Carbohydrate storage in cells: a laboratory activity for the assessment of glycogen stores in biological tissues

Carbohydrates and fats constitute our primary energy sources. The importance of each of these energy substrates varies across cell types and physiological conditions. For example, the brain normally relies almost exclusively on glucose oxidation, whereas skeletal muscle shifts from lipids toward higher carbohydrate oxidation rates as exercise intensity increases. Understanding how carbohydrates are stored in our cells and which tissues contain significant carbohydrate stores is crucial for health professionals, especially given the role of carbohydrate metabolism in various pathophysiological conditions. This laboratory activity uses a simple and low-cost iodine binding method to quantify glycogen in mouse skeletal muscle and liver samples. By integrating the results of this activity with literature data, students can determine overall glycogen storage in the human body. The primary goal of the activity is to enhance students' understanding of the importance and limitations of glycogen stores in energy metabolism.NEW & NOTEWORTHY Carbohydrates are one of the primary energy sources utilized by our cells. Liver and skeletal muscle glycogen, which are the main carbohydrate reserves in the body, play a central role in energy metabolism, especially during periods of fasting and exercise. In this laboratory activity, students measure glycogen levels in tissues to gain insights into how carbohydrates are stored in our cells and understand the role and limitations of liver and muscle carbohydrate stores.