Structure: Glucose is an aldohexose, meaning it has an aldehyde group (CHO) at the end of its carbon chain. In its cyclic form, glucose forms a six-membered ring known as a pyranose ring.
Structure: Fructose is a ketohexose, meaning it has a ketone group (C=O) within its carbon chain. In its cyclic form, fructose forms a five-membered ring known as a furanose ring.
Natural Sources: Glucose is found in various foods, including fruits, vegetables, and honey. It is also a component of more complex carbohydrates like starch and glycogen.
Biological Role: Glucose is the primary energy source for most cells in the body and is essential for brain function. It is also stored in the liver and muscles as glycogen for later use.
Biological Role: Fructose is metabolized primarily in the liver, where it can be converted into glucose or other metabolites. It is also used to produce energy and can contribute to fat storage if consumed in excess.
Metabolism
Glucose Metabolism:
Pathway: Glucose enters cells through specific transporters and undergoes glycolysis, a process that breaks down glucose into pyruvate, producing ATP (adenosine triphosphate) and NADH (nicotinamide adenine dinucleotide). Pyruvate can then enter the citric acid cycle (Krebs cycle) to produce more ATP.
Pathway: Fructose is metabolized in the liver through a process called fructolysis. It is first phosphorylated by fructokinase to form fructose-1-phosphate, which is then split into dihydroxyacetone phosphate (DHAP) and glyceraldehyde. These intermediates can enter glycolysis or be used to produce glucose or fat.
Chemical Structure: Glucose has an aldehyde group and forms a six-membered ring, while fructose has a ketone group and forms a five-membered ring.
Sources: Glucose is found in various foods and is essential for energy production, while fructose is primarily found in fruits and honey and is metabolized mainly in the liver.
Metabolism: Glucose metabolism is tightly regulated by hormones and involves glycolysis and the citric acid cycle, whereas fructose metabolism occurs primarily in the liver through fructolysis and can lead to different metabolic outcomes.