Section 2

Question 1

What is a buffer system, in general?

Answer 1

In general, a buffer system is made up of two chemicals that undergoes a reversible chemical reaction that can either remove H+ or add H+ in order to keep the pH steady

Question 2

What are the four different buffer systems of the body?

Answer 2

• the [H2CO4]:[HCO3] buffer system
• the protein buffer system
• the haemoglobin buffer system
• the phosphate buffer system

Question 3

Describe the carbonic acid/bicarbonate buffer pair. Describe what would change adding a base/acid.

Answer 3

This pair dissociates following this equation:
H2CO3 <–> (HCO3-) + (H+)

• When a base is added, the base binds to the free H+ resulting in the reaction moving forward so more H+ dissociates
• Opposite for acid, reaction moves backwards so less H+ dissociates

Question 4

Describe the effect of adding a strong acid into an unbuffered VS buffered solution.

Answer 4

When HCl is added to an unbuffered solution, all the added H+ remain free and contribute to the acidity of the solution.

When HCl is added to the buffered solution, bicarbonate ions, HCO3-, bind with some of the added H+, and remove them from solution so they do not contribute to the acidity of the solution.

Question 5

Why is the H2CO3:HCO3- buffer pair considered the most important buffer in the human body?

Answer 5

The H2CO3:HCO3- buffer pair is considered the most important buffer in the human body because it is responsible for buffering pH changes arising from everything other than CO2-generated H2CO3. It cannot buffer against changes in H2CO3 or HCO3- because a buffer system cannot buffer itself.

Question 6

What are the two reasons that make the H2CO3:HCO3- buffer system highly effective?

Answer 6

1. High quantities in the extracellular fluid (ECF): Both H2CO3 and HCO3- are present in high quantities in the extracellular fluid, giving this system a high capacity for buffering changes in pH.
2. Regulation of concentrations: Both H2CO3 and HCO3- are highly regulated in the body to keep their concentrations relatively stable. The kidneys regulate HCO3- while the respiratory system regulates H2CO3 by regulating CO2.

Question 7

Describe how the H2CO3:HCO3- buffer pair operates to minimize changes in pH during intense exercising

Answer 7

Recall the equation:
CO2 + H2O <–> H2CO3 <–> HCO3- + H+

Intense exercise results in the formation of lactic acid. This lactic acid means a higher concentration of H+ in the body, which will bind to HCO3- and drive the reaction to the left. This effectively removes the H+ so that it cannot increase the acidity of the ECF

Question 8

Describe how the H2CO3:HCO3- buffer pair operates to minimize changes in pH during vomiting

Answer 8

Recall the equation:
CO2 + H2O <–> H2CO3 <–> HCO3- + H+

A decrease of H+, which occurs following vomiting, causes H2CO3 to dissociate to release a H+ and prevent the ECF from becoming too basic

Question 9

What is the Henderson-Hasselbalch equation?

Answer 9

defines the relationship between H+ and a buffer system pair. This equation allows you to calculate the pH around which the buffer pair works.

pH= pKa + log[HCO3- / H2CO3]
concentration of H2CO3 is basically the same as CO2 in the body so we can rewrite:
pH= pKa + log[HCO3- / CO2]

Question 10

What is the normal ratio of HCO3- to CO2?

Answer 10

20 to 1

Question 11

Why are proteins considered excellent buffers?

Answer 11

Proteins are excellent buffers because they are composed of amino acids, which contain many acidic and basic groups that can give up or accept H+, respectively.

Question 12

Where is the protein buffer system primarily important?

Answer 12

The protein buffer system is primarily important for intracellular fluids, as the insides of cells are very rich in protein.

Question 13

Describe what happens when the pH of the intracellular fluid rises or falls.

Answer 13

If the pH of the intracellular fluid rises (alkaline medium), amino acids act as acids and release H+.

If the pH of the intracellular fluid falls (acidic medium), amino acids act as bases and absorb H+.

Question 14

What is the haemoglobin buffer system, and what role does haemoglobin play in it?

Answer 14

The haemoglobin buffer system involves haemoglobin (Hb), a protein found within red blood cells. Haemoglobin plays an essential role in gas transport and acts as a buffer of H+ generated from metabolically produced CO2 to prevent venous blood from becoming too acidic.

Question 15

Describe how the haemoglobin buffer system operates to ensure venous blood doesn’t become too acidic.

Answer 15

CO2 in Plasma: As CO2 leaves the tissues and enters the blood, most of it forms H2CO3 in the red blood cells with the help of the enzyme carbonic anhydrase.

O2 in Plasma: Most of the H+ generated from H2CO3 will immediately bind to haemoglobin, preventing it from contributing to the acidity of body fluids. This allows the oxygen bound to haemoglobin to be released to the tissues.

HCO3- in Plasma: Some of the H2CO3 will immediately dissociate into bicarbonate (HCO3-) and H+.

Question 16

What is the significance of the reaction being reversed within the lungs?

Answer 16

The reaction being reversed within the lungs allows for the release and expulsion of CO2 from the body.

Question 17

What is the phosphate buffer system, and how does it function?

Answer 17

The phosphate buffer system utilizes an acid phosphate salt that can donate an H+ when [H+] falls or accept an H+ when [H+] increases, as defined by the equation:

Na2HPO4 + H+ ↔ NaH2PO4 + Na+.

This system acts as a buffer to maintain pH balance.

Question 18

Why does the phosphate buffer system not play a major role in extracellular fluid (ECF)?

Answer 18

The concentration of the acid phosphate salt is low in ECF, so the phosphate buffer system does not play a major role there.

Question 19

In what environment does the phosphate buffer system play an important role?

Answer 19

The phosphate buffer system plays an important role INSIDE cells because the concentrations of phosphates are higher there.

Question 20

What is another important role of the phosphate buffer system (other than inside the cells)?

Answer 20

Another important role of the phosphate buffer system is to buffer the pH of the URINE. Excess phosphate from the diet is filtered by the kidneys but not reabsorbed, leading to its accumulation in the tubular fluid. There, it buffers any excreted H+, making it the only buffer system present in the urine.

Question 21

Primary ECF buffer against non-carbonic acids changes

Answer 21

Carbonic acid: Bicarbonate buffer system

Question 22

Primary ICF buffer, also buffers ECF

Answer 22

Protein buffer system

Question 23

Primary buffer against carbonic acid changes

Answer 23

Haemoglobin buffer system

Question 24

Important urinary buffer; also buffers ICF

Answer 24

Phosphate buffer system

Question 25

What is the role of chemical buffer systems in maintaining pH balance in body fluids?

Answer 25

Chemical buffer systems act as the first line of defense against changes in H+ concentration in body fluids by quickly adding or removing H+ through chemical reactions, occurring in just fractions of a second.

Question 26

Why are chemical buffer systems considered the first line of defense?

Answer 26

Chemical buffer systems are considered the first line of defense due to their speed in reacting to changes in H+ concentration.

Question 27

What is a limitation of chemical buffer systems?

Answer 27

Chemical buffer systems have a limited capacity to absorb H+. They can become overwhelmed by constant additions of H+ to body fluids.

Question 28

How do the respiratory and renal systems contribute to pH control?

Answer 28

The respiratory and renal systems contribute to pH control by eliminating H+ from the body, rather than buffering it. They remove excess H+ to help maintain proper pH balance.