Is A Carbohydrate A Monomer Or Polymer: Detailed Insights

Carbohydrates or carbs can be both monomers and polymers, depending on their complexity.

Monomermers of carbohydrates are called monosaccharides and are small molecules having a 3-6 carbon chain. while complex carbohydrates are generally referred to as polysaccharides. These polysaccharides can be formed of 2 or more monomers which can be identical or different.

Carbohydrates, including sugars, starches, and fibers, are composed of 3 main elements- Carbon(C), Hydrogen, and Oxygen(O).

CARBOHYDRATE MONOMERS OR MONOSACCHARIDES:

Monomers of carbs are simple or technically single sugar molecules. The word monosaccharide is composed of two terms- “mono,” meaning single, and saccharide, which is sugar.
Monosaccharides are carbohydrate monomers because they cannot be broken into any further smaller molecules.
Monosaccharides have a 3-7 carbon backbone. They cannot be bigger or smaller than that as it affects the stability of the molecule.
The most common monosaccharide that we know of is table sugar which is nothing but a monosaccharide called glucose. This is the same sugar that plants produce during photosynthesis.
Another important sugar is the one that makes the backbone of our genetic material, i.e., DNA and RNA. The sugars involved are Deoxyribose and Ribose, respectively.
If sugars have a ketone group R-C=O, they are called ketoses, while if they have an aldehyde group R-CHO, they are called aldoses. (The R stands for a carbonyl group which means a long carbon chain with other groups attached)
They are labelled based on the number of C atoms present in the main backbone structure. So 5 C monosaccharides are classified pentoses while 6 C monosaccharides are classified as hexose.

MONOSACCHARIDE STRUCTURES:

The most commonly occurring monosaccharides usually contain 5 or 6 Carbon backbones, meaning pentose and hexose sugars are more abundant in nature. This is because they, in the free form they form stable pentagonal and hexagonal structures that do not hydrolyze further.

SOME COMMON MONOSACCHARIDES:

PENTOSE:

RIBOSE AND DEOXYRIBOSE:

They are both pentose sugars meaning they have five carbon atoms, the only difference being that the 2’C is attached to a Hydroxyl(-OH) group in the case of ribose and a Hydrogen in the case of Deoxyribose. This one feature, along with its double-stranded nature, is what makes the DNA structure more stable.

HEXOSE:

GLUCOSE:

Glucose is the most monosaccharide that we are familiar with. The most commonly occurring hexose sugar is a monosaccharide that runs all bodily activities of living organisms.

GALACTOSE:

Another hexose sugar is very similar to glucose.

FRUCTOSE:

These hexose sugars are present in fruits, and what gives them their sweetness is hence commonly referred to as fruit sugars.

DEXTROSE:

This is a hexose sugar that is specifically present in honey—considered one of the healthiest sugars after fructose.

CARBOHYDRATE POLYMERS OR POLYSACCHARIDES:

They are usually polymers composed of 2 or more monomers that can be attached linearly or can form connected layers . These monomers can be the same or a mix of more than one type.
most naturally occurring form of carbohydrates
They are also called glycans.
If they are made of the same type of monomers, they are called homopolysaccharides, while if they are made of 2 or more different types o monomers, they are called heteropolysaccharides.
Heteropolysaccharides can also have other biomolecules associated with them other than monosaccharides. These polysaccharides are classified according to the molecules associated with them.
Glycoproteins and glycolipids are heteropolysaccharides associated with proteins and lipids or fatty acids, respectively.
They usually require specific hydrolyzing enzymes to digest or break them down to their monomeric forms—E.g., lactase and amylase.

SOME COMMON POLYSACCHARIDES:

HOMOPOLYSACCHARIDES

GLYCOGEN:

Another homopolysaccharide composed of glucose (C₆H₁₀O₅)_n is the primary form of carbohydrate stored in higher animals. Stored in the human muscle and liver cells, glycogen is broken down to glucose when required by the body in a process called glycogenolysis.

CELLULOSE:

The component of plant cells walls is one of the largest polysaccharide molecules(C6H10O5)n. Cellulose can be made up of more than 3000 molecules of glucose connected in straight lines as in layers. They are the most abundant organic matter found in nature.

Is-a-carbohydrate-a-monomer-or-polymer — Cellulose
Image: Wikipedia

STARCH:

This is another glucose polysaccharide produced by plants that are used as a food reserve(C₆H₁₀O₅)_n. Stored in specific parts like roots, tubers, and seeds, they are energy reserves to be used in unfavorable environmental conditions or during germination or dormancy. They are formed by α 1,4 linkages between the glucose molecules.

PECTIN:

Pectins are another homopolysaccharide found in the cell wall and intracellular tissues of some plants. Because of their stretch and jelly-like composition, they are used to make gelatin for food products.

CHITIN:

A polysaccharide is found in the hard exoskeletons of insects and crustaceans. But unlike most common homopolymers, the chitin monomers are N-acetyl-D-glucosamine, a derivative of the glucose molecule.

HETEROPOLYSACCHARIDES

LACTOSE:

A disaccharide with the formula C₁₂H₂₂O₁₁ is made of 2 monomers, glucose, and galactose. Lactose is the major sugar present in milk. Lactose requires an enzyme called lactase to break it down into its monomers. If lactase is not naturally produced by an individual in the required quantity, they are said to be lactose intolerant.

SUCROSE:

The disaccharide sucrose C₁₂H₂₂O₁₁ is used in our everyday life as what we know as table sugar and is composed of one molecule of glucose attached to one molecule of fructose.

HEPARIN:

An anticoagulant drug(a medicine used to remove blood clots during allergic reactions or surgeries) also occurs naturally in human lung and liver tissues. Composed of 3 monomers D-glucuronic acid, L-iduronic acid, and N-sulfo-D-glucosamine

HYALURONIC ACID:

Often used in cosmetic creams and serums, hyaluronic acid is another polysaccharide commonly occurring in the human body. Made up of repeating monomers of D-glucuronic acid and N-acetyl-D-glucosamine, it has great water-retaining properties. Due to this reason, it works as a moisture barrier, lubricant, and shock absorbent liquid in connective tissue and the skin.

CONCLUSION:

As seen from the above examples, it can be confidently said that in nature, carbohydrates occur in both monomer and polymers forms. Both are equally important and have their specific functions. While monomers are mainly used as immediate energy sources, polymers function as energy reserves, structural components, or as drugs. They are both equally essential to normal organic reactions.

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Trisha Dey

I am Trisha Dey, a postgraduate in Bioinformatics. I pursued my graduate degree in Biochemistry. I love reading .I also have a passion for learning new languages.
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