Final answer:
Osmosis in vegetables like carrots and celery rehydrating when placed in water is a real-life example of water moving in and out of cells, which demonstrates the essentials of cellular transport.
Step-by-step explanation:
A real-life example of water moving in and out of cells is osmosis, such as when carrots and celery become limp from water loss and are made crisp again by placing them back in water.
Osmosis is the diffusion of water across a semipermeable membrane. In biological systems, cells are surrounded by such membranes, and osmosis is vital for maintaining cellular integrity as well as adapting to the solute composition in the extracellular environment. When carrots or celery are placed in water, water moves into their cells by osmosis, rehydrating and causing them to become crisp once more. Another example is when a cucumber becomes a pickle after being placed in a salt solution, losing water by osmosis and absorbing some salt. In contrast, active transport is used by the kidneys to move water and substances against the concentration gradient, which requires energy. Both of these examples demonstrate essential processes of cellular transport in living organisms.