Erythrocyte biochemistry

Question 1

What is the lifespan of an erythrocyte?

Answer 1

120 days

Question 2

Erythrocytes are destroyed by macrophages where?

Answer 2

in the spleen and kupfer cells of the liver

Question 3

What is the effect of 2,3,BPG on erythrocytes?

Answer 3

it binds to the haemoglobin- reducing its affinity for O2 in the periphery

Question 4

When do we see an increase in 2,3,BPG?

Answer 4

in high altitude environments

in patients with emphysema

and in patients with chronic anaemia

Question 5

How does glucose enter erythrocytes?

Answer 5

it enters via a specific transporter - not insulin dependent

*therefore diabetics with poor glucose control have high erythrocyte glucose*

Question 6

By what mechanism does the glucose enter the erythrocyte?

Answer 6

it binds to haemoglobin and produces glycated Hb (HbA1c)

this is an excellent measure of long- term glycaemic control in diabetics

Question 7

what is the purpose of the pentose-phosphate pathway?

Answer 7

it produces 2 NADPH per glucose 6 phosphate oxidized - this is a erythrocyte protectant b/c the NADPH is available for reduction of the CO2 that would otherwise damage the cell

Question 8

what is the regulatory mechanism of the Pentose phosphate pathway?

Answer 8

The irreversible oxidation of the G6P by G6Pdehydrogenase is inhibited fairly potently by the NADPH product - so it’s self regulated

Question 9

What three key enzymes protect cells from reactive oxygen species?

Answer 9

• catalase
• superoxide dismutase (SOD)
• glutathione peroxidase

the SOD and Catalase- convert ROS to O2 and H2O

the Glutathione peroxidase detoxifies H2O2 using glutathione which is then converted to the oxidized form

he

Question 10

What is the consequence of a disorder involving glucose 6 phosphate dehydrogenase?

Answer 10

eventually this will cause haemolysis of the erythrocyte - you’re NADH deficient so you cannot produce the reduced form of NADPH to protect from CO2 in the blood

Question 11

What causes erythrocytes to age?

Answer 11

erythrocytes age primarily through the accumulation of damage from oxidative stress. = eventually the cell isn’t able to protect itself from Reactive oxigenative species and it willa ge

Question 12

What is a heameoglobin with Fe3+ instead of Fe2+ called?

Answer 12

methaemoglobin

Question 13

why is it dangerous when the haem has Fe3+ instead of Fe2+?

Answer 13

Fe3+ binds water instead of O2

Question 14

what is the haem broken down into?

Answer 14

it is broken down into bilirubin and excreted via the gut

Question 15

What is glucose6phosphate dehydrogenase deficiency?

Answer 15

this enzyme is normally responsible for the formation of NADPH in eryrthrocytes as a protection from damage by oxidative species- so if you have a deficiency, your erythrocytes are not able to properly protect themselves from damage and they therefore have a limited lifespan

This condition is made worse by oxidant drugs (triple A)

• antibiotics
• antimalarials
• antipyretics
• as well as ingestion of fava beans
• infection
• and neonatal jaundice

Question 16

What is the cause of sickle cell anaemia?

Answer 16

point mutation in glutamate - to valine on the haemoglobin beta chain -this forms a “sticky patch” in low O2 conditions -

This results in stacking of the fibers into a sickle shape at low O2 conditions - and blocks capillaries - anoxia for tissues and eventual cell death