Structure and function of normal red cells

Question 1

properties of a RBC

Answer 1

Full of haemoglobin 
no nucleus 
no mitochondria 
high surface area/volume ratio to allow gas exchange 
flexible to squeeze through capillaries

Question 2

consequences of RBC structure

Answer 2

high oncotic pressure due to oxygen rich environment

no nucleus - so cant decide and replace damage (limited lifespan)

limited to glycolysis (no mitochondria)

high surface area/volume ratio - need to keep water out

specialised membrane that can go wrong

Question 3

what is the RBC membrane like

Answer 3

like a geodesic tent

• complex structure
• protein ‘spars’ and anchors
• makes it flexible

Question 4

what to RBCs need energy for

Answer 4

maintain specific ion concentration gradients and keep water out

sodium/potassium pump keeps the water out but needs ATP to work

Question 5

what is the structure of haemoglobin

Answer 5

tetrameric globular protein

HbA (adult) is 2 alpha and 2 beta chains

haemorrhage group is iron inside a flat porphyrin ring

once oxygen is added to the haemoglobin the Fe2+ becomes Fe3+ (because oxidation is loss so a -ve electron is lost)

Question 6

functions of haemoglobin

Answer 6

delivers oxygen to tissues

acts as a buffer for H+

Co2 transport

Question 7

what regulates red cell production

Answer 7

erythropoietin

hypoxia sensed by kidney

erythropoietin produced

erythropoietin stimulates red cell production in bone barrow

more red cells carry more oxygen so erythropoietin drops

Question 8

what is the average red cell lifespan

Answer 8

120 days

Question 9

how are red blood cells destroyed

Answer 9

age red cells are taken up by macrophages to take them out of circulation

red cell contents are recycled

• globin chains - recycled to amino acids
• heme group broken into iron and bilirubin (taken to liver and conjugated)

Question 10

where does red cell destruction occur

Answer 10

spleen (and liver)

Question 11

what happens to bilirubin

Answer 11

taken to the liver and conjugated

comes out in faeces making it brown and urine making it yellow

Question 12

how do free radicals damage RBCs

Answer 12

makes Fe2+ go to Fe3+ which doesn’t transport oxygen

Question 13

what is the Embden- Meyerhof pathway

Answer 13

glycolysis

production of ATP

Question 14

how is Fe2+ prevented from becoming Fe3+

Answer 14

2NAD+ converted to 2NADH

protects Fe2+

Question 15

what are reactive oxygen species

Answer 15

free radicals with unpaired free electrons

eg. superoxide or hydrogen peroxide

they are capable of interacting with other molecules and damaging their structure

Question 16

what protects us from hydrogen peroxide

Answer 16

Glutathione

• protects us from hydrogen peroxide by reacting with it to form an oxidised glutathione product

rate limiting step here is glucose-6-phosphate dehydrogenase

this is the hexose monophosphate shunt

Question 17

how is CO2 transported from tissues to lungs

Answer 17

10% dissolved in solution
30% young to Hb as cab amino-Hb
60% as bicarbonate

Question 18

what enzyme is responsible for creating bicarbonate

Answer 18

carbonic anhydrase

converse CO2 and H20 to bicarbonate

Question 19

how many molecules of O2 are carried per one Hb

Answer 19

4

Question 20

what is HbF

Answer 20

Hb fetus

fetal Hb has two alpha and two gamma units

Question 21

what is the disassociation curve for oxygen binding to Hb

Answer 21

sigma curve

as one oxygen binds to Hb cooperative binding/allosteric effect occurs

alters how easy it is for the next O2 to bind to a different subunit

Question 22

different types of Hb have different dissociation curves

Answer 22

fetal Hb saturates more at the same pO2 so effectively takes O2 from the maternal circulation

in muscles, myoglobin drops oxygen v easily in the tissues

Question 23

what is the rapapoport-lubering shunt

Answer 23

2,3BPG molecule generation

small molecules which interfere with Hb to make it harder to bind oxygen by getting in between the alpha and beta groups

if we stop producing these molecules it makes oxygen binding easier

Question 24

what is the rapapoport-lubering shunt

Answer 24

2,3BPG molecule generation

small molecules which interfere with Hb to make it harder to bind oxygen by getting in between the alpha and beta groups

this means it can get into the tissues

if we stop producing these molecules it makes oxygen binding easier