Red blood cells

Question 1

What’s the first cell recognisable as an RBC precursor?

Answer 1

Proerythroblasts

Question 2

Name 4 properties of proerythroblasts

Answer 2

They’re relatively large cells
They have clearly visible nuclei
They have loose, lacy chromatin
They have basophilic cytoplasm

Question 3

What hormone is responsible for stimulating the production of RBCs by erythropoiesis and where’s it produced?

Answer 3

Erythropoietin is produced in the kidneys

Question 4

What’s the function of hypoxia-inducible transcription factor HIF?

Answer 4

HIF enhances the expression of iron-absorbing genes

Question 5

What’s the function of hepcidin?

Answer 5

Hepcidin is a key regulator of the entry of iron into circulation in mammals.

Question 6

What is iron important to in RBC production?

Answer 6

The synthesis of haemoglobin

Question 7

Name 4 causes of iron deficiency

Answer 7

Blood loss
Low dietary iron intake
Reduced absorption, due to coeliac disease, a gastrectomy or gastric bypass
Increased demands due to pregnancy or a growth spurt

Question 8

What is cyanocobalamin another name for?

Answer 8

Vitamin B12

Question 9

What are the 2 important metabolic functions of vitamin B12?

Answer 9

1) B12 acts as a coenzyme for methionine synthase in the methylation of homocysteine to methionine in cytosol
2) B12 acts as a coenzyme in the conversion of L-methylmalonyl coenzyme A to succinyl coenzyme A in the mitochondria, which is essential for RBC maturation and DNA synthesis

Question 10

What does B12 deficiency cause?

Answer 10

Abnormal and diminished DNA, which leads to failure of nuclear maturation.

Question 11

Why does vitamin B12 deficiency result in megaloblastic anaemia?

Answer 11

The active forms of folate cannot be formed and DNA synthesis fails

Question 12

What is folate?

Answer 12

Folate is a B-vitamin (B9) required to produce white and red blood cells in the bone marrow, as well converting carbohydrates into energy and producing DNA and RNA

Question 13

What is megaloblastic anaemia?

Answer 13

A condition in which the bone marrow produces unusually large, structurally abnormal, immature red blood cells (megaloblasts).

Question 14

Name 3 reasons for vitamin B12 deficiency

Answer 14

• Inadequate intake through diet
• Acquired disorders of B12 absorption
• Inherited disorders of B12 absorption

Question 15

Name 3 haematological tests for B12 deficiency

Answer 15

• Full blood count
• Blood film
• Bone marrow examination

Question 16

How is folate essential to DNA synthesis?

Answer 16

Folate acts as a coenzyme in the synthesis of thymidine triphosphate

Question 17

Name 4 causes of folate deficiency

Answer 17

• Inadequate dietary intake
• Absorption defects such as coeliac disease, Crohn’s disease, tropical sprue and alcohol abuse
• Increased demand due to pregnancy, haemolysis or cancer
• Antifolate drugs such as anticonvulsants, methotrexate or metformin

Question 18

What is tropical sprue?

Answer 18

An acquired malabsorptive condition of probable infectious aetiology. Features include altered small bowel mucosa, chronic diarrhoea and signs and symptoms of multiple vitamin and nutrient deficiencies

Question 19

What is hereditary spherocytosis?

Answer 19

Loss of membrane integrity allows the RBCs to become spherical. This is a common hereditary haemolytic anaemia in Northern Europe.

Question 20

What is thalassaemia?

Answer 20

Any group of hereditary haemolytic diseases caused by faulty haemoglobin synthesis

Question 21

What are the 2 main red blood cell enzymes?

Answer 21

Glucose-6-phosphate dehydrogenase (G6PD) and pyruvate kinase (PK).

Question 22

What metabolises 10% of red cell glucose?

Answer 22

The hexose monophosphate shunt (HMS), aka the pentose phosphate pathway (PPP)

Question 23

What enzyme is involved in the pentose phosphate pathway?

Answer 23

G6PD

Question 24

What’s an important product of the pentose phosphate pathway?

Answer 24

NADPH, which plays a role in protecting the RBC from oxidative damage

Question 25

In G6PD deficiency, generation of what 2 molecules is impaired?

Answer 25

NADPH and GSH

Question 26

What’s the most common enzymopathy?

Answer 26

G6PD deficiency

Question 27

What does the glycolytic pathway generate? What is the importance of the pathway?

Answer 27

ATP to maintain RBC shape and deformability. It regulates intracellular cation concentration via cation pumps.

Question 28

What substance is depleted in PK deficiency?

Answer 28

ATP

Question 29

What does the depletion of ATP in PK deficiency mean for cation pumps?

Answer 29

Cation pumps fail to function, so cells lose large amounts of potassium and water, causing chronic non-spherocytic haemolytic anaemia.