Carbohydrates - Disaccharides (A-level Biology)
Carbohydrates: Disaccharides
Disaccharides
- Disaccharides are made from two monosaccharides. Disaccharides are dimeric molecules, made of two monomer monosaccharides.
- Disaccharides can be homogenous or heterogenous. The constituent monosaccharides can be the same (homogenous) or different (heterogenous).
- Disaccharides are made via condensation reactions. We learnt about condensation reactions earlier in tutorial 2 Polymers. Disaccharide formation occurs via a condensation reaction between two monosaccharides. Figure 1 below demonstrates this reaction to synthesise the disaccharide maltose.
- The covalent bond joining two monosaccharides together is a glycosidic bond.
Outlined below for you are the disaccharide forming mechanisms you need to learn:
- Maltose is formed via a condensation reaction between two molecules of α-glucose.
- Sucrose is formed via a condensation reaction between a molecule of glucose and a molecule of fructose.
- Lactose is formed via a condensation reaction between a molecule of glucose and molecule of galactose.
Carbohydrates are a group of organic compounds that are important sources of energy for living organisms. They are composed of carbon, hydrogen, and oxygen atoms, and are classified based on the number of sugar units they contain.
Disaccharides are carbohydrates that are made up of two sugar units joined together by a glycosidic bond. They are considered simple sugars, as they can be broken down into their constituent monosaccharides by the action of digestive enzymes.
Some common disaccharides include:
Sucrose, which is made up of glucose and fructose
Lactose, which is made up of glucose and galactose
Maltose, which is made up of two glucose units
Disaccharides are formed by the bonding of two monosaccharides, such as glucose and fructose, through a glycosidic bond. They can be broken down in the body by the action of digestive enzymes, which split the bond and release the individual monosaccharides.
Disaccharides are important in biology because they serve as sources of energy for living organisms. They are also used as a means of storing and transporting energy, as well as for structural purposes in some organisms.
Digestive enzymes play a crucial role in the breakdown of disaccharides by splitting the glycosidic bond and releasing the individual monosaccharides. This allows the body to absorb and utilize the energy contained in the disaccharides.
In A-Level Biology, knowledge of disaccharides is important for understanding the digestive process, the utilization of energy in living organisms, and the role of carbohydrates in cellular metabolism. This knowledge is also important for understanding related medical conditions, such as lactose intolerance, and the effects of diet on health.
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