An amoeba excretes waste by moving the waste through the cytoplasm within the cell to the cell membrane, and it is then sent out through the contractile vacuole. This organelle within the cell is the only way that excess waste can leave the body of the cell.
An amoeba is an organism that is made up of only one cell. This cell is composed of the various parts of the amoeba including the organelles and the cytoplasm. Cytoplasm makes up the body of the amoeba and holds the organelles in place while allowing important information, such as DNA, to be transmitted throughout the cell. The amoeba is surrounded by a structure called the cell membrane, which allows it to breathe and take in nutrition.
The cell membrane is responsible for holding the amoeba together, but it also allows the amoeba to get what it needs from the outside world while eliminating what it makes that is in excess. Water and oxygen are able to pass through the cell membrane through the process of osmosis because their particles are so small. Waste that is leaving the cell cannot exit through osmosis or diffusion the way that water does because the waste particles are too big. The contractile vacuole contracts to allow an exit space for waste to leave the cell.