The cytoskeleton of an eukaryotic cell is a composite polymer material with unique structural (mechanical) properties. To investigate the role of individual cytoskeletal polymers in the deformation response of a cell to an external force (stress), we created two structural models - a thick shell model for the actin cortex, and a three-layered model for the whole cell. These structural models for a cell are based on data obtained by deforming suspended cells, where each cell is stretched between two counter-propagating laser beams using an optical stretcher. Our models, with the data, suggest that the outer actin cortex is the main determinant of the structural response of the cell.