6. Mary read somewhere that congee (ganji) contains carbohydrates. Explain the test you suggested her to confirm it.
Answers
Carbohydrates
Carbohydrates are macronutrients and are one of the three main ways by which our body obtains its energy. They are called carbohydrates as they comprise carbon, hydrogen and oxygen at their chemical level. Carbohydrates are essential nutrients which include sugars, fibers and starches. They are found in grains, vegetables, fruits and in milk and other dairy products. They are the basic food groups which play an important role in a healthy life.
The food containing carbohydrates are converted into glucose or blood sugar during the process of digestion by the digestive system.
Our body utilizes this sugar as a source of energy for the cells, organs and tissues. The extra amount of energy or sugar is stored in our muscles and liver for further requirement. The term ‘carbohydrate’ is derived from a French term ‘hydrate de carbone‘ meaning ‘hydrate of carbon‘. The general formula of this class of organic compounds is Cn(H2O)n.
Carbohydrates
Classification of Carbohydrates
The carbohydrates are further classified into simple and complex which is mainly based on their chemical structure and degree of polymerization.
Simple Carbohydrates (Monosaccharides, Disaccharides and Oligosaccharides)
Simple carbohydrates have one or two sugar molecules. In simple carbohydrates, molecules are digested and converted quickly resulting in a rise in the blood sugar levels. They are abundantly found in milk products, beer, fruits, refined sugars, candies, etc. These carbohydrates are called empty calories, as they do not possess fiber, vitamins and minerals.
Plants, being producers, synthesize glucose (C6H12O6) using raw materials like carbon dioxide and water in the presence of sunlight. This process of photosynthesis converts solar energy to chemical energy. Consumers feed on plants and harvest energy stored in the bonds of the compounds synthesized by plants.
Also, read more about Photosynthesis
1. Monosaccharides
Glucose is an example of a carbohydrate monomer or monosaccharide. Other examples of monosaccharides include mannose, galactose, fructose, etc. The structural organization of monosaccharides is as follows:
Monosaccharides
Monosaccharides may be further classified depending on the number of carbon atoms:
(i)Trioses (C3H6O3): These have three carbon atoms per molecule. Example: Glyceraldehyde
(ii)Tetroses (C4H6O4): These monosaccharides have four carbon atoms per molecule. Example: Erythrose.
Similarly, we have-
(iii) Pentoses,
(iv) Hexoses, and
(v) Heptoses
2. Disaccharides
Two monosaccharides combine to form a disaccharide. Examples of carbohydrates having two monomers include- Sucrose, Lactose, Maltose, etc.
Disaccharides
3. Oligosaccharides
Carbohydrates formed by the condensation of 2-9 monomers are called oligosaccharides. By this convention, trioses, pentoses, hexoses are all oligosaccharides.
Complex Carbohydrates (Polysaccharides)
Complex carbohydrates have two or more sugar molecules, hence they are referred to as starchy foods. In complex carbohydrates, molecules are digested and converted slowly compared to simple carbohydrates. They are abundantly found in lentils, beans, peanuts, potatoes, peas, corn, whole-grain bread, cereals, etc.
Polysaccharides are complex carbohydrates formed by the polymerization of a large number of monomers. Examples of polysaccharides include starch, glycogen, cellulose, etc. which exhibit extensive branching and are homopolymers – made up of only glucose units.
Polysaccharides
Starch is composed of two components- amylose and amylopectin. Amylose forms the linear chain and amylopectin is a much-branched chain.
Glycogen is called animal starch. It has a structure similar to starch, but has more extensive branching.
Cellulose is a structural carbohydrate and is the main structural component of the plant cell wall. It is a fibrous polysaccharide with high tensile strength. In contrast to starch and glycogen, cellulose forms a linear polymer.
Functions of Carbohydrates
The main function of carbohydrates is to provide energy and food to the body and to the nervous system.
The test to confirm whether what Mary read that congee (ganji) contains carbohydrates are listed below:
- Fehling's test
- Benedict's test
- Tollen's test
- Iodine test
The Iodine Test to confirm whether congee contains carbohydrates is explained below:
- Take a clean test tube and fill it with the solution of congee.
- In this solution, add two to three drops of iodine solution.
- In a while, the solution of congee will show blue colour. This appearance of blue colour is because of the reaction of iodine with starch.
- Thus, if the congee solution exhibits blue colour, then carbohydrates are present in it.