10. Biomolecules

A living system grows, sustains and reproduces itself. The most amazing thing about a living system is that it is composed of non-living atoms and molecules. The pursuit of knowledge of what goes on chemically within a living system falls in the domain of biochemistry. Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc.

This chunk introduces biomolecules as fundamental components that make up living systems. It highlights the distinction between living systems and non-living atoms/molecules, establishing the focus on biochemistry as a science that studies these interactions. Students should understand that biomolecules are complex structures that play vital roles in life processes.

Think of a living organism like a car. Just as a car is made up of various non-living parts (like metal and rubber) that work together to drive, a living organism is composed of non-living atoms and molecules that interact to support life.

Carbohydrates are classified on the basis of their behavior on hydrolysis. They have been broadly divided into the following three groups: (i) Monosaccharides: A carbohydrate that cannot be hydrolysed further to give simpler units of polyhydroxy aldehyde or ketone is called a monosaccharide. About 20 monosaccharides are known to occur in nature. (ii) Oligosaccharides: Carbohydrates that yield two to ten monosaccharide units on hydrolysis are called oligosaccharides. (iii) Polysaccharides: Carbohydrates which yield a large number of monosaccharide units on hydrolysis are called polysaccharides.

In this chunk, carbohydrates are classified into three main groups based on how they react to hydrolysis (the chemical process that breaks them down in the presence of water). Monosaccharides are single sugar units, oligosaccharides consist of a few sugar units (2-10), and polysaccharides are made up of many sugar units. Each type plays different roles in biological systems, like energy storage or structural support.

Imagine a LEGO set: monosaccharides are like single LEGO bricks. Oligosaccharides are like small structures made of a few bricks combined, while polysaccharides are large buildings made up of many bricks. Just as each type has different complexity and function, so do these carbohydrate groups.

Monosaccharides cannot be hydrolysed further and are the simplest form of carbohydrates. Common examples include glucose, fructose, and ribose.

Monosaccharides are the most basic units of carbohydrates and can’t be broken down into simpler sugars. In nature, they are found in various foods. Glucose, for example, is crucial for energy. This part emphasizes the significance of these simple sugars in nutrition and metabolism.

Think of monosaccharides as the building blocks of a house; they are essential and can stand alone, just like these sugars provide energy and serve as the foundation for more complex carbohydrates.

Disaccharides on hydrolysis yield two molecules of either the same or different monosaccharides. The two monosaccharides are joined together by a glycosidic linkage formed by the loss of a water molecule.

Disaccharides are composed of two monosaccharide units linked by a glycosidic bond, formed via a dehydration synthesis reaction where water is removed. This section illustrates how disaccharides like sucrose (glucose + fructose) function in our diet and how they serve as an energy source.

Imagine joining two pieces of string into a single longer piece: the water that is lost in a disaccharide formation is like taking away a knot that connects them. They work beautifully together as a longer string, just as two sugars do to form a new structure.

Polysaccharides contain a large number of monosaccharide units joined together by glycosidic linkages. These are the most commonly encountered carbohydrates in nature. They mainly act as food storage or structural materials.

Polysaccharides, such as starch and cellulose, are large macromolecules formed from many monosaccharides. Their primary roles include energy storage (like starch in plants) and providing structure (like cellulose in plant cell walls). Understanding their function helps appreciate their vast impacts on both human nutrition and plant structure.

Think of polysaccharides as a library stacked high with books (monosaccharides). Each book (sugar) contributes to a larger body of knowledge (energy storage or structure), making it an essential source of wisdom for life processes.

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