What are carbohydrates?Carbohydrates are one of the main types of nutrients. They are the most important source of energy for your body.
Functions Carbohydrates perform numerous roles in living organisms.Polysaccharides serve for the storageof energy (e.g., starch and glycogen), and as structural components (e.g., cellulose in plants and chitin in arthropods). The 5-carbon monosaccharide ribose is an important component of coenzymes(e.g., ATP, FAD and NAD) and the backbone of the geneticmolecule known as RNA. The relatedDeoxyribose is a component of DNA..
monosaccharide MONOSACCHARIDES also known as simple sugars classified by 1. The number of carbons and 2. Whether aldoses or ketoses.
Fischer projection formulasA striking feature of carbohydrates structure is thepresence of chirality centers. All carbohydrates exceptfor dihydroxyacetone contain one or more chiralitycenters. The simplest aldose, glyceraldehyde, has onechirality center---one carbon atom bonded to fourdifferent groups. Thus, there are two possibleenantiomers---mirror images that are not superimposable
The most common monosaccharideGlucoseGlucose -C6H12O6, (alsoknown as D-glucose,dextrose, or grape sugar) is asimple monosaccharide foundin plants. It is one of the threedietary monosaccharide,along with fructose andgalactose, that are absorbeddirectly into the bloodstreamduring digestion.
Fructose or fruit sugar is asimple monosaccharide foundin many plants. It is one of thethree dietarymonosaccharide, along withglucose and galactose, thatare absorbed directly into thebloodstream during digestion.
DisaccharidesA disaccharide or biose is thecarbohydrate formed when twomonosaccharide undergo acondensation reaction which involvesthe elimination of a small molecule,such as water, from the functionalgroups only. Like monosaccharide,disaccharides form an aqueous solutionwhen dissolved in water. Threecommon examples are sucrose,lactose, and maltose.
ClassificationThere are two different types of disaccharides:reducing disaccharides, in which onemonosaccharide, the reducing sugar, still has a freehemiacetal unit; and non-reducing disaccharides, inwhich the components bond through an acetal linkagebetween their anomeric centers and neithermonosaccharide has a free hemiacetal unit. Cellobioseand maltose are examples of reducing disaccharides.Sucrose and tetrahalose are examples of non-reducingdisaccharides
Lactose Lactose is a disaccharide sugar that is found most notably in milk and is formedfrom galactose and glucose. It is extracted from sweet or sour whey. The name comes from lac or lactis, the Latin word for milk, plus the -ose ending used to name sugars. It has a formula of C12H22O11.
Sucrose Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystallinepowder with a sweet taste, it is best known for its nutritional role. The molecule is adisaccharide composed of the monosaccharide glucose and fructose with the molecular formula C12H22O11. The word was formed in mid-19th century from Latin sucrum= "sugar" and the chemical suffix -ose.
MaltoseMaltose (pronunciation: alsoknown as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with anα(1→4) bond, formed from a condensation reaction. The isomer isomaltose has two glucose molecules linked through an α(1→6) bond.
Polysaccharides Polysaccharides are long carbohydrate molecules of repeated monomer unitsjoined together by glycosidic bonds. They range in structure from linear to highly branched
Comparison of Polysaccharide wit Mono- and DisaccharidesProperties Mono- and Polysaccharides Disaccharides• Molecular weight • Low • Very high• Taste • Sweet • Tasteless• Solubility in water • Soluble • Insoluble• Size of particles • Pass through a • Do not pass through a membrane membrane• Test with Cu(OH)2 • Positive (except for • Negative (an oxidizing agent) sucrose)
As a group, the polysaccharides play diverse andimportant roles within the biology of life processes;however, they can be divided into two broad groups.Structural polysaccharides, and Polysaccharides usedas energy stores.
Structural polysaccharides Cellulose Cellulose is a major component of plant cell walls. It is an unbranched polymerwith about ten thousand glucose units per chain.
Chitin Chitin is closely related in structure to cellulose, also being an unbranchedpolysaccharide. Large amounts of chitin is found in the cuticles of arthropods, with smaller amounts being found in sponges, molluscs and annelids. Chitin can also befound in the cell walls of most fungi and in some green algae.
Polysaccharides used as energy storesPolysaccharides make ideal storage molecules for energy fora number of reasons; they are large, this makes them insoluble in water and therefore they exert no osmotic or chemical effect on the cell; they fold into compact shapes; they are easily converted into the required sugars when needed.
Glycogen Glycogen is a branched polysaccharide found in nearly allanimal cells and in certain protozoa and algae. In humans and other vertebrates it is principally stored in the liver and muscles.
StarchStarch is similar to glycogen, however it is found in plant cells, protists and certain bacteria. The starch granules can be seen in the cell through a light microscope. The starch granules are made up of two polysaccharides, amylose and amylopectin.
Derivatives of carbohydrates Means modification of sugar molecules by the addition of substituents other than hydroxylgroup, after modification, a transformed molecule of sugar resembles structure of a sugar and an added substituent; however, it is not considered as sugar anymore because its functions and characteristics has change.
Amino Sugars-generally known as monosaccharidecarbohydrate sugars that have replaced an–NH2 amine group with the 2’-carbonhydroxyl substituent. Examples: • Galactosamine • Sialic acid • Glucosamine • N-acetyl glucosamine
Deoxy sugars-carbohydrates derivatives that are lacking an –OH hydroxyl group at the 2’carbon of the sugarcyclic ring, hence “deoxy,” de- being a prefixmeaning “to remove,” and “oxy” representingoxygen. • Deoxyribose • Fucose • Rhamnose
Dideoxy and TrideoxySugarsAcidic SugarsGlucuronic AcidAscorbic AcidArtificial sweeteners
Health Complications Associated with Carbohydrates
Tooth decayCause by oral bacteriasuch as Streptococcus mutans
Lactose intolerance a.k.a. lactase deficiency and hypolactasia. ---is the inability to digest lactose.Symptoms:Cause??? _insufficient levels of _bloating _pain orlactase cramps _borborygmi _flatulence _diarrhea _nausea and vomiting
Impaired glucose intolerance A pre-diabetic state of hyperglycemia that is associated with insulinresistance and increased risk of cardiovascular pathology.
DIABETES MELLITUSDiabetes mellitus_a disease that causes the body tometabolize sugar poorly, occurs wheneither: The body attacks the cells producing insulin, the hormone that allows the metabolizing of sugar (Type 1 diabetes) The body’s cells exhibit impaired responses to insulin (Type 2 diabetes)
Blood Glucose Tests A test that measures the amount of a type of sugar, called glucose, in your blood.Different types of blood glucose test:• Fasting blood sugar(FBS) measures blood glucose after you have not eaten for at least 8 hours. It is often the first test done to check for prediabetes and diabetes.• 2-hour postprandial blood sugar measures blood glucose exactly 2 hours after you start eating a meal. This is not a test used to diagnose diabetes.
• Random blood sugar(RBS) measures blood glucose regardless of when you last ate.• Oral glucose tolerance test is used to diagnose prediabetes and diabetes.• Glycohemoglobin A1c measures how much sugar is stuck to red blood cells.
References:Michael S. Matta and Antony Wilbraham: General,Organic, and Biological Chemistry-2nd edition.Benjamin/Cummings Publishing company, Inc., 2727Sand Hill Road Menlo Park, California. 1986, chap.16Ronald M. Schultz and George I. Sackheim: Chemistry forthe Health Sciences-3rd edition. Macmillan Publishing Co.,Inc.-NY. Collier Macmillan Publishers-London., 1969 and1973, chap.21Janice Gorzynski Smith: General, Organic, and BiologicalChemistry. The McGraw-Hill Companies, Inc. NY,2010.chap.20George Odian M.A., Ph.D. & Ira Blei M.A., Ph.D.: General,Organic, and Biological Chemistry for Nursing and AlliedHealth-2nd edition. The McGraw-Hill Companies,Inc.USA.1994 2009.chap.18