffuses into the pulmonary (lung) capillaries
Carbon dioxide (and some water) diffuses out into the air of the alveoli to be exhaled
What are the conditions in the blood at the alveoli?
pH of 7.4 (more basic)
Temperature of 37ºC (cooler)
What is the combination of hemoglobin and oxygen called?
Oxyhemoglobin (HbO2)
What colour is the blood when it is rich in oxyhemoglobin?
Red
What is the equation for hemoglobin and oxygen?
Hb + O2 → HbO2
Where does hemoglobin bind to oxygen?
In the blood at the alveoli
What is internal respiration?
Gas exchange between the blood and tissues
What does the concentration of oxygen and carbon dioxide look like in the blood before capillary fluid exchange?
Oxygen concentration is high and carried as HbO2, carbon dioxide is low
What does the concentration of oxygen and carbon dioxide look like in the tissues?
Oxygen concentration is low and carbon dioxide concentration is high
Why is oxygen concentration high and carbon dioxide concentration low in the tissues?
Oxygen is always used up to make ATP, carbon dioxide is produced as a waste product in cellular respiration
Between the blood and the tissues, where does carbon dioxide diffuse and where does oxygen diffuse?
From [H] to [L]
Oxygen diffuses into the tissues, carbon dioxide diffuses into the blood capillaries to be returned to the lungs
What are the conditions in the blood at the tissues?
pH of 7.3, more acidic
Temperature of 38º, warmer
In what conditions does hemoglobin readily release oxygen?
At the beginning of the capillary beds, in more acidic and warmer temperatures
What happens when the oxyhemoglobin reaches the tissues?
The oxygen diffuses into the tissues and the hemoglobin is now free to transport
What is the reverse equation for oxyhemoglobin?
HbO2 → Hb + O2
What happens at the end of the capillary bed?
Carbon dioxide enters the blood
What are the three ways carbon dioxide can be transported
Bicarbonate ions, carbaminohemoglobin, carbon dioxide
How much of the carbon dioxide in the blood is transported as bicarbonate?
Most, 7%
How is carbon dioxide transported as bicarbonate?
CO2 reacts with water in the plasma under the influence of the red blood cell enzyme carbonic anhydrase to be transported as bicarbonate ions
What is the equation for CO2 to bicarbonate ions?
CO2 + H2O → (facilitated by carbonic anhydrase) → H2CO3 (carbonic acid) → (facilitated by carbonic anhydrase) → HCO3 (bicarbonate ion) + H+
What happens to the bicarbonate ions after they are created?
They are one of the most widely recognized buffers in the human body and are transported freely in the blood plasma
What happens to the hydrogen ions after they are created?
They would cause a decrease in the pH if transported freely in the plasma, so they bind onto hemoglobin
What is the combination of hemoglobin and hydrogen ions called?
Reduced hemoglobin HHb
What is the equation to create reduced hemoglobin?
H+ + Hb → HHb
What is hemoglobin considered since it creates reduced hemoglobin?
It is often considered a buffer in the blood as it counteracts the otherwise inevitable drop in pH
How much carbon dioxide turns into carbaminohemoglobin?
Some, 23%
What is the equation for carbaminohemoglobin?
Hb + CO2 → HbCO2
How much carbon dioxide stays in the blood?
Very little, 7%
What happens to the carbon dioxide that stays in the blood?
It is transported as a dissolved CO2 gas in the plasma
Why would some CO2 need to stay in the blood?
It helps with the concentration gradient of oxygen and carbon dioxide
What characteristics does the deoxygenated blood arriving back at the alveolar capillaries have?
It is transporting bicarbonate ions and a little CO2 gas
The hemoglobin is transporting either CO2 or H+ ions (HbCO2 or HHb)
What 2 things happen when the deoxygenated blood arrives back at the alveolar capillaries?
Due to the conditions of the blood at the alveoli (cold, basic, low pressure), the hemoglobin lets go of the CO2 and H+ and the enzyme carbonic anhydrase catalyzes the reverse reaction it did before
What are the equations for hemoglobin letting go of the CO2 and H+?
HbCO2 → Hb + CO2
HHb → Hb + H+
What reverse reaction does carbonic anhydrase facilitate?
HCO3- + H+ → H2CO3 → CO2 + H2O
What happens to the CO2 after is it created by carbonic anhydrase or released by hemoglobin?
It diffuses into the alveoli to be exhaled
What three things can happen to the H2O created by carbonic anhydrase?
It can also be exhaled
Enter the alveoli and stay to keep them moist
Remain in the plasma/blood
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