Which of these is a polysaccharide?
A) cellulose
B) galactose
C) glucose
D) sucrose
E) lactose
The Correct Answer and Explanation is :
The correct answer is A) cellulose.
Explanation:
Polysaccharides are complex carbohydrates composed of long chains of monosaccharide units linked by glycosidic bonds. These large molecules serve various structural, storage, and energy-related functions in living organisms. Let’s break down each option to understand why cellulose is the correct answer:
- Cellulose (A):
- Cellulose is a polysaccharide made up of many glucose molecules linked together by β-1,4-glycosidic bonds. It is the primary structural component of plant cell walls, providing rigidity and support. Humans cannot digest cellulose because we lack the enzymes required to break down β-1,4-glycosidic bonds. However, it is important for providing fiber in the diet, which helps in digestion and maintaining bowel health.
- Galactose (B):
- Galactose is a monosaccharide, not a polysaccharide. It is a simple sugar that can be found in dairy products and is a component of the disaccharide lactose. Monosaccharides are the simplest form of carbohydrates and serve as the building blocks for more complex carbohydrates.
- Glucose (C):
- Glucose is also a monosaccharide. It is one of the most important sources of energy for cells in the body and is often involved in metabolic processes like glycolysis. Glucose can polymerize to form polysaccharides like starch and cellulose, but on its own, it is a simple sugar.
- Sucrose (D):
- Sucrose is a disaccharide composed of one molecule of glucose and one molecule of fructose. It is commonly known as table sugar and is found in plants like sugar cane and sugar beets. It is not a polysaccharide because it consists of only two sugar units.
- Lactose (E):
- Lactose is another disaccharide composed of one molecule of glucose and one molecule of galactose. It is found in milk and dairy products. Like sucrose, it is not a polysaccharide because it consists of only two sugar units.
In summary, cellulose is the only polysaccharide among the options, consisting of long chains of glucose molecules, while the other options are either monosaccharides or disaccharides.