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c > carriage of oxygen in the blood > Flashcards

carriage of oxygen in the blood Flashcards

1
Q

what are the roles of the cardiovascular system?

A

supply oxygen and metabolic fuel to tissues
remove metabolic waste from tissues
defence against pathogens

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2
Q

what is oxidation?

A

loss of electrons

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3
Q

what is an oxidising agent?

A

a substance that is reduced so that it can oxidise another molecule

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4
Q

give examples of oxidising agents in anaerobic bacteria

A

sulphate
nitrate
sulphur

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5
Q

what does oxidation do to a substrate?

A

simplifies the electronic structure

releases energy

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6
Q

what is reduction?

A

gain of electrons

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7
Q

what does reduction do to substrates?

A

allows complex molecules to be made from simple ones

requires energy

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8
Q

when are oxidation reactions irreversible?

A

when they release a large amount of energy

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9
Q

what does NAD stand for?

A

nicotinamide adenine dinucleotide

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10
Q

how is NAD used in the body?

A

NADH gives electrons

NAD can store electrons

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11
Q

give an equation for NAD to NADH

A

NAD+ + H+ + 2e- –> NADH

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12
Q

what is microcytic anaemia?

A

smaller than usual RBCs

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13
Q

what is microcytic anaemia?

A

larger than usual RBCs

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14
Q

what are reticulocytes?

A

immature RBCs that have just left the bone marrow

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15
Q

what % of RBCs are reticulocytes?

A

1-2%

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16
Q

how long does it take for reticulocytes to turn into mature RBCs?

A

1 day after being in circulation

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17
Q

how is the rRNA arranged in reticulocytes?

A

reticular, mesh-like structure

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18
Q

what does a blood smear with high levels of reticulocytes show?

A

lots of haemolysis

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19
Q

why can RBCs not repair themselves?

A

they don’t have a nucleus or organelles

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20
Q

how long do RBCs survive in the bloodstream?

A

120 days

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21
Q

why do RBCs require a small amount of ATP?

A

maintain the Na+ pumps in the cell membranes

actin filaments

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22
Q

how do RBCs make ATP?

A

glycolysis

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23
Q

what is the glucose uptake system in RBCs?

A

glut1 - works by facilitated diffusion

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24
Q

what is the pH of RBCs?

A

low - acidic

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25
Q

why do RBCs contain antioxidants? name an antioxidant

A

to protect haemoglobin against oxidative stress

vitamin C

26
Q

describe the process of an RBC being destroyed?

A

ageing RBC undergoes changes to its plasma membrane
recognised by phagocytes
undergoes phagocytosis in the spleen, liver and bone marrow

27
Q

what is a haem group?

A

porphyrin ring with a ferrous iron centre

28
Q

what does hexavalent mean?

A

can form 6 bonds with surrounding atoms

29
Q

how many electrons does ferrous iron have in its outer shell and how are they arranged?

A

6 d electrons

4 in one plane held to nitrogen atoms in the porphyrin ring

one bound to a histidine group underneath the porphyrin ring

one sticking out

30
Q

why does oxygen form a weak reversible bond to haemoglobin?

A

oxygen cannot get close enough to remove the electron fully because of steric hindrance

31
Q

what causes steric hindrance in a haemoglobin molecule?

A

3D folding of the subunit

32
Q

what makes up a haemoglobin molecule?

A

4 subunits each with a haem group attached

4 polypeptide chans connected by salt bridges, hydrogen bonds and hydrophobic interactions

33
Q

what is methaemoglobin?

A

haemoglobin with ferric iron

34
Q

when is methaemoglobin made?

A

over time, RBCs gradually accumulate methaemoglobin so they can no longer carry oxygen

35
Q

what does methaemoglobin reductase do?

A

converts methaemoglobin back to haemoglobin

36
Q

what does methaemoglobin reductase rely on?

A

NADH

37
Q

what percentage of people’s haemoglobin is methaemoglobin?

A

1-2%

38
Q

what is methaemoglobinemia and what causes it?

A

abnormally high Methaemoglobin

genetics or exposure to chemicals

39
Q

how does a high level of methaemoglobin lead to the death of a RBC?

A

markers on the surface of the RBC change
change is detected by the cells of the liver and spleen
they signal to dendritic cells and macrophages

40
Q

how do individuals with methaemoglobin reductase deficiency compensate for the defect?

A

make more RBCs than normal

polycythemia

41
Q

what are the subunits of adult haemoglobin?

A

2 alpha

2 beta

42
Q

what are the subunits of fetal haemoglobin?

A

2 alpha

2 gamma

43
Q

what is an advantage of fetal haemoglobin having a higher affinity for oxygen?

A

can remove it more easily from placental blood

44
Q

what does 2,3 DPG stand for and what does it do?

A

2-3 diphosphateglycerate

enhances ability of RBCs to release oxygen in hypoxic tissue

binds to beta subunit as it starts to deoxygenate and increases steric hindrance

45
Q

define percent saturation

A

proportion of haemoglobin bound to oxygen

46
Q

how can % Hb be measured?

A

pulse oximeter

uses a laser to detect the colour of blood which is a good indicator of levels of venous blood

47
Q

what should be the levels of % Hb in healthy individuals?

A

96-99%

48
Q

what is hypoxaemia?

A

arterial oxygen saturation below 90%

49
Q

what shape is the oxygen/haemoglobin curve?

A

sigmoid shape

50
Q

how does heat shift the oxygen/haem curve?

A

heat shifts curve to the right

51
Q

how does pH shift the oxygen/haem curve?

A

low pH shifts the curve to the right

52
Q

describe the structure of myoglobin

A

single subunit with haem group on it

53
Q

how does myoglobin act as an oxygen store?

A

loads O2 as Hb unloads it

only releases O2 when pO2 is very low and Hb cannot supply O2 fast enough

54
Q

where does the myoglobin curve lie with respect to the HbA curve?

A

to the left - has a higher affinity for oxygen

55
Q

what is rhabdomyolysis?

A

the process of myoglobin being released from damaged muscle tissue

56
Q

how can myoglobin cause acute kidney failure?

A

rhabdomyolysis occurs
myoglobin is filtered by the kidneys
toxic to the renal tubular epithelium
causes acute renal failure

57
Q

what controls haematocrit levels?

A

erythropoietin (EPO)

58
Q

where is EPO released from?

A

interstitial cells in the kidneys

59
Q

what part of the body does EPO act on?

A

bone marrow

60
Q

describe the negative feedback loop of EPO raising haematocrit levels

A 
normal haematocrit = 45%
haematocrit falls
renal hypoxia
EPO increases
stimulates RBC production in the bone marrow
haematocrit levels restored
61
Q

how is CO2 carried in red blood cells?

A

CO2 converted to bicarbonate via carbonic anhydrase

bicarbonate diffuses out of RBC

chloride moves in to maintain the electrical neutrality (chloride shift)

62
Q

how is CO2 removed from the blood in the lungs?

A

venous blood containing bicarbonate brought to the lungs
bicarbonate re-enters RBC and converted back to CO2
CO2 diffuses into alveoli air space
chloride leaves the RBC to balance the electrical charge of bicarbonate entering

c (25 decks)

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