In DIFFUSION AND FACILITATED DIFFUSION no energy is used. The one that needs a helper to get thing across is FACILITATED DIFFUSION.<span> Facilitated diffusion involves the diffusion of materials across the cell plasma membrane with the aid of membrane proteins such as carriers and channels. The process of diffusion does not need a carrier, the molecules to be transported just move on their own from the area of high concentration to the region of low concentration until the concentration in the space become uniform.</span>
Answer:
Biological evolution refers to the cumulative changes that occur in a population over time. These changes are produced at the genetic level as organisms' genes mutate and/or recombine in different ways during reproduction and are passed on to future generations.
Explanation:
Recall that apoptosis is programmed cell death—think of it as the cell deciding to self-destruct. So you might ask yourself, why would a cell need to die?
Remember that, in the cell cycle, there are certain checkpoints where a cell may stop and ensure everything is going smoothly. If something went wrong, the cell could potentially become cancerous, in which case it is much safer for a cell to undergo apoptosis rather than risk developing cancer.
Another example would be in the immune system. When cells get infected, cells called <em>cytotoxic t cells</em> go around and force these infected cells to undergo apoptosis in order to reduce the spread of infection.
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