Carbohydrates Chemistry & Metabolism Part 1 Lecture Notes 2023-2024 PDF

2023-2024 Chapter (3): Carbohydrates chemistry & Metabolism part I Lecture 1  What are carbohydrates The term carbohydrate is originated from the compounds of this class e.g starch, sucrose, glycogen and glucose. These compounds were hydrated of carbon ( cont...

2023-2024 Chapter (3): Carbohydrates chemistry & Metabolism part I Lecture 1  What are carbohydrates The term carbohydrate is originated from the compounds of this class e.g starch, sucrose, glycogen and glucose. These compounds were hydrated of carbon ( contain hydrogen and oxygen in the same proportion of H2O). So, carbohydrate could be represented by Cn(H2O)n , where n= 3 or more.  Classification of carbohydrates According to No. of sugar units (1) Monosaccharides (one sugar unit): can't be hydrolyzed into simpler compounds (2) Disaccharides ( two sugar units) (3) Oligosaccharides (from 3-10 sugar units) (4) Polysaccharides ( polymers of more than 10 sugar units)  Classification of monosaccharides According to no. of carbon atom Trioses (3C), tetroses (4C) pentoses (5C) hexoses(6C) According to active sugar group as Aldoses (-HC=O) or ketoses (C=O) According to both (active sugar group + no. of carbon atom) Aldopentose (5C+ aldhyde group) Aldohexose (6C+ aldehyde group): glucose Ketohexoses (6C+ Ketone group):fructose Disaccharides : 2 monosaccharides linked together by – O – glyosidic bond Maltose (Malt sugar) (Glucose+ Glucose) Lactose (Milk sugar) (Galactose+ Glucose) Sucrose (Cane sugar) (Glucose+ Fructose)  Lactose Intolerance Cause : deficiency of lactase. The deficiency may be congenital (primary) ; due to gene defect, or acquired (secondary) after surgery or intestinal bacterial or viral infection or even due to aging. There will be fermentation by the action of intestinal bacteria ; gases production, distension, nausea, colic and frequent diarrhea. It can be managed by intake of lactose free milk. And yogurt at older age.As lactose in yogurt is partially hydrolysed during fermentation.  Sucrose and dental caries If human teeth are rinsed with a sucrose solution for 3 min; the pH of plaque (dental biofilm) dropped from 6.5 to 5.0 and remained such for 40 min  Dental caries is caused by the action of acids on the enamel surface. The acid is produced when sugars (mainly sucrose) in foods or drinks react with bacteria present in the dental biofilm (plaque) on the tooth surface. The acid produced leads to a loss of calcium and phosphate from the enamel; this process is called demineralization  Simple polysaccharides 1- Starch: Storage form of carbohydrate in plants. It has two types of chain: a- Straight chains (Amylose) : It is formed of α-D glucose linked together by α 1-4 glucosidic bonds b- Branched chain (Amylopectin) : It is formed of α-D glucose linked togather by α 1-4 glucosidic bonds, and α 1-6 glucosidic bonds at the branching point.  2- Glycogen: - Is the storage form of carbohydrates in animals. - It is formed of highly branched chains of α-D- glucose linked together by α 1-4 glucosidic bonds, and α 1-6 glucosidic bonds at the branching point.