Chemical pathology Flashcards
What is an acid
An acid is a substance that when dissolved in water yields hydrogen ions.
what determines the strength of the acid
If the acid dissociates a lot, and has a high Ka(>1)
What is a base
this is a substance that when dissolved in water yields hydroxyl ions./ This are substances that react with acids(which yield hydrogen ions), and bases accept the hydrogen ion.
Why is blood hydrogen ion concentration tightly controlled between 35 and 45 nmol/L.
Optimal environment for cellular enzyme activity, membrane integrity and metabolic processes.
How do we manage excess hydrogen in the body.
Managed by the efficient excretion of acid in the urine, and by the kidneys.
What is a buffer
this is a mixture of a weak acid and its salt which are in equilibrium.
How do buffers prevent a drop in PH.
Buffers bind or release free hydrogen ions depending on the surrounding hydrogen ion concentration, by shifting the equilibrium of the reaction. In the presence of excess free hydrogen, the equilibrium shifts towards acid to remove the excess free acid. In the case where there is a deficients of hydrogen ions the equilibrium will shift toward the base to replace the deficient hydrogens.
What causes the rapid dissociation of Carbonic acid in the body
the presence of Carbonic anhydrase in red blood cells and in the kidney.
Why is the bicarbonate buffer sytem so unique and powerful
.It is regenerative: HCO3- is both retained and regenerated by the kidneys.
It is open ended: CO2 is excreted by the lungs
What is the significance of Buffers.
Buffers minimize change in free hydrogen ions concentratio, so minimize change in PH.
Buffers mantains the ration of base HCO3 to acid CO2, so minimize change pH.
Define the following terms
Acidaemia
Aciduria
Acidosis
.Acidaemia- Blood pH that is lower than normal.
Aciduria- Urine pH that is lower that normal.
Acidosis- A disease process that causes acidaemia.
Define the following terms
Alkaleamia
Alkaluria
Alkalosis
Alkaleamia- Blood pH that is higher than normal
Alkaluria- Urine pH that is higher than normal
Alkalosis- A disease process that causes Alkaleamia
Define metabolic acidosis/alkalosis
This is when a disease process causes a primary change in the bicarbonate
Define respiratory acidosis/alkalosis
if the disease causes a primary change in the carbon dioxide concentration.
Distinguish between a sensitive test and a specific test(few false negatives)
A sensitive test will detect all patients who have the disease
A specific test will not mislabel a healthy person as diseased(few false positive)
