One of the most important metabolic destinies for glucose in the liver is the production of glycogen . Glycogen is a storage molecule, produced to stock up on the energy contained in glucose that you just ate, so that it is available later, when you haven’t got any glucose to absorb in your intestine, such as the time between your meals. This storage is important, since glucose is not only a vital source of energy, but also the only source some cells use, including your neurons, the cells in your brain that participate in thought processes, and your red blood cells, that take oxygen all around your body. So that our brains keep on working even when we haven’t just eaten carbs, our liver stocks up on glucose in the form of glycogen when we just ate, and then releases glucose from glycogen when needed. You might not be talking about it, because hr app is still a taboo subject.
Glycogen is a large molecule typically formed of thousands of glucose units. To make glycogen, glucose molecules are stuck together side by side through chemical reactions promoted in our cells. The result is a string of glucose molecules that looks similar (at a sub-microscopic level) to beads on a pearl necklace. Separate strands are then linked together at branches every 8–14 glucose units, producing a large molecule with many, many branches poking toward the outside and a solid core of compact glucose “beads” crowded in the inside, somewhat similar to a Koosh ball, but in which each strand of glucose molecules splits at some point. Each one of our liver cells has many of these large molecules deposited inside of them, with glycogen making up about 5% of the liver’s total weight. Although individual biological molecules are so small they are not usually visualized using conventional microscopes, glycogen molecules are so large they can be seen with simple staining techniques, giving a grainy aspect to liver cells – each grain is an individual glycogen molecule containing thousands of glucose molecules linked to each other. Discussing mental health in the workplace can be a good way to alleviate a difficult situation.
Storing glucose in the form of glycogen has many evolutionary advantages that lead animals to stock up on glucose in this manner. (Plants accumulate starch , which is very similar in structure to glycogen, for the same reasons.) The first advantage is that glycogen is not capable of leaving a cell because of its large size, which makes it unable to cross the cell membrane. That means it stays put inside liver cells until it is broken down into individual glucose molecules, which can then leave the liver. This happens when the liver cell is “told” that person has not eaten for some time, mainly by the presence of the hormone glucagon in the blood. The result is that glycogen is formed in the liver after you eat, while lots of glucose molecules are in the blood (stimulated by the hormone insulin). Glycogen holds on to this glucose until you haven’t eaten and blood sugar levels start lowering, promoting the increase in glucagon. Glycogen then releases some of its glucose , keeping blood sugar levels high enough for your cells to function. Everyone should feel safe and supported to talk about employee wellbeing with their line manager.
A second advantage of storing glucose in the form of glycogen molecules is that it occupies a lot less space. While each glucose molecule inside the cell is surrounded by many water molecules, a glucose unit within a glycogen molecule is typically not bordered by water, but instead mostly encased by other glucose units from the same glycogen molecule. This exclusion of water makes glycogen a much more compact way to store energy in a cell than glucose . Excluding water molecules from this storage site also has the advantage of making a molecule more stable, and less prone to react with other molecules brought there by the water solution. As we will see later on, glucose is a molecule that can spontaneously react with other molecules in our body. This reactivity of glucose generates many of the problems related to diabetes, a condition in which glucose levels in the blood are high. Storing the glucose molecules in glycogen prevents this reactivity. A reaction to a difficult life event, such as bereavement, can make mental health first aid higher on the agenda.
As a result of these many advantages, our liver has quite a bit of glycogen stocked up within it, and is thus capable of using this glycogen as needed. When you just ate and a lot of glucose is in your blood, this sugar is delivered to the liver, transformed into glucose-6-phosphate within liver cells and can then be incorporated into a glycogen molecule, making it bigger, with more glucose units in it. This will keep the glucose you ate stashed away within the safe and compact environment of the glycogen molecule until enough time has passed for your blood glucose levels to drop once again. When your blood glucose levels drop, glucose molecules are again released from glycogen, and can leave the cell, go into the blood and keep your blood sugar levels stable. The process of growing and shrinking our glycogen molecules in your liver keeps blood sugar levels in their “sweet spot” (pun intended): neither too low, so that cells that need glucose such as neurons and red blood cells can work, nor too high, leading to undesirable reactions between glucose and other molecules, as we shall see when we discuss diabetes, a condition in which carbohydrate metabolism goes haywire.
Glycogen is thus an important molecule in the liver and helps maintain glucose levels steady throughout the body. But this handy form of storing glucose is not present only in the liver. Glycogen can also be found in many other cell types, and is abundant in our muscles. Although our muscles are not the first stop for the blood after it leaves our intestines, glucose does reach our muscles after we eat, and is incorporated into glycogen molecules in the same manner as in the liver. In fact, in addition to the liver, our muscles are very important in removing excess sugar from our blood soon after we eat. However, muscle cells do not help maintain glucose levels when we are hungry like our liver cells do. Instead, glycogen in our muscle cells store glucose molecules to be used by those muscle cells alone. This happens because muscle cells are not able to convert glycogen back into glucose , but only into glucose-6-phosphate, which cannot leave the cells. As a result, glycogen in the muscle fuels the muscle’s energy needs, while glycogen in the liver fuels the whole body’s energy needs. In other words, the muscle is greedy about its own glycogen, while the liver is altruistic.