IB DP2 Chemistry Option B: Human Biochemistry

1. IBDP2 ChemistryOption B:Human Biochemistry What compounds are living organisms built from?

2. Option B: Human Biochemistry B1 Energy (0.5 hour) B.1.1 Calculate the energy value of a food from enthalpy of combustion data. B2 Proteins (3 hours) B.2.1 Draw the general formula of 2-aminoacids. B.2.2 Describe the characteristic propertiesof 2-amino acids B.2.3 Describe the condensation reaction of2-amino acids to form polypeptides. B.2.4 Describe and explain the primary,secondary (α-helix and β-pleated sheets), tertiary and quaternary structure of proteins. B.2.5 Explain how proteins can be analysed by chromatography and electrophoresis. B.2.6 List the major functions of proteins in the body. B3 Carbohydrates (3 hours) B.3.1 Describe the structural features of monosaccharides. B.3.2 Draw the straight-chain and ring structural formulas of glucose and fructose. B.3.3 Describe the condensation of monosaccharides to form disaccharides and polysaccharides. B.3.4 List the major functions of carbohydrates in the human body. B.3.5 Compare the structural properties of starch and cellulose, and explain why humans can digest starch but not cellulose. B.3.6 State what is meant by the term dietary fibre. B.3.7 Describe the importance of a diet high in dietary fibre. B4 Lipids (3.5 hours) B.4.1 Compare the composition of the three types of lipids found in the human body. B.4.2 Outline the difference between HDL and LDL cholesterol and outline its importance. B.4.3 Describe the difference in structure between saturated and unsaturated fatty acids. B.4.4 Compare the structures of the two essential fatty acids linoleic (omega–6 fatty acid) and linolenic (omega–3 fatty acid) and state their importance. B.4.5 Define the term iodine number and calculate the number of C=C double bonds in an unsaturated fat/oil using addition reactions. B.4.6 Describe the condensation of glycerol and three fatty acid molecules to make a triglyceride. B.4.7 Describe the enzyme-catalysed hydrolysis of triglycerides during digestion. B.4.8 Explain the higher energy value of fats as compared to carbohydrates. B.4.9 Describe the important roles of lipids in the body and the negative effects that they can have on health. B5 Micronutrients and macronutrients (2 hours) B.5.1 Outline the difference between micronutrients and macronutrients. 2 Micronutrients are substances required in very small amounts (mg or μg) and that mainly function as a co-factor of enzymes (<0.005% body weight). B.5.2 Compare the structures of retinol (vitamin A), calciferol (vitamin D) and ascorbic acid (vitamin C). B.5.3 Deduce whether a vitamin is water- or fat-soluble from its structure. B.5.4 Discuss the causes and effects of nutrient deficiencies in different countries and suggest solutions. B6 Hormones (3 hours) B.6.1 Outline the production and function of hormones in the body. B.6.2 Compare the structures of cholesterol and the sex hormones. B.6.3 Describe the mode of action of oral contraceptives.

3. Image: http://en.wikipedia.org/wiki/Human_body

4. What are the chemical constituents of food? Image: http://en.wikipedia.org/wiki/File:Salami_sandwich.jpg

5. Food builds the bodies of living organisms Nutrients: food components for growth, energy and replacement. Water Macronutrients • Proteins built from amino acids • Carbohydrates • Lipids Micronutrients • Vitamins • Minerals

6. Energy in food

7. Energy density of foods

8. Too much or too little? Caloric starvation: Weakness, anaemia, muscle wasting..... Excessive foood: Fat storage, diabetes, cardiovascular diseases. Energy: • Young active male: 14700kJ (~3500 Cal) • Young active female: 8400 kJ (~2000 Cal) • At rest: ~60%

9. Metabolism Catabolism: breaks down organic matter and harvests energy by way of cellular respiration Anabolism: uses energy to construct components of cells such as proteins and nucleic acids Image: http://en.wikipedia.org/wiki/File:ATP-3D-vdW.png

10. Energy units (Joules, but…) • 1 Calorie = 1000 calories = 1 kcal • 1 Cal: increases 1kgH2O by 1oC • 1 cal: increases 1g H2O by 1oC 1 Cal = 4.18 kJ 1 cal = 4.18 J

11. Calorimeter- burns food to heat water Images: http://www.chem.ufl.edu/~itl/2045/lectures/lec_9.html, http://www.azosensors.com/equipment-details.aspx?EquipID=285

12. Example:15.0g of apple raises the temperature of 200gwater by 45.3oC. Heat capacity of the container: = 85JoC-1 Calculate the energy released by the apple and the energy density of the apple. Heat produced = heat absorbed by water + heat absorbed by calorimeter Image: http://en.wikipedia.org/wiki/Apple

13. Micronutrients

14. Macronutrients and micronutrients • Macronutrients- need in relatively large amounts >0.0005% of body weight • protein, fat, carbohydrates, minerals (na, Mg, K, Ca, P, S, Cl) Micronutrients • vitamins and trace minerals

15. Vitamins- water or fat soluble • Vitamin A (retinol) • Vitamin C (ascorbic acid) • Vitamin D (calciferol) Malnutrition and deficiency diseases

16. Proteins

17. Proteins built from 2-amino acids

18. Zwitterion Image: http://en.wikipedia.org/wiki/Zwitterion

19. Image: http://en.wikipedia.org/wiki/File:Amino_Acids.svg

20. …joined by peptide bonds in a primary structure Image: http://en.wikipedia.org/wiki/Peptide_bond

21. Secondary and tertiary structures Image: http://en.wikipedia.org/wiki/Secondary_structure#Secondary_structure

22. Chromatography Image: http://en.wikipedia.org/wiki/Planar_chromatography Image: http://glossary.periodni.com/glossary.php?en=paper+chromatography

23. PAGE Polyacrimide Gel Electrophoresis

24. Electrophoresis + Move faster to anode Move faster to cathode -

25. Carbohydrates

26. Functions in the human body • provide energy • store energy (as glycogen) • precursors • dietary fibre

27. Calculating empirical and molecular formulae A substance has the composition by mass 40% carbon, 7% hydrogen and 53% oxygen. Calculate the empirical formula. Calculate the molecular formula of the molecule with a molecular mass of 180g/mol.

28. Saccharides- empirical formula CH2O Pentoses Hexoses

29. Chiral molecule: alpha-D glucose or beta-D-glucose

30. Disaccharides Glycosidic link forms by condensation reaction between monosaccharides Image: http://en.wikipedia.org/wiki/Disaccharide

31. Polysaccharides- amylose and amylopectin Image: http://en.wikipedia.org/wiki/Polysaccharide

32. Cellulose glycosidic bond hydrogen bond between layers Image: http://en.wikipedia.org/wiki/Cellulose

33. Lipids

34. Lipids • large and diverse group • naturally occurring organic compounds • soluble in nonpolar organic solvents (e.g. ether, chloroform, acetone & benzene) • generally insoluble in water

35. Triglycerides • Ester of three fatty acid molecules and a glycerol molecule • Ester-group slightly polar but R-groups large and non-polar insoluble in water. • R normally even number of C, 16-20. • Examples: • Stearic acid C17H35CO(OH), saturated acid (only single bonds) solid(e.g. butter) • Oleic acid: C17H33CO(OH): unsaturated (some double bonds) oil Example of an unsaturated fat triglyceride. Left part:glycerol, right part from top to bottom: palmitic acid, oleic acid,alpha-linolenic acid. C55H98O6 Image: http://en.wikipedia.org/wiki/Triglyceride

36. Phospholipids • Fatty acid substituted by phosphor-choline group and gives a lecithin structure. • More polar than triglycerides and build up the bilayer structure in cell membranes. • Also used as a source of choline. Image:http://en.wikipedia.org/wiki/Phospholipid

37. Phospholipids Image:http://en.wikipedia.org/wiki/Phospholipid

38. Steroids • three 6-memberd rings + one 5-memberd ring are steroid skeleton that is found in many different steroids (e.g. sex hormones) and vitamins (e.g. Vit-D) Image: http://en.wikipedia.org/wiki/Steroid

39. Cholesterol • produced mainly in the liver, found in the bloodstream and body cells • present in dairy products, meat and eggs. • not water soluble so it must have transport help in the blood from a protein.

40. HDL and LDL • HDL high density lipoprotein. 40-55% protein • LDL low density lipoprotein. 20-25% protein  • HDL “good cholesterol”: Prevents the build up of cholesterol in the arteries. HDL can absorb more cholesterol and carry it away from the arteries. • LDL“bad cholesterol”: Higher cholesterol content can give deposition in arteries  plaque, a hard thick substance  narrowing of arteries  cardiovascular diseases.

41. Saturated fats: only single bonds between the carbons in the fatty acid. • common in animal (mammalian) fat (except seals and whales), milk and butter • usually solid at room temperature because regular tetrahedral arrangement makes it possible to pack molecules close together so van der Waals forces are large Image: http://en.wikipedia.org/wiki/Butter

42. Unsaturated fats: one or more double bonds • often found in vegetable oils. • usually liquid at room temperature • C=C makes it hard to pack chains close togetherlower Van der Walls forces • the greater the number of double bonds, the lower m.p. • Monounsaturated: only one double bond (e.g. olive oil, rapeseed oil) • Polyunsaturated: more than one double bond (e.g fish oil) Image:http://en.wikipedia.org/wiki/Oil

43. Linoleic and Linolenic acid • Essential fatty acid, EFA: a fatty acid that our body cannot make and therefore must be present in our food in order for a properly body function. • Linoleic acid with 18 carbon atoms. 2 double bonds. Omega-6 fatty acid the last C=C in the chain is 6 atoms away from the end of the chain; the CH3 group (the omega carbon). • Linolenic acid with18 carbon atoms. 3 double bonds. Omega-3 fatty acid the last C=C is three atoms away from the methyl-group. • Linoleic and linolenic are essential fatty acids. Important precursors for hormone like chemicals as prostaglandin and leukotrienes. • Omega-3 is important for brain development during pregnancy. • EFAgood effect oncholesterollevels, good health, good circulation, immune system, etc.

44. Iodine number H2C=CH2 + I2H2IC=CH2I addition Colourless coloured Colourless • Titrate fat solution with iodine solution  measurement of the number of double bonds. • 1 molI2 1 mol double bonds • Iodine number: number of grams iodine that adds to 100gof fat. • more double bonds  greater iodine number.

45. Example: Calculate iodine number of linoleic acid. 1 Linoleic acid + 2 I2tetraiodo-lionoleic acid m 280 g 506 g M 280 g/mol 253 g/mol n 1 mol1:22 mol Iodine number = mass of iodine × 100 mass of linoleic acid = 506/280×100 = 181

46. Example: The iodine number of a fatty acid (Mr = 278g/mol) is 274. Calculate the number of C=C double bonds.

47. Hydrolysis of a fat: the reverse reaction from an esterification/condensation reaction. • 1 Fat  1 glycerol + 3 fatty acids. • catalysed be the enzyme Lipase. The reaction goes step by step: triglyceride diglyceridemonoglyceride

48. Fats and carbohydrates as energy sources • Both fats and carbohydrates are used in nature as energy source/storage. • React with oxygen and release energy (oxidation- an exothermic reaction). • Carbohydrates contains more oxygen than fats carbohydrates already more oxidised less energy available • Fats very rich in energy: ~double of carbohydrates

49. Positive role of lipids in the human body • Energy storage • Insulation and protection of organs • Steroid hormones • Structural component of cell membrane • Omega-3 polyunsaturated fatty acids reduce the risk of heart disease. • Poly-unsaturated fats may lower levels of LDLcholesterol

50. Negative effects of lipids include • Increased risk of heart disease from elevated levels of LDL cholesterol and trans fatty acids. The major source of LDL cholesterol is saturated fats, in particular lauric (C12), myristic (C14) and palmetic (C16) acids. • Obesityis a disease in which excess body fat has accumulated to such an extent that health may be negatively affected.