Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Respiratory > Lecture 7- CO2 transport in the blood > Flashcards

Lecture 7- CO2 transport in the blood Flashcards

1
Q

how is carbon dioxide transported in the blood

A
  • dissolved (CO2 is more soluble than oxygen)
  • CO2 reacts chemically with water to form bicarbonate- HCO3-
  • As a carbamino-haemoglobin compound
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

total content of O2 in arterial blood

A

8.9 mmol/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

total content of CO2 in arterial blood

A

21

Lots of CO2 in blood going to tissues- not a waste product.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

CO2 has a major role in

A

controlling blood pH (acid-base balance)

Chemical reactant in the major pH buffering system of blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

blood pH must be kept within a narrow range

A

arterial pH 7.35 – pH 7.45; venous 7.31-7.41

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

body has several buffering systems to control blood pH but…..

A

one using CO2 most important

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is a buffer

A
  • Buffers are compounds which are able to bind or release hydrogen ions such that they dampen swings in the pH.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

outline the bicarbonate buffer system

A
  • CO2 reacts with H20 to form carbonic acid
  • carbonic acid dissoaciates to form H+ and HCO3-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how to workout CO2 dissolved in arterial blood

A

[CO2] dissolved= solubility x pCO2

  • solubility factor for CO2 at 37 degrees= 0.23 mmol/L/kPa
  • pCO2 of CO2 arterial blood= 5.3 kPa
  • therefore:
  • 5.3 kPa x 0.23 mmol/L/kPa= 1.2 mmol/L dissolved CO2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

why is [CO2] dissolved higher than [O2] dissolved

A

more dissolved CO2 even though lower pCO2 than pO2 because of markedly increased solubility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

carbon dioxide in plasma

A
  • dissolved CO2 reacts with water to form carbonic acid –> H2CO3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Carbonic acid very quickly

A

dissociates to H+ and HCO3-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

bicarbonate buffer equation is

A

reversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

the direction the bicarbonate buffer favours depends on

A
  • The rate of the reaction depends on the amount of reactants (on the left) and productions (on the right)- “law of mass action”
  • Reaction can go on either direction- dependent on conc of chemical
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

which equation can be used to calculate the pH of plasma

A

Henderson-Hasselbalch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Henderson Hasselbalch equation applied to the carbon dioxide-bicarb buffer system

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

plasma pH is dependent on

A
  • on how much [CO2] reacts with water to form H+
  • if CO2 is high then the reaction will be favoured towards the right producing lots of H+ and HCO3-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

higher [HCO3-] in plasma will

A

push the reaction to the left

in the body the reaction is favoured in this direction because HCO3-> CO2- why our body pH slightly alkaline 7.4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q
  • Amount of Co2 dissolved depends directly
A
  • on the partial pressure of CO2
    *
20
Q

If pCO2 rises (and no change in bicarbonate)

A

plasma pH will fall (become more acidic)

21
Q

If pCO2 falls (and there is no change in bicarbonate)

A

plasma pH will rise (become more alkaline)

22
Q

what is the determining factor of the amount of CO2 dissolved

A
  • The pCO2 of alveoli’s is the determining factor- determines arterial pCO2
  • Alveolar, and hence arterial pCOP2 controlled by altering the rate of breathing
23
Q
A
24
Q

how much HCO3- in plasma

A

25 mmol/L

  • cation associated with this is mainly na+ not H+
25
Q

where is most of HCO3- made

A

the RBC

the high [HCO3-] cannot coem from O2 alone in plasma- not enough dissolved CO2 in plasma to create this much HCO3-

26
Q

why is HCO3- production in the RBC much faster than the plasma

A
  • Reaction speeded up by Carbonic anhydrase (CA) enzyme present in RBC but not present in plasma
27
Q

why does HCO3- production in the RBC proceed in the froward direction

A
  • produces HCO3- because the products are mopped up in the RBC
28
Q

How are products of HCO3- production mopped up in the RBC (to keep reaction in forward direction)

A
  • HCO3- is transported out of the RBC by the chloride/ HCO3- exchanger
    • creates a plasma conc of 25 mmol/L HCO3-
  • H+ is bound to Hb
29
Q

although RBC are the major producers of HCO3-, they do not control the levels. Where does this happen?

A

the kidineys

30
Q

Role of kidney and lungs in CO2: bicarbonate levels

A
  • [HCO3-] normally doesnt change much with changed in pCO2- low levels dissolved CO2
  • HCO3- comes from the RBCs (reaction is mostly determined by H+ binding to Hb)
  • Kidneys control amount of H CO3- by varying excretion- can also create more HCO3-
  • therefore pH is dependent on:
    • how much CO2 is present (controlled by rate and depth of breathing)
    • how much HCO3- is present (controlled by kidneys)
31
Q

what does bicarbonate buffer

A

extra acid

  • As part of normal metabolism body produces acids
    • Lactic acids, keto acids, suphuric acid
32
Q

how does bicarbonate act as a buffer for extra acids

A
  • Acids react with HCO3- to produce CO2
    • Reaction pushed to the left
    • CO2 levels increase
    • removed by increased ventilation- pH changes are minimised (buffered)
    • More HCO3- needs to be produced to replenish
33
Q

pCO2 is ………. in venous blood

A

higher

  • due to veins draining metabolically acitive tissues
  • more CO2 will be dissolved
34
Q

Properties of Hb important for H+ buffering

A
  • Buffering of H+ by Hb depends on level of oxygenation
    • There are always H+ ions bound to Hb, but amount depends on the state of the Hb molecule
      • If more O2 binds Hb → R-state and less H+ ions bind
      • As at lungs
  • If less O2 binds Hb → T-state and more H+ ions bind – As at tissues
35
Q

H+ buffering At the tissues to venous blood

A
  • Less O2 binds to Hb → T-state and more H+ ions bind
  • If Hb binds more H+ in RBCs in venous blood then more HCO3- can be produced as ↓H+ drives reaction to right - CO2 + H2O → H+ + HCO3- IN RBCs
  • Therefore more HCO3- transported out of RBCs into plasma in venous blood
  • Effectively increasing amount transported CO2 in blood – in form of bicarbonate (HCO3- )
  • Also increased dissolved CO2 in blood – down partial pressure gradient from tissue to blood
36
Q

What happens when venous blood arrives at the lungs

A
  • Hb picks up O2 and goes into R state ( due to higher pO2)- lower affinity for H+
  • This causes Hb to go into the relaxed state and give up the extra H+ it took on at the tissues
  • H+ reacts with HCO3- to form CO2
  • Reaction push to the left
  • CO2 diffuses out of the blood into the alveoli
  • CO2 is breathed out
37
Q

Red blood cells, CO2 and bicarbonate in body tissue and the lungs - summary

A
38
Q

Formation of carbamino compounds

​

A
  • CO2 can bind directly to Hb- not same site as O2
  • Binds directly to amine groups on globin of Hb- carbamino compound
39
Q

Binding of molecular CO2 onto Hb is not part of

A

acid base balance but contributes to CO2 transport

40
Q

More carbamino compounds are formed at

A

the tissues- both because pCO2 higher, and unloading of O2 from Hb facilitates binding of CO2 to Hb- oxygen poor Hb (T state Hb binds CO2 better)

This CO2 is given up at the lungs as Hb becomes oxygen rich- oxygenated Hb unloading CO2= Haldane effect

41
Q

Haldane effect

A

CO2 is given up at the lungs as Hb becomes oxygen rich- oxygenated Hb unloading CO2

42
Q

how much CO2 is transported to be eliminated?

A
  • Calculations reveal that at rest only ~8% of CO2 is transported to the lungs to be eliminated- remember more CO2 can be eliminated if there is extra acid that needed to be buffered
  • The rest of the CO2 in blood is there as part of the pH buffering system
43
Q

% of dissolved CO2 transported to the lungs

A

10%

44
Q

% of bicarbonate transported to the lungs

A

60% of CO2 in blood

45
Q

% of dissolved carbamino compounds transported to the lungs

A

30% of dissolved CO2 transported to the lungs

Respiratory (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions