Carbohydrate Metabolism from a Dietitian's perspective

Glycolysis, gluconeogenesis, glycogenesis, glycogenolysis are all processes that which carbohydrates are metabolized into the body.  You eat something containing carbohydrate, it is digested, absorbed and they used for energy, right? Well it's sort of like that, but WAY more complicated which is why I spent a whole semester of my undergraduate degree learning about the biochemical pathways in which food is metabolized.  One of the reasons I love being a Dietitian is that I have been taught the intricate ways in which our body uses food.  When I look at a piece of bread, I don't just think about making a sandwich with it. I think about how my body is going to break it down, digest it, absorb it, and then use it for energy during my workout later.  Food is fuel! I am about to embark on a chemistry lesson, so if you aren't interested in learning about how our bodies metabolize carbohydrates, an excellent source of energy, navigate away from my blog because you might become bored very soon. 

Carbohydrate metabolism begins with digestion in the small intestine where monosaccharides are absorbed into the blood stream.  Blood sugar concentrations are controlled by three hormones: insulin, glucagon, and  epinephrine.  If the concentration of glucose in the blood is too high, insulin is secreted by the pancreas. Insulin stimulates the transfer of glucose into the cells, especially in the liver and muscles, although other organs are also able to metabolize glucose. In the liver and muscles, most of the glucose is changed into glycogen by the process of glycolysis (anabolism). Glycogen is stored in the liver and muscles until needed at some later time when glucose levels are low. If blood glucose levels are low, then epinephrine and glucogon hormones are secreted to stimulate the conversion of glycogen to glucose. This process is called glycogenolysis (catabolism). 

If glucose is needed immediately upon entering the cells to supply energy, it begins the metabolic process called glycolysis (catabolism). The end products of glycolysis are pyruvic acid and ATP.  Since glycolysis releases relatively little ATP, further reactions continue to convert pyruvic acid to acetyl CoA and then citric acid in the citric acid cycle. The majority of the ATP is made from oxidations in the citric acid cycle in connection with the electron transport chain. During strenuous muscular activity, pyruvic acid is converted into lactic acid rather that acetyl CoA. During the resting period, the lactic acid is converted back to pyruvic acid. The pyruvic acid in turn is converted back to glucose by the process called gluconeogenesis (anabolism). If the glucose is not needed at that moment, it is converted into glycogen by glycogenesis. 

This, in a nutshell, is carbohydrate metabolism.  Do you see why we need carbohydrates for energy? Do me a favor, and do not go on a carbohydrate restricted diet.  Instead, focus on the types of carbohydrates you consume.