What is the Difference Between Glucose and Starch

The key difference between glucose and starch is that glucose is the simplest form of carbohydrate that can easily be absorbed by the digestive system, while starch is a complex form of carbohydrate that cannot be easily absorbed by the digestive system.

Carbohydrates are a type of macronutrient normally found in certain types of food and drinks. They are biomolecules that typically consist of carbon (C), hydrogen (H), and oxygen (O). Carbohydrates are made up of monomers called monosaccharides. Examples of monosaccharides are glucose, fructose, and glyceraldehydes. Two monosaccharides combine together through a glycosidic bond to form a disaccharide. Examples of disaccharides include sucrose, maltose, and galactose. Moreover, an oligosaccharide (raffinose and stachyose) has 2 to 10 monosaccharides. In addition, a polysaccharide has more than 10 monosaccharides. Starch and cellulose are popular polysaccharides.

CONTENTS

1. Overview and Key Difference
2. What is Glucose 
3. What is Starch
4. Similarities – Glucose and Starch
5. Glucose vs Starch in Tabular Form
6. Summary – Glucose vs Starch

What is Glucose?

Glucose is the simplest carbohydrate, with the molecular formula of C₆H₁₂O₆. It is easily absorbed by the digestive system due to its simplicity. It is a monosaccharide with six carbons and an aldehyde group; therefore, it is called aldohexose. Glucose is the most abundant monosaccharide on the planet. Most plants and algae produce glucose through photosynthesis. It can be made by combining water and carbon dioxide in photosynthesis. However, the energy of sunlight is critical for photosynthesis reaction.  Later, plants use these glucose molecules to form cellulose, the most abundant carbohydrate on the earth. Glucose is the most important energy source in all organisms. Glucose used for metabolism is mainly stored as a polymer. In plants, it is mainly stored as starch or amylopectin. But in animals, it is mainly stored as glycogen.

Glucose circulates in the blood of animals as blood sugar. Insulin is the hormone that stimulates the liver to store glucose as glycogen. The deficiency of insulin hormone increases the blood sugar level. This ultimately leads to the medical condition known as diabetes.  Moreover, glucose is an intravenous sugar solution that is on the list of essential medicines of the World Health Organization.

What is Starch?

Starch is a complex form of carbohydrate that is not easily absorbed by the digestive system. It is a polymer composed of numerous glucose units joined by glycosidic linkage. This polysaccharide is normally made by many plants for energy storage. It is the most common carbohydrate in the human diet. Starch is usually found in the food items such as wheat, potato, maize, rice, cassava. The basic chemical formula of starch molecules is (C₆H₁₀O₅)_n.

The pure starch is a white, tasteless, and odorless powder. It is also insoluble in cold water or alcohol. The starch consists of two molecules: linear amylase and branched amylopectin. Starch usually contains 20% of amylase and 80% of amylopectin by weight. In the industry, starch is converted to sugars and then used to produce beer, whiskey, and biofuel through malting and fermentation. It is also processed to produce many sugars in the processed food industry. The industrial non-food usage of starch is as adhesive in papermaking. Moreover, starch also can be used as a thickening, stiffening, and glueing agents.

What are the Similarities Between Glucose and Starch?

• Glucose and starch are two types of carbohydrates.
• Both molecules consist of elements like carbon (C), hydrogen (H), oxygen (O).
• These molecules are extremely important for humans that are taken through the diet.
• Both molecules have the same stoichiometric formula; (CH₂O)n.
• They are both made up of monomers called monosaccharides.
• They are macromolecules.

What is the Difference Between Glucose and Starch?

Glucose is the simplest form of carbohydrate that can be easily absorbed by the digestive system while starch is a complex form of carbohydrate that cannot be easily absorbed by the digestive system. Thus, this is the key difference between glucose and starch. Furthermore, glucose is the most abundant monosaccharide on the planet, while starch is the most common polysaccharide in the human diet.

The below infographic presents the differences between glucose and starch in tabular form for side by side comparison.

Summary – Glucose vs Starch

Carbohydrates are macromolecules. Glucose and starch are two types of carbohydrates that are extremely important for the survival of humans. Glucose is the simplest form of carbohydrate that is easily absorbed by the digestive system, while starch is a complex form of carbohydrate that is not easily absorbed by the digestive system. So, this is the key difference between glucose and starch

Reference:

1. “Glucose.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.
2. “Starch.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Beta-d-glucose” (CC BY-SA 3.0) via Commons Wikimedia
2. “Amylose-amylopectin”  By Angela Taylor Baltimore – Own work (CC BY-SA 4.0) via Commons Wikimedia