For the RBC's to survive for 120 day lifespan, the following conditions are necessary:
(a)the red cell membrane must be deformed
(b)hemoglobin structure and function must be adequate
(c) the red cell metabolic pathways must be active
old RBC's are removed by
immature RBCs are less deformable
mature/ old RBCs are less deformable because of the hardening of the membrane
Functions of RBC Membrane
- Separates intracellular from extracellular fluid
- Allows nutrient and ion passage selectively (Selective Permeability)
- Allows the cell to deform when needed
o Influenced by Cell shape Cytoplasmic Viscosity Membrane deformability and stability
Cell surface area of RBC is greater than the cell volume
-Semi-permeable lipid bilayer supported by a mesh-like cytoskeleton
-52 % CHON, 40 % lipids, 8 % CHO
-Over 300 RBC antigens have been identified in the membrane
glycolipids make up the surface antigen
2 kinds of proteins of erythrocyte membrane
: Integral proteins and Peripheral proteins
membrane proteins that extend from the outer surface and traverse the entire membrane to the inner cytoplasmic site of RBCs. Embedded on lipid bilayers.
situated right beneath the inner leaflet.
outer layer of membrane
inner layer of membrane
- Phospholipids and unesterified cholesterol are present in nearly equimolar quantities
- Free fatty acids and glycolipids are present in small quantities.
Phospholipids that are situated on the outer leaflet are collectively called
represent the controlling points in the major pathways of lipid renewal
also known as flippase. It functions to help the phospholipid to easily enter the membrane.
Aminophospholipid translocase (ATP dependent enzyme)
are the gateways in the entry of phospholipids. Those phospholipids need enzyme for entry and these enzymes are ATP-dependent
Phosphatidylcholine and Sphingomyelin
maintains the precise lipid pattern that is critical in normal survival of RBC in circulation.
Inner leaflet has negative charge, the outer leaflet is still negative charge but is not from the phospholipid
Negative charge phospholipid in the inner leaflet of the aged RBC if will be flipped will result in