Acids and Bases Flashcards
Regarding the hydrogen ion and pH (true or false:
The hydrogen ion concentration can affect ionic bonds in compounds
True. Hydrogen ions can affect all types of bonds in molecules.
Regarding the hydrogen ion and pH (true or false:
Enzyme activity is dependent upon the hydrogen ion concentration
True. Hydrogen ions can affect all types of bonds in molecules including enzymes, which is why hydrogen ion concentration and its control is physiologically important.
Regarding the hydrogen ion and pH (true or false:
pH varies linearly with hydrogen ion concentration
False. pH varies in a logarithmic fashion with hydrogen ion concentration: pH = - log10 [H+].
Regarding the hydrogen ion and pH (true or false:
A change in pH from 7.4 to 7.1 represents an almost doubling of hydrogen ion concentration
True. Hydrogen ion concentration rises from 40 nmol/L to 79 nmol/L. pH has therefore been criticized as being misleading, as a seemingly small change represents a large physiological insult
Regarding the hydrogen ion and pH (true or false:
The pH of water is 7.4 regardless of the temperature at which it is measured
False. Temperature has a marked effect on the dissociation of water into hydrogen and hydroxyl ions. The higher the temperature, the more dissociated the water, the higher the hydrogen ion concentration and the lower the pH.
In acid-base chemistry (true or false):
Ammonia/ammonium is a quantitively important buffer in the body under normal conditions
False. The three most important buffer systems are bicarbonate, proteins and phosphates.
In acid-base chemistry (true or false):
Local anaesthetic agents are weak bases
True. Local anaesthetics are weak bases. Under acidic conditions, e.g. infected tissue, they are more ionized and so don’t diffuse across lipid membranes as readily, limiting their effectiveness.
In acid-base chemistry (true or false):
The pKa is the pH at which an acid is present in equal amounts in an ionized and an un-ionized form
True. pKa refers to a weak acid and pKb to a weak base.
In acid-base chemistry (true or false):
A weak acid is usually completely dissociated at physiological pH
False. It is incompletely dissociated. A strong acid is completely dissociated.
In acid-base chemistry (true or false):
Lactate exists as a strong ion in the body
True. Lactic acid is essentially fully dissociated at physiological pH and therefore the lactate ions that are formed are strong ions.
Regarding acid-base chemistry and pH measurement (true or false):
The Henderson-Hasselbalch equation relates the pH to the bicarbonate concentration and the partial pressure of carbon dioxide in the blood
True
Regarding acid-base chemistry and pH measurement (true or false):
The pKa of the carbonic acid/bicarbonate equilibrium is 6.1
True. Therefore, at physiological pH there is a higher concentration of bicarbonate than dissolved carbon dioxide in the blood.
Regarding acid-base chemistry and pH measurement (true or false):
The Henderson-Hasselbalch equation is often helpful in determining the cause of an acid-base disturbance
False. This is why base deficit and anion gap have become useful.
Regarding acid-base chemistry and pH measurement (true or false):
In the glass electrode, a potential difference is generated dependent upon the hydrogen ion concentration difference between blood and a reference solution
True
Regarding acid-base chemistry and pH measurement (true or false):
In the glass electrode, the hydrogen ion sensitive glass is so called because it allows selective movement of hydrogen ions across it
False. There is no movement of hydrogen ions across the glass. Changes in acidity on the sample side of the hydrogen ion sensitive glass cause a change in the ionic constitution of the buffer solution on the other side of the glass. This causes current flow in the circuit, which is dependent upon the pH of the sample.
