.The cell membrane acts like a filter allowing necessary materials in and waste out, while keeping the organelles and cytoplasm in. This means that a cell membrane is selectively

Permeable

Explanation:

The cell membrane is the outermost covering around the animal cells but it is also surrounded by the cell wall in the case of the plant cells. The cell membrane plays an important role in the cell that is it allows the entry of only certain substances like ions, molecules, atoms within the cell and only allows the exist of certain substances out of the cell. This is the selective permeability of the membrane. This process occurs through osmosis in which the desired molecules move from higher to lower concentration. Also it helps in maintaining the balance of nutrients and water within the cell. This helps in getting rid of the waste outside the cell. It provides the protection to the organelles and cytoplasm in the cell against the external injury caused by the external stressor outside the cell like water, pressure, pathogen, and others.

the ratio of the conjugate base to the acid required to attain the desired ph.

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explanation:

because it is