Is Butter a Carb? PDF

C H A P T E R 5 Carbohydrates & Sugars Outline discussion: Definition Types of carbohydrates Chemical structure Absorption of carbohydrates Adrian Lui Dasigo, MSPH Scan QR code for a copy of lecture Introduction...

C H A P T E R 5 Carbohydrates & Sugars Outline discussion: Definition Types of carbohydrates Chemical structure Absorption of carbohydrates Adrian Lui Dasigo, MSPH Scan QR code for a copy of lecture Introduction C H A P T E R Carbohydrates & Sugars 5 Carbohydrates are a major source of energy from our diet. Composed of the elements C, H and O. Also called saccharides Main functions: Main source of energy for all living organisms. Structural support Acts as “road markers” Adrian Lui Introduction C H A P T E R Carbohydrates & Sugars 5 Can be represented by the stoichiometric formula (CH2O)n where n is the number of carbons in the molecule. The ratio of carbon to hydrogen to oxygen is 1:2:1 Adrian Lui Carbohydrates as structural support C H A P T E R Carbohydrates & Sugars 5 Adrian Lui Carbohydrates as road markers C H A P T E R Carbohydrates & Sugars 5 Adrian Lui Carbohydrates as road markers C H A P T E R Carbohydrates & Sugars 5 Adrian Lui Classification of Carbohydrates: C H A P T E R Carbohydrates 5 Monosaccharide Disaccharide Oligosaccharide Polysaccharide Adrian Lui Monosaccharides Monosaccharide C H A P T E R Carbohydrates 5 Are the simplest carbohydrates. Cannot be broken down to smaller carbohydrates. One sugar unit Important single sugar are: Glucose Fructose Galactose Adrian Lui Monosaccharide C H A P T E R Carbohydrates 5 The number of carbon usually ranges from three to seven. Most monosaccharide name end with the suffix - ose. Adrian Lui Monosaccharide C H A P T E R Carbohydrates 5 If the sugar has an aldehyde group then it is named as aldose. If the sugar has a ketone group, it is known as ketose. Adrian Lui Monosaccharide C H A P T E R Carbohydrates 5 Depending on the number of carbons in the sugar, they also may be known as trioses, pentoses, and or hexoses. Adrian Lui Monosaccharide C H A P T E R Carbohydrates 5 They can exist as linear chain or as ring-shaped molecules. In aqueous solution, they are usualyl found in ring forms a position: if the OH group is in carbon number 1. b position: if the OH group is above the plane. Adrian Lui Types of Monosaccharides Glucose C H A P T E R Carbohydrates 5 Glucose is an alpha-carbohydrates (a- carbohydrates) Dextrose or blood sugar Primary fuel for the body Not commonly found in diet but can be produced by breaking down complex structures with the help of enzyme. Adrian Lui Glucose & Diabetes C H A P T E R Carbohydrates 5 Adrian Lui Fructose C H A P T E R Carbohydrates 5 Are classified as b-carbohydrates. Sugar of fruit, honey Sweetest of all simple sugar Usually present in soft drink, ready to use cereals and desserts. Converts to glucose in the body. Adrian Lui Galactose C H A P T E R Carbohydrates 5 Are classified as b-carbohydrates. Found combined with glucose in the disaccharide lactose present in milk. They are known as milk sugar. Adrian Lui Disaccharides Disaccharides C H A P T E R Carbohydrates 5 Consist of two monosaccharide units that are joined together. They can be split into two monosaccharides Maltose = glucose + glucose Lactose = glucose + galactose Sucrose = glucose + fructose Adrian Lui  Disaccharides C H A P T E R Carbohydrates 5 Consist of two monosaccharide units that are joined together. They can be split into two monosaccharides Maltose = glucose + glucose Lactose = glucose + galactose Sucrose = glucose + fructose How does it forms? Adrian Lui Maltose formation through condensation reaction C H A P T E R Carbohydrates 5 + = An OH group from one glucose and an OH group from The two glucose molecules bond together with a single another glucose combine to create a molecule of H20 O atom to form the dissacride maltose. Adrian Lui Disaccharides C H A P T E R Carbohydrates 5 Formation of covalent bonds which are known as glycosidic bonds. It can be alpha or beta bond a bond - formed when OH group on carbon 1 of the first glucose is below the ring plane. b bond - formed when the OH group on the carbon 1 is above the ring plane.  Maltose breaking down process to form two glucose C H A P T E R Carbohydrates 5 -> + The dissacharide maltose splits into two glucose molecules with H added to one and OH to the other (from water) Adrian Lui Lactose C H A P T E R Carbohydrates 5 + = Glucose Galactose Adrian Lui Sucrose C H A P T E R Carbohydrates 5 + = Sucrose Fructose Adrian Lui Oligosaccharides Oligosaccharides C H A P T E R Carbohydrates 5 Type of carbohydrate formed when three to 10 simple sugars are linked together. Short chain of monosaccharides Small amounts occur naturally in many plants. Cna have many functions including cell recognition and cell binding. Adrian Lui  C H A P T E R Carbohydrates 5 Maltotriose + + = Adrian Lui Role of oligosaccharides in recognition and adhesion at the cell surface Polysaccharides Polysaccharides C H A P T E R Carbohydrates 5 Are large molecules of monosaccharides that are connected to each other through their anomeric carbons. Classifications: Contain only single monosaccharide (can be branched or unbranched) Contain two or more monosaccharide (can be branched or unbranched) Types: Storage polysaccharides - contain only a-glucose units (starch, glycogen and amylopectin). Structural polysaccharides - contain only b-glucose units (cellulose and chitin). Adrian Lui Starch C H A P T E R Carbohydrates 5 Can be branched or unbranched Adrian Lui If starch is unbranched, then it is... C H A P T E R Carbohydrates 5 Amylose Makes up 20% of plant starch. Long chains of amylose tend to coil. Can be found in plant foods. If starch is branched, then it is... Amylopectin Makes up 80% of plant starch. More complicated structure. Breaking down of starch C H A P T E R Carbohydrates 5 Fruit ripening Enzyme Adrian Lui Glycogen C H A P T E R Carbohydrates 5 Can be similar in structure with starch Storage form of polysaccharide found in animals. When glucose is needed, glycogen is hydrolyzed in the liver to glucose. Adrian Lui Glycogen is similar in structure with C H A P T E R Carbohydrates 5 starch Amylopectin Glycogen Adrian Lui Cellulose C H A P T E R Carbohydrates 5 Contains glucose units bonded The chain of glucose units is straight. This allow chains to align next to each other to form a strong rigid structure. Adrian Lui C H A P T E R Carbohydrates 5 Adrian Lui C H A P T E R Carbohydrates 5 Adrian Lui Sources of carbohydrates C H A P T E R Carbohydrates 5 Adrian Lui Digestion & Absorption of Carbohydrates Digestion in Mouth Mechanical digestion Chewing also known a mastication, crumble the carbohydrate food into smaller and smaller pieces forming bolus. Chemical digestion Salivary glands in oral cavity secrets saliva. Starch -> maltose Only 5% of starch are broken down in mouth. Adrian Lui Digestion in Stomach Mechanical digestion Peristalsis Chemical digestion Action pf ptyalin continues only inside bolus. About 30-40% of dietary starch is digested before bolus is broken down and acidified. Enzymatic reaction stops when chyme is passed down to small intestine. Adrian Lui Digestion in Small Intestine Mechanical digestion There is no mechanical digestion. Chemical digestion Action of pancreas Pancreatic juice Absorption Adrian Lui Intestinal enzymes Adrian Lui Undigested Carbohydrates Certain carbohydrate like cellulose ar eundigested by human due to lack of enzymes like cellulase. However, it provide fibers for absorption of water into the large intestine which expand the muscle walls and trigger muscle contraction for egestion. Adrian Lui Glucose when needed, are transported in most cells through: Adrian Lui Excess intake of Carbohydrates: Places a large metabolic load on the body which leads to weight gain, poor metabolic health and increased risk of heart disease. Consuming too many carbs especially those with a high glycemic load, can increase the risk of several disorders, including type II diabetes. Diet containing too many carbohydrates can also raise fat the travels in the blood leading to cardiovascular disease. Adrian Lui Low intake of Carbohydrates: Long-term restriction of carbs in the diet may lead to kidney damage, increased risk of cancer, impairment of physical activity and lipid abnormalities. Adrian Lui Assignment M1: Illustrate chemical structure of all sugars discussed in this lecture. Paper size: A4 only Write your name, year and section. Date of submission: next meeting Adrian Lui Thank you for listening! I used the following references in creating this lecture: Voet, D., Voet, J. G., & Pratt, C. W. (2016). Fundamentals of biochemistry (5th ed.). John Wiley & Sons. Nelson, DL. Lehninger (2017). Principles of Biochemistry (7th ed.)