Summary
The main sugar broken down to supply cellular energy.
In depth
Blood glucose is tightly regulated. Glucose can be stored as glycogen, converted to fat, or used by tissues; the brain uses about 120 g per day. Other fuels include fatty acids and, in starvation, ketone bodies.
Glucose enters cells via GLUT transporters, regulated by insulin in muscle and fat. Cells keep glucose phosphorylated to trap it.
Remember: excess glucose is converted to glycogen and fat.
Glucose is the central fuel of many organisms because it is soluble, transportable in blood, and can be broken down both with and without oxygen. The brain relies heavily on it, using about 120 g per day, and red blood cells use only glucose.
Blood glucose is kept near 4 to 6 mmol per litre by insulin and glucagon. Excess is stored as glycogen in the liver and muscles (about 1 to 2 days of energy) and as fat. Plants make glucose by photosynthesis and store it as starch, while animals eat starch and sugars.
Example: low blood glucose (hypoglycaemia) causes dizziness and confusion.
Frequently asked questions
What is Glucose as Fuel?
The main sugar broken down to supply cellular energy.
Which area of biology covers Glucose as Fuel, and how advanced is it?
Glucose as Fuel is one of the 53 topics in Metabolism & Bioenergetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Gluconeogenesis, Ketone Body Metabolism, Glycolysis.
Why does Glucose as Fuel matter?
Glucose is also a precursor for many other molecules.
Can you give an example of Glucose as Fuel?
Red blood cells rely wholly on glycolysis since they have no mitochondria.
What should I learn before Glucose as Fuel?
Glucose as Fuel is a Beginner topic, so no earlier topic is required. Other Beginner topics in Metabolism & Bioenergetics that pair well with it include Metabolism, Anabolism and Catabolism, ATP.
What topics are related to Glucose as Fuel?
The closest topics to Glucose as Fuel are Gluconeogenesis, Ketone Body Metabolism, Glycolysis, Beta-Oxidation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Glucose as Fuel?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Glucose as Fuel. To practise the whole of Metabolism & Bioenergetics, use the Metabolism & Bioenergetics quiz.
How is Glucose as Fuel different from Gluconeogenesis?
Glucose as Fuel: The main sugar broken down to supply cellular energy. Gluconeogenesis: Synthesis of glucose from non-carbohydrate precursors such as lactate and amino acids, mainly in the liver. Read both side by side and note what each one explains.
How should I study Glucose as Fuel step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Gluconeogenesis and explain the difference aloud. Finally, take the Metabolism & Bioenergetics quiz and come back to this page for any question you miss.