Human Biochemistry

1. Human Biochemistry IB Chemistry 3 Robinson High School Andrea Carver

2. Biochemistry is… • The study of the chemical processes occurring in living organisms. • Includes processes involving the flow of both energy and information. • Deals with biomolecules such as proteins, carbohydrates, lipids, and nucleic acids.

3. Energy: IB Objectives • B.1.1 Calculate the energy value of a food from enthalpy of combustion data.

4. Energy • Every living cell contains thousands of biological molecules each of which is involved in the interlinked processes of metabolism. • Cellular respiration is the oxidative process by which energy stored in food is made available for use by the cell. O2 Starch Protein Rxns of Respiration CO2 + H2O Glucose Glycogen Fats Energy

5. Measuring Energy Production • Combustion analysis is used to determine the amount of energy produced from a unit of a particular food. • A bomb calorimeter measures the heat of combustion of a reaction. • Food is burned within the calorimeter, and heat released raises the temperature of a known quantity of water.

6. Calculation of Energy Release • Formula: q=mc∆T • q= the energy evolved (J) • m= the mass of water (g) • c= the specific heat of water (4.18 J/g•K) • ∆T= the temperature change of water (K) • Example: A 0.78 food sample combusts raising the temperature of 105.10 g water from 15.4°C to 30.6°C. Calculate the energy value of food in kJ/g.

7. Proteins: IB Objectives • B.2.1 Draw the general formula of 2-amino acids. • B.2.2 Describe the characteristic properties of 2-amino acids. • B.2.3 Describe the condensation reaction of 2-amino acids to form polypeptides. • B.2.4 Describe and explain the primary, secondary (alpha helix and beta pleated sheets), tertiary , and quaternary structure of proteins. • B.2.5 Explain how proteins can be analyzed by chromatography and electrophoresis. • B.2.6 List the major functions of proteins in the body.

8. Proteins: Function • Structure- Proteins make up many diverse protective, contractile, and supporting structures in the body. • Examples: keratin, collagen, myosin, immunoproteins, hemoglobin, casein, mucoproteins • Tools- Proteins are valuable operators on the molecular level such as enzymes and hormones. • Examples: lactase, insulin

9. Proteins: Structure • Amino Acids are the building blocks of proteins.

10. Amino Acids • 2-amino acids- Numbering begins with carbonyl carbon and R group is bound to carbon 2. • Carbon 2 is also bound to H, NH2, and COOH. • R group- defines the amino acid. Amino acids can be classified by the chemical nature of this group (non-polar, polar, basic, acidic). • 20 amino acids occur naturally.

12. Characteristics of Amino Acids • Crystalline, high melting points, greater solubility in water than in non-polar solvents. • Exist as dipolar ions- contain both positive and negative charges- zwitterions. • Amphoteric- can react as both an acid and a base. • Amino acids can act as buffers.

13. Isoelectric Point • This is the pH at which the amino acid is electrically neutral (typically when the amino acid is a zwitterion).

14. Condensation of Amino Acids • Amino acids link together through condensation reactions to form proteins. • Condensation reaction- H2O is eliminated as a new bond is formed. • Forms a peptide bond. • Two amino acids combine to form a dipeptide. • Three amino acids combine to form a tripeptide. • More amino acids combine to form a poly peptide. • The sequence of linked amino acids will determine the nature of the polypeptide=> variety of proteins (millions of possibilities).

16. Structure of Proteins • Primary Structure-Number and sequence of amino acids in polypeptide chain. • Secondary Structure- Folding of polypeptide chain due to hydrogen bonding between peptide groups. • Tertiary Structure- Further twisting, folding of the chain due to interactions between R-groups (side chains). • Quaternary Structure- Association between more than one polypeptide subunit.

18. Primary Structure • Forms covalent backbone of molecule. • Held together by peptide bonds. • All other levels of structure determined by primary structure. • What determines primary structure of a protein?

19. Secondary Structure • Two main types: • Beta pleated sheets • “side by side” polypeptides • Pleated sheets cross-linked • Inter-chain H-bonds • Flexible, but inelastic • Alpha helix • Regular, coiled • Flexible and elastic • Intra-chain H-bonds • H-bonds four AA’s apart

20. Tertiary Structure • Determines protein’s conformation. • Important for function of enzymes, hormones, etc. • Most stable arrangement accounting for all possible interactions between side chains. • Possible Interactions: • Hydrophobic Interactions • Hydrogen Bonding • Ionic Bonding • Disulfide Bridges

21. Quaternary Structure • The association of more than one chain in proteins.

23. Analysis of Proteins • First, amino acid composition can be determined by hydrolyzing the peptide bonds which link together amino acids in the polypeptide chain. • Specific linkages can be hydrolyzed using certain enzymes. • Then peptides can be separated based on differences in size and charge using the following techniques. • Chromatography • Electrophoresis

24. Chromatography Amino acids are treated with a locating reagent to colorize them. A small amount of the mixture is placed at the origin. Stationary Phase- does not move (paper) Mobile Phase- travels taking some sample with it (solvent) Movement of peptide fragments determined by size. Rf= distance traveled by amino acid distance traveled by solvent Specific amino acids have characteristic Rf values.

25. Electrophoresis Separates amino acids based on movement of charged particles. A charge gradient is established on a gel. Proteins migrate based upon charge of side chains present. Proteins settle near their isoelectric points.

26. Carbohydrates: IB Objectives • 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 fiber. • B.3.7 Describe the importance of a diet high in dietary fiber.

27. Lipids: IB Objectives • 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 catalyzed hydrolysis of triglycerides during digestion. • B.4.8 Explain the higher energy value of fats 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.

28. Micronutrients & Macronutrients: IB Objectives • B.5.1 Outline the difference between micronutrients and macronutrients. • 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.

29. Hormones: IB Objectives • 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. • B.6.4 Outline the use and abuse of steroids.

30. Enzymes: IB Objectives • B.7.1 Describe the characteristics of biological catalysts (enzymes). • B.7.2 Compare inorganic catalysts and biological catalysts (enzymes). • B.7.3 Describe the relationship between substrate concentration and enzyme activity. • B.7.4 Determine Vmax and the value of Michaelis constant (Km) by graphical means and explain its significance. • B.7.5 Describe the mechanism of enzyme action, including enzyme substrate complex, active site, and induced fit model. • B.7.6 Compare competitive inhibition and non-competitive inhibition. • B.7.7 State and explain the effects of heavy-metal ions, temperature changes, and pH changes on enzyme activity.

31. Nucleic Acids: IB Objectives • B.8.1 Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). • B.8.2 Distinguish between the structures of DNA and RNA. • B.8.3 Explain the double helical structure of DNA. • B.8.4 Describe the role of DNA as the repository of genetic information, and explain its role in protein synthesis. • B.8.5 Outline the steps involved in DNA profiling and state its use.

32. Respiration: IB Objectives • B.9.1 Compare aerobic and anaerobic respiration of glucose in terms of oxidation/reduction and energy released. • B.9.2 Outline the role of copper ions in electron transport and iron ions in oxygen transport.