Lecture 17 Flashcards
What is the normal pH range of tissue fluid?
7.35-7.45
A ___ buffer is a system (for example the respiratory or urinary system) that stabilizes pH by controlling the body’s output of acids, bases, or CO2.
physiological
Any substance that binds H+ and removes it from solution as its concentration begins to rise, or releases H+ into solution as its concentration falls is classified as a ______ buffer. Examples include proteins, bicarbonate, and phosphate.
chemical
What are the three major chemical buffer systems of the body?
The phosphate buffer system
The protein buffer system
The bicarbonate buffer system
The most important buffer system in the blood is the bicarbonate buffer, which is a solution of ______ acid and bicarbonate ions.
weak
carbonic acid is a weak acid
Which would be considered a normal pH value for arterial blood?
7.4
The bicarbonate buffer system would not work very well in the human body if not for the action of the lungs and the kidneys doing which of the following?
Removing CO2 produced by the buffer system
Which two organ systems form physiological buffers that help stabilize pH by controlling the body’s output of acids, bases, or CO2? Select two options from the list below.
Urinary system
Respiratory system
The ______ buffer system is a solution of H(PO4)2 and H2(PO4).
phosphate
Which type of buffer is defined as a substance that binds H+ and removes it from solution as its concentration begins to rise, or releases H+ into solution as its concentration falls?
chemical
How can the respiratory system compensate for a drop in blood H+ concentrations?
Reduced pulmonary ventilation allows CO2 to accumulate, lowering the pH back to normal.
Name the three important chemical buffer systems in the body.
bicarbonate
phosphate
protein
Order the events during neutralization of hydrogen ions in the kidney from the moment H2CO3 forms until HCO3- returns to blood. Begin with the formation of H2CO3 in the blood at the top.
1) H+ in blood reacts w/ HCO3- to form H2CO3
2) H2CO3 decomposes into H2O and CO2, which enter the tubule cell
3) Tubule cells obtain CO2 from blood, and tubular fluid
4) CAH combines H2O and CO2 to re-form H2CO3
5) H2CO3 ionizes to form HCO3- (which returns to the blood) and H+
What is the complete chemical equation for the bicarbonate buffer system?
CO2 + H2O <-> H2CO3 <-> HCO3- + H+
If the pH of the tubular fluid drops too low, H+ concentration in the fluid is so high that tubular secretion ceases. What is the limiting pH for tubular secretion?
4.5
The bicarbonate system works quite well because the lungs and kidneys constantly remove which of the following? This prevents equilibrium from being reached.
CO2
The renal tubules are incapable of reabsorbing HCO3- directly. Instead, an enzyme breaks down the H2CO3 in the tubular fluid to form CO2, which can be reabsorbed. What is the name of the enzyme?
Carbonic anhydrase
Choose all the statements that are true regarding the phosphate buffer system.
- it plays an important role in the renal tubules
- it has a weaker buffering effect than an equal amount of bicarbonate buffer
- it plays an important role in the ICF where there is constant production of metabolic acids
- its optimal pH is 6.8
It plays an important role in the renal tubules.
It plays an important role in the ICF where there is constant production of metabolic acids.
Its optimal pH is 6.8.
Since there is so much chloride in the tubular fluid, why is H+ excreted as ammonium chloride (NH4Cl) and not simply excreted as hydrochloric acid (HCl)?
Because HCl is too strong of an acid and would drop the pH of the tubular fluid below the limiting pH
