Cellulose is a polysaccharide or multi-sugar compound, one of the most abundant carbohydrates. Known for its flexible rigidity it supports plant structure and environmental health. For humans it provides fiber.
The purpose of cellulose in nature is primarily structural support and protection of plant cells. By forming rigid cell walls, cellulose helps plants keep their shapes and resist pressures from other plants, wind or animals.
Cellulose allows plants to grow tall and reach for sunlight. About 40% of wood is cellulose. It's also integral to the intercellular transport of water and nutrients.
When plants die or shed leaves, their cellulose decomposes to enrich the soil around them with organic matter. This process promotes beneficial microbial activity in soil and overall ecosystem health.
Cellulose exists in various forms and many biological processes. It strengthens cell walls of plants, algae and some bacteria. Plants produce an estimated 100 billion tons of cellulose each year through photosynthesis.
Cellulose is a major polysaccharide. These are macromolecules formed by aggregation of numerous monosaccharide units through glycosidic linkages. They can be divided into two main categories:
Storage polysaccharides, such as starch found in potatoes and glycogen stored in animal liver, which serve as energy reserves.
Structural polysaccharides, like cellulose and chitin, which provide structural support.
Functions of polysaccharides are tied to their chemical structures. Cellulose is made of long chains of glucose molecules linked by glycosidic bonds, or bonds connecting a carbohydrate (sugar) molecule to another group.
Cellulose is a favorite food of mold. This enables its breakdown in nature but can present fungi-related issues for humans.
While cellulose is indigestible to humans, it helps promote digestive health as dietary fiber. Too much fiber has symptoms such as bloating, gas and blockage. Digestion is facilitated by timeless methods such as fermentation.
Creation of Cellulose in Nature
Creation of cellulose starts with photosynthesis, the process by which plants convert sunlight into chemical energy. During photosynthesis, carbon dioxide and water are transformed into glucose and oxygen.
Once glucose is available, it undergoes a series of enzymatic reactions and is polymerized into long cellulose chains. The enzyme cellulose synthase helps link the glucose units together.
These long chains crystallize, forming microfibrils of great strength. This process also aids in water retention and nutrient transport.
Cellulose is the primary structural component in the cell walls of green plants, algae and many fungi. As chitin, cellulose is also integral to the many arthropod exoskeletons.
It's abundant in agricultural products like cotton, flax and wood. Its flexible strength enables flax to be spun into linen, considered the first textile.
Characteristics & Properties
Insolubility: Cellulose is not soluble in water, enabling it to support aquatic or wetland plants and algae.
High Tensile Strength: This property enables plants to resist breaking under physical stress, allowing them to grow tall without collapsing. The linear structure of cellulose fibers is key to their strength. Tensile strength of cellulose can reach 600 MPa, comparable to steel.
Crystallinity: The way cellulose chains organize into crystalline structures enhances their mechanical strength and resistance to breakdown, ensuring durability.
Biodegradability: Cellulose can be broken down by microbiota and enzymes to reintegrate into the soil.
Non-toxic: It is generally recognized as safe for human consumption in its natural form.
Notable Human Uses
Paper Production: Cellulose is the primary material for paper. The pulp extracted from wood and non-wood sources is processed to obtain cellulose fibers, which are then pressed and dried into paper.
Textiles: Cotton is nearly pure cellulose (up to 99%), a significant natural textile world-wide. Cellulosic fibers from various plants are spun into threads for a wide array of fabrics.
Food Industry: Cellulose is featured as a food additive to provide texture and stabilize mixtures. For instance, it's a thickener in puddings and bulking agent in low-calorie snacks.
Biofuels: With the growing interest in renewable energy, cellulose is recognized as a valuable resource for biofuel production. Through enzymatic hydrolysis, cellulose can be transformed into glucose, which is then fermented into ethanol.
Pharmaceuticals: Cellulose is commonly used as an excipient in drug formulations. It acts as a binder, filler, or coating agent in tablets, enhancing the stability and delivery of active ingredients.
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