RBCs

structure of RBCs

Biconcave disc, lack a nucleus and cytoplasmic organelles. They contain haemoglobin, a flexible membrane, and a cytoskeleton for deformability.

What is the main functions of RBCs?

• Gas Transport: Carry oxygen and CO₂

What are the two main metabolic pathways in RBCs?

• Anaerobic Glycolysis: Produces ATP for energy.

• Pentose Phosphate Pathway:

  • Maintains iron in the Fe²⁺ state for oxygen binding.

  • Prevents oxidation to non-functional Fe³⁺.

What is the role of 2,3-DPG in RBC metabolism?

2,3-DPG decreases oxygen affinity of haemoglobin, enhancing oxygen delivery to tissues

What regulates RBC production?

Erythropoietin, a cytokine produced by the kidneys in response to hypoxia

What is the maturation process of an RBC?

Stem cell → Proerythroblast → Erythroblast → Reticulocyte → Erythrocyte

What is the average lifespan of an RBC?

around 120 days in circulation

What happens to RBCs after 120 days?

They are removed by macrophages in the spleen, which acts as a filter

What are the end products of RBC destruction?

• Haem is broken down into bilirubin, excreted in bile and urine.

• Iron is recycled for new RBC production

What is the structure of haemoglobin?

Haemoglobin is a tetramer with:

• 4 globin chains

• 4 haem groups

What is haemoglobin's function in oxygen transport

• Fe²⁺ binds O₂ reversibly.

• Cooperative binding allows high O₂ affinity in lungs and low O₂ affinity in tissues for efficient release.

How does haemoglobin transport CO₂?

• 25% binds to haemoglobin.

• 70% is converted to bicarbonate via carbonic anhydrase.

What is anaemia?

reduced haemoglobin in the blood

What are the symptoms of anaemia?

Fatigue, pallor, lethargy, shortness of breath, palpitations. Severe cases can cause heart failure or confusion.

How is anaemia classified?

• Normocytic, Normochromic: Normal size and Hb content (e.g., acute blood loss, renal failure).

• Microcytic, Hypochromic: Small RBCs, low Hb (e.g., iron deficiency, thalassemia).

• Macrocytic, Normochromic: Large RBCs, normal Hb (e.g., B12 or folate deficiency).

What are haemoglobinopathies?

Genetic disorders affecting haemoglobin structure or production

What are the two main categories of haemoglobinopathies

• Structural Variants: Abnormal amino acid substitutions in globin chains (e.g., HbS in sickle cell).

• Thalassemia: Reduced or absent production of globin chains (e.g., α-thalassemia, β-thalassemia).

What is sickle cell disease?

A condition where HbS forms insoluble crystals when deoxygenated, causing RBC sickling, and haemolysis.

How is sickle cell disease managed?

Transfusion therapy and gene therapy

What are the potential advantages of artificial RBCs?

• Longer shelf-life.

• Universal compatibility.

• No risk of disease transmission.

What are the limitations of artificial RBCs

• Free haemoglobin is toxic and has a short half-life (~30 minutes).

• No currently licensed artificial RBC products in Europe/US.