Maximum number of monosaccharide units present in oligosaccharides is: (a) 5 (b) 10 (c) 15 (d) 20

Monosaccharide units are the simplest form of carbohydrates, often referred to as simple sugars. These fundamental building blocks include glucose, fructose, and galactose, each consisting of a single sugar molecule. In biochemistry, they play a crucial role as they serve as energy sources and as structural components. When we speak of monosaccharides in the context of oligosaccharides, we're looking at how these simple sugars can join together to form more complex structures.

Through a process known as dehydration synthesis or condensation, monosaccharides link up to create disaccharides, trisaccharides, and up to decasaccharides, which still fall under the category of oligosaccharides due to their low monomer count. Remembering that 'oligo' signifies a few, the distinction between monosaccharides and oligosaccharides becomes clear: it's all about the number of sugar units and how they are combined.

Glycosidic bonds are the connections that link monosaccharide units together within oligosaccharides. Think of them as the glue that holds the sugars in place. These covalent bonds are formed during a dehydration reaction, where a water molecule is removed as the bond is created between two sugar molecules.

There are two main types of glycosidic bonds: alpha and beta. The orientation of the hydroxyl group (-OH) connected to the anomeric carbon (the carbon derived from the carbonyl group of the monosaccharide) determines the type of bond. Alpha-glycosidic bonds have the hydroxyl group facing down, while beta-glycosidic bonds have it pointing up. These orientations have significant implications in the function and digestibility of the carbohydrate. For example, humans have enzymes that can easily break down alpha bonds (like those in starch), but most cannot break down beta bonds found in cellulose, which is why it is a dietary fiber.

The structure of carbohydrates varies from the simple monosaccharides to complex polymers such as starches and fibers. Oligosaccharides fall in between these two extremes. Their structure generally consists of a short chain of monosaccharide units linked by glycosidic bonds. The configuration, length, and type of glycosidic linkages influence the physical and functional attributes of these carbohydrates significantly.

From a structural point of view, carbohydrates can be linear or branched. Branching occurs when monosaccharides attach to different points on a central sugar molecule, creating a tree-like structure. This branching can impact how the carbohydrate behaves in biological systems, such as how quickly it can be digested or how it interacts with other molecules. In addition, the way these sugars arrange in three-dimensional space adds to the complexity of carbohydrates, enabling a vast range of biological functions and diversity among oligosaccharides.