Question

Which of the following has a glucosidic linkage? (a) Amylose (b) Sucorse (c) Maltose (d) Galactose

Short answer

a) Amylose and c) Maltose have glucosidic linkages.

Step-by-step solution

Define Glucosidic Linkage

A glucosidic linkage, or glycosidic bond, involves the connection of two monosaccharide molecules by an oxygen bridge, formed via a dehydration reaction.

Analyze Each Option

- **Amylose:** A polysaccharide made of several glucose units connected by α-D-(1→4) glucosidic linkages. - **Sucrose:** A disaccharide composed of glucose and fructose linked by an α-(1→2)-β bond. - **Maltose:** A disaccharide consisting of two glucose molecules joined by an α-(1→4) glycosidic bond. - **Galactose:** A simple monosaccharide, not linked via a glucosidic bond to others in this form.

Determine Which Compounds Have Glucosidic Linkages

From the analysis, **Amylose** and **Maltose** both contain glucosidic linkages. Amylose contains multiple α-(1→4) linkages in its polymer, while Maltose consists of two glucose units connected by one glucosidic bond.

Key concepts

Amylose

Amylose is a type of polysaccharide composed of glucose monomers. These glucose units are linked together by what is known as an α-D-(1→4) glycosidic linkage. This means that each glucose molecule is connected to the next by a bond between the first carbon (C1) of one glucose and the fourth carbon (C4) of the adjacent glucose.

These α-(1→4) linkages result in a long, unbranched chain that tends to coil into a helical form. This structural formation is significant because it affects how amylose interacts with water and enzymes. For example, the helical structure is less accessible to enzymatic breakdown compared to its branched counterpart, amylopectin.

• Amylose represents about 20-30% of the starch content in plants, integrating tightly packed helices that make it less soluble in water.
• This structure accounts for its role in energy storage, as it allows for compact packing within plant tissues.

Maltose

Maltose is a disaccharide, meaning it consists of two simple sugar units. It is composed of two glucose molecules. These glucose units are held together by an α-(1→4) glycosidic bond. This bond forms due to a dehydration reaction, where a water molecule is removed when the two glucoses connect.

Maltose is commonly created during the breakdown of starches. When plants or animals metabolize starch, enzymes like amylase cleave the starch into maltose units. The presence of the glycosidic bond is key to maltose's function and its ability to serve as an intermediary in carbohydrate digestion.

• Maltose is less sweet than table sugar (sucrose) and serves primarily as an energy source.
• Being a reducing sugar, maltose can participate in chemical reactions that other sugars, like sucrose, cannot.

Glycosidic Bond

A glycosidic bond is a form of covalent bond that joins a carbohydrate (sugar) molecule to another molecule, which can be another sugar or a different type of compound. The formation of a glycosidic bond involves a reaction between the hydroxyl group (–OH) of one sugar with the anomeric carbon of another. This results in the release of a water molecule, a process referred to as a dehydration reaction.

Glycosidic bonds are central to the structure and function of carbohydrates. They determine whether a carbohydrate will form a straight or branched structure. The type of glycosidic linkage, such as α-(1→4) or β-(1→4), influences the chemical properties and digestibility of the carbohydrate.

• The configuration, whether alpha or beta, affects how the molecules interact with biological enzymes. For example, humans can digest α-linked glucose polymers like starch but not β-linked cellulose.
• Understanding glycosidic bonds is crucial for fields ranging from biochemistry to nutrition, as they impact everything from cellular energy to plant structure.