Importance of Carbohydrates in living organisms free essay sample

Carbohydrates contain carbon, hydrogen and oxygen in the ratio of 1. 2. 1.. There are many different types of carbohydrate, all of which are useful to living organisms. The most important carbohydrate is probable glucose. Glucose is a monosaccharide and is the monomer unit which makes up more complex polysaccharides. Two glucose molecules can be joined in a condensation reaction, whereby water is removed, for example to produce maltose, a disaccharide. The bond between the glucose molecules is a ? 1-4 glycosidic bond. Glucose is also soluble, a reducing sugar and the blood sugar of mammals. It is respired to produce ATP (adenosine triphosphate, a chemical energy store) and is therefore required for growth. During glycolysis, a process which occurs in the cytoplasm and generates 2 ATP, glucose is phosphorylated to produce a 6 carbon phophorylated sugar. Glucose is essential for respiration and therefore essential for ATP production. ATP is required for various activities, for example active transport systems such as glucose reabsorption in the kidney, or muscle contraction. We will write a custom essay sample on Importance of Carbohydrates in living organisms or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page There are two other monosaccharides: fructose and lactose. Fructose is found in sperm and in fruits, to make them more attractive to animals. Lactose is found in the milk of mammals and is an important energy supply for their young. These monosaccharides also help to build disaccharides. Glucose and fructose join together to form sucrose and glucose and lactose join to form galactose. Sucrose is the major transport carbohydrate of green plants. It is transported in the phloem by translocation. It is formed in the leaves by photosynthesis. The Calvin cycle (the light independent reactions) which takes place in the stroma produces glucose, which in turn is changed into sucrose. Complex carbohydrates (polysaccharides) are produced from glucose, monomers. Cellulose, for example, is a long chain of glucose units (about 3000 units). Each unit is joined to the next by a ? 1- glycosidic bond. About 2000 cellulose chains are packed into cellulose fibres which make up plants’ cell walls. Cellulose, therefore, is major structural carbohydrate of green plants. The cell wall containing cellulose provides support in herbaceous plants and when impregnated with lignin it acts as a water proofing layer and provides great strength. Starch is another polysaccharide of green plants, it is their storage carbohydrate. Starch is made up of amylose and amylopectin. Amylose is a long chain of glucose monomers, joined by ? 1-4 glycosidic bonds whereas amylopectin is made up of shorter branched chains of glucose monomers. Starch is stored in chloroplasts as starch grains. It is used, in green plants, as the carbohydrate which respired to produce energy. It enters into glycolysis in the cytoplasm, in place of glucose. Therefore starch is extremely important for green plants because it is essential for ATP production. In green plants, ATP is used in the Calvin cycle, to help turn glycerate-3-phosphate into glyceraldehyde-3-phosphate and to help turn this back to ribulose bisphosphate. Glycogen is a third polysaccharide, it is the storage carbohydrate of animals. Glycogen is formed from glucose in the liver cells, under the influence of the hormone insulin. This process is called glycogenesis. Glycogen is a n energy store and if blood sugar levels fall too low (for example during periods of dieting or fasting) it is turned back into glucose. This is called glycogenolysis and is influenced by the hormone glucagon. Glycogen, therefore, is important in homeostasis, the maintaining of a constant internal environment. In conclusion, carbohydrates are extremely important to all living organisms and without them these organisms would die.