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Lecture 7 Carbohydrates Page43 • Carbohydrates are compounds containing carbon, hydrogen and oxygen, with hydrogen and oxygen present in the same ration as in water ie H2O. They include sugars (eg glucose, fructose, sucrose) and starches (eg amylose, amylopectin). 3.4 Monosaccharides are the simplest carbohydrates • Carbohydrates range from small sugar molecules (monomers) to large polysaccharides – Sugar monomers are monosaccharides, such as glucose and fructose – These can be hooked together to form the polysaccharides Copyright © 2009 Pearson Education, Inc. • Common carbohydrates: – Sugar – Starch • Naming: – Normally have “sacchar-” or “-ose” in their name – Ex: glucose, dextrose Carbohydrates • Hydrophilic molecules • General formula (CH2O)n n = # of carbon atoms Ex: glucose n=6 C6H12O6 • 2:1 ratio of hydrogen to oxygen 3.4 Monosaccharides are the simplest carbohydrates • The carbon skeletons of monosaccharides vary in length – Glucose and fructose are six carbons long – Others have three to seven carbon atoms • Monosaccharides are the main fuels for cellular work – Monosaccharides are also used as raw materials to manufacture other organic molecules Copyright © 2009 Pearson Education, Inc. Carbohydrate Monomers • Monosaccharide = simple sugar – Glucose (blood sugar) – Fructose (fruits) – Galactose (component of lactose – milk) – Ribose (RNA) – Deoxyribose (DNA) Glucose (an aldose) Fructose (a ketose) Structural formula Abbreviated structure Three representations of the ring form of glucose Simplified structure Carbohydrates • Contain carbon, hydrogen, and oxygen • Their major function is to supply a source of cellular food • Examples: – Monosaccharides or simple sugars Figure 2.14a 3.5 Cells link two single sugars to form disaccharides • Two monosaccharides (monomers) can bond to form a disaccharide in a dehydration reaction – An example is a glucose monomer bonding to a fructose monomer to form sucrose, a common disaccharide Copyright © 2009 Pearson Education, Inc. Glucose Glucose Glucose Glucose Maltose Important disaccharides • Disaccharides = sugars composed of two monosaccharides – Sucrose (table sugar) = glucose + fructose – Lactose (milk sugar) = glucose + galactose – Maltose (malt beverages & germinating wheat) = glucose + glucose Carbohydrates • Disaccharides or double sugars Figure 2.14b • Polysaccharides = long chains of glucose (MW 500,000 ~ glucose MW= 180) – Glycogen (animal energy storage) – Starch (plant product) – Cellulose (plant product) 3.7 Polysaccharides are long chains of sugar units • Polysaccharides • are polymers of monosaccharides – They can function in the cell as a storage molecule or as a structural compound Copyright © 2009 Pearson Education, Inc. 3.7 Polysaccharides are long chains of sugar units • Starch is a storage polysaccharide composed of glucose monomers and found in plants • Glycogen is a storage polysaccharide composed of glucose, which is hydrolyzed by animals when glucose is needed • Cellulose is a polymer of glucose that forms plant cell walls • Chitin is a polysaccharide used by insects and crustaceans to build an exoskeleton Copyright © 2009 Pearson Education, Inc. 3.7 Polysaccharides are long chains of sugar units • Polysaccharides are hydrophilic (water-loving) – Cotton fibers, such as those in bath towels, are water absorbent Copyright © 2009 Pearson Education, Inc. Starch granules in potato tuber cells Glycogen granules in muscle tissue STARCH Glucose monomer GLYCOGEN CELLULOSE Cellulose fibrils in a plant cell wall Hydrogen bonds Cellulose molecules Starch • Energy storage polysaccharide of plants • Created during photosynthesis Starch granules in potato tuber cells STARCH Glucose monomer Glycogen • Polysaccharide for energy storage • Long, branching glucose polymer • Made in liver, muscle, brain, uterus, and vaginal cells Glycogen granules in muscle tissue GLYCOGEN Carbohydrates • Polysaccharides or polymers of simple sugars PLAY Polysaccharides Figure 2.14c Cellulose • Structural polysaccharide of plants • Gives strength to the plant cell wall – Wood, cotton, paper • Most abundant organic compound on earth • Humans have no enzymes to digest cellulose • Cellulose is present in the diet, however it cannot be digested, thus no nutrients are received from it • It is beneficial – it can swell with water and help move other materials thru the intestine • “fiber”, “roughage”, “bulk” CELLULOSE Cellulose fibrils in a plant cell wall Hydrogen bonds Cellulose molecules Carbohydrates • Source of energy that can be quickly mobilized • Carbs are digested/converted to glucose, glucose is used to produce ATP (energy source for the cell) • Carbohydrates can have other functions outside of energy Conjugated Carbohydrates • Conjugated = covalently bound to proteins and/or lipids • Glycolipid = carbohydrate + lipid • Glycoprotein = carbohydrate + protein – Roles on the external surface of the cell’s membrane (receptors, signals) – Component of mucus • Protect the GI tract, traps particles in the respiratory tract, prevents infections Proteoglycans • Macromolecule with a dominant carbohydrate and a smaller protein component – Gel that holds cells and tissues together – Lubricates joints – Rubbery, tough texture of cartilage – Gelatinous filler in the umbilical cord and eye Cellular respiration generates ATP energy for cells – Cellular respiration breaks down glucose molecules and stores their energy in ATP – Some energy lost as heat (2nd law of thermodynamics) C6H12O6 Glucose + O2 6 Oxygen gas Figure 6.3 6 CO2 Carbon dioxide + 6 H2O Water + ATPs Energy When glucose is converted to carbon dioxide • It loses hydrogen atoms, which are added to oxygen, producing water Loss of hydrogen atoms (oxidation) C6H12O6 + 6 O2 6 CO2 Glucose 6 H2O + Energy (ATP) Gain of hydrogen atoms (reduction) Figure 6.5A + – Glucose loses hydrogen atoms = oxidization (oxidation is loss) – Oxygen gains hydrogen atoms = reduction (reduction is gain) – “OIL RIG” Loss of hydrogen atoms (oxidation) C6H12O6 + 6 O2 6 CO2 Glucose 6 H2O + Energy (ATP) Gain of hydrogen atoms (reduction) Figure 6.5A + Thank you