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cardiorespiratory biology > Carriage of Oxygen > Flashcards

Carriage of Oxygen Flashcards

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AP® Biology flashcards
1
Q

3 ways in which oxygen is transported in the body

A

Physically dissolved in plasma (~3 %)
combined with Hb as carbamino-haemoglobin (HbCO2) (3%)
Chemically bound to the haemoglobin molecule (Hb) in the red blood cells (RBC) (~92 %)

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2
Q

why is the percentage of oxygen dissolved in plasma so low

A

poor solubility of oxygen in plasma

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3
Q

what is haemoglobin Hb

A

heterotetramer consisting of 4 subunits (2 α and 2 β chains)

Each haemmolecule contains one ironatom

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4
Q

when oxygen is bound to haemoglobin what does it form

A

binds with iron to form oxyhaemoglobin

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5
Q

why is oxygens reversibility to being to bound to haemoglobin useful

A

allows O2 to be carried from the respiratory organs and released to the rest of the body

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6
Q

how many oxygen molecules can bind to Hb

A

4

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7
Q

allosteric affect of oxygen

A

Hb conformation from atensestate (loweraffinityfor oxygen) to arelaxed state(higheraffinityfor O2).

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8
Q

colour of oxygenated Hb, HboO2

A

Bright red (normal arterial blood

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9
Q

colour of deoxygenated Hb

A

dark red, blue

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10
Q

colour of carboxyhaemoglobin COHb

A

cherry red

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11
Q

oxygen content of blood

A

the amount of O2 in the blood (sum of both forms, dissolved and bound to Hb)
blood.

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12
Q

in a typical ml O2 per 100ml of blood name its oxygen content

A

(or volume %) = 0.3 ml (plasma) + 19.5 ml (RBC) = 19.8 ml/100 ml blood.

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13
Q

how do we calculate O2 blood content in tissue

A

Arterial O2 blood content - venous O2 blood content

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14
Q

oxygen carrying capacity of the blood

A

the maximum amount of O2 that can be carried by Hb. Each gram of Hb, when fully saturated, can combine with 1.34 ml of oxygen.

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15
Q

% saturation calculation

A

O2 content / O2 capacity

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16
Q

tool used to measure % saturation

A

pulse oximeter

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17
Q

how are arterial blood gas pressures measured

A

arterial blood samples and a blood gas analyser

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18
Q

P50 is the partial pressure of

A

oxygen

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19
Q

relationship of % saturation and PO2is a

A

sigmoid shape

plateau when percentage saturation is closest to 100%

20
Q

why is it important that there is a plateau near 100% saturation

A

this is a protection against altitude and respiratory disease

21
Q

cons of the plateau in sigmoid shape

A

however, the plateau reduces the usefulness of hyperventilation and O2 therapy

22
Q

benefits of steep portion at start of graph reflecting in % saturation and PO2

A

allows for O2 unloading in the tissues

23
Q

under what conditions can the increased affinity for O2 and there the left shift of the sigmoid shape occur

A 
decrease in pCO2 partial pressure
decrease hydrogen ions
decrease 2,3 DPG 
decrease temp
HbR
24
Q

under what conditions can the decreased affinity for O2 and there the right shift of the sigmoid shape occur

A

increase in pCO2 partial pressure
increase hydrogen ions
increase 2,3 DPG
increase temp

25
Q

bohr effect

A

in the tissues, the increase in PCO2 and H+ causes the haemoglobin to release more O2, the Bohr effect
that haemoglobin’s oxygen binding affinity is inversely related to both acidity and PCO2

26
Q

what does the Bohr effect facilitate

A

O2 release from Hb at tissues (curve shifts right due to increased PCO2)

27
Q

how does the bohr effect apply to 2,3 DPG

A

by an increase in temperature and 2,3-diphosphoglycerate

28
Q

Where is DPG diphosphoglycerate

A

formed in the RBC and binds to the beta chains of haemoglobin causing O2 release

29
Q

when is 2,3 DPG increased

A

increased in exercise, altitude, anaemia and respiratory disease and is reduced in stored blood

30
Q

which haemoglobin binds to O2 better and why
haemoglobin F
or haemoglobin A

A

haemoglobin F (fetal) binds O2 better than haemoglobin A (adult) because 2,3-DPG binds poorly to the gamma chains of haemoglobin F - improves O2 transfer across placenta

31
Q

where is myoglobin found and does it have a higher or lower affinity for O2 than Hb

A

myoglobin is found in skeletal and cardiac muscle. It has a higher O2 affinity than Hb and acts as a tissue store of O2

32
Q

how is Hb saturation affected in anemia

A

not affected

33
Q

how is arterial content reduced and why

A

but the arterial content of blood is reduced because the decreased amount of Hb per 100 ml blood decreases the O2 carrying capacity of the blood

34
Q

in what direction does the CO shift the oxyhaemoglobin dissociation curve

A

to the left

35
Q

what condition can CO lead to

A

severe tissue hypoxia

36
Q

signs of cyanosis

A

blue colouration of the skin and mucous membranes, especially the tongue, mouth, lips and nail beds

37
Q

when does cyanosis

A

it occurs when the arterial blood is 85% saturated (PO2=50 mmHg or 6.7 kPa) or when the capillary blood is 70% saturated (37.5 mmHg or 5 kPa)
central cyanosis is due to arterial blood desaturation

38
Q

what causes cyanosis

A

due to reduced tissue blood flow due to vasoconstriction (exposure to cold, Raynaud’s disease etc.), vascular obstruction or decreased cardiac output (heart failure, shock etc.)

39
Q

right shift in oxyhaemoglobin dissociation shift mean

A

increased oxygen unloading

40
Q

chloride shift at tissue

A

CO2 diffuses in rbc -> bicarbonate in rbc then into plasma because of permeability of cell membrane to negative ions
Cell membranes. impermeable to charged ions - rbc can exchange bicarbonate w/ Cl wi/ an anion exchanger protein Band 3
rbc - positive charge - neutralised by entering Cl- ions

41
Q

benefits of chloride shift at tissue

A

ensuresionicand electricalstability

duringthetransportofcarbondioxide

42
Q

reverse chloride shift

A

O2 diffuses in rbc and CO2 diffuses out
O2 binds to haemoglobin and causes release of hydrogen
fall in RBC pH -> converts bicarbonate to CO2 and water
conc of bicarbonate falls -> bicarbonate exchanged w/ chloride

43
Q

haldane effect

A

the deoxygenation of blood increases its ability to carry CO2
the loss of O2 allows Hb to bind more CO2 and H+ so more CO2 is carried as carbamino compoundsand as HCO3-

44
Q

how does haldane effect affect pH

A

the pH falls from 7.4 in the arterial blood to 7.35 in the venous blood

45
Q

conc of paCO2 during hyperventilation

A

“overbreathing” i.e. the PaCO2 is less than 40 mmHg

respiratory alkalosis

46
Q

conc of PaCO2 during hypoventilation

A

means that the PaCO2 is greater than 40 mmHg

cardiorespiratory biology (25 decks)

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