The shape of RBC is biconcave due to?

Membrane proteins of RBC There are following membrane proteins of RBC: (A) Integral proteins These are embedded in membrane via hydrophobic interactions with lipids Integral proteins are: (1) Band-3: It has two functions: Anionic transport: Exchange bicarbonate for chloride Structural: Linkage of the lipid bilayer to underlying membrane skeleton and important for prevention of surface loss. (2) Glycophorins: Imparts a negative charge to the cell, reducing interaction with endothelium and other cells. (3) Aquaporin 1: These selective pores for water transport allow RBC to remain in osmotic equilibrium with ECF. I) Peripheral membrane proteins These are located on the cytoplasmic surface of the lipid bilayer and constitute membrane cytoskeleton. These are anchored via integral proteins These are responsible for elastibility and maintenance of RBC shape & stability. Important peripheral proteins are: Spectrin: It is the chief protein component and is responsible for the biconcave shape of RBC. Actin: Spectrin tail is associated with actin filament. Protein 4.1: Stabilizes actin-spectrin interactions. Adducin: Stabilizes actin-spectrin interactions. Ankyrin: Interacts with band 3 and spectrin to achieve linkage between bilayer and skeleton. It is aug­mented by protein 4.2.