What carbohydrates or sugars are found in living organisms

Saccharide is a very important organic compound in cells. It contains C, H and O, and their ratio is generally 1:2:1. Its chemical formula is written as Cn(H₂O)n. sometimes, so it is also called carbohydrate. But there is an exception, deoxyribose lacks one oxygen atom and its chemical formula is C₅H₁₀O₄. Saccharide is the main energy substance needed for life activities. Some Saccharides are also raw materials for biological macromolecules (proteins and nucleic acids). Saccharides are divided into monosaccharides, oligosaccharides and polysaccharides according to their constituents.

GlucoseC₆H₁₂O₆It is the main energy source for life, and all plant and animal contain glucose.
FructoseC₆H₁₂O₆Sweet fruit and honey
GalactoseC₆H₁₂O₆mammal milk, plant gum, nerve system
LactoseGlucose + Galactosemammal milk
SucroseGlucose + FructoseIt can store energy in the plant.
MaltoseGlucose + GlucosePlant tissue in which starch hydrolysis occurs


Monosaccharides are the smallest units that make up sugars. The common monosaccharides are glucose, fructose, and galactose. They are all sugars consisting of 6 carbon atoms and are isomers of each other.

Glucose or grape sugar

Glucose was first isolated from raisins or grapes and it is also known as grape sugar. Starch, glycogen and sucrose are all digested into glucose before they can be used by the body. Glucose is the main source of energy needed for cellular life activities. Many plant fruits are rich in glucose.

Fructose or fruit sugar

Fructose is also named fruit sugar. It is a isomer of glucose, where the aldehyde group in glucose is replaced with a ketone group. Fructose is not available to humans directly; it must be converted to glucose in the liver before it can be used to provide energy to cells. It is 1.8 times sweeter than sucrose and is commonly used as a sweetener in the food industry. Some particularly sweet natural foods contain large amounts of fructose, such as pears, lychees and honey.


Galactose is an isomer of glucose and they have a different arrangement of hydroxyl groups on the carbon ring. It needs to be converted to glucose in liver before being used by body. It is usually found as a polysaccharide in plant gums or as lactose in mammal milk, or as glycolipids in nervous system..


Two monosaccharide molecules form a disaccharide through a glycosidic bond. Lactose, sucrose and maltose are all common disaccharides.


Lactose is found in mammalian milk and it is composed of glucose and galactose. Lactose is not digested and absorbed in the human stomach and goes directly to the intestine where it is broken down by lactase into glucose and galactose. Galactose is a component of glycolipids that make up brain and nerve tissue and is important for infant intellectual development.


Sucrose is the most common disaccharide, and it is composed of glucose and fructose. Much of glucose formed by photosynthesis is converted to sucrose and stored, making it one of the most abundant sugars in plant tissues. Edible sucrose is mainly obtained from sugar cane and beet.


Maltose consists of two glucoses. It is found only in the tissues where starch is hydrolyzed. Maltose is present in large amounts in germinated grains; amylase in saliva hydrolyzes starch into maltose, which is why rice tastes a little sweet when it is chewed.

Frequently Asked Questions

Why do some people get diarrhea after drinking milk?

Some people experience diarrhea after drinking milk due to a condition known as lactose intolerance. It is a common digestive disorder in which the body is deficient in lactase and unable to digest lactose, a type of sugar found in milk and other dairy products. When a lactose-intolerant person consumes milk, the lactose passes undigested into the intestine, where it is fermented by bacteria. This fermentation produces gas and can cause symptoms such as abdominal bloating, cramping, and diarrhea.

What are the risks of eating a lot of sucrose?

Fruits are rich in fructose and one sucrose is made up of one glucose and one fructose. Fructose cannot be used directly as cellular fuel like glucose. It has to be converted to glucose, glycogen and fat in the liver, a process that consumes a lot of ATP to produce uric acid, which increases the risk of gout. Fructose is more likely to be converted into fat which accumulate in the liver, causing fatty liver. It is importantto reduce the intake of snacks in your daily diet, especially carbonated drinks, because they contain a lot of sucrose.