Biconcave disc

A biconcave disc model of a discocyte

A biconcave disc — also referred to as a discocyte — is a geometric shape resembling an oblate spheroid with two concavities on the top and on the bottom. It is meta-stable, and involves the continuous adjustment of the asymmetric transbilayer lipid distribution, which is correlated with ATP depletion.

Mathematical model

A biconcave disc can be described mathematically by

$z(r)=D{\sqrt {1-{\frac {4r^{2}}{D^{2}}}}}\left(a_{0}+{\frac {a_{1}r^{2}}{D^{2}}}+{\frac {a_{2}r^{4}}{D^{4}}}\right)$

where z(r) is the height of the surface as a function of radius r, D is the diameter of the disc, and a_0, a_1, a_2 are coefficients describing the shape. The above model describes a smooth surface; actual cells can be much more irregular.

Biology

Erythrocytes are in the shape of a biconcave disc.