Key difference - sugar vs starch

Sugar and starch are two types of carbohydrates found in plants and animals. Three types of carbohydrates can be identified as monosaccharides, disaccharides, and polysaccharides. They are made up of three atoms: carbon (C), hydrogen (H) and oxygen (O). Autotrophs produce the simple monosaccharide glucose from carbon dioxide and water during photosynthesis . The combination of two monosaccharides creates disaccharides. Polysaccharides are formed by combining a large number of glucose monomers. The main difference between sugar and starch is that sugars are disaccharides or monosaccharides while starch is a polysaccharide.

This article explains

1. What is sugar - definition, structure, properties 2. What is starch - definition, structure, properties 3. What is the difference between sugar and starch?

What is a sugar

Sweet and soluble carbohydrates are commonly referred to as sugars. Hence, both monosaccharides and disaccharides are sugars. Monosaccharides have the general chemical formula (CH ₂ O) _n . There are three common types of monosaccharides: glucose, fructose, and galactose.

glucose

Glucose is the organic molecule that is used as a source of energy in metabolism . Hence, it is very important for the physiology, nutrition and nutrition of animals. All other forms of carbohydrates are also converted into glucose during digestion. Glucose is more common in ripe fruits and vegetables such as beetroot.

Fructose and galactose

Fructose is the fruit sugar. It is also found in honey . Galactose is found in mammalian milk.

Figure 1: Glucose, Fructose and Galactose

Disaccharides are formed when two monosaccharides are linked together by a glycosidic bond. The most common types of disaccharides are lactose, sucrose, and maltose . They have the general formula C ₁₂ H ₂₂ O ₁₁ . Sucrose is found in sugar cane and sugar beets . It is formed by connecting a glucose and a fructose molecule through an α (1 → 2) β bond. Lactose is created by connecting a glucose molecule to a galactose molecule through a β (1 → 4) bond. It is found in mammalian milk. Maltose is created by connecting two glucose molecules via an α (1 → 4) bond. It occurs in cereals such as barley. The structure of sucrose is shown in Figure 2 .

Figure 2: sucrose

What is strength

Starch is the polysaccharide that green plants synthesize from glucose as the main energy store. Plants store starch in staple foods like fruits, tubers like potatoes, seeds like rice, wheat, corn and cassava. Starch comes in two types: amylose and amylopectin. Amylose is a linear, helical chain that is formed by the linkage of glucose molecules via α (1 → 4) bonds by the enzyme starch synthase. Amylopectin is formed by the branching of the amylose chain via α (1 → 4) bonds by the starch branching enzyme. About 25% of the starch in plants is amylose while the rest is amylopectin. At the storage areas, starch is arranged in a semi-crystalline structure. It's in the granules called amyloplasts. Amylose and amylopectin are shown in Figure 3.

Figure 3: Amylose and amylopectin

Difference Between Sugar and Starch

Carbohydrate types

Sugar: Sugars are monosaccharides and disaccharides.

Starch: Starch is a polysaccharide.

Number of monomers

Sugars: Monosaccharides are made up of a single monomer and disaccharides are made up of two monomers.

Starch: Starch is made up of 300 to 1,000 glucose molecules.

complexity

Sugar: Sugars are less complex.

Starch: Starch is more complex than sugar.

absorption

Sugar: Sugar is easily absorbed by organisms from the digestive tract.

Strength: Strength takes time to be absorbed.

Blood sugar level

Sugar: Sugar increases blood sugar levels quickly.

Starch: Starch slowly increases blood sugar levels.

diploma

Sugar and starch are carbohydrates. Monosaccharides, disaccharides, and polysaccharides are three types of carbohydrate groups that occur in nature. Monosaccharides and disaccharides are water-soluble substances. Because mono- and disaccharides are water-soluble, they are sweet. Sweet carbohydrates are called sugars. Therefore, monosaccharides such as glucose, fructose and galactose and the disaccharides such as sucrose, maltose and lactose are sugars. Starch is a polysaccharide made up of a variety of glucose monomers. Hence, the main difference between sugar and starch is their complexity of structure.

Reference: 1. Berg, Jeremy M. "Complex carbohydrates are formed by linking monosaccharides." Biochemistry. 5th edition. US National Library of Medicine, January 1, 1970. Web. May 18, 2017.. 2. "Types of sugar". Monosaccharides and disaccharides. Np, nd web. May 18, 2017..

Image Courtesy: 1. From OpenStax College - Anatomy & Physiology, Connexions website. June 19, 2013 (CC BY 3.0) via Commons Wikimedia 2. "Sucrose" (Public Domain) via Commons Wikimedia 3. "219 Three Important Polysaccharides-01" From OpenStax College - Anatomy and Physiology, Connexions website . June 19, 2013. (CC BY 3.0) via Commons Wikimedia