7 Carbon Dioxide in Blood Flashcards

1
Q

In plasma, CO2 may facilitate the formation of hydrogen ions and hydrogen carbonate ions. Why is this reaction slow?

A

Little carbonic anhydrase in plasma

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2
Q

What is the dissolved concentration of CO2 in plasma at a pCO2 ​of 5.3kPa?

A

1.2mmol/L

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3
Q

How is the hydrogen carbonate which is present in blood plasma formed?

A

In Red blood cells

reaction with CO2

Requires carbonic anhydrase

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4
Q

What happens to the pH if:

pCO2 rises

[HCO3-] rises

A
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5
Q

Write out the Henderson- Hasselbach equation.

A
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6
Q

Why is it important that In plasma the ratio of [HCO3-] to dissolved CO2 stays consistent?

A

[HCO3-] : CO2

20:1

As long as this ratio stays consistent, pH will be 7.4

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7
Q

What happens to the hydrogen ions which are formed from the reaction of CO2 with H2O in the presence of carbonic anhydrase? What does this cause?

A

Hydrogen ions bind to haemoglobin

Result: reaction drawn towards production of HCO3-

(Amount of CO2 produced largely depends on buffering capacity of haemoglobin, only minor effect due to change in pCO2)

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8
Q

How is the HCO3- exported from the red cell?

A

Exported in exchange for Cl-

Chloride bicarbonate exchanger

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9
Q

Name an organ in the body which has control over [HCO3-].

A

Kidney

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10
Q

List all the forms in which carbon dioxide is carried in the blood:

A

(Carbamino compounds- formed by reaction of carbon dioxide with protein part of haemoglobin)

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11
Q

Why is haemoglobin a ‘better buffer’ in venous blood?

A

Haemoglobin less saturated with oxygen

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12
Q

What % of CO2 is transported in the blood in the form of:

  • Dissolved CO2
  • Hydrogen carbonate
  • Carbaamino compounds
A
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13
Q

Why is it that hyperventilation reduces the CO2 content in the blood but has little effect on the oxygen concentration?

A

Relationship with pCO2 and CO2 is not sigmoidal. = almost linear (see graphs)

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14
Q

How much carbon dioxide is taken from tissues and given off (ie transported)? What function does the rest of the carbon dioxide in the blood serve?

A

8% transported

Other CO2 acts as buffering system

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