What Is Glucose? - Formula, Definition & Regulation

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  • 0:00 What is Glucose?
  • 1:05 Regulation
  • 3:35 Formulas
  • 4:15 Lesson Summary
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Lesson Transcript
Instructor: Shannon Compton

Shannon teaches Microbiology and has a Master's and a PhD in Biomedical Science. She also researches cancer and neurodegenerative diseases.

The glucose molecule is an important carbohydrate, essential for the production of ATP, or the molecule of energy in the body. Glucose is tightly regulated, and both excessive and inadequate glucose levels result in disease states.

What Is Glucose?

The name glucose is from the Greek word for 'sweet' , which is 'glukus.' Glucose is a monosaccharide, which is another term for a simple sugar. It is one of three monosaccharides that are used by the body, but it is the only one that can be used directly to produce ATP. ATP is used by the body for energy; in fact, ATP is the only molecule that can be used for energy. Thus, adequate glucose levels are essential.

Glucose is both helpful and harmful to organisms. As mentioned, glucose is used by cells to make ATP and power the body. Hyperglycemia (high blood glucose), however, is cytotoxic (cell-killing) and can induce severe inflammation throughout the body. Hypoglycemia (low blood glucose) occurs when there is not enough glucose in the blood. This too is harmful and potentially deadly.

The body has several ways to detect changing glucose levels and mechanisms to correct harmful situations. When the body cannot regulate glucose levels, diseases such as diabetes occur.


When you eat, the carbohydrates in your food are either already simple sugars or are re-broken down into simple sugars. The simple sugars are readily absorbed into your bloodstream from your digestive system, causing your blood glucose level to rise. Your pancreas detects rising blood glucose and responds by secreting insulin. Insulin is a regulatory molecule whose purpose is to control carbohydrate and fat metabolism.

Once released into the blood, insulin directs cells of the liver, skeletal muscle, and fat tissue to absorb glucose from the blood. Once blood glucose levels decrease to a safe level, insulin secretion from the pancreas stops.

Can you feel hyperglycemia? Usually, you cannot feel that your blood sugar is above normal levels. However, in extreme cases, you can feel very thirsty, very hungry, urinate frequently, and even lose consciousness. Sudden onset of hyperglycemia is an emergency situation that usually only affects insulin-dependent diabetics.

Alternatively, when you go for a while without eating, the glucose levels in your blood drop. This situation is also sensed by the pancreas, which releases a different molecule called glucagon. Glucagon stimulates the liver to convert glycogen (a starch-like stored form of glucose) to glucose and release it into the blood. Glucagon release stops when blood glucose levels rise back into a safe range.

Can you feel hypoglycemia? Yes. When your blood sugar drops below a critical threshold you can feel dizzy, have trouble thinking, your hands shake, and you can lose consciousness.

Insulin and glucagon work oppositely but in a coordinated way to regulate blood glucose levels. Their function is to maintain blood glucose levels within an acceptable range. Symptoms and complications of hypoglycemia are as mild as dysphoria (feeling unwell) to as serious as seizures, unconsciousness, brain damage, and death. Symptoms and complications of hyperglycemia are kidney damage, brain damage, heart damage, eye damage, and nerve damage in the feet and hands. The complications of hypoglycemia occur within minutes to hours of the onset of hypoglycemia. In contrast, the complications of hyperglycemia can take months to years of chronic excessive blood glucose exposure to develop. Here is a diagram of the glucose regulatory loop.

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