Question

Which of the following carbohydrates is a polymer of the monosaccharide glucose? A. Cellulose B. Lactose C. Ribose D. None of the above

Short answer

A. Cellulose is the polymer of the monosaccharide glucose.

Step-by-step solution

Understanding Monosaccharides and Polymers

First, understand that monosaccharides are the simplest form of carbohydrates, which are single sugar molecules. Polymers of monosaccharides are chains of these molecules linked together. Glucose is a common monosaccharide.

Identifying the Polymer of Glucose

Next, identify which of the options is a polymer of glucose. A polymer of glucose would be a carbohydrate made up of multiple glucose units linked together.

Eliminating Incorrect Options

Lactose is a disaccharide composed of glucose and galactose, not a polymer. Ribose is a different monosaccharide, not a polymer of glucose. Thus, eliminate B and C.

Choosing the Correct Answer

Cellulose is a complex carbohydrate and a polymer of glucose, where many glucose units are linked together to form long chains. Therefore, Cellulose (option A) is the correct answer.

Key concepts

Carbohydrates

Carbohydrates are essential biomolecules that serve as energy sources and structural components in living organisms. Structurally, these organic compounds are made up of carbon (C), hydrogen (H), and oxygen (O) atoms, usually with a 2:1 hydrogen to oxygen ratio akin to water. Hence the name 'carbohydrate', which means 'hydrated carbon'.

Biologically, carbohydrates are categorized based on their size and complexity into monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides such as glucose, fructose, and galactose are the simplest form of carbohydrates, consisting of single sugar units. When two monosaccharides join, they form a disaccharide, like sucrose or lactose. Polysaccharides are large polymers composed of many monosaccharide units and can serve a variety of functions, from energy storage (as in starch or glycogen) to structural support (as in cellulose).

The role of carbohydrates in nutrition cannot be overstated. They provide energy to cells when broken down through metabolic pathways, and they are a part of a balanced diet. However, the function and importance of carbohydrates extend beyond their caloric value, as some forms are fundamental in processes such as cellular communication and the immune response.

Glucose

Glucose, a six-carbon monosaccharide, is often regarded as the primary source of energy for living cells. It's integral to cellular respiration, which is a set of metabolic reactions converting biochemical energy from nutrients into adenosine triphosphate (ATP), and then releasing waste products.

Chemically, glucose is classified as an aldohexose because it contains six carbon atoms and an aldehyde group. The formula for glucose is \( C_6H_{12}O_6 \). It exists in various isomeric forms, with the most common being the 'D' form, which predominantly occurs in nature and is the one referred to when discussing glucose in human biology.

The importance of maintaining glucose at a constant level in the blood is paramount for homeostasis. The body manages this through hormones like insulin and glucagon, which regulate glucose uptake and release into the bloodstream, ensuring that tissues receive a steady supply of energy.

Cellulose

Cellulose is an abundant natural biopolymer on Earth and a critical component of plant cell walls, where it provides rigidity and strength. Composed of \(\beta(1\rightarrow4)\)-linked D-glucose units, cellulose fibers are linear chains that bundle together to form microfibrils – the structural framework that supports plant cells. Contrary to starch or glycogen, which have \(\alpha(1\rightarrow4)\) linkages, cellulose's \(\beta(1\rightarrow4)\) linkages give it a straight, unbranched structure, making it insoluble in water and resistant to breakdown by human digestive enzymes.

However, certain organisms, like ruminants and termites, possess the necessary enzymes to degrade cellulose. Industrial applications of cellulose include the production of paper, textiles, and biofuels. With growing interest in sustainable materials, the versatile use of cellulose in the production of biodegradable plastics and other eco-friendly materials is on the rise.