All cells within the body are affected by the glucose level of concentration in the blood. Similar to temperature, blood glucose is kept within a tight range: 80 – 100 mg 100 cm^-3.

• Hypoglycaemia is where the concentration of blood is too low.
• Hyperglycaemia is where the concentration of blood is too high.

Glucose is mainly produced through digestion. Dietary carbohydrate, which predominantly consists of starch, is absorbed by the intestine. The blood then carries it to the liver and then transports it to the rest of the body. In general, animals don’t produce their own glucose. However, if dietary glucose is low then it can be synthesised using proteins and nucleic acids in a process known as gluconeogenesis.

The main use of glucose is respiration which takes place in all the cells of the body. However, it can also be used to create amino acids. If it’s not needed it’s converted into glycogen (by glycogenesis) and stored in the liver and muscle cells. The glycogen can then be converted back into glucose through the reverse process known as glycogenolysis.

If there’s too much glucose then this can be converted into triglycerides by lipogenesis in the liver. These are then transferred to adipose tissue as lipoproteins where they’re stored. Unlike glycolysis, this process is irreversible. Instead, triglycerides can be used for aerobic respiration.