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BSMS 103 > Theme 2. - RBCs > Flashcards

Theme 2. - RBCs Flashcards

1
Q

what do RBCs do in the lungs?

A

pick up O2 and deposit CO2

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2
Q

how soluble is oxygen in plasma?

A

poorly soluble

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3
Q

how much more O2 is carried on Hb than dissolved in the blood?

A

70%

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4
Q

how can hypoxia occur even if PO2 is normal?

A

most oxygen is carried on Hb so if there is insufficient Hb to carry it there will be hypoxia (eg in anaemia)

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5
Q

what is co-operativity?

A

Hb can bind O2 in the lungs and release it in tissues

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6
Q

what % of a RBC is Hb?

A

95%

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7
Q

what makes up a Hb molecule?

A

4x haem groups, 4x polypeptide globin chains (2xalpha and 2xbeta)

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8
Q

what makes up a haem group?

A

Porphyrin ring plus an Fe atom

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9
Q

how is Fe bound to the porphyrin ring of haem?

A

through non covalent bonding

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10
Q

where does the O2 sit in the haem molecule

A

in the centre of the Fe

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11
Q

what makes Hb red?

A

the porphyrin rings and movement of electrons in the covalent bonds in response to light

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12
Q

what type of iron is Hb conjugated to?

A

Ferrous (Fe2+)

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13
Q

how many oxygens can each haem bind?

A

one

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14
Q

what composition of Hb does HbA and HbM have?

A

2x alpha and 2x beta

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15
Q

what composition of Hb does HbF (foetal) have?

A

2x alpha and 2xgamma

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16
Q

which Hb has the highest affinity for oxygen - HbA. HbM or HbF?

A

HbF

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17
Q

what is the Bohr effect?

A

increased CO2 in the blood causes a decreased affinity of Hb for oxygen

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18
Q

name two things that decrease Hb affinity for oxygen

A

Co2 and low pH

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19
Q

what kind of alteration does Co2 make to Hb when it binds?

A

allosteric - alters conformation to make it want to bind O2 less

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20
Q

what two molecules can bind Hb to make its affinity for oxygen less?

A

Co2 and H+ - bind at a different site to oxygen so its not competitive inhibition

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21
Q

what is the distribution of dissolved Co2 in the blood, was HCO3- and in carbamino compounds?

A

10% in blood, 68% asa HCO3- and 22% as carbamino compounds

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22
Q

how do carbamino compounds bind CO2?

A

CO2 displaces one of the NH3 groups to make COOH

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23
Q

are co2 levels higher outside or inside the cell?

A

outside

24
Q

CO2 + carbonic anhydrase = ?

A

carbonic acid

25
Q

what does carbonic acid dissociate into

A

H+ and HCO3-

26
Q

how does HCO3- exit the RBC?

A

through the HCO3-/Cl- exchanger (HCO3- moves out so most is dissolved in the plasma)

27
Q

what is the chloride shift?

A

in the body - Cl- moves into the cell in exchange for HCO3- so there is no build up of electrical charge
then in the lungs - Cl- moves out of the cell and HCO3- moves in

28
Q

what is the oxygen storage compound found in muscles?

A

myoglobin

29
Q

in an oxygen binding curve what is the partial pressure of oxygen and fractional saturation?

A

PP of oxygen - concentration of oxygen

Fraction sat - % of haem groups that have oxygen bound to them

30
Q

does myoglobin or haemoglobin have a higher fractional saturation of oxygen?

A

myoglobin

- right shift means there will be more oxygen bound to myoglobin than Hb at any given concentration

31
Q

what does a right shift in an O2 saturation curve mean?

A

affinity for oxygen is lower

32
Q

what 4 things cause a right shift of the O2 saturation curve and what are they associated with?

A

Cl-, 2,3 DPG, H+ and Co2

- associated with increased muscle activity

33
Q

where is 2,3 DPG found and what does it do?

A
  • found in low concentration in RBCs (5mM)

- it binds Hb and lowers its affinity for O2

34
Q

Does HbF have a higher or lower affinity for 2,3 DPG than HbM?

A

lower therefore binds oxygen with a higher affinity

35
Q

how much oxygen with HbA release in the tissues?

A

50%

36
Q

how much oxygen with HbF be bound to?

A

75% - 50% then picks up half of the 50% that HbA drops in tissue

37
Q

what is co-operativity in relation to HbA having an S shaped oxygen saturation curve?

A

can pick up and drop off oxygen where needed

38
Q

myoglobin, Hb F and HbA - which have the highest affinity for oxygen?

A

myoglobin then right shift = HbF then right shift = HbA

39
Q

what is the main control of breathing?

A

oxygen, Co2 and H+ levels in the blood

- mostly by Co2 or H+ (in CSF)

40
Q

which two brain structures monitor CSF to control breathing rate?

A

pons and medulla

41
Q

how big are RBCs?

A

7 microns

42
Q

what is the haematocrit?

A

% of whole blood taken up by CF once spun

43
Q

where does erythropoiesis occur in development and after birth?

A

development - liver, spleen, LNs and yolk sac

post birth - BM only

44
Q

what is EPO and where is it made?

A

hormone/cytokine made in the kidneys (in response to hypoxia) that drives erythropoiesis

45
Q

how long to reticulocytes last?

A

2 days

46
Q

what do reticulocyte levels indicate?

A

bone marrow activity

47
Q

what is methaemoglobinaemia and what causes it?

A

defective/pathological met Hb in RBC that cant carry oxygen

  • Iron in Hb is ferric (Fe3+) instead of ferrous (Fe2+)
  • can be caused by congenital globin mutations or hereditary decreases in NADH or toxic substance exposure
48
Q

how much stronger does CO bind Hb than O2?

A

250x

49
Q

what will PP of O2 in the blood be in CO poisoning?

A

normal - just not enough O2 being carried by Hb

50
Q

how is CO poisoning treated?

A

give patient 95% oxygen and 5% CO2 to drive out CO from binding pocket on Hb

51
Q

what is polycythaemia and how is it detected?

A

too many red blood cells

- high PCV - increased viscosity of blood that can clog BVs

52
Q

when is polycythaemia seen physiologically?

A

at high altitude

53
Q

when is polycythaemia seen pathologically?

A

neoplasm called polycythaemia vera - treat

54
Q

how much of total iron is found on Hb in adults?

A

65%

55
Q

how much iron is stored intracellularly and in what form?

A

30% - stored as ferritin and haemosiderin

56
Q

what system is iron stored in the body?

A

reticulo-endothelial system - liver, spleen, RBC, BM, macrophages/monocytes

BSMS 103 (23 decks)

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