Cell shape is determined by cellular mechanics. Cell deformations in animal cells, such as those required for cell migration, division or epithelial morphogenesis, are largely controlled by changes in mechanical stress and tension at the cell surface. The plasma membrane and the actomyosin cortex control surface mechanics and determine cell surface tension. Tension in the actomyosin cortex primarily arises from myosin-generated stresses and depends strongly on the ultrastructural architecture of the network. Plasma membrane tension is controlled mainly by the surface area of the membrane relative to cell volume and can be modulated by changing membrane composition, shape and the organization of membrane-associated proteins. We review here our current understanding of the control of cortex and membrane tension by molecular processes. We particularly highlight the need for studies that bridge the scales between microscopic events and emergent properties at the cellular level. Finally, we discuss how the mechanical interplay between membrane dynamics and cortex contractility is key to understanding the biomechanical control of cell morphogenesis.
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