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Introduction to Biochemistry II

Review of Carbon Atom.

Biochem019
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Introduction to Biochemistry II

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  1. Biochemistry: The Chemistry of the Human Body Part IV - Macromolecules

  2. Macromolecules • Many of the common macromolecules are synthesized from monomers.

  3. Carbohydrates Monosaccharides Disaccharides Polysaccharides

  4. Carbohydrates • Compounds which provide energy to living cells. • Made up of carbon, hydrogen and oxygen with a ratio of two hydrogens for every oxygen atom. • The name carbohydrate means "watered carbon" or carbon with attached water molecules. • Are used directly to supply energy to living organisms.

  5. Carbohydrates • Many carbohydrates have empirical formuli which would imply about equal numbers of carbon and water molecules. • The general formula for carbohydrates is (CH2O)n. • The names of most sugars end with the letters -ose. • The pentose sugars ribose and deoxyribose are important in the structure of nucleic acids like DNA and RNA.

  6. Carbohydrates • Three key classification schemes for sugars are: • Monosaccharides • Disaccharides • Polysaccharides

  7. Monosaccharides • Simple sugars, having 3 to 7 carbon atoms. • Are linear molecules but in aqueous solution they form a ring form structure. • In aqueous solution, monosaccharides with five or more C atoms form cyclic ring structures. • These 6-membered ring compounds are called pyranoses. • These rings form due to a general reaction that occurs between alcohols and aldehydes or ketones to form derivatives called hemiacetals or hemiketals.

  8. Monosaccharides

  9. Monosaccharides • May form several types of stereoisomers since they share the same molecular formula. • Four Classes of Stereoisomers: • Diastereomers • Enantiomers • Epimers • Anomers

  10. Monosaccharides: Isomers

  11. Monosaccharides: Diastereomers • Stereoisomers that are not mirror images of each other. • Diastereomers for the molecular formula C5H10O5:

  12. Monosaccharides: Diastereomers • Diastereomers for the molecular formula C6H12O6:

  13. Monosaccharides: Enantiomers • Stereoisomers that are mirror images of each other. • Two types: D or L

  14. Monosaccharides: Epimers • Two diastereomers that differ around one chiral center.

  15. Monosaccharides: Anomers • Stereoisomers that differ in the configuration around the anomeric carbon. • Two types of anomers are: α or β. • In hemiacetals, the anomeric carbon is at position 1.

  16. Monosaccharides: Anomers

  17. Monosaccharides: Anomers • In hemiketals, the anomeric carbon is at position 2.

  18. Disaccharides • Glycosides • Formed from two monosaccharides. • The -OH of one monosaccharide condenses with the intramolecular hemiacetal of another monosaccharide, forming a glycosidic bond. • Glycosidic bonds can be: α or β.

  19. Disaccharides

  20. Disaccharides • Common disaccharides are: • Sucrose • Lactose • Maltose • Trehalose

  21. Disaccharides

  22. Sucrose • Prevalent in sugar cane and sugar beets

  23. Sucrose

  24. Lactose • Found exclusively in milk.

  25. Lactose

  26. Maltose • Major degradation product of starch.

  27. Maltose

  28. Trehalose • Found in bacteria, yeast, invertebrates, mushrooms and seaweed. • Glycosidic Linkages: • Protects organisms from extreme temperatures and drying out.

  29. Trehalose Is used: • As a preservative for foods and to minimize harsh flavors and odors. • As a moisturizer in cosmetics. • As an natural sweetener for diabetics. • Antioxidant to stabilize proteins and lipids in neurodegenerative diseases like Alzheimer's and Huntington's Disease. • To protect organs for transplants.

  30. Trehalose Is: • Involved in the regulation of developmental and metabolic processes in plants. • The major transport sugar in shrimp, insects and plants. • The major carbohydrate energy storage molecule used by insects for flight.

  31. Trehalose • In plants, synthesis is carried out by trehalose phosphate synthase and trehalose phosphatase: 

  32. Trehalose

  33. Trehalose • Degradation: Trehalase

  34. Polyssacharides • Ten or more monosaccharides bonded together to form long chains. • The chains are typically contain hundreds of monosaccharaides. • Can have one, two or many different types of monosaccharides. • Homopolysaccharides • Heteropolysaccharides

  35. Polyssacharides

  36. Polyssacharides • Are classified as: • Cellulose • Chitin • Glycogen • Starches

  37. Cellulose & Chitin • Are polysaccharides with 1500 glucose rings chain together. • Function is support and protection. • The monomers of cellulose and chitin are bonded together in such a way that the molecule is straight and unbranched. • The molecule remains straight because every other glucose is twisted to an upside-down position compared to the two monomers on each side.

  38. Cellulose & Chitin • Humans and most animals do not have the necessary enzymes needed to break the linkages of cellulose or chitin. • Some bacteria and some fungi produce enzymes that digest cellulose. • Some animals have microorganisms in their gut that digest cellulose for them. • Fiber is cellulose, an important component of the human diet.

  39. Cellulose • Is composed of beta-glucose monomers. • Cellulose fibers are composed of long parallel chains of these molecules. • The chains are attached to each other by hydrogen bonds between the hydroxyl groups of adjacent molecules. • The cell walls of plants are composed of cellulose.

  40. Cellulose

  41. Chitin • The cell walls of fungi and the exoskeleton of arthropods are composed of chitin. • The glucose monomers of chitin have a side chain containing nitrogen.

  42. Chitin

  43. Glycogen • Animals and some bacteria store extra carbohydrates as glycogen. • In animals, glycogen is stored in the liver and muscle cells. • Between meals, the liver breaks down glycogen to glucose in order to keep the concentration of glucoses in the blood stable. • After meals, as glucose levels in the blood rise, glucose is removed from the blood and stored as glycogen.

  44. Glycogen

  45. Glycogen • Homopolymer of glucose. • Two types of glycosidic linkage: • α–(1, 4) for straight chains • α–(1, 6) for branched chains, occurring every 8-10 residues.

  46. Glycogen • Glycogen is a very compact structure that results from the coiling of the polymer chains. • This compactness allows large amounts of carbon energy to be stored in a small volume, with little effect on cellular osmolarity.

  47. Starches • Starch and glycogen are composed of 300 – 1000 alpha-glucose units join together. • It is a polysaccharide which plants use to store energy for later use. • Starches are smaller than cellulose units, and can be more readily used for energy.

  48. Starches • Foods such as potatoes, rice, corn and wheat contain starch granules which are important energy sources for humans. • The human digestive process breaks down the starches into glucose units with the aid of enzymes, and those glucose molecules can circulate in the blood stream as an energy source.

  49. Starches • Amylopectin is: • A form of starch that is very similar to glycogen. • Branched but have less branches than glycogen. • Amylose is: • A form of starch that is unbranched.

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