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Question Video: Stating the Name of the Storage Molecule that Sugar is Converted To Biology • Third Year of Secondary School

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What is the name of the polysaccharide storage molecule that sugar is converted to in the liver?

04:06

Video Transcript

What is the name of the polysaccharide storage molecule that sugar is converted to in the liver?

To answer this question, let’s first summarize the control of blood glucose and why it is so important that blood glucose concentration is maintained within a specific and narrow range. Glucose is a very simple form of a carbohydrate consisting of a single ring of six carbon atoms. We can number the carbons in the ring structure of glucose from one to five, as shown in the diagram. Glucose can exist in two different forms: 𝛼 glucose and 𝛽 glucose.

You will notice from the diagram that the difference in structure is that the OH and H groups are flipped on the first carbon or the one prime carbon in the 𝛽 glucose. As it’s made of only one ring, glucose is an example of a monosaccharide. Mono- means one, and saccharide means sugar. The food we eat contains glucose and larger carbohydrates, such as starch, which are digested or broken down to form glucose. The glucose is then absorbed into the blood through the walls of the small intestine. It can then be transported around the body to the cells that require it.

In our cells, glucose is required for cellular respiration. This is the process through which carbon-containing compounds, such as glucose, are broken down to release energy in the form of ATP. It is very important that the concentration of glucose in the blood is kept at a fairly constant level.

But how does the body maintain this? Changes in blood glucose concentration are mainly detected by cells of the pancreas. The pancreatic cells respond by releasing hormones that return the blood glucose concentration to a normal level. If the blood glucose concentration increases, cells in the pancreas release a hormone called insulin into the blood. Insulin is a peptide hormone released from the 𝛽 cells of the pancreas. It binds to receptors on various body cells and via a number of mechanisms lowers blood glucose levels back down to normal.

Let’s have a closer look at how insulin lowers blood glucose levels. Most human body cells have insulin receptors on their cell surface membrane. When insulin binds to these receptors, it causes more glucose to be transported from the blood into the cells. The body cells can either store this glucose or metabolize it in cellular respiration to release energy. Insulin also causes cells called adipose cells or fat cells to convert glucose into lipids for storage.

Some cells, such as those in the liver and muscle, will convert glucose into a polysaccharide called glycogen to store it. We’ve previously referred to glucose as a monosaccharide, mono- meaning one and saccharide meaning sugar. The term “polysaccharide” describes polymers of monosaccharides. Poly- means many, and saccharide, sugar. In the cells of the liver and muscle, glucose molecules are joined together to form a large, poorly soluble polymer of glycogen. This process is an anabolic reaction and requires energy. All these processes result in the lowering of blood glucose concentration back down to normal levels.

Let’s have another look at our question. The question is asking us the name of the polysaccharide storage molecule that sugar is converted to in the liver. We have just seen how the liver and muscles convert glucose into glycogen, a polysaccharide. So the answer to our question is glycogen.

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