Introduction
The body produces and uses various distinct kinds of sugar, including monosaccharides, disaccharides, and polysaccharides. These groups encompass a variety of sugars. Glucose and glycogen are two such sugar molecules that are frequently misunderstood in general.
Now, let’s understand the differences between glucose and glycogen in a bit more detail.
Glucose vs Glycogen
Now, according to studies, the chief difference between glucose and glycogen is that while glycogen is non-osmotic and only weakly soluble, glucose can be saved and stored in cells using it as a solution because it is highly soluble in water and has osmotic properties.
One monosaccharide is glucose. Now, the word glucose comes from the Greek word "glycols," which means sweet. It is produced during the photosynthesis process by plants and algae. Furthermore, there are two types of glucose: D-glucose, which is derived naturally, and glucose, which is generated synthetically (L-glucose).
A subset of polysaccharides is glycogen. It stands for the body's main source of glucose storage. It is mostly synthesized and stored within skeletal muscles and living cells. The average individual has 4 grams of glucose in their blood at any given time.
Difference Between Glucose and Glycogen in Tabular Form
| Parameters of Comparison | Glucose | Glycogen |
| Meaning | It’s a simple monosaccharide. | It’s a major form of carbohydrate stored in animals. |
| Solubility | This is highly soluble in water. | This is weakly or poorly soluble in water. |
| Osmotic properties | Its osmotic. | It not osmotic. |
| Type of Energy Source | It’s a primary source of energy. | It’s a secondary source of energy. |
| Found in | All living beings. | Its found in animals and fungi. |
| Production | Majorly in the chloroplast in plants. | Majorly in the liver in animals. |
What is Glucose?
A basic sugar, glucose has the chemical formula C6H12O6. The most prevalent monosaccharide, a type of carbohydrate, is glucose. The majority of plants and algae produce glucose during photosynthesis from water and carbon dioxide with the help of solar energy, which is utilized to create cellulose, the most prevalent carbohydrate in nature, in the cell walls.
Glucose is the most significant source of energy in all species' energy metabolism. For use in metabolism, glucose is stored as a polymer, mostly as starch and amylopectin in plants and glycogen in mammals. Animals' blood contains glucose as blood sugar. D-glucose is the type of glucose that is created naturally, whereas l-glucose is synthesized in very tiny amounts and has lower biological activity.
Now, glucose is an aldohexose because it is a monosaccharide with six carbon atoms and an aldehyde group. The glucose molecule can exist as an acyclic open-chain or cyclic ring structure. Fruits and other plant components contain free glucose, which is a naturally occurring substance. Glycogenolysis, a process that occurs when glycogen is broken down in animals, releases glucose.
The list of essential medicines maintained by the World Health Organization includes glucose as an intravenous sugar solution. Sodium chloride is also on the list.
German scientist Andreas Marggraf discovered glucose in 1747 while attempting to separate it from raisins. Johann Tobias Lowitz, a separate German chemist, first identified glucose as a substance distinct from cane sugar in grapes in 1792. (sucrose). The name "glucose" was first used in the chemical literature in 1838 by Jean Baptiste Dumas. Given that the plane of linearly polarised light is twisted to the right in an aqueous solution of glucose, Friedrich August Kekulé proposed the name dextrose (from the Latin dexter, meaning "right").
In contrast, linearly polarised light is turned to the left by the ketohexoses l-glucose and l-fructose. The d- and l-notation, which refers to the absolute configuration of the asymmetric center furthest from the carbonyl group and is consistent with the configuration of d- or l-glyceraldehyde, later replaced the earlier notation based on the rotation of the plane of linearly polarised light (d and l-nomenclature).
Since glucose is a fundamental requirement for many species, a correct understanding of its chemical composition and structure made significant progress in organic chemistry as a whole. Emil Fischer, a German scientist who won the 1902 Nobel Prize in Chemistry for his discoveries, conducted extensive research that contributed significantly to this understanding. By establishing the structure of organic matter, the synthesis of glucose provided the first conclusive evidence for Jacobus Henricus van 't Hoff's theories of chemical kinetics and the configurations of chemical bonds in carbon-containing molecules.
Fischer used Van 't Hoff's theory of asymmetrical carbon atoms between 1891 and 1894 to determine the stereochemical configuration of all known sugars and make accurate predictions about potential isomers. Natural substances were originally mentioned in the names. The advent of systematic nomenclatures, which considered absolute stereochemistry, gave their enantiomers the identical name.
Otto Meyerhof won the Nobel Prize in Physiology or Medicine in 1922 for his discovery of glucose metabolism. In 1929, Hans von Euler-Chelpin and Arthur Harden shared the Chemistry Nobel Prize for their "research on the fermentation of sugar and the role of enzymes in this process."
Moreover, Carl and Gerty Cori and Bernardo Houssay shared the 1947 Nobel Prize in Physiology or Medicine for their discoveries of the conversion of glucose to glycogen and the function of the pituitary gland in the metabolism of glucose and the generated carbohydrates, respectively. Luis Leloir received the Nobel Prize in Chemistry in 1970 for his discovery of sugar nucleotides generated from glucose in the production of carbohydrates.
It is classified as a hexose, a subcategory of the monosaccharides, because it contains six carbon atoms. One of several sixteen aldohexose stereoisomers is d-glucose. The l-isomer, l-glucose, does not occur in nature, whereas the d-isomer, d-glucose, often known as dextrose, does. Carbohydrates like milk sugar (lactose), cane sugar (sucrose), maltose, cellulose, glycogen, etc. can be hydrolyzed to produce glucose.
In the US and Japan, tapioca starch and potato and wheat starch are the most often used raw materials in the commercial production of dextrose. The hydrolysis step of the manufacturing process involves pressurized steaming in a jet at a regulated pH, followed by further enzymatic depolymerization. One of the primary components of honey is unbonded glucose.
Typically, glucose exists as a closed pyran ring monohydrate in solid form (dextrose hydrate). On the other hand, it is mostly found as - or -pyranose in an aqueous solution, where it is open-chain to a modest extent and interconverts.
Several cyclic isomers, each of which has a ring of carbons closed by one oxygen atom, are in equilibrium with the open-chain form of glucose (either "D-" or "L-") in solutions. However, more than 99 percent of the glucose molecules in an aqueous solution take the form of pyranose. The open-chain form only makes up around 0.25 percent of the total, and there are hardly any furanose forms at all. For these cyclic forms as well, "glucose" and "D-glucose" are often used in terminology.
An intramolecular nucleophilic addition process between the aldehyde group (at C-1) and either the C-4 or C-5 hydroxyl group forms a hemiacetal linkage, generating the ring from the open-chain form.
The most prevalent monosaccharide is glucose. The majority of living things utilize glucose the most among the aldohexoses. This could be explained by the fact that glucose is less likely than other aldohexoses to interact in an unintended manner with protein amine groups. Many proteins are damaged or rendered useless as a result of the glycation reaction, as is the case with glycated hemoglobin.
What is Glycogen?
A polymer of glucose known as glycogen is used by both fungi and animals to store energy. The polysaccharide structure of glucose reveals the body's main glucose storage type. The liver and muscles' cells, which are hydrated with the four parts of water, produce and store glycogen. It serves as a backup source of long-term energy storage. Muscle cells swiftly convert muscle glycogen into glucose, while liver glycogen does the same for the entire body, including the central nervous system.
Long polymer chains of glucose units bound together by an alpha acetal linkage make up glycogen. The carbonyl group and the alcoholic group come together to produce an acetal connection. Hemiacetal is the term used if the carbonyl group is an aldehyde group, such as (-CHO), or if there is a ketonic group. The term "acetal group" is used when two alkoxy groups are linked to the same carbon atom.
The term "glycogen" refers to the glucose polymer equivalent of starch, which serves as a form of energy storage in plants. Its structure is comparable to that of the starch component amylopectin, but it is more densely branched and compact. This polymer of glucose residues is joined by glycosidic linkages (1,4) and (1,6). It is present in the cytoplasm of various cell types as granules and is essential for the glucose cycle. It builds up an energy supply that is simple to tap into when a glucose emergency arises.
Because glycogen is generated, each glycogen granule has glycogen in a protein core. The hydrated form of glycogen is stored in the liver, fat cells, and muscles. It is made up of three to four parts of water and 0.45 millimoles of potassium for every gram of glycogen.
Functions of glycogen are:
- Hepatocytes release liver glycogen, which serves as a glucose reserve, when maintaining normal blood sugar levels is necessary. Body fluids contain roughly 40 kcal, however, after a fasting night, hepatic glycogen can produce about 600 kcal.
- Skeletal and cardiac muscles utilize glucose from glycogen reserves as an energy source during muscular contractions.
- Astrocytes in the brain contain a modest quantity of glycogen. It builds up as you sleep and becomes mobile when you move. Additionally, glycogen stores provide a mediocre level of defense against hypoglycemia.
- In type II pulmonary cells of the embryonic lung, it plays a specific function. Around 26 weeks into the pregnancy, these cells begin to store glycogen and eventually produce pulmonary surfactant.
Now, a small quantity of glucose is converted by the brain into glycogen, which serves as its main energy storage. So, the amount of glycogen in the brain is normally 3 to 4 times greater than free glucose, but it is still only about 4 mol/g, and if it were used as the only fuel source, it would be depleted in a matter of minutes. Plus, recent research reveals that it functions as a metabolic buffer system and is digested slowly, which explains why it typically takes 3 to 5 days for the entire turnover of brain glycogen stores.
Glycogen synthase must work on glucose subunits that have already been phosphorylated by ATP for glycogenesis to take place. Although the essential enzymes are present in both astrocytes and neurons, the production of glycogen is often restricted to astrocytes. In addition, astrocytes almost exclusively store glycogen, which increases neuronal energy needs during periods of high activity and pathological glucose shortages.
Neurotransmitters include norepinephrine, vasoactive intestinal polypeptide, histamine, serotonin, and several metabolic by-products of neuronal activity, such as K+ and adenosine, stimulating glycogenolysis by the enzyme glycogen phosphorylase to generate lactate.
This lactate has been proposed to be transported from astrocytes to neurons for use as an energy substrate, which is covered in more detail in the following section. 48 The release of glucose equivalents from glycogen does not need to be "primed" with ATP beforehand, in contrast to how glucose is processed.
Main Differences Between Glucose and Glycogen In Points
- Glycogen is a type of carbohydrate storage found primarily in mammals, whereas glucose is a simple sugar that is a monosaccharide.
- Glycogen is a kind of polysaccharide, whereas glucose is a monosaccharide.
- As an element, glucose is very soluble in water. However, water does not readily dissolve glycogen.
- Glycogen is not osmotic, in contrast to glucose, which is osmotic.
- All living things use glucose as their main energy source, while glycogen serves as a backup.
- Every living thing contains glucose. However, only animals and fungi contain glycogen.
- The body's regular operations are supported by glucose. Glycogen, however, supports a variety of processes, including those that the central nervous system does.
- While glycogen is mostly created in the liver of animals, glucose is synthesized in the chloroplast of plants.
Conclusion
Hence, now we can say that we have gathered enough knowledge about the differences between glucose and glycogen.
References
- Glucose. (n.d.). Retrieved from WIKIPEDIA: https://en.wikipedia.org/wiki/Glucose
- Glycogen. (n.d.). Retrieved from BYJU'S: https://byjus.com/chemistry/glycogen/
- Glycogen. (n.d.). Retrieved from ScienceDirect: https://www.sciencedirect.com/topics/neuroscience/glycogen
