You have already studied that carbohydrates are primary fuel of the body i.e., the source of energy. Beside this, they also play various important roles in the body. Importance of carbohydrates in the body can be explained in the following way:
Carbohydrates as a Basic Fuel for Energy to Body
Starches and sugars are the basic fuel forms of carbohydrates that occur in our food.
Plants by the process of photosynthesis transform sun energy into a typical form of carbohydrate specially found in plant known as starch. In this process, carbon dioxide from the air and water from the soil are converted into starch and sugar by chlorophyll, the green pigment present in leaves.
Carbohydrates are called "quick energy" foods. This is because they are rapidly broken down in the body to provide energy. About 50 to 60 per cent of total kilo calorie requirement of a person comes from dietary carbohydrates. The amount of carbohydrates stored in the body is relatively small. Stored glycogen and glucose can provide energy sufficient for about half a day at moderate activity. Thus regular intake of carbohydrates containing food at moderately frequent intervals is essential to meet the constant energy demands of the body.
Carbohydrates as Chief Dietary Constituents
Carbohydrates are one of the major components of the diets all over the world. The reason behind this is their wide availability and lower cost. They may be grown and stored easily. Carbohydrates rich foods can be kept in dry storage for relatively longer period without spoilage. In some countries, carbohydrates constitute almost entire diet of the people.
Carbohydrates in Different Role in Biological Systems
Glucose: This is the most important carbohydrate. It is absorbed into the blood stream after the digestion of food. It can be converted into other forms of carbohydrates in the body. Glucose can also be obtained from complex carbohydrates by degradation in the liver. It is from glucose that all other carbohydrates in the body are formed. Glucose is a major fuel of the tissues of mammals (except ruminants) and a universal fuel of the fetus. It is converted to other forms of carbohydrates having highly specific functions. Some of the special functions of carbohydrates in body tissues are as follows:
i) Stored form of energy: In living system glycogen and starch are stored form of energy. Glycogen is found in animals whereas starch in plants. Glycogen reserved in liver and muscle of animal provide a constant supply of glucose to fulfil energy needs of the body. Thus, this reserve protects cells
from depressed metabolic functions and injury.
ii) Protein sparing function: Carbohydrates regulate protein metabolism. I Presence of sufficient carbohydrates prevents the breakdown of protein for energy requirement so that the proteins are used in the body for its basic ,structural purpose of tissue building. Excess of carbohydrates in body is utilized for the carbon skeleton of protein.
iii) Anfiketogenic effect: Carbohydrates also regulate the fat metabolism. The amount of carbohydrates in the diet decides the formation and disposal rate of ketones from lipids. If a carbohydrate is inadequate or unavailable for energy needs, excess fat is oxidized leading to accumulation of ketones and results in ketoacidosis. Excess 6f carbohydrate is transformed into fats. It should be noted that ,fat and protein always bum in flame of carbohydrate i.e., even for oxidation of fat or protein as energy source, some carbohydrate or its metabolite is required.
iv) Heart action: Heart action is a life sustaining muscular exercise. Glycogen reserve in cardiac muscle is an important emergency source of contractile energy. Low carbohydrate intake or poor glycogen stores may cause cardiac symptoms and angina.
v) Central nervous system function: The brain, central nervous system regulatory center do not contain stored glucose and are dependent on glucose supply from the blood. Hypoglycemia, (decrease in blood glucose level), may cause irreversible brain damage; So, carbohydrates are necessary for functional integrity of nerve tissue.
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