RBCs

Question 1

State why being full of haemoglobin is a problem for RBCs

Answer 1

• high oncotic pressure (water wants to come in)
• oxygen-rich environment (oxidation risk)

Question 2

State why having no nucleus is a problem for RBCs

Answer 2

• can’t divide
• can’t replace damaged proteins
• limited cell lifespan

Question 3

State why having no mitochondria is a problem for RBCs

Answer 3

• limited to glycolysis for generation of energy (can’t perform citric acid cycle)

Question 4

State why having a high surface area/vol ratio is a problem for RBCs

Answer 4

need to keep water out

Question 5

State why being flexible is a problem for RBCs

Answer 5

specialised membrane required can go wrong

Question 6

What keeps the ion concentrations right (& therefore keeps water out) in RBCs

Answer 6

sodium-potassium pump (requires significant energy though)

Question 7

Describe the haem group in haemoglobin

Answer 7

Fe2+ in a flat porphyrin ring

Question 8

State the 3 functions of haemoglobin

Answer 8

• deliver oxygen to the tissues
• act as a buffer for H+
• CO2 transport

Question 9

Where does RBC production occur?

Answer 9

bone marrow

Question 10

What hormone regulates RBC production and where is it released from?

Answer 10

Erythropoietin (released from kidneys)

Question 11

What causes erythropoietin to be released from the kidneys?

Answer 11

senses hypoxia (NOT a cell counter)

Question 12

State the average RBC lifespan

Answer 12

120 days

Question 13

How are RBCs recycled?

Answer 13

Aged cells eaten by macrophages
Contents recycled:
- global chains recycled to amino acids
- heme group broken down to iron & bilirubin
- bilirubin taken to liver & conjugated, then excreted in bile

Question 14

What product of glycolysis is useful to the RBC & why

Answer 14

NADH (electron donor)
can recover Fe3+ to Fe2+ (3+ cannot carry oxygen)

Question 15

What molecule protects us from hydrogen peroxide (reactive O2 species) & how is it replenished

Answer 15

GLUTATHIONE (reacts with it to form water)/GSH
Replenished by NADPH (in turn generated by the hexose monophosphate shut)

Question 16

State the enzyme involved in the shunt to generate NADPH (needed to reform GSH) & its importance

Answer 16

G6PD - rate-limiting enzyme

Question 17

How is the majority of CO2 transported?

Answer 17

As bicarbonate

Question 18

Describe the unusual kinetics of O2 binding to Hb

Answer 18

Allosteric effect - when one binds, others more likely

Question 19

Describe the structural difference between foetal Hb & adult Hb

Answer 19

Foetal = alpha2 gamma2
Adult = alpha2 beta2

Question 20

State the difference between saturation with oxygen in foetal and adult haemoglobin

Answer 20

foetal saturates more at the same partial pressure of O2 (takes O2 from maternal circulation

Question 21

Describe the role of the Rapapoport-Lubering Shunt

Answer 21

• generates 2,3 DPG
• this shifts oxygen dissociation curve & allows more O2 to be released