The primary function of the plasma membrane is to protect thecellfrom its surroundings. Composed of a phospholipid bilayer with embeddedproteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates themovementof substances in and out of cells.

Function. The most prominent roles ofmitochondriaare to produce the energy currency of the cell, ATP (i.e., phosphorylation of ADP), through respiration, and to regulate cellular metabolism. The central set of reactions involved in ATP production are collectively known as the citric acid cycle, or the Krebs cycle.

The main function of the centriole is to help withcelldivision in animal cells. The centrioles help in the formation of the spindle fibers that separate the chromosomes duringcelldivision (mitosis).

Inside a cell, numerous organellesfunctionto remove wastes. One of the key organelles involved in digestion and waste removal is thelysosome.Lysosomesare organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria.