Complete Functions and Structure of a Cell

Cell structure and functions-Complete insight (golgi bodies and mitochondria)
Golgi Bodies
The Golgi Bodies (gol'je ba'dez) is named for Camillo Colgi, the Italian scientist who first dis­covered its presence in cells. It is composed of a stack of six or more saccules that look like flattened vacuoles (Iarge, membranous sacs). At the edges of the saccules are rounded vacuoles and vesicles.
The Golgi bodies are especially well developed in cells that secrete (export) a product-for example, in the pancreatic cells that make digestive enzymes or the bronchial cells that produce mucus. When the Colgi appa­ratus packages a product for export, the product is enclosed within a vesicle that moves toward the plasma membrane, where the vesicle discharges its contents.
Lysosomes
A lysosome (Ii'so-s6m) is a special type of vesicle formed by the Golgi apparatus. All lysosomes carry out intracellu­lar digestion and contain digestive enzymes. Following for­mation, the lysosome may fuse with an incoming vesicle that contains a substance to be digested. The products of digestion enter the cytoplasm, and only nondigested residue is retained.
Tay Sachs (ta silks) is a genetic disease in which a new­born has a faulty lysosomal digestive enzyme. The cells fill with nonfunctioning lysosomes, and the death of the child follows.
Lysosomes cany out autodigestion when they dispose of worn-out or damaged cell components, such as mitochon­dria. This is an essential part of the normal process of cyto­plasmic maintenance and turnover. Turnover refers to the cell's constant process of breaking down and remaking its parts.
Mitochondria
A mitochondIion (mi"to-kon'dre-on), a rather complex organelle with an outer membrane and convoluted inner membrane, produces ATP molecules. As discussed previ­ously, every cell needs a supply of ATP molecules to carry out general cell functions. Some cells have specialized functions. For example, muscle cells use ATP for muscle contraction, and nerve cells need ATP to conduct nerve impulses.
Mitochondria are often referred to as the powerhouses of the cell because, just as powerhouses burn fuel to pro­duce electricity, mitochondria burn glucose products to produce ATP molecules. The word burn is used advisedly because mitochondria use up oxygen and give off carbon dioxide and water. Several systems of the body function to make this possible. The digestive system digests food, and as a result, glucose enters the blood vessels and is taken to the cell. Within the celL glucose is first broken down to a molecule called pyruvate, and then pyruvate en­ters mitochondria. In the meantime, oxygen that has en­tered the lungs of the respiratory system is also transported to the cell, where it enters mitochondria. Following ATP formation, water and carbon dioxide exit the mitochondria and the cell. The lungs expel the carbon dioxide.
Since gas exchange is involved, mitochondria are said to carry on aerobic cellular respiration. One way to indi­cate the chemical transformation associated with aerobic cellular respiration is:
carbohydrate + oxygen ---->  Carbon dioxide + water + ATP energy
Centrioles and Related Organelles Centrioles
Centrioles (sen'tre-olz) are short cylinders that contain ine tubules called microtubules. Usually, two centrioles lie at right angles to one another near the nucleus. Before a cell divides, the centrioles duplicate, and the members of each pair are also at right angles to one another.
Centrioles are believed to give rise to basal bodies that direct the formation of cilia and flagella. Centrioles may be involved in the movement of material throughout the cells and in the organization of the spindle during cell division.
Cilia and Flagella
Cilia (sire-ah) and flagella (flah-jel'ah) are plasma mem­brane extensions that contain microtubules. They can ove either in an undulating fashion, like a whip, or stiffly, like an oar. Cells that have these organelles are capable of producing movement. For example, sperm cells, carrying genetic material to the egg, move by means of flagella. The cells that line the upper respiratory tract are cili­zied. The cilia sweep debris trapped within mucus back up the throat, which helps keep the lungs clean.
Centrioles lie near the nucleus and may be involved in the production of the spindle during cell division and in the formation of cilia and flagella.

Posted in Human Anatomy and Physiology