Lecture 4 Flashcards
(11 cards)
What does acidity depend on?
The conc of free hydrogen ions (not those bound to anions)
Where do most acids come from in the body?
The breakdown of proteins, incomplete oxidation of fats or glucose, transporting CO2 in the blood
How is the acid-base balance regulated?
In the body by the lungs, kidneys and chemical buffers
What do buffers do?
They prevent large changes in pH, when pH drops they bind to H+ ions in the blood and release H+ ions in the blood when it gets too high
What’s the difference between a strong and weak acid?
A strong acid will always dissociate its H+ ions in solution but a weak acid will only dissociate its ions in a high pH solution
What is pKa
The pH value at which half of the acid has dissociated (formula: -logKa)
What is the Henderson-Hasselbalch equation?
pH= pKa + log[conjugate base]/[acid}
What are the physiological buffers in the body?
In blood, saliva and other fluids. H2CO3–>HCO3(-), pKa 6.1. H2PO4(-)–>HPO4(2-), pKa 6.8
What amino acid is the best at acting as a buffer?
Histidine
Why is deoxyhaemoglobin a better hydrogen acceptor than oxyhaemoglobin at the pH of blood?
It has a higher pKa (7.8 compared to 6.8) than blood (7.4) and so will only begin dissociating 50% of its hydrogen ions if the pH if at 7.8 (which it wouldn’t be because that’s very high for blood)
Can charged molecules move across membranes more readily?
No
