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Phagocytosis - Time to Eat!

Simply put, cells need to eat and drink just like you. Phagocytosis is the process of a cell eating. It is one type of endocytosis. Endocytosis happens when a cell goes out and takes in something. Phagocytosis is the situation when it gets a solid. Pinocytosis is the act of grabbing some liquid. The whole cell works during the process. It is not just some membrane proteins taking in a couple of molecules as in active transport.

Phagocytosis is a cell taking in a large object that it will eventually digest. The classic example is an amoeba eating a bacterium. First, the cell senses the bacterium because of chemicals in the environment. The cell then moves towards the prey. Once contact is made, the amoeba slowly wraps its cell membrane around the object. When the membranes reach out for the prey, they are called pseudopodium. When the cell membrane surrounds the object, the object has actually been sealed in a new vesicle.

The final step is digestion of the prey. If a cell does not act quickly, the bacterium could begin to reproduce. Lysosomes quickly attach to the vesicle of food and release digestive enzymes. The enzyme action is called an oxidative burst. The food is then broken down and the amoeba absorbs the nutrients. Waste particles remain in the vesicle and can then be sent out of the cell.

Hunting for Dinner

The ability to hunt down and eat food was a huge accomplishment for cells. Once the process was refined, unicellular organisms became able to eat other objects that were almost as big as they were. They were also able to become independent of processes like diffusion and active transport. Overall, cells could grow faster and larger. That faster growth meant it would take less time for the cell to reproduce.

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