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Erythrocyte Membrane Structure, Metabolism, and Destruction


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Normal RBC Membrane Structure
  • Lipids 42%
    • phospholipids
    • glycolipids and cholesterol
  • Proteins 50%
    • integral penetrating proteins
    • peripheral structural proteins
      • spectrin & actin: help keepRBC shape
Functions of RBC Membrane
  • RBC cell shape
  • controls volume and water content
    • sodium-potassium pump (est 300/cell)
    • Passive influx of Na+ & K+ is controlled by 300 cationic pumps that actively transport Na+ out of cell & K+ into cell

Erythrocyte Metabolism:


Embden-Meyerhof pathway 

  • anerobic glycolysis
    • GLC--> GLC 6-P --> Fructose 6-P --> 1,3-diP-glycerate +3-P-glycerate--> lactate
  • 2 ATP generated
  • NADH generated

Erythrocyte Metabolism:


Methemoglobin Reductase 

  • NADH keeps hemoglobin reduced by methemoglobin reductase
  • oxidized to methemoglobin
  • Accumulation of Methemoglobin Fe2+ --> Fe3+

Erythrocyte Metabolism:


Leubering-Rapaport shunt 

  • Makes 2,3-diP-glycerate
    • ability of Hgb to open and close to oxygen

Erythrocyte Metabolism:


Heoxse monophosphate shunt (Phosphogluconate) 

  • Deficient in G-6-PD results in oxidized Hgb.
  • Get formation of Heinz bodies with subsequent extravascular hemolysis
  • G-6-P + NADPH --> NADP produces 6-P-gluconate --> pentos-P
Spleen anatomy and blood flow
  • white pulp contains lymphocyte
  • red pulp contains RBC, WBC, platelets, fixed and free macrophages
  • slow blood flow goes from arterie --> sinuses lined by macrophages --> veins
RBC and Spleen interaction
  • RBC must squeeze betwen cords of cells and return to normal shape
  • RBC goes to spleen about 120 times/day
  • 30 sec/journey for normal RBCs
  • abnormal cells stay min-hrs
  • environment is stagnant, acidic, hypoxic (loss of O
Functions of Spleen
  • Hematopoietic: germinal center of WBC
  • Culling: macrophages phagocytose bad cells
  • Pitting: macrophage takes out part of cell & leave membrane intact
    • reticulocyte
  • Immunologic: lymphocytes
  • reservoi
Consequences of splenectomy
  • slight increase in reticulocytes in blood
  • abnormal RBC morphology
    • howell-jolly bodies, other inclusions
    • target and burr cells
    • high platelet count withlarge abnormal platelets (Increase 20-30%)
    • WBC increa

Erythrocyte Senescence ("old"):



  • membrane bound IgG
  • density
  • spheroidal shape: less membrane
  • MCHC
  • internal viscosity
  • agglutinability
  • Na+
  • methemoglobin (oxidized hgb- no NADH to keep it reduced)
  • oxygen affinity

Erythrocyte Senescence ("old"):


  • several enzyme activities
  • deformability
  • MCV: fluid taken out
  • phospholipid
  • cholesterol
  • K+
  • protoporphyrin

Erythrocyte Destruction  


Extravascular 90%

  • phagocytosed by reticuloendothelial system (RES) cells & digested by their lysosomes
  • refer to notes for pathway

Erythrocyte Destruction 


Intravascular 10% 

  • RBC breakdown occurs within lumen of blood vessels.
  • refer to notes for pathway

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