11.3 Gas Exchanges in the Body Flashcards
What is respiration?
the exchange of gases in the lungs (external respiration) and the exchange of gases in the tissues (internal respiration
Where is most of the O2 carried in the blood?
attached to the iron-containing heme portion of the protein hemoglobin (Hb) found in red blood cells
What is hemoglobin?
iron-containing respiratory pigment occurring in red blood cells
What is external respiration?
the exchange of gases between air in the alveoli and blood in the pulmonary capillaries
What is partial pressure and what are its symbols?
the amount of pressure each gas exerts
PO2 and PCO2
Where is PCO2 higher?
blood in the pulmonary capillaries has a higher PCO2 than atmospheric air does therefore CO2 diffuses out of the plasma into the lungs
What are bicarbonate ions?
the form in which most of the CO2 is carried in the plasma
What is carbonic anhydrase?
an enzyme present in red blood cells that speeds the breakdown of carbonic acid (H2CO3) as free CO2 begins to diffuse out of the plasma during external respiration
What is the external respiration reaction equation?
CA
H+ + HCO3- —–> H2CO3 —–> H2O + CO2
hydrogen ion + bicarbonate ion —–> carbonic acid —–> [with carbonic anhydrase] water + carbon dioxide
What happens when you hyperventilate?
- remove more CO2 and pushing the external respiration reaction even further to the right
- blood will have fewer H+
- RESPIRATORY ALKALOSIS (high blood pH) results
What are symptoms of hyperventilation? What occurs after hyperventilation?
- breathing at a high rate
- breathing will be inhibited
- dizzy and disoriented
What happens when you hypoventilate?
holding your breath
- drives the external respiration reaction to the left
- H+ builds up in the blood
- RESPIRATORY ACIDOSIS (low blood pH) occurs
What does increased H+ and CO2 levels do?
stimulates your respiratory centre, and your breathing rate will most likely increase
if not, you might be confused, sleepy or comatose
Describe the pressure pattern for O2 during external respiration.
REVERSE OF THAT OF CO2
- blood returning from the systemic capillaries has a lower PO2 than alveolar air does therefore in the lungs, O2 diffuses into plasma and then into red blood cells
What is oxyhemoglobin?
HbO2
compound formed when oxygen combines with hemoglobin
How is oxyhemoglobin formed during external respiration?
since hemoglobin has a higher affinity for oxygen at lower temperatures and higher pH, it takes up oxygen and becomes oxyhemoglobin (HbO2)
Hb + O2 —-> HbO2
What is used during normal external respiration?
only a relatively small percentage of the oxygen present in atmospheric air
What percentage of oxygen is in the air at sea level?
air contains about 21% O2, and exhaled air contains 16-17% O2
What does the inefficient system of external respiration explain?
how a person whose heart and lungs have failed can sometimes be revived by mouth-to-mouth resuscitation, which involves filling the person’s lungs with exhaled air
What is internal respiration?
the exchange of gases between the blood in systemic capillaries and the tissue fluid
What does internal respiration serve?
tissue cells
What happens without internal respiration cells?
internal respiration could not continue to produce the ATP that allows internal respiration cells to exist
What colour is blood in systemic capillaries during internal respiration and why?
blood is bright red because red blood cells contain oxyhemoglobin
What does oxyhemoglobin do in internal expiration?
gives up O2, which diffuses out of the blood into the tissues
HbO2 —-> Hb + O2
What happens in the warmer, more acidic conditions of the tissues during internal respiration?
oxygen diffuses out of the blood into the tissues because the PO2 of tissue fluid is lower than that of blood
What is the lower PO2 of tissue fluid in internal respiration due to?
cells continuously using up oxygen in cellular respiration
Why does CO2 diffuse into the blood from the tissues in internal expiration?
because the PCO2 of tissue fluid is higher than that of blood
Where is CO2 collected?
tissue fluid
What happens after CO2 diffuses into the blood in internal expiration?
it enters the red blood cells, where about 10% is taken up by hemoglobin, forming CARBAMINOHEMOGLOBIN (HbCO2)
What is carbaminohemoglobin?
HbCO2
a compound formed when hemoglobin binds with CO2
What does most of the remaining 90% of CO2 do?
combines with water in the blood plasma, forming carbonic acid (H2CO3), which dissociates to hydrogen ions (H+) and bicarbonate ions (HCO3-)
What drives the internal respiration reaction to the right?
the increased concentration of CO2 in the blood
[carbonic anhydrase]
CA CO2 + H2O ----> H2CO3 ----> H+ + HCO3-
carbonic bicarbonate
acid ion
Describe what happens during internal respiration.
- bicarbonate ions diffuse out of red blood cells and are carried in the plasma
- globin portion of hemoglobin combines with excess hydrogen ions produced by the overall reaction, and becomes reduced hemoglobin (HHb) and this is how the pH of blood remains fairly constant
What is reduced hemoglobin?
HHb
a compound formed when the globin portion of hemoglobin combines with excess hydrogen ion
Why is blood that leaves the systemic capillaries during internal reaction dark maroon?
because red blood cells contain reduced hemoglobin
If blood that leaves the systemic capillaries is dark maroon, why do veins actually look blue under the skin?
due to the bluish colour of carbaminohemoglobin
What happens when blood reaches the lungs?
CO2 readily diffuses out of the blood and is exhaled
What has a greater affinity for hemoglobin?
carbon monoxide has a much greater affinity for hemoglobin than oxygen does therefore it stays combined for several hours, making hemoglobin unavailable for oxygen transport
What do carbon monoxide detectors in homes do?
can help prevent accidental death due to a malfunctioning furnace or inadequate exhaust system
External Respiration vs Internal Respiration
external: in the lungs, carbon dioxide leaves the blood and oxygen enters the blood
internal: in the tissues. carbon dioxide enters the blood and oxygen leaves the blood
