Dr.Asaad (Carbohydrates12-6).pdf
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University of Warith Al-Anbiyaa College of medicine Department of Biochemistry Lecturer Dr. Asaad Abbas Chapter one 2023 Head of Department Dr. Riadh Abdul ALrasool Biochemistry Metabolism: A series of chemical reactions catalyzed by an enzyme that begins with one molecule and transforms into...
University of Warith Al-Anbiyaa College of medicine Department of Biochemistry Lecturer Dr. Asaad Abbas Chapter one 2023 Head of Department Dr. Riadh Abdul ALrasool Biochemistry Metabolism: A series of chemical reactions catalyzed by an enzyme that begins with one molecule and transforms into another molecule. Catabolic processes: It is a series of enzymatic reactions in which large molecules convert sugars, lipids, proteins into their simple components And the smallest and easy to move, and these processes are accompanied by the release of energy in the form of ATP molecules Anabolic processes: It is a series of enzymatic reactions in which large, complex molecules are built from low-weight elements and raw materials molecular inside the body, and these processes are always accompanied by the consumption of energy in the form of ATP Energy is in the form of adenosine triphosphate (ATP) Carbohydrates What are Carbohydrates? Flour Fruits Vegetables Nuts OVERVIEW Classification of Food Based on Chemical Composition 1- Carbohydrates 2- Fats 3- Proteins 4. Minerals 5. Vitamins Dietary carbohydrates include starch, sucrose, lactose, and indigestible fibre The major product of digestion of carbohydrates is glucose, but some galactose and fructose are also produced Glucose is a major fuel source that is oxidized by cells for energy. After a meal, glucose converted to glycogen or to triacylglycerols and stored. Glucose tis also converted to compounds such as proteoglycans, glycoproteins, and glycolipids. Glycogen is the major storage form of carbohydrate in organisms. The largest stores are in muscle and liver. Muscle glycogen is used to generate ATP for muscle contraction. Liver glycogen is used to maintain blood glucose levels during fasting or exercise. The maintenance of blood glucose levels is a major function of the liver. The liver produces glucose by glycogenolysis and gluconeogenesis. Carbohydrates Carbohydrates are organic compounds that contain of carbon, hydrogen, oxygen and are polyhydroxy aldehyde group or keto group Most carbohydrates come from plants (exception lactose from milk) Carbohydrates are found in fruits, vegetables, rice, wheat, milk and processed sweets Formula for many of carbohydrates is (CH2O)n. Glucose Functional groups present include hydroxyl groups -ose indicates sugar Chain Ring How does the body use carbohydrates? How carbohydrates convert into glucose sugar in the body ? 1- Mouth: Some starch is broken down to polysaccharide and disaccharide units by salivary amylase. 2-Stomach: Salivary amylase is inactivated by the acidity in the stomach. 3-Pancreas: Pancreatic amylase is secreted into the small intestine to break polysaccharides into disaccharides. 4-Small intestine: Enzymes in the wall of the small intestine break down the disaccharides into monosaccharides. 5- The absorbed monosaccharides are transported to the liver by the portal vein. Liver converts monosaccharides into glucose (blood stream) which is then used as an energy source to produce ATP. 6-Large intestine: Some soluble fiber is metabolized into acids and gases by bacteria in the large intestine. 7-Insoluble fiber escapes digestion and is excreted in feces. Regulation of blood glucose Iesulin and glucagon are key factors in controlling blood glucose. When blood glucose rises above the normal range, insulin is released to lower it .Blood glucose then falls back into the normal range. (Anabolic hormone) When blood glucose falls below the normal range. glucagon is released. which has the opposite effect of insulin. This then restores blood glucose to the normal range. (Catabolic hormone) Carbohydrates of Classification Carbohydrates Classification Carbohydrates are divided into four major groups: 1. Monosaccharides 2. Disaccharides 3. Oligosaccharides 1. Polysaccharides. Biomedical Importance of Carbohydrates Carbohydrates are the major source of energy in most tissues (brain and Red Blood Cells). Constituents of compound lipids and conjugated proteins. Degradation products act as “promoters” or ‘catalysts’. Certain carbohydrate derivatives are used as drugs like cardiac glycosides /antibiotics. Lactose principal sugar of human milk. The fiber help achieve a healthy weight The fiber reduces risk of heart and diabetes disease The fiber prevents diseases of gastrointestinal tract and constipation Diseases associated with carbohydrate Derangement of glucose metabolism is seen in diabetes mellitus Galactosemia Glycogen storage disease Lactose intolerance. Monosaccharides Indicate whether the carbon marked with arrow is chiral (asymmetric a carbon atom) An asymmetric carbon atom has four different chemical groups attached to it. Monosaccharides Monosaccharides (single sugar): include glucose, fructose, ribose. All of Monosaccharides have isomer D form and L form)The configuration of the asymmetric carbon atom farthest from the aldehyde or ketone group determines whether a monosaccharide belongs to the D or L series. In the D form, The hydroxyl group is on the right; in the L form, it is on the left( An asymmetric carbon atom has four different chemical groups attached to it. D-sugars are naturally occurring sugars and body can metabolize only D-sugars Types of Monosaccharides 1-Trioses 2-Tetroses 3- Pentoses 4-D- Hexoses 5-D-Fructose stability of carbohydrates In solution, mutarotation occurs. The α and β forms equilibrate via the straight-chain aldehyde form (Anomers sugar). Disaccharides Glycosides Condensation between monosaccharides and another compound (monosaccharides or Aglycone ) Aglycone is any compound a non-carbohydrate Examples 1-Disaccharides ( sugar + sugar) 2- sugar nucleotide ( sugar + adenine ) 3-Glycolipid (sugar + lipid ) 4- Glycoproteins (sugar + protein ) 5- Digitalis (sugar + steroid) O-Glycosides Glycosidic bonds form when the hydroxyl group on the anomeric carbon of a monosaccharide reacts with an – OH or – NH amino group of another compound. o O-Glycosides o N-Glycosides (OH of monosaccharide + OH hydroxyl group) (OH of monosaccharide + NH amino group ) N-Glycosides Disaccharides Disaccharides )2 sugars combined) The important disaccharides are: 1-Maltose 2- Sucrose 3- Lactose Maltose= glucose+ glucose )barley( Lactose= glucose+ Galactose (milk( Sucrose= glucose+ fructose (Table sugar( Their general molecular formula is C12H22O11 and they are hydrolysed by hot acids or corresponding enzymes as follows: Properties of Disaccharides Maltose: Maltose or malt sugar is an intermediary in acid hydrolysis of starch and can also be obtained by enzyme hydrolysis of starch. In the body, dietary starch digestion by Amylase in gut yields maltose, which requires a specific enzyme maltase to form glucose. It is a rather sweet sugar and is very soluble in water. On hydrolysis Maltose yields two molecules of glucose. There is -1,4 linkage Lactose: Lactose is milk sugar. It is not very soluble and is not so sweet. The Specific enzyme which hydrolyses Lactose is lactase present in intestinal juice. On hydrolysis it yields one molecule of D-Glucose and one molecule of D-Galactose. As one of the aldehyde group is free, it has reducing properties. As anomeric carbon of glucose is free, can form α and β forms. Sucrose: Ordinary table sugar is sucrose. It is also called as ‘Cane sugar’. Also obtained from sugar beet, and sugar maple. It is occurring free in most fruits and vegetables, e.g. pineapples, and carrots. It is very soluble and very sweet. On hydrolysis yields one molecule of D-Glucose and one molecule of D-Fructose. The specific enzyme which hydrolyses sucrose is sucrase present in intestinal juice. As both aldehyde and ketone groups are linked together (α 1 → 2), it does not have reducing properties Lactose intolerance/ disaccharide diseases Lactose intolerance is a condition in which the lactose in milk cannot be digested well in the small intestine. The undigested lactose then moves into the large intestine where bacteria attack it, forming large amounts of gas. Symptoms of lactose intolerance include bloating, cramps, nausea, and vomiting. Avoidance of foods containing lactose is recommended for people who show signs of lactose intolerance. Which of the following is found in Lactose intolerance? Low stool osmotic gap Negative stool reducing agent Low pH stool Negative Hydrogen breath test Polysaccharides Polysaccharides Polysaccharides products of many monosaccharide units (3 or more sugars combined) o Oligosaccharides == 3 sugars combined The important Polysaccharides are: 1-Starch 2- Glycogen 3- Inulin 4- Fiber (Cellulose) Homoglycans are composed of single kind of monosaccharides, e.g. starch, glycogen and cellulose. Heteroglycans are composed of two or more different monosaccharides, e.g. hyaluronic acid, chondroitin sulphate. Starch : Starch is glucose storage in plants Sources: Potatoes, cereals (rice, wheat) and other food grains. 1 Starch is composed of amylose and amylopectin. o o o Amylose is a straight chain formation of a group of glucose Amylose has 300- several thousand units of D-glucose units. Amylose is less soluble in water. Amylose can be hydrolyzed with α amylase and β amylase enzymes completely. o Amylose is a great storage system for energy. o o o Amylopectin is branched chain formation of a group of glucose Amylopectin is more soluble in water. Amylopectin constitutes about 70-80% of the starch. Amylopectin cannot be hydrolyzed with α amylase and β amylase enzymes completely. o Amylopectin only stores a small amount of energy. 2 Glycogen Glycogen is glucose storage in organisms Molecular weight of glycogen is about 5 million. Glycogen is not readily soluble in water. Glycogens have a complex structure of highly branched chains. It is a polymer of D-Glucose units and resemble amylopectin. But It is more branched and compact than amylopectin. Inulin Inulin is a natural storage carbohydrate present in more than 36,000 species of plants. It is a polymer of D-fructose and has a low molecular weight (MW = 5000). Because of the β )2,1) linkages, inulin is not digested by enzymes in the human alimentary system. Biomedical importance of Inulin 1-Dietary inulin inhibits development of colon cancers. 2-Dietary inulin may reduce risk of cardiovascular disease. Cellulose Cellulose is a polymer of glucose. Cellulose is a very stable insoluble compound. it forms a considerable part of our vegetable food. Cellulose is of considerable human dietetic value that it adds bulk to the intestinal contents (roughage) thereby stimulating peristalsis and elimination of indigestible food residues. Sources: Found in vegetables and fruits Thank you for listening
