External respiration is the process of taking oxygen into and expelling carbon dioxide from the body. External respiration is essential for life as it supplies oxygen to extract energy from food via internal or cellular respiration. Additionally, it removes carbon dioxide, which is a waste product of respiration.
The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction.It is commonly the most prominent organelle in the cell. The nucleus is surrounded by a structure called the nuclear envelope.This membrane separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed within the nucleus.he nucleus is surrounded by a structure called the nuclear envelope. This membrane separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed within the nucleus.
LINK / CITE ADD TO WORD LIST. noun. A model of an atom showing the nucleus. A model of an atom showing the nucleus. The nucleus is the center core of an atom that has a positive charge and that contains most of the atom's mass, or the central heart of an organization or group.1  An example of a nucleus is the center core of an atom.INK / CITE ADD TO WORD LIST. noun. A model of an atom showing the nucleus. A model of an atom showing the nucleus. The nucleus is the center core of an atom that has a positive charge and that contains most of the atom's mass, or the central heart of an organization or group.