Disaccharides

• When two monosaccharides are joined through glycosidic linkage disaccharide is formed.
• The word disaccharides; Di means two and saccharides means sugars.
• They are soluble in water like monosaccharides.
• On hydrolyzes two monosaccharides( simple sugar molecules are formed), which may be the same or different. For example, maltose is made up of the same monosaccharides (glucose) and lactose is made up of two different monosaccharides (galactose and glucose).
• Disaccharides are typically broken down into their constituent monosaccharides by specific enzymes during digestion, allowing for efficient absorption and utilization of sugars in the body for energy production and various biochemical processes.
• For. example sucrose, lactose, and maltose. These are common disaccharides.

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Structure

Disaccharides are carbohydrate molecules composed of two monosaccharide units joined by a glycosidic bond. The structure of a disaccharide involves the linkage between the anomeric carbon atom of one monosaccharide and a hydroxyl group of another, forming either an α or β configuration depending on the orientation of the glycosidic bond relative to the ring structure of the monosaccharides involved.

Common examples include maltose, consisting of two glucose molecules linked by an α-1,4-glycosidic bond; lactose, composed of one glucose and one galactose linked by a β-1,4-glycosidic bond; and sucrose, formed by the α,β-1,2-glycosidic linkage between glucose and fructose. These disaccharides play crucial roles as dietary sources (such as lactose in milk and sucrose in table sugar).

Example

Sucrose

• Sucrose is a common disaccharide, upon hydrolyzed to give glucose and fructose.
• Sucrose is formed by one molecule of glucose and fructose linked by an α,β-1,2-glycosidic bond.
• Its molecular formula is C₁₂H₂₂O₁₁.
• It is also called table sugar or cane sugar.
• It is sweet in taste and is used as a sweetener in foods and beverages, Therefore commonly known as table sugar.
• It is abundant in plant nature where it serves as a carbohydrate storage reservoir e.g. in sugar beet and sugarcane.
• Sucrase (enzyme) in the digestive system breaks down sucrose into simple sugar (monosaccharides) and then is absorbed into the bloodstream as an energy source.
• It is an important constitute of the human diet due to its sweet taste.
• The excessive use of sucrose poses stress on health and is responsible for health issues like dental caries and obesity commonly.

Maltose

• A disaccharide composed of glucose molecules through (α-1,4-glycosidic bond).
• It is also known as maltobiose.
• Its molecular formula is C₁₂H₂₂O₁₁.
• Maltose serves as an intermediate in the breakdown of complex carbohydrates into simpler sugars that can be readily absorbed and utilized for energy in the body.
• It has a sweet taste but is much less sweet compared to sucrose.
• In industrial applications, maltose is used in brewing beer and in the production of maltodextrins and other food products.
• Maltose is commonly found in germinating grains, barley.
• It is also produced during the digestion of starch (by the enzyme amylase).
• Structurally, maltose forms when the anomeric carbon atom of one glucose molecule links with the hydroxyl group on the fourth carbon atom of another glucose molecule. This linkage gives maltose a specific orientation in which the two glucose units are connected in a linear chain.

Lactose

• Lactose is an example of a disaccharide, composed of one molecule of glucose and galactose ( linked by a β-1,4-glycosidic bond).
• Its molecular formula is C₁₂H₂₂O₁₁.
• Lactose is primarily found in milk( also known as milk sugar and lactobiose) and dairy products, where it plays a role as a carbohydrate source.
• Structurally, lactose forms when the anomeric carbon atom of galactose bonds with the hydroxyl group on the fourth carbon atom of glucose, creating a β-glycosidic linkage between them.
• This orientation gives lactose a specific configuration in which the glucose and galactose units are connected in a linear chain.
• In the digestive system, lactase enzymes break down lactose into monosaccharides ( glucose and galactose) which are then absorbed into the bloodstream for energy purposes.
• Some individuals have lactose intolerance( a digestive issue )in which individual can not digest lactose due to a deficiency of a specific enzyme (lactase) which is essential for the breakdown of lactose into glucose and galactose.
• Lactose is also used in various food industries as a sweetener and for its functional properties in enhancing texture and flavor etc.