Give two examples of cells where 'cell shape' changes frequently.

Amoeba is a classic example of a cell that constantly changes its shape through a process called amoeboid movement. This unicellular organism extends temporary projections of its cytoplasm called pseudopodia (false feet) in different directions to move, engulf food through phagocytosis, and respond to environmental stimuli. The shape changes are facilitated by the dynamic rearrangement of its cytoskeleton, particularly actin filaments, which allow the cell membrane to bulge outward and flow in the direction of movement, making the amoeba's shape highly variable and constantly shifting.

White blood cells (leukocytes), particularly neutrophils and macrophages, also exhibit frequent shape changes as they perform their immune functions. These cells use amoeboid movement to squeeze through tiny gaps between cells in blood vessel walls (a process called diapedesis) to reach infection sites in tissues. Once at the site of infection, they change shape dramatically to engulf and destroy pathogens through phagocytosis, extending pseudopodia around bacteria or cellular debris. This shape flexibility is crucial for their role in the immune response, allowing them to navigate through complex tissue environments and effectively capture foreign invaders regardless of their size or location.