The Chemistry of Life

1. Chapter 2 The Chemistry of Life

2. Introduction • Cells, tissues and organs composed of chemicals • Chemical reactions important for function • Chemistry is the study of: • Elements, compounds, chemical reactions, molecular structure

3. Atomic Structure

4. Atomic Structure (cont’d.) • Atoms • Smallest particles of elements • Maintain all characteristics of element • Nucleus contains protons and neutrons • Electrons orbit nucleus in shells

5. Elements, Isotopes, Compounds

6. Elements, Isotopes, Compounds (cont’d.) • Element: atoms contain same numbers of protons and electrons • Compound: contains two or more elements • Isotope: number of neutrons varies • Periodic table of the elements • Arranges elements by increasing atomic number

7. Elements, Isotopes, Compounds (cont’d.) • Orbital: area where electron is found • Energy levels: grouping of orbitals • Represented as concentric circles surrounding nucleus

8. Bonds and Energy

9. Bonds and Energy (cont’d.) • Ionic: one atom gains and one atom loses electrons • Covalent: atoms share electrons • Hydrogen: weak bonds, hold water molecules together • Electron donors vs. acceptors vs. carriers • Bonds are energy containing

10. Bonds and Energy (cont’d.)

11. Bonds and Energy (cont’d.)

12. Common Substances in Living Systems

13. Water • Most abundant substance in cells • Universal solvent • Transport of materials • Absorbs and reduces heat • Protects body structures

14. Carbon Dioxide • Waste product of cellular respiration • Used in photosynthesis to produce usable energy sources • Must be removed quickly from cells • Carbon in molecules comes from carbon dioxide gas

15. Molecular Oxygen • Formed from covalent bond of two oxygen atoms • Required by all organisms that breathe air • Necessary to convert food into ATP • Level in atmosphere is 21%

16. Ammonia • By-product of amino acid breakdown • Amino acids are building blocks of proteins • Amino acids contain nitrogen • Converted to urea in the liver

17. Mineral Salts • Composed of small ions • Calcium: muscle contraction and strong bones • Phosphate - ATP synthesis • Sodium, potassium, and chloride are necessary for muscle contraction and nervous transmission

18. Carbohydrates • 1:2:1 ratio of carbon, hydrogen and oxygen • Five- and six-carbon simple sugars are smallest • Five-carbon: deoxyribose and ribose • Six-carbon: glucose and fructose • Functions: energy storage and cell structure

19. Lipids • Insoluble in water • 95% of fats in body are triacylglycerols • Saturated fat: fatty acids have single covalent bonds • Unsaturated fat: fatty acids have one or more double covalent bonds • Functions: energy, insulation and protection

20. Proteins • Contain carbon, oxygen, hydrogen, nitrogen and sulfur • Amino acids are building blocks of proteins • Functions: energy and structure • Enzymes: protein catalysts for chemical reactions

21. Proteins (cont’d.) • Structure • Primary: amino acid sequence • Secondary: determined by hydrogen bonds • Tertiary: folding caused by interactions within peptide bonds and sulfur atoms • Quaternary: determined by spatial relationships between units

22. Nucleic Acids • Deoxyribonucleic acid: genetic material of the cell • Ribonucleic acid: protein synthesis • Messenger RNA • Transfer RNA

23. Nucleic Acids (cont’d.) • Structure • DNA: double helical chain • RNA: single chain

24. Nucleic Acids (cont’d.) • Nucleic acids are made up of chains of nucleotides • Nucleotide: nitrogen base, sugar and phosphate group • Nitrogen bases: purines (two) and pyrimidines (three)

25. Adenosine Triphosphate • Fuel for cell function and maintenance • Molecule consists of sugar, adenine, and three phosphates • Energy is stored in the second and third phosphates • Breakdown of glucose provides energy to make ATP

26. Movement of Materials Into and Out of Cells

27. Introduction • Plasma membrane is selectively permeable • Only selected materials can enter and exit • This is because of chemical structure • Water can enter and exit with ease

28. Diffusion • Movement of molecules from area of high concentration to low concentration • Brownian movement: random collision of diffusing molecules • Accelerated by increased temperature • O2 - CO2 exchange is an example of diffusion

29. Osmosis • Movement of water through semipermeable membrane from high concentration to low concentration • Isotonic solution: salt concentration is the same outside the cell as inside • Hypotonic solution: salt concentration inside cell is higher than outside cell

30. Osmosis • Movement of water through semipermeable membrane from high concentration to low concentration • Hypertonic solution: salt concentration higher outside the cell than inside

31. Osmosis (cont’d.)

32. Osmosis (cont’d.) • Active transport • Used by cells to obtain sugars, amino acids, larger proteins and fats • Needs energy in the form of ATP • Molecules move from areas of low concentration to areas of high concentration

33. pH

34. pH (cont’d.) • Negative logarithm of hydrogen ion concentration • Acids: pH values below 7 • Bases: pH values above 7 • Buffers: help maintain pH levels

35. pH (cont’d.)

36. Summary • Discussed basic chemical concepts such as bonds and energy and how they apply to living systems • Discussed specific chemical substances and how they are used in living systems

37. Summary (cont’d.) • Described three ways that substances move into and out of cells • Introduced pH and acids/bases