Erythropoiesis

Question 1

structure that enables RBCs to function

Answer 1

Hb carries O2
no nucleus so deformable and more room for Hb
high SA/ volume ratio
specialised membrane makes it flexible

Question 2

what does the high oncotic pressure of RBCs risk?

Answer 2

draws water in so risks lysis

Question 3

what does the oxygen rich environment of the RBC risk?

Answer 3

oxidation

Question 4

adverse of RBCs having no nucleus?

Answer 4

unable to divide and replace damaged proteins so limited life span

Question 5

adverse of no mitochondria in the RBC

Answer 5

limited to glycolysis for energy

Question 6

how does the RBC keep water out?

Answer 6

Na+/K+ pump (needs ATP)

Question 7

what makes the RBC membrane flexible?

Answer 7

lipid bilayer with lots of proteins makes it flexible

Question 8

which molecule is a tetrameric globular protein?

Answer 8

Hb

Question 9

what chains are present in adult Hb?

Answer 9

2 alpha

2 beta

Question 10

what does the haem group consist of?

Answer 10

Fe2+ in a flat porphyrin ring (one haem per subgroup)

Question 11

how many oxygen molecules can bind to Fe2+

Answer 11

1

Question 12

how many oxygen molecules are there per Hb?

Answer 12

4

Question 13

how many ml of oxygen can 1g Hb carry when fully saturated?

Answer 13

1.34ml

Question 14

can Fe3+ bind oxygen?

Answer 14

no

Question 15

describe the steps in formation of the Hb molecules

Answer 15

1. iron/Fe2+ is transported to RBC cytosol
2. combines with porphyrin ring (now called haem)
3. combines with globin chain (alpha or beta)
4. subunits combine

Question 16

role of Hb

Answer 16

delivers oxygen to tissues
acts as a buffer for H+ (H+ can stick to it)
CO2 transport

Question 17

what regulates production of RBCs in the bone marrow?

Answer 17

erythropoietin

Question 18

what produces erythropoietin?

Answer 18

kidney

Question 19

where does RBC destruction occur?

Answer 19

spleen (and liver)

Question 20

average lifespan of a RBC?

Answer 20

120 days

Question 21

what takes up aged RBCs?

Answer 21

macrophages

Question 22

what are globin chains recycled to?

Answer 22

amino acids

Question 23

what is the haem group recycled to?

Answer 23

iron and bilirubin

Question 24

how is bilirubin excreted?

Answer 24

taken to the liver, conjugated and excreted in bile (colours faeces and urine)

Question 25

cascade of haem breakdown

Answer 25

haem > porphyrin > biliverdin > bilirubin

Question 26

what can free radicals do to Fe2+?

Answer 26

oxidise it to Fe3+ (metHb)

Question 27

what stops oxidation of Fe2+?

Answer 27

NADH in glycolysis

Question 28

examples of reactive oxygen species

Answer 28

superoxide | hydrogen peroxide

Question 29

what do reactive oxygen species have?

Answer 29

unpaired free electrons that are capable of interacting with molecules and damaging their structure

Question 30

where is glutathione (GSH) found?

Answer 30

in RBCs

Question 31

role of glutathione (GSH)?

Answer 31

protects from hydrogen peroxide by reacting with it to form water and an oxidised glutathione product (GSSG)

Question 32

what replenishes the oxidised glutathione product GSSG?

Answer 32

NADPH generated by the hexose monophosphate shunt

Question 33

what enzyme is involved in the hexose monophosphate shunt?

Answer 33

glucose-6-phosphate dehydrogenase (G6PD)

Question 34

is G6PD X-linked?

Answer 34

yes

Question 35

what happens if there is X-linked deficiency of G6PD?

Answer 35

boys will have low levels leading to impaired defence and oxidative damage

Question 36

what shape is the oxygen dissociation curve?

Answer 36

sigmoidal

Question 37

what is the allosteric effect?

Answer 37

when one oxygen binds to the Hb molecule it becomes easier for others to bind

Question 38

foetal Hb oxygen dissociation curve

Answer 38

saturates more pO2 so shifts curve to the left

Question 39

function of myoglobin?

Answer 39

in muscles it takes O2 from red cells

Question 40

what produces 2,3-BPG?

Answer 40

Rapapoport-Lubering shunt

Question 41

what increases 2,3-BPG?

Answer 41

chronic anaemia leading to increased oxygen release