What are Amylose and Amylopectin?
Amylose is used in numerous industries as a biomaterial. It is a polysaccharide in nature. Amylose is a linear component and it is made up of between 100-10,000 glucose monomers and these are all linked by 1, alpha bindings. An amylose is a form of sugar, however, it has very different properties from native maize starch. The structure of this is a spread polymer that has around 6000 glucose deposits separated into branches of 1 in each 24 glucose rings.
What are the Chemical Properties of Amylose?
The IUPAC name of this compound is (1→4)-α-D-Glucopyranan.
Amylase has a density of 1.25 g/mL
It is insoluble in water
The boiling point of Amylose is 627.7 ± 55.0 °C at 760 mmHg.
It has a variable molecular mass
The chemical formula for this compound is (C6H10O5)n
It also has a surface tension of 74.4 ± 5.0 dyne/cm
It forms α glycosidic bonds
When exposed to hydrogen amylase molecules tend to form very tight bonds which make these molecules less prone to enzymatic degradation.
When it reacts with iodine, it forms a very distinct blue-colored compound.
What are the Physical Properties of Amylose?
Amylase has a characteristic unpleasant odor
It is formed in white crystals
The surface tension of Amylose is 74.4±5.0 dyne/cm.
Uses of Amylose (C6H10O5)n
Now let us take a look at what is amylose used for. Its uses are described as follows.
Amylose is used in the permanent textile finishes, film making, plastics, and bonding of paper pulp fiber.
Higher amylose starches are used together along with food gum or instant starch as a binder which helps in providing a crisp coating while making french fries which, in turn, also reduces the oil absorption.
It is also used as starches for food wrappers and sausage casings, incorporation into pasta and bread crusts for even heating in the microwave.
The Function of Amylose (C6H10O5)n
Let us now discuss what is the function of amylose.
Amylase plays a very deterministic role in the energy that is stored by plants. When it is converted to amylopectin, it is not digested very easily, since amylase has a helical shape that takes up less space as compared to the space taken up by amylopectin. Amylase accounts for at least 30 percent of the starch that is stored in all plants.
Amylase enzyme α-amylase breaks it down further into maltose and maltotriose, and these give energy to the plants.
FAQs on Amylose
1. What is amylose and how does it differ from amylopectin?
Amylose is a polysaccharide and one of the two main components of starch, the other being amylopectin. It is a linear polymer composed of D-glucose units linked by α-(1→4) glycosidic bonds. According to the CBSE 2025-26 syllabus on Biomolecules, the key differences are:
- Structure: Amylose is an unbranched, straight-chain polymer that coils into a helical shape. Amylopectin is a highly branched-chain polymer.
- Chemical Bonds: Amylose contains only α-(1→4) glycosidic linkages. Amylopectin has these same linkages in its linear sections but also features α-(1→6) glycosidic linkages at its branch points.
- Proportion in Starch: Starch is typically composed of 20-30% amylose and 70-80% amylopectin.
2. What is the chemical structure of amylose?
The chemical structure of amylose is a long, unbranched chain of D-glucose monomers. These glucose units are chemically joined together by α-(1→4) glycosidic bonds. This linear arrangement allows the amylose chain to coil into a stable helical structure, which is vital for its properties and function. The general chemical formula for amylose is (C₆H₁₀O₅)n, where 'n' can range from 100 to 10,000.
3. What is the main function of amylose in plants?
The primary function of amylose in plants is long-term energy storage. As a key component of starch, amylose serves as a compact and efficient reserve of glucose synthesized during photosynthesis. Its tightly packed helical structure occupies less volume than the branched amylopectin, making it an ideal molecule for storing energy that can be broken down into glucose when the plant requires it for metabolic processes.
4. What are some examples of foods that are high in amylose?
Foods high in amylose are often described as having high "resistant starch" because amylose is digested more slowly by the human body. Common examples of such foods include:
- Legumes like lentils, chickpeas, and beans
- Certain grains such as long-grain rice and barley
- Unripe (green) bananas
- Potatoes and pasta that have been cooked and then cooled
- High-amylose cornstarch
5. Why does amylose turn blue-black in the presence of iodine?
Amylose gives a characteristic blue-black colour with iodine due to its helical structure. The long, linear chain of amylose coils into a helix, creating a hollow core. When iodine solution is added, the triiodide ions (I₃⁻) fit perfectly inside this core. This arrangement forms a charge-transfer complex that absorbs light from the red-orange part of the visible spectrum, causing the solution to appear a deep blue-black. Amylopectin's branched structure prevents this, resulting in a reddish-brown colour instead.
6. Is there a difference between amylose and the enzyme amylase?
Yes, there is a fundamental difference. Amylose is a carbohydrate (a polysaccharide) that is a component of starch found in plants. In contrast, amylase is a digestive enzyme produced by organisms, including in human saliva and the pancreas. The function of the amylase enzyme is to break down starch, including amylose, into smaller sugars like glucose and maltose for energy.
7. Why is amylopectin generally easier to digest than amylose, despite amylose having a simpler linear structure?
While it seems counterintuitive, amylopectin is digested more quickly than amylose precisely because of its structure. The highly branched nature of amylopectin provides many terminal ends for digestive enzymes like amylase to act upon simultaneously. This allows for a rapid breakdown into glucose. In contrast, the linear chains of amylose pack together tightly into a dense, helical structure that is less accessible to enzymes, leading to a slower, more gradual digestion process.
8. From a health perspective, what are the effects of consuming high-amylose foods?
Consuming foods with a high proportion of amylose, also known as resistant starch, is generally considered beneficial for health. Because it is digested slowly, it causes a more gradual increase in blood sugar and insulin levels, which is important for blood sugar management and may reduce the risk of type 2 diabetes. Furthermore, it can increase feelings of fullness (satiety) to aid in weight management and acts as a prebiotic, promoting the growth of beneficial gut bacteria.
