Why are the mitochondria often called the powerhouse of the cell?

Exocytosis is the process by which materials are released from a cell by fusing vesicles containing the materials with the plasma membrane, causing the vesicle contents to be expelled into the extracellular environment. It is a form of bulk transport that is used by cells to export molecules such as proteins, neurotransmitters, hormones, and waste products. Exocytosis plays essential roles in various cellular functions, including secretion, cell communication, and the removal of cellular waste.

The cytoskeleton is critical to cellular motility, providing structural support and facilitating movement within the cell. It is a dynamic network of protein filaments and tubules that extend throughout the cytoplasm, giving the cell its shape, organizing its internal structure, and enabling various cellular processes. The cytoskeleton is involved in cell motility through the interaction of its components, such as actin filaments, microtubules, and intermediate filaments, with motor proteins that generate force and movement. Cytoskeletal elements are responsible for processes such as cell crawling, cell division, intracellular transport, and the maintenance of cell shape and integrity.

The cell membrane, also known as the plasma membrane, contains two layers of phospholipids arranged in a bilayer structure. Each phospholipid molecule consists of a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. In the bilayer structure, the hydrophilic heads face outward, interacting with the aqueous environments both inside and outside the cell, while the hydrophobic tails face inward, shielded from the surrounding water. This arrangement forms a barrier that separates the internal environment of the cell from the external environment, regulating the passage of substances into and out of the cell.

Animals are composed primarily of eukaryotic cells. Eukaryotic cells are characterized by having a true nucleus enclosed within a membrane, along with other membrane-bound organelles such as mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. These cells are structurally and functionally more complex than prokaryotic cells, which lack a nucleus and membrane-bound organelles. Animal cells are the building blocks of animal tissues and organs, and they perform various functions necessary for the survival and functioning of multicellular animal organisms.