W1: Red Blood Cells

Question 1

3 features or rbcs (erythrocytes)

Answer 1

*biconcave disc shape
*no nuc/ cytoplasmic organelles in mature rbcs
*contain Hb

Question 2

what stops rbcs from aggregating?

Answer 2

neg charge of outer surface of rbc membranes

Question 3

why do rbcs have transmembrane proteins?

Answer 3

to give shape + some rigidity

Question 4

function of band 3 protein

Answer 4

anion transport e.g chloride + bicarbonate

Question 5

function of glycophorin A

Answer 5

maintenance of neg charge – electrostatic repulsion to prevent aggregation, sugar transport

Question 6

function of glycophorin C

Answer 6

regs cell shape, mem
deformability + mem mechanical stability

Question 7

function of ankyrin

Answer 7

links lipid bilayer to spectrin

Question 8

function of spectrin

Answer 8

maintenance of bioconcave disc

Question 9

function of “actin complex”

Answer 9

links lipid bilayer to spectrin

Question 10

most abundant rbc cytoskeletal protein

Answer 10

spectrin

Question 11

how do rbcs obtain ATP + why

Answer 11

anaerobic glycolysis bc they do not contain mito

Question 12

what is MetHb?

Answer 12

a form of haemoglobin that cannot carry oxygen to deliver to tissues, inoperative O2 carrier

Question 13

what product of glycolysis regulates O2 affinity of Hb?

Answer 13

2,3 DPG (= 2,3 BPG)

Question 14

define erythropoiesis

Answer 14

prod of new rbcs

Question 15

what regs rbc prod?

Answer 15

erythropoetin (epo), prod in kidneys

Question 16

how does no. of rbcs incr?

Answer 16

epo acts on committed erythroid precursors to incr cell division

Question 17

what’s renal hypoxia + how does it affect epo prod?

Answer 17

low O2 levels (in kidneys)
incr epo prod

Question 18

what makes rbcs flexible to fit through capillaries?

Answer 18

bc nucleus is extruded + phagocytosed before release from marrow

Question 19

what’s a reticulocyte?

Answer 19

immature rbc

Question 20

important role of cytoplasmic organelles of reticulocytes

Answer 20

they continue to synthesise Hb for 1-2d after release into circ

Question 21

what does a high reticulocyte count indicate?

Answer 21

incr rate of rbc prod - acute bone marrow stress/ malignancy

Question 22

what organ is described as the rbc quality control organ

Answer 22

spleen

Question 23

how are rbcs destroyed?

Answer 23

by macrophages in spleen if senescent/ defective

Question 24

what incr rate of destruction by splenic macrophages in red pulp?

Answer 24

loss of mem pliability
antibody coating

Question 25

what is recycled by splenic macrophages?

Answer 25

Fe

Question 26

function of Hb

Answer 26

transportation of:
*O2 from lungs to respiring tissue
*CO2 from respiring tissue to lungs

Question 27

oxyhaemoglobin vs deoxyhaemoglobin

Answer 27

oxyhaemoglobin - oxygenated state – bright red colour
Deoxyhaemoglobin - deoxygenated state – dark red

Question 28

what is the main catalysing enzyme for CO2 transportation?

Answer 28

mem-associated carbonic anhydrase

Question 29

what does mem-associated carbonic anhydrase catalyse?

Answer 29

*CO2 + H2O → H2CO3- (= carbonic acid), rapidly dissociates to H+ & HCO3-
*HCO3- diffuses back into the plasma, (~70% of transported CO2)
*HCO3- dissociates back into CO2 + H2O in alveoli, CO2 released to air

Question 30

how does Hb act as a buffer?

Answer 30

H+ ions left from dissociation of carbonic acid to bicarbonate bind to globin chains of Hb

maintains stable plasma pH + protects against respiratory acidosis

Question 31

structure of Hb

Answer 31

terametric molecule
4 globin chains - 2 alpha, 2 beta
4 haem groups

Question 32

what does a haem group consist of?

Answer 32

an Fe atom in a porphyrin ring (physical not chem interaction)

Question 33

what’s O2 affinity?

Answer 33

relationship btwn Hb O2 saturation + partial pressure of O2

Question 34

why is O2 dissociation a curve shaped graph?

Answer 34

bc binding of 1st O2 is difficult but 2nd + 3rd easier
want to conserve O2 in arteries + give it up easily in tissues

Question 35

what specifically adjusts O2 affinity?

Answer 35

conformational change varies access to/ from haem groups

Question 36

what does 2,3DPG bind to + cause?

Answer 36

to deoxyHb + reduces O2 affinity further

Question 37

how does acidosis affect O2 affinity + O2 supply

Answer 37

reduces O2 affinity (Bohr effect) + incr O2 supply

Question 38

what is increased affinity of HbF due to?

Answer 38

less active binding (by y chains) to 2,3DPG
essential for developing foetus

Question 39

6 advs of artificial rbcs vs transfused human rbcs

Answer 39

*storage temp + shelf-life
*immediate, universal administration
*no lag in effectiveness unlike natural blood (due to 2,3-DPG (metabolite) + nitric oxide depletion during storage)
*no risk of disease transmission e.g HIV
*not dependant on donors
*avoid religious/ cultural issues e.g. Jehovah’s Witnesses

Question 40

why can’t Hb transfused in solution?

Answer 40

bc free globin chains are toxic to kidneys, scavenge nitrous oxide - leads to vasoconstriction + hypertension
unfavourable, fixed O2 affinity, short half life (30mins)