Glucose - a molecule of great importance to life as it provides a ready source of energy for both plant and animal cells. Glucose can only be formed in plants with the aid of sunlight. This process of photosynthesis sustains all animal life on earth. The glucose molecule is formed by a ring of a six carbon atoms. It is progressively broken down in a process called glycolysis during both aerobic and anaerobic respiration6 into ATP

Glucuronic acid- a glucose molecule with an acid carboxyl group. One of the two molecules which makes up the repeating disaccharide unit of glycosaminoglycans other molecule is a glucosamine.

Glycine - one of 20 amino acids commonly found in proteins.

Glycogen - a polysaccharide made up of repeated glucose units. Animals make glycogen and store it in liver and muscles.

Glycolysis - the breakdown of glucose in series of metabolic steps. Energy in the form of ATP is released even if there is no oxygen available as in anaerobic respiration. In the presence of oxygen as in aerobic respiration the breakdown is more complete and yields more energy.

Glycoproteins - are proteins which have many sugar molecules attached to them. They are an important component of saliva where they provide lubrication for the teeth. They also have a wide range of other functions in connective tissues. Examples are fibronectin, osteonectin, osteopontin and interferon. Glycoproteins are also found in cell membranes where they define part of the cells identity. The four major blood groups are defined by glycoproteins on the cell membranes of red blood cells.

Glycosaminoglycans (GAGs) - large to huge molecules of the connective tissue matrix, made up of repeating disaccharide units linked to a protein core. The disaccharide units are made of glucosamine and glucuronic acid. The position of a sulphate molecule on the glucosamine determines the type of GAG.

Golgi apparatus - a cell organelle which is part of the inner cell membrane. It collects and stores the products from the endoplasmic reticulum. It is prominent in actively secreting cells.

Gomphosis - a form of tooth attachment in which the root is help in a bony socket by a fibrous ligament.

Gonial angle - the angle made by the posterior part of the ramus and the lower border of the mandible.

Ground substance - a jelly-like substance which surrounds cells and provides, with fibre, a supportive matrix around each cell. It consists of water and huge molecules which helps transport nutrients to cells and carries away cell products.