Glucose

Glucose is a sugar with the molecular formula C6H12O6[1]. It is the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is produced by plants through photosynthesis using sunlight, water, and carbon dioxide and can be used by all living organisms as an energy and carbon source[1]. However, most glucose does not occur in its free form, but in the form of its polymers, such as lactose, sucrose, starch, and others, which are energy reserve substances, and cellulose and chitin, which are components of the cell wall in plants or fungi and arthropods, respectively[1]. These polymers, when consumed by animals, fungi, and bacteria, are degraded to glucose using enzymes[1]. All animals are also able to produce glucose themselves from certain precursors as the need arises[1].

Glucose is the main type of sugar in the blood and is the major source of energy for the body's cells[2]. It comes from the foods we eat or the body can make it from other substances[2]. Glucose is carried to the cells through the bloodstream, and several hormones, including insulin, control glucose levels in the blood[2]. Insulin is a hormone that moves glucose from the blood into cells for energy and storage[3]. If blood glucose levels are too high for a long period, it can damage kidneys, eyes, and other organs[3].

Glucose molecules in the bloodstream mainly come from foods rich in carbohydrates, such as bread, potatoes, and fruit[3]. As food is digested, glucose is released and absorbed into the bloodstream, where insulin helps it get inside cells[3]. The body's designed to keep the level of glucose in the blood constant, and special cells in the pancreas called beta cells monitor blood sugar levels and release insulin accordingly[3]. Most cells in the body use glucose along with amino acids and fats for energy, but blood sugar is the main source of fuel for the brain[3]. After the body has used the energy it needs, the leftover glucose is stored in little bundles called glycogen in the liver and muscles[3].

Glucose is a ubiquitous source of energy for every organism and is essential to fuel both aerobic and anaerobic processes[4]. It often enters the body in isometric forms such as galactose and fructose, lactose and sucrose, or starch[4]. The body stores excess glucose as glycogen, which becomes liberated in times of fasting[4]. Glucose is also derivable from products of fat and protein breakdown through the process of gluconeogenesis[4]. Once glucose is in the body, it travels through the blood and to energy-requiring tissues, where it is broken down in a series of biochemical reactions releasing energy in the form of ATP[4].

Glucose reserves are stored as the polymer glycogen in humans, primarily in the liver and muscle tissues[4]. The regulation of glycogen, and thus glucose, is controlled primarily through the peptide hormones insulin and glucagon[4]. Glucose is the simplest type of sugar, and our bodies process it, store it in our cells, and then use it as an energy source to function[5]. If blood sugar levels dip too low (hypoglycemia) or grow too high (hyperglycemia), they can affect the body's everyday functioning[5]. Unmanaged glucose levels may have permanent and severe effects, making it important to measure and manage blood glucose levels, especially for those living with diabetes[5].

Citations:

[1] https://en.wikipedia.org/wiki/Glucose

[2] https://kidshealth.org/en/parents/glucose.html

[3] https://www.webmd.com/diabetes/glucose-diabetes

[4] https://www.ncbi.nlm.nih.gov/books/NBK545201/

[5] https://www.healthline.com/health/glucose