02 Lecture Ppt


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02 Lecture Ppt

  1. 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 2 Basic Chemistry and Cells
  2. 2. All Matter Is Composed of Chemical Elements 2-
  3. 3. 2.1 Six elements are basic to life <ul><li>Six Elements of Life </li></ul><ul><ul><li>Carbon – C </li></ul></ul><ul><ul><li>Hydrogen – H </li></ul></ul><ul><ul><li>Nitrogen – N </li></ul></ul><ul><ul><li>Oxygen – O </li></ul></ul><ul><ul><li>Phosphorus – P </li></ul></ul><ul><ul><li>Sulfur – S </li></ul></ul><ul><li>Element : substance that cannot be degraded by chemical means into a substance having different properties </li></ul><ul><ul><li>Every element has a name and an atomic symbol </li></ul></ul><ul><li>Atoms : the smallest particles that retain the properties of an element </li></ul>2-
  4. 4. Figure 2.1 Elements that make up the Earth’s crust and its organisms 2-
  5. 5. 2.2 Atoms contain subatomic particles <ul><li>Two main parts of an atom </li></ul><ul><ul><li>Nucleus </li></ul></ul><ul><ul><ul><li>Center of the atom where almost all the mass is located </li></ul></ul></ul><ul><ul><li>Electron Shells </li></ul></ul><ul><ul><ul><li>Area surrounding the nucleus where the electrons are located </li></ul></ul></ul>2-
  6. 6. Subatomic Particles <ul><li>Protons </li></ul><ul><ul><li>Positively charged particles located in the nucleus </li></ul></ul><ul><ul><li>Protons have mass </li></ul></ul><ul><li>Electrons </li></ul><ul><ul><li>Negatively charged particles located in the electron cloud </li></ul></ul><ul><ul><li>Electrons have so little mass that they are not considered when determining the mass of an atom </li></ul></ul><ul><li>Neutrons </li></ul><ul><ul><li>Neutrally charged (no charge) particles located in the nucleus </li></ul></ul><ul><ul><li>The mass of a neutron is equal to that of a proton </li></ul></ul>2-
  7. 7. 2-
  8. 8. Figure 2.2A The stippled area shows the probable location of electrons 2-
  9. 9. Figure 2.2B The shells in this atomic model represent the average location of electrons 2-
  10. 10. Figure 2.2C Atomic model of a carbon atom 2-
  11. 11. Isotopes <ul><li>Atoms of a single element that differ in their number of neutrons </li></ul><ul><ul><li>Isotopes have the same number of protons, but different atomic masses </li></ul></ul>2-
  12. 12. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 2.3 Radioactive isotopes have many medical uses <ul><li>Low Levels </li></ul><ul><ul><li>Small amounts of radiation can be used as a tracer allowing doctors to ‘see’ inside of the body </li></ul></ul><ul><li>High Levels </li></ul><ul><ul><li>Lots of radiation will damage DNA and kill cells </li></ul></ul><ul><ul><li>Can also be used to kill pathogens and treat disease, like cancer </li></ul></ul>2-
  13. 13. Atoms React with One Another to Form Molecules 2-
  14. 14. 2.4 After atoms react, they have a completed outer shell <ul><li>Atoms are most stable when the outer shell has eight electrons </li></ul><ul><ul><li>Atoms exchange electrons in order to have a complete outer shell or valence shell </li></ul></ul>2-
  15. 15. Figure 2.4A A portion of the periodic table of the elements 2-
  16. 16. Figure 2.4B Models of the six elements that are predominant in living things 2-
  17. 17. Compounds and Molecules <ul><li>Compound – two or more different elements bonded together </li></ul><ul><li>Molecule – the smallest part of a compound that still has the properties of that compound </li></ul>2-
  18. 18. 2.5 An ionic bond occurs when electrons are transferred <ul><li>Ion - an atom or molecule that has either lost or gained electrons </li></ul><ul><ul><li>Losing an electron results in a net positive </li></ul></ul><ul><ul><li>Gaining an electron results in a net negative charge </li></ul></ul><ul><li>Ions with opposite charges attract and form bonds known as ionic bonds </li></ul>2-
  19. 19. Figure 2.5 Formation of sodium chloride (table salt) 2-
  20. 20. 2.6 A covalent bond occurs when electrons are shared <ul><li>When two atoms do not have completely full outer shells , they may share electrons so that each has a full outer shell </li></ul><ul><ul><li>Example: Hydrogen (H 2 ) </li></ul></ul><ul><li>Bond Notation </li></ul><ul><ul><li>Single covalent bonds are written as H-H </li></ul></ul><ul><ul><li>Double covalent bonds are written as O=O </li></ul></ul><ul><ul><li>Triple covalent bonds are written as N≡N </li></ul></ul>2-
  21. 21. Figure 2.6A Electron models and formulas representing covalently bonded molecules 2-
  22. 22. Figure 2.6B Other types of molecular molecules—in this case, for methane (CH 4 ) 2-
  23. 23. Chemical Reactions <ul><li>The exchange of electrons between atoms create chemical reactions </li></ul>2-
  24. 24. 2.7 A covalent bond can be nonpolar or polar <ul><li>Nonpolar covalent bond – when the sharing of electrons between atoms is fairly equal </li></ul><ul><ul><li>Electronegativity – the attraction of an atom for the electrons in a covalent bond </li></ul></ul><ul><li>Polar covalent bond – unequal sharing of electrons </li></ul>2-
  25. 25. Figure 2.7 Three models of water 2-
  26. 26. 2.8 A hydrogen bond can occur between polar molecules <ul><li>Polar bonds have charges on either end and often attract to each other </li></ul><ul><li>When a hydrogen is bonded to an electronegative atom, it becomes electropositive </li></ul><ul><li>This causes it to be attracted to electronegative parts of the same or other molecules </li></ul>2-
  27. 27. Figure 2.8 Hydrogen bonding between water molecules 2-
  28. 28. The Properties of Water Benefit Life 2-
  29. 29. 2.9 Water molecules stick together: Cohesion <ul><li>The tendency of water molecules to cling together </li></ul><ul><ul><li>Due to the four hydrogen bonds water has </li></ul></ul><ul><li>Cohesion contributes to water transport in plants </li></ul><ul><ul><li>Adhesion of water to the walls of the vessels also helps prevent the water column from breaking apart </li></ul></ul>2-
  30. 30. Figure 2.9 Water as a transport medium in trees 2-
  31. 31. 2.10 Water warms up and cools down slowly <ul><li>Calorie – the amount of heat energy needed to raise the temperature of 1 g of water 1°C </li></ul><ul><li>Water has a high heat of vaporization because so many hydrogen bonds must be broken </li></ul>2-
  32. 32. 2.11 Water dissolves other polar substances <ul><li>A solution contains dissolved substances called solutes that which is dissolved </li></ul><ul><li>Water’s hydrogen bonds help it dissolve other polar molecules </li></ul><ul><li>Hydrophilic (water-loving) molecules form hydrogen bonds with water </li></ul><ul><li>Hydrophobic (water-fearing) molecules do not form hydrogen bonds with water </li></ul>2-
  33. 33. Figure 2.11 An ionic salt dissolves in water 2-
  34. 34. 2.12 Frozen water is less dense than liquid water <ul><li>When water freezes, the crystal lattice expands </li></ul><ul><li>With a greater volume and the same mass, the density decreases and the solid, ice, floats in the denser liquid, water </li></ul>2-
  35. 35. Figure 2.12A Ice is less dense than liquid water 2-
  36. 36. 2- Living Things Require a Narrow pH Range
  37. 37. 2.13 Acids and bases affect living things <ul><li>When water ionizes it releases equal amounts of hydrogen ions (H + ) and hydroxide ions (OH - ) </li></ul><ul><li>Some substances release more or fewer or each </li></ul><ul><ul><li>Acids - Excess hydrogen ions </li></ul></ul><ul><ul><li>Bases - Excess hydroxide ions </li></ul></ul>2-
  38. 38. Figure 2.13A Dissociation of water molecules 2-
  39. 39. <ul><li>Figure 2.13B Acids cause H + to increase </li></ul><ul><li>Figure 2.13C Bases cause OH - to increase </li></ul>2-
  40. 40. 2.14 The pH scale measures acidity and basicity <ul><li>The pH scale goes from 0 to 14, </li></ul><ul><ul><li>7 is neutral </li></ul></ul><ul><li>The greater the H + concentration, the lower the pH and the lower the hydrogen ion concentration, the higher the pH </li></ul>2-
  41. 41. Figure 2.14 The pH scale 2-
  42. 42. 2.15 Buffers help keep the pH of body fluids relatively constant <ul><li>Buffer system : the combination of a weak acid and the base that forms when the acid dissolves in water </li></ul><ul><li>By binding or releasing H + ’s , it maintains a constant concentration of free H + ’s in the solution </li></ul>2-
  43. 43. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 2.16 Acid deposition has many harmful effects <ul><li>Air pollution, particularly from burning fossil fuels, acidifies rainwater </li></ul><ul><ul><li>Leaches toxic aluminum and creates methyl mercury in lakes </li></ul></ul><ul><ul><li>Destroys leaves, stopping photosynthesis and making trees susceptible to disease </li></ul></ul><ul><ul><li>Increases respiratory disease and erodes buildings and monuments </li></ul></ul>2-
  44. 44. Connecting the Concepts: Chapter 2 <ul><li>Cells are made up of chemicals and therefore we must understand chemistry </li></ul><ul><ul><li>Cells are composed of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur </li></ul></ul><ul><ul><ul><li>Carbon forms long chains of carbon atoms </li></ul></ul></ul><ul><li>Water is a polar molecules and can dissolve other polar substances </li></ul><ul><ul><li>Water’s cohesiveness, tendency to change temperature slowly, ability to expand as it freezes are due to hydrogen bonding </li></ul></ul>2-