Lecture 16 Flashcards
What is the composition of air?
Dry and wet at standard atmospheric pressure of 760 mmHg
What is Dalton’s law?
The total pressure of a mixture of gases is the sum of their individual partial pressures
What can partial pressure information influence?
How much gas we have in a solution
Concentration of a gas dissolved in a solution is determined by…
Henry’s law
What is the equation of Henry’s law?
Concentration of dissolved gas = Solubility coefficient x Partial pressure of gas
Does plasma carry a lot of oxygen?
no
What is the molecular weight of haemoglobin?
68 kD
What is the globin chain combination for adult haemoglobin?
2 alpha chains and 2 beta chains
What is the globin chain combination for fetal haemoglobin?
2 alpha chains and 2 gamma chains
What is a haem unit?
Porphyrin ring containing a single iron atom
What enzyme converts Fe (3+) to Fe (2+) in the haem unit?
Methaemoglobin reductase
How much of hemoglobin is saturated in arterial blood?
98%
What is the effect of temperature on hemoglobin saturation?
If temperature increases, curve shifts to the right
- hemoglobin carries less oxygen
If temperature decreases, curve shifts to the left
- hemoglobin carries more oxygen
What is the effect of pH on hemoglobin saturation?
pH and CO2 are closely interlinked factors
CO2 (weak acid)
Increase in CO2: acidification - shifts to the right
(less oxygen)
Alkalization - shifts to the left (more oxygen)
What is the name for changes in saturation due to pH changes?
Bohr effect
What is the effect of 2,3-Diphosphoglycerate (2,3-DPG)?
Interacts with beta-chain and changes the interaction of hemoglobin with oxygen
- an increase in 2,3 DPG concentration shifts curve to the right, decrease shifts to the left
2,3, DPG tends to bind more to hemoglobin in an deoxygenated state
- changes affinity for oxygen so that it aids oxygen offloading
What is fetal hemoglobin like?
Globin chains are insensitive to 2,3 DPG
Fetal hemoglobin is like adult hemoglobin at 0 concentration of 2,3 DPG
What is the advantage to the insensitivity to 2,3 DPG in fetal hemoglobin?
Helps fetus scavenge oxygen from mother’s blood more efficiently
How does the blood carry CO2 as?
Dissolved CO2 Carbonic acid Bicarbonate (largest component) Carbonate Carbamino compounds (CO2 interacts with proteins in the lung)
How is bicarbonate efficient as a buffering system?
22~25 bicarbonate in plasma
1.2 mM
ph 7.4
helps maintain that pH within tight barriers
Hyperventilating: blowing of CO2 - effect on plasma pH
How much of CO2 stays in the plasma?
10% stays in plasma
How much of CO2 remains dissolved?
6%
How much of CO2 combines with proteins to form carbamino compounds?
less than 1
What enzyme speeds up process of bicarbonate formation?
Carbonic anhydrase type 2
What are channels used for CO2 transport?
aquaporin 1, Reces A (50% of transport)
What happens when CO2 binds to hemoglobin?
Proton formed
- local acidification in RBC
- favors oxygen being released from iron group
- leaves RBC
- supply to tissues
What role does AE 1 (band 3 - anchoring chain) have in bicarbonate transport?
Important role in anchoring cytoskeleton (contributes to shape of RBC)
- Cl moves in and HCO3 out
- Hamburger shift (Cl shift)
- all processes are in reverse in lungs - higher affinity to bind to oxygen
