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CTB Block 2 > B2 W1 - Gas Transport - Carbon Dioxide > Flashcards

B2 W1 - Gas Transport - Carbon Dioxide Flashcards

1
Q

What are the three main ways CO2 is transported in the blood?

A

Dissolved in plasma, as bicarbonate, and as carbamino compounds.

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2
Q

What percentage of CO2 transport in the blood is attributed to bicarbonate?

A

About 69%.

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3
Q

What percentage of CO2 transport in the blood is attributed to carbamino compounds?

A

Around 21%.

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4
Q

Why is the partial pressure of CO2 higher on the venous side compared to the arterial side?

A

Tissues produce CO2, leading to a higher concentration on the venous side as it travels back to the lungs.

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5
Q

What is formed when CO2 reacts with water?

A

Carbonic acid (H2CO3).

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6
Q

What does carbonic acid dissociate into?

A

H+ (a proton) and HCO3- (bicarbonate).

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7
Q

What is the definition of an acid?

A

A substance that releases or donates H+ (a proton).

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8
Q

What is the definition of a base?

A

A substance that can accept H+ (a proton).

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9
Q

What is the difference between a strong acid and a weak acid?

A

A strong acid completely dissociates in solution, while a weak acid only partially dissociates.

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10
Q

What is the pH scale?

A

A scale from 1 to 14 that measures acidity, with lower values indicating higher acidity.

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11
Q

What is the normal pH range for blood?

A

7.36 to 7.44.

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12
Q

What is the relationship between pH and H+ concentration?

A

An inverse relationship: as H+ concentration increases, pH decreases.

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13
Q

What are volatile acids?

A

Acids like H+ generated from CO2 production that can leave the solution and be excreted by the lungs.

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14
Q

How are non-volatile acids excreted?

A

By the kidneys.

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15
Q

How does increasing the partial pressure of CO2 affect pH?

A

It leads to a decrease in pH.

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16
Q

What is the Henderson-Hasselbalch equation?

A

An equation that relates pH to the concentrations of bicarbonate and CO2: pH = pK + log10([HCO3-]/[CO2]).

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17
Q

What does the pK value represent in the Henderson-Hasselbalch equation?

A

A constant for the reaction, giving an indication of the ratio of dissociated and undissociated weak acid.

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18
Q

How do the lungs regulate pH?

A

By excreting CO2 through breathing.

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19
Q

How do the kidneys regulate pH?

A

By controlling bicarbonate ion excretion.

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20
Q

What is the Haldane effect?

A

The Haldane effect describes the relationship between the binding of oxygen and carbon dioxide to haemoglobin. An increase in the partial pressure of oxygen promotes the release of carbon dioxide from haemoglobin, while a decrease in the partial pressure of oxygen promotes the binding of carbon dioxide to haemoglobin.

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21
Q

How do carbamino compounds contribute to CO2 transport?

A

CO2 can bind to the amino groups of proteins, particularly haemoglobin, forming carbamino compounds. This accounts for around 21% of CO2 transport in the blood.

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22
Q

What is the primary source of CO2 in the body?

A

CO2 is primarily produced as a byproduct of aerobic respiration in the tissues, where glucose is broken down to generate energy.

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23
Q

How does the solubility of CO2 in water compare to that of oxygen?

A

CO2 is more soluble in water than oxygen. This contributes to its transport in the blood.

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24
Q

How do the partial pressures of oxygen and CO2 differ between arterial and venous blood?

A

Arterial blood has a higher partial pressure of oxygen and a lower partial pressure of CO2 compared to venous blood. This is because oxygen is taken up in the lungs and delivered to the tissues, while CO2 is produced in the tissues and transported to the lungs for removal.

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25
Q

What happens to the reaction between CO2 and water in the presence of high bicarbonate concentrations?

A

The reaction between CO2 and water to form carbonic acid is slowed down in the presence of high bicarbonate concentrations. This is because the reaction can proceed in both directions to reach equilibrium, and the high concentration of bicarbonate pushes the equilibrium towards the reactants (CO2 and water).

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26
Q

What is the role of the enzyme carbonic anhydrase in CO2 transport?

A

Carbonic anhydrase is an enzyme that catalyzes the rapid interconversion of CO2 and water to carbonic acid (and vice versa).This enzyme plays a crucial role in CO2 transport, particularly in red blood cells.

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27
Q

Aside from transport, what are the other major roles of CO2 in the body?

A

CO2 plays crucial roles in:Controlling blood pH.Regulating breathing rate.

28
Q

What happens to pH when the concentration of bicarbonate increases?

A

An increase in bicarbonate concentration leads to an increase in pH, making the blood more alkaline. This is because bicarbonate acts as a base by accepting H+ ions.

29
Q

What are some examples of non-volatile acids produced in the body?

A

Examples of non-volatile acids include:Sulphuric acidLactic acidKeto acids

30
Q

How do volatile and non-volatile acids differ in their excretion pathways?

A

Volatile acids, primarily derived from CO2, are excreted by the lungs.Non-volatile acids are excreted by the kidneys.

31
Q

Under what physiological conditions are lactic acid and keto acids produced?

A

Lactic acid is produced under anaerobic conditions when there is insufficient oxygen available for aerobic respiration. Keto acids are produced during the breakdown of fats when glucose availability is low, such as during starvation or in individuals with uncontrolled diabetes.

32
Q

Explain the logarithmic nature of the pH scale and how it relates to changes in proton concentration.

A

The pH scale is a logarithmic scale, meaning that each unit change in pH represents a tenfold change in hydrogen ion (H+) concentration. For example, a solution with a pH of 6 has ten times the H+ concentration of a solution with a pH of 7. This logarithmic relationship allows for a wide range of H+ concentrations to be expressed on a convenient scale from 1 to 14.

33
Q

What is the role of nitrogen in the context of gas exchange in the lungs?

A

While nitrogen is the most abundant gas in the atmosphere and is present in the alveoli, it does not participate in gas exchange under normal physiological conditions. Therefore, its partial pressure remains relatively constant in both inspired and expired air.

34
Q

Explain the steps involved in calculating pH using the Henderson-Hasselbalch equation, including the conversion of CO2 concentration to partial pressure.

A

The Henderson-Hasselbalch equation is: pH = pK + log10([HCO3-]/[CO2]). To use this equation, you need the pK value (a constant), the bicarbonate concentration, and the CO2 concentration, which needs to be converted to partial pressure. The conversion is done using a solubility coefficient specific for CO2 in plasma. Once you have the partial pressure of CO2, you can plug the values into the equation and solve for pH.

35
Q

Describe the chemical structures of carbamino compounds and the specific amino acid residues involved in CO2 binding.

A

Carbamino compounds are formed when CO2 reacts with the terminal amino groups (-NH2) of proteins, primarily haemoglobin. This reaction forms a carbamate group (-NHCOO-). The specific amino acid residues involved in CO2 binding on haemoglobin are the N-terminal valine residues of the alpha chains. This binding is reversible and influenced by the partial pressure of CO2 and oxygen.

36
Q

What enzyme catalyses the reaction between CO2 and water in red blood cells?

A

Carbonic anhydrase (or carbonic dehydrates).

37
Q

Where is carbonic anhydrase found?

A

Carbonic anhydrase is present in red blood cells, but not in the blood plasma.

38
Q

Why does the reaction between CO2 and water occur more rapidly in red blood cells than in plasma?

A

The reaction between CO2 and water occurs more rapidly in erythrocytes because the enzyme carbonic anhydrase is present in red blood cells but not in plasma.

39
Q

How are the products of the reaction between CO2 and water removed from the red blood cell?

A

H+ is buffered by haemoglobin, and bicarbonate is transferred out of the cell into the blood plasma.

40
Q

How does haemoglobin buffer H+?

A

H+ binds to histidine amino acid side chains (histidine residues) in the polypeptide chains of haemoglobin.

41
Q

What happens to bicarbonate after it is produced in the red blood cell?

A

Bicarbonate leaves the cell and enters the blood plasma via an antiport system with chloride ions.

42
Q

How is the majority of carbon dioxide transported in the blood?

A

The majority of carbon dioxide is transported in the blood as bicarbonate in the blood plasma.

43
Q

How does deoxygenation affect the buffering ability of haemoglobin?

A

Deoxygenation enhances the buffering ability of haemoglobin.

44
Q

What is the Bohr effect?

A

The Bohr effect is the phenomenon where the taking up of carbon dioxide reduces the oxygen affinity of haemoglobin.

45
Q

How does the presence or absence of oxygen affect the ability of haemoglobin to take up H+?

A

The presence or absence of oxygen affects the ability of haemoglobin to take up H+, which determines the ability to carry CO2.

46
Q

What are carbamino compounds?

A

Carbamino compounds are formed when CO2 reacts with amino groups, especially in haemoglobin.

47
Q

What is carbamino haemoglobin?

A

Carbamino haemoglobin is formed when CO2 reacts with the amino groups of haemoglobin.

48
Q

How does the formation of carbamino haemoglobin affect oxygen affinity?

A

The formation of carbamino haemoglobin alters the conformation of the molecule, reducing its oxygen affinity.

49
Q

What are the three methods of carbon dioxide transport in blood?

A

The three methods are: dissolved in blood plasma (10%), bound to haemoglobin as carbamino compounds (20%), and as bicarbonate in the blood plasma (the majority).

50
Q

What happens to the amount of dissolved CO2 as the partial pressure of CO2 increases?

A

The amount of dissolved CO2 increases with increasing partial pressure of CO2.

51
Q

What effect does deoxygenation of haemoglobin have on the amount of CO2 carried in the blood?

A

Deoxygenation of haemoglobin leads to an increase in the amount of CO2 carried in the blood as bicarbonate.

52
Q

Does CO2 content saturate with increasing partial pressure of CO2?

A

No, CO2 content does not saturate with increasing partial pressure of CO2, unlike oxygen.

53
Q

What is the typical oxygen saturation on the venous side of the circulatory system?

A

Typical oxygen saturation on the venous side is about 65-70%.

54
Q

What is the typical partial pressure of carbon dioxide in arterial blood?

A

The typical partial pressure of carbon dioxide in arterial blood is about 5.3 kPa.

55
Q

What is the typical partial pressure of carbon dioxide in mixed venous blood?

A

The typical partial pressure of carbon dioxide in mixed venous blood is about 6.1 kPa.

56
Q

What is the relationship between partial pressure of carbon dioxide and CO2 content in the blood within the normal physiological range?

A

Within the normal physiological range of partial pressure of carbon dioxide, the dissociation curve is nearly linear, meaning increases in partial pressure lead to proportional increases in CO2 content.

57
Q

Why does mixed venous blood have a higher CO2 content than arterial blood?

A

Mixed venous blood has a higher CO2 content for two reasons: 1) the partial pressure of CO2 is higher; and 2) the haemoglobin is less oxygenated, increasing its capacity to carry CO2 (Haldane effect).

58
Q

Where does the water that reacts with CO2 in red blood cells come from?

A

Water enters the red blood cell, likely from the plasma.

59
Q

What is the shape of a red blood cell?

A

Red blood cells have a characteristic biconcave disc shape.

60
Q

How do the Haldane and Bohr effects occur?

A

Both the Haldane and Bohr effects occur by modifying the haemoglobin conformation; this refers to the subtle, three-dimensional aspects of the shape of the molecule.

61
Q

What happens as bicarbonate leaves the red blood cell?

A

As bicarbonate leaves the red blood cell and enters the blood plasma, chloride ions enter the cell in exchange. This exchange is known as an antiport system.

62
Q

What is the name given to haemoglobin with an extra hydrogen ion bound to it?

A

When a hydrogen ion binds to haemoglobin, it becomes a version of haemoglobin with an extra hydrogen on it and a neutral charge.

63
Q

What happens to the oxygen saturation of haemoglobin in acidic conditions or increased CO2 conditions?

A

In acidic conditions or increased CO2 conditions, the oxygen saturation curve of haemoglobin shifts to the right, meaning that for any given partial pressure of oxygen, the haemoglobin binds less oxygen.

64
Q

What is the effect of increasing oxygen binding on the affinity of haemoglobin for hydrogen ions?

A

Increasing oxygen binding reduces the affinity of haemoglobin for hydrogen ions.

65
Q

What percentage of total CO2 carried in the blood is dissolved in the blood plasma?

A

Only about 10% of the total CO2 carried in the blood is dissolved in the blood plasma.

66
Q

What percentage of total CO2 carried in the blood is bound to haemoglobin as carbamino compounds?

A

Only around 20% of the total CO2 carried in the blood is bound to haemoglobin as carbamino compounds.

CTB Block 2 (5 decks)

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