A theoretical study on the stability of biocolloidal particles immersed in an electrolyte solution is presented. The outer border of each biocolloid is covered with an ion-penetrable membrane carrying nonuniformly distributed positive and negative fixed charges. The results of numerical simulations reveal that the classical point-charge model underestimates the stability ratio of a biocolloidal suspension, W, for both constant total amount of positive fixed charges and that of negative ones in membrane phase. W predicted by the case of a nonlinear distribution of positive and negative fixed charges is larger than that predicted by the case of a corresponding linear one. A thick membrane causes a small W, and the larger the dielectric constant of a suspension, the larger the value of W. Increasing the sizes of mobile cations or positive fixed charges provokes a reduction in W. The reverse is true for mobile anions or negative fixed charges. A small value of W can result from (1) a large average concentration of positive fixed charges, (2) a small average concentration of negative fixed charges, (3) a large nonuniformity index for positive fixed charges, or (4) a small nonuniformity index for negative fixed charges.