Carbohydrates PDF

# Carbohydrates ## Definition: * Carbohydrates are organic compounds which contain carbon, hydrogen and oxygen. H and O are being in the same proportion as in water. ## Biochemical importance of carbohydrates: 1. **Energy:** Carbohydrates are the body's main source of energy. 2. **Glycogen:*...

# Carbohydrates ## Definition: * Carbohydrates are organic compounds which contain carbon, hydrogen and oxygen. H and O are being in the same proportion as in water. ## Biochemical importance of carbohydrates: 1. **Energy:** Carbohydrates are the body's main source of energy. 2. **Glycogen:** can be stored in the muscles and liver and later used for energy. 3. **Cellulose of Fibers:** fibers contain cellulose which is important to prevent constipation because it increases intestinal motility and waste elimination. 4. Carbohydrates combine with lipids (glycolipids) and proteins (glycoproteins). Both enter in the structure of cell 5. Carbohydrate foods contain some water soluble vitamins and minerals. ## Classification of carbohydrates: Carbohydrates are classified into three classes: * **Monosaccharides:** They are the simplest unit of carbohydrate, contain one sugar unit * **Oligosaccharides** contain 2-10 sugar units * **Polysaccharides** contain More than 10 Sugar units -------- ## Monosaccharides ### Definition: They are the simplest carbohydrates, contains only one sugar unit. ### Classification: Monosaccharides are classified according to the number of carbon atoms present: 1. **Trioses:** Monosaccharides which contain three carbon atoms. 2. **Tetroses:** Monosaccharides which contain four carbon atoms. 3. **Pentoses:** Monosaccharides which contain five carbon atoms. 4. **Hexoses:** Monosaccharides which contain six carbon atoms, e.g. Glucose, Fructose, Galactose & Mannose. ### Biochemical importance of hexoses: 1. **Glucose:** Glucose is the sugar of grape. It is the sugar of blood. It is the principle sugar that is utilized by the tissues giving CO2, H₂O and energy. Glucose is stored in the body as glycogen. 2. **Fructose:** It present in fruit juices and honey, Fructose is the sugar of fetal blood & seminal fluid. 3. **Galactose:** is present in combination with glucose in milk sugar (Lactose). 4. **Mannose:** occurs in Mucoproteins -------- ## Oligosaccharides These sugars are formed by condensation of two to ten molecules of monosaccharides - Disaccharides are the most important group. -------- ## Disaccharides They are formed by condensation of 2 monosaccharides. | Structure | Importance | | :-------------------- | :---------------- | | 1 Galactose + 1Glucose | Milk Sugar | | 1Glucose + 1 Fructose | Cane sugar, beet sugar or table sugar | | 1Glucose + 1 Glucose | produced during digestion of cooked starch by salivary amylase | -------- ## Polysaccharides They are composed of a great number of monosaccharide units (more than 10 sugar units) attached together ### A-Homopolysaccharides Contain only one type of sugar **Examples:** starch, glycogen, cellulose, dextrins, dextrans, and agar-agar ### B-Heteropolysaccharides Contain different Sugars **Examples:** gums, pectin and mucopolysaccharides -------- ## A- Homopolysaccharides: These are polysaccharides contain similar sugar units. ### 1) Starch: Starch is the main carbohydrate of food. * It is the main storage from of carbohydrates in plants. * It exists in cereals (e.g. rice, barley, maize and wheat) and in roots and tubers (e.g. potatoes and sweat potatoes). * Starch never presents in animals. Starch granule is formed of: * **a-Amylose:** This forms the inner layer of granule. It is formed of straight chain of glucose units attached together. * **b- Amylopectin:** This forms the outer layer of the granule. It is formed of branched chains of glucose units The document includes a simple diagram illustrating the structure of starch, composed of Amylose and Amylopectin.