In higher animals phagocytosis is chiefly a defensive reaction against infection and invasion of the body by foreign substances (antigens). The process by which cells engulf solid matter is called phagocytosis.

Pinocytosis, a process by which liquid droplets are ingested by living cells. Pinocytosis is one type of endocytosis, the general process by which cells engulf external substances, gathering them into special membrane-bound vesicles contained within the cell.

The cell membrane regulates what goes into and out of the cell. In a house this is like the door. In both the door and cell membrane things go in and out of them. The cell wall is located inside of the plant.

A door’s essential and primary purpose is to provide security by controlling access to the doorway (portal). Conventionally, it is a panel that fits into the portal of a building, room, or vehicle. Doors are generally made of a material suited to the door’s task.

Windows and doors perform several functions in a residential structure, such as: shield an opening from the elements, add decoration, emphasize the overall design, provide light and ventilation, and expand visibility.

A window is defined as an opening in a wall of a building to serve one or more of the functions like natural light, natural ventilation and vision. The main function of a door in a building is to serve as a connecting link between the internal parts and to allow free movement to the outside of the building.

Windows facilitate the entry of natural light indoors. They enable the occupants of a house to enjoy the views of the neighbourhood or locality. In addition, they serve to keep the house cross-ventilated. As such, houses with ample windows will seldom look gloomy or feel stuffy.