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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?

24
Q

CO2 + carbonic anhydrase = ?

A

carbonic acid

25
what does carbonic acid dissociate into
H+ and HCO3-
26
how does HCO3- exit the RBC?
through the HCO3-/Cl- exchanger (HCO3- moves out so most is dissolved in the plasma)
27
what is the chloride shift?
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
what is the oxygen storage compound found in muscles?
myoglobin
29
in an oxygen binding curve what is the partial pressure of oxygen and fractional saturation?
PP of oxygen - concentration of oxygen | Fraction sat - % of haem groups that have oxygen bound to them
30
does myoglobin or haemoglobin have a higher fractional saturation of oxygen?
myoglobin | - right shift means there will be more oxygen bound to myoglobin than Hb at any given concentration
31
what does a right shift in an O2 saturation curve mean?
affinity for oxygen is lower
32
what 4 things cause a right shift of the O2 saturation curve and what are they associated with?
Cl-, 2,3 DPG, H+ and Co2 | - associated with increased muscle activity
33
where is 2,3 DPG found and what does it do?
- found in low concentration in RBCs (5mM) | - it binds Hb and lowers its affinity for O2
34
Does HbF have a higher or lower affinity for 2,3 DPG than HbM?
lower therefore binds oxygen with a higher affinity
35
how much oxygen with HbA release in the tissues?
50%
36
how much oxygen with HbF be bound to?
75% - 50% then picks up half of the 50% that HbA drops in tissue
37
what is co-operativity in relation to HbA having an S shaped oxygen saturation curve?
can pick up and drop off oxygen where needed
38
myoglobin, Hb F and HbA - which have the highest affinity for oxygen?
myoglobin then right shift = HbF then right shift = HbA
39
what is the main control of breathing?
oxygen, Co2 and H+ levels in the blood | - mostly by Co2 or H+ (in CSF)
40
which two brain structures monitor CSF to control breathing rate?
pons and medulla
41
how big are RBCs?
7 microns
42
what is the haematocrit?
% of whole blood taken up by CF once spun
43
where does erythropoiesis occur in development and after birth?
development - liver, spleen, LNs and yolk sac | post birth - BM only
44
what is EPO and where is it made?
hormone/cytokine made in the kidneys (in response to hypoxia) that drives erythropoiesis
45
how long to reticulocytes last?
2 days
46
what do reticulocyte levels indicate?
bone marrow activity
47
what is methaemoglobinaemia and what causes it?
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
how much stronger does CO bind Hb than O2?
250x
49
what will PP of O2 in the blood be in CO poisoning?
normal - just not enough O2 being carried by Hb
50
how is CO poisoning treated?
give patient 95% oxygen and 5% CO2 to drive out CO from binding pocket on Hb
51
what is polycythaemia and how is it detected?
too many red blood cells | - high PCV - increased viscosity of blood that can clog BVs
52
when is polycythaemia seen physiologically?
at high altitude
53
when is polycythaemia seen pathologically?
neoplasm called polycythaemia vera - treat
54
how much of total iron is found on Hb in adults?
65%
55
how much iron is stored intracellularly and in what form?
30% - stored as ferritin and haemosiderin
56
what system is iron stored in the body?
reticulo-endothelial system - liver, spleen, RBC, BM, macrophages/monocytes

BSMS 103 (23 decks)

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