Chemistry of Life

1. Chemistry of Life

2. 3.1 Life’s molecular diversity is based on the properties of carbon • A carbon atom forms four covalent bonds • It can join with other carbon atoms to make chains or rings Structuralformula Ball-and-stickmodel Space-fillingmodel Methane The 4 single bonds of carbon point to the corners of a tetrahedron.

3. Ethane Propane Carbon skeletons vary in length. • Carbon skeletons vary in many ways Butane Isobutane Skeletons may be unbranched or branched. 1-Butene 2-Butene Skeletons may have double bonds, which can vary in location. Cyclohexane Benzene Skeletons may be arranged in rings.

5. 3.3 Cells make a huge number of large molecules from a small set of small molecules • Most of the large molecules in living things are macromolecules called polymers • Polymers are long chains of smaller molecular units called monomers • A huge number of different polymers can be made from a small number of monomers

6. Cells link monomers to form polymers by dehydration synthesis 1 2 3 Short polymer Unlinked monomer Removal ofwater molecule 1 2 3 4 Longer polymer

7. Polymers are broken down to monomers by the reverse process, hydrolysis 1 2 3 4 Addition ofwater molecule 1 2 3 Coating of capture strand

8. Macromolecules • Carbohydrates (simple sugar) • Lipids (fatty acids) • Proteins (amino acids) • Nucleic acids (nucleotides)

9. Carbohydrates • have the general formula [CH2O]n where n is a number between 3 and 6 • function in • short-term energy storage (such as sugar); • as intermediate-term energy storage (starch for plants and glycogen for animals); and • as structural components in cells (cellulose) in the cell walls of plants and many protists), and chitin in the exoskeleton of insects and other arthropods.

10. They contain the same atoms but in different arrangements • The monosaccharides glucose and fructose are isomers Glucose Fructose

11. Carbohydrates • Monosaccharides are single (mono=one)sugars • ribose (C5H10O5) • glucose (C6H12O6)

12. Carbohydrates • formed when two Monosaccharides are chemically bonded together • Sucrose, a common plant disaccharide is composed of the monosaccharides glucose and fructose. • Lactose, milk sugar, is a disaccharide composed of glucose and the monosaccharide galactose.

13. Dehydration reaction

14. Synthesis and digestion of disaccharides

15. 3.6 Connection: How sweet is sweet? • Various types of molecules, including non-sugars, taste sweet because they bind to “sweet” receptors on the tongue Table 3.6 http://www.cancer.gov/cancertopics/factsheet/Risk/artificial-sweeteners

16. Sweets

17. Discovery • Charles Zuker, a neuroscientist at Howard Hughes Medical Institute, made a startling announcement: All the sweet things in life are perceived by two receptors. • More than 30 receptors code for bitter taste but only a single receptor devoted to sweet. • Bitter there are many and many are toxic • Sweet all tasty and good http://www.discover.com/issues/aug-05/departments/chemistry-of-artificial-sweeteners/

18. G-coupled Receptor Family

19. G-coupled proteins • a protein family of transmembrane receptors that transduce an extracellular signal (ligand binding) into an intracellular signal (G protein activation). http://upload.wikimedia.org/wikipedia/en/3/33/G-protein-coupled_receptor.png http://en.wikipedia.org/wiki/G-protein_coupled_receptor

20. Receptor binding • Sucralose, for instance, fits more snugly in the receptor than sucrose, partly because its chlorine atoms carry a stronger charge than the oxygen atoms they replaced.

21. (Polysaccharide) • are large molecules composed of individual monosaccharide units. • The formation of the ester bond by condensation • (the removal of water from a molecule) allows the linking of monosaccharides into disaccharides and polysaccharides.

22. Carbohydrates (Polysaccharide)

23. Cellulose is a polysaccharide in plant cell walls • Starch and glycogen are polysaccharides that store sugar for later use Starch granules in potato tuber cells Glucosemonomer STARCH Glycogen granules in muscle tissue GLYCOGEN Cellulose fibrils ina plant cell wall CELLULOSE Cellulosemolecules Figure 3.7

24. Starch • starch is a combination of two polymeric carbohydrates (polysaccharides) called amylose and amylopectin. They differ in the glycosidic bonds they make in between glucose molecules. • Can humans digest starch? • What enzyme is used to digest starch?

25. Glycogen • Glycogen is a polysaccharide that is the principal storage form of glucose (Glc) in animal and human cells. • Glycogen is found in the form of granules in the cytosol in many cell types.

26. Glycogen • Hepatocytes (liver cells) have the highest concentration of it - up to 8% • In the muscles, glycogen is found in a much lower concentration (1% of the muscle mass), but the total amount exceeds that in liver. • Glycogen plays an important role in the glucose cycle.

27. Glucose cycle • When glucose enters a cell it is rapidly converted to glucose 6-phosphate, by hexokinase. The glucose cycle can occur in liver cells due to a liver specific enzyme glucose-6-phosphatase, which catalyse the dephosphorylation of glucose 6-phosphate back to glucose.

28. Insulin • http://en.wikipedia.org/wiki/Insulin

29. Glucagon • http://en.wikipedia.org/wiki/Glucagon

30. Cellulose • Plants make it except tunicates (animals) • Cellulose is synthesized in higher plants by enzyme complexes localized at the cell membrane called cellulose synthase http://en.wikipedia.org/wiki/Cellulose

31. Lipid • involved mainly with long-term energy storage • They are generally insoluble in polar substances such as water. • Secondary functions of lipids are as structural components (as in the case of phospholipids that are the major building block in cell membranes) and as "messengers" (hormones) that play roles in communications within and between cells.

32. Lipid • Lipids are composed of three fatty acids (usually) covalently bonded to a 3-carbon glycerol.The fatty acids are composed of CH2 units, and are hydrophobic/not water soluble.

33. They are also called triglycerides • A triglyceride molecule consists of one glycerol molecule linked to three fatty acids • Fats are lipids whose main function is energy storage Fatty acid Figure 3.8B

34. Structure of Fatty Acids

35. Saturated and unsaturated fatty acids

36. These prevent them from solidifying at room temperature • Saturated fats (lard) lack double bonds • They are solid at room temperature • The fatty acids of unsaturated fats (plant oils) contain double bonds Figure 3.8C

37. Structure of Triacylglycerols (Fats)

38. Synthesis of fat

39. Phospholipids

40. Structure of Phospholipids

41. Phosphatidylcholine • Major component of lecithin, protective sheats of the brain

42. Phosphatidylethanolamine • Major component of cephalin; it is found particularly in nervous tissue such as the white matter of brain, nerves, neural tissue, and in spinal cord. • Major phospholipid of bacteria

43. Structure of Phospholipids

44. Sphingomyelin • sphingomyelin is a major component of myelin, the fatty insulation wrapped around nerve cells by Schwann cells or oligodendrocytes. • Multiple Sclerosis is a disease characterized by deterioration of the myelin sheath, leading to impairment of nervous conduction.

45. Structure of Glycolipids

46. Glycolipids • Glycolipids are carbohydrate-attached lipids. Their role is to provide energy and also serve as markers for cellular recognition. • Ganglioside is a compound composed of a glycosphingolipid (ceramide and oligosaccharide) with one or more sialic acids (AKA n-acetylneuraminic acid) linked on the sugar chain. It is a component the cell plasma membrane which modulates cell signal transduction events. They have recently been found to be highly important in immunology. Natural and semisynthetic gangliosides are considered possible therapeutics for neurodegenerative disorders.

47. 3.9 Phospholipids, waxes, and steroids are lipids with a variety of functions • Phospholipids are a major component of cell membranes • Waxes form waterproof coatings • Steroids are often hormones Figure 3.9

48. Cholesterol in the membrane

49. Cholesterol • Cholesterol is a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals.

50. LDL and HDL • When doctors talk to their patients about the health concerns of cholesterol, they are often referring to "bad cholesterol", or low-density lipoprotein (LDL). "Good cholesterol" is high-density lipoprotein (HDL); this denotes the way cholesterol is bound in lipoproteins, the natural carrier molecules of the body. http://en.wikipedia.org/wiki/Low-density_lipoprotein