Which of these forces is not utilized by cell-cell and cell-surface adhesion?

Covalent forces are not typically involved in cell-cell and cell-surface adhesion processes. Adhesion in biological systems primarily relies on weaker, non-covalent interactions that allow for reversible binding, which is essential for the dynamic nature of cellular interactions. These non-covalent interactions include steric stabilization forces, van der Waals forces, and electrostatic forces.

Steric stabilization forces arise from the physical presence of molecular structures that prevent close approach of cells or surfaces, contributing to stability in adhesion. Van der Waals forces, although weak individually, can cumulatively provide significant adhesive strength due to the proximity of molecules. Electrostatic forces occur when charged molecules attract or repel each other, playing a vital role in mediating interactions between cell surfaces.

In contrast, covalent forces involve the formation of strong, permanent bonds between atoms and are not typically utilized for adhesion because they do not allow the necessary flexibility and reversibility needed for effective cellular communication and interaction. Thus, this is why covalent forces stand out as the correct answer in this context.