Carbohydrate Pathways

Carbohydrate Pathways

The average human diet consists largely of carbohydrates, which are changed by digestion to mono-saccharides, such as glucose. These substances are used primarily as cellular energy sources, which means they usually enter the catabolic pathways of cellular respiration.

The first phase of this process occurs in the cytoplasm and is anaerobic It is called glycolysis and involves the conversion of glucose into molecules ot pyruvic acid. During the second phase of the process the pytuvic acid is transformed into a substance called acetyl coenzyme A. 

It, in turn, is transported into a mitochondrion and is changed into a number of intermediate products by a complex series of chemical reactions known as the citric acid cycle (Kreb's cycle). As these changes occur, energy is released and some of it is transferred to molecules of A IP. while the rest is lost as heat Ihe end products of the oxidation process are molecules of carbon dioxide and water Any excess glucose may enter anabolic pathways and be converted into storage forms such as glycogen. 

Carbohydrate metabolism process OR Kreb's Cycle

Although cells generally can produce glycogen, the liver and muscle cells store the greatest amounts. Following a meal, when the blood glucose level is relatively high, liver cells obtain glucose from the blood and convert it to glycogen. Between meals, when the blood glucose level is lower, the reaction is reversed, and glucose is released into the blood. 

This mechanism ensures that various tissues will continue to have an adequate supply of glucose molecules to support their respirator processes. Glucose can also be converted into fat molecules, which are later deposited in fat tissues. 

This happens when a person takes in more carbohydrates than can be stored as glycogen or are needed for normal activities. The body has an almost unlimited capacity to perform this type of anabolic metabolism, so an excessive intake of nutrients can result in overweight (obesity).