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The Chemistry of Life

Learn about the importance of chemistry in biology, including the concept of atoms, elements, isotopes, chemical compounds, and the properties of water. Understand the role of chemical bonds, the pH scale, and how buffers help maintain pH balance in living organisms.

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The Chemistry of Life

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  1. The Chemistry of Life Honors Biology

  2. Why do we have to learn about Chemistry in Biology?

  3. Matter Anything that takes up space and has a mass is made of matter Atom The basic unit of matter The concept of the atom was first introduced 2500 years ago by the Greek philosopher Democritus!!! Atoms

  4. How big is an Atom? • It would take 100 million atoms lined up side by side to stretch across the tip of your pinky finger.

  5. Parts of an Atom

  6. What are Atoms made of? • Subatomic particles • Protons/Neutrons/Electrons • Charge? • Location? • Size?

  7. Elements • A pure substance that consists of only one type of atom • Atomic number = # protons or electrons • Atomic weight or mass = average weight of all known isotopes of that element • Protons + Neutrons • Atomic mass - Atomic number = # of neutrons

  8. How many protons does Nitrogen have? • 7 • 14.997 • 7.007 • 21 Practice!

  9. Isotopes Nonradioactive carbon-12 Radioactive carbon-14 Nonradioactive carbon-13 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons 6 electrons 6 protons 8 neutrons Atoms of the same element that have the same number of Protons but different numbers of neutrons.

  10. Radioactive Isotopes • Have unstable nuclei which break down at a constant rate over time

  11. Uses of Radioactive Isotopes • Radiation is dangerous BUT radioactive isotopes can also be used to: • Age fossils and rocks • Treat cancer • Kill bacteria that spoils food • Chemical “tracers” to follow the movements of substances inside an organism

  12. Bohr Diagram • Model of atom showing location of all electrons

  13. Oxidation number: number of electrons that have to be gained or lost to make the atom stable (full outer shell) • Valence number: number of electrons in the last energy level

  14. Shows the number of electrons in the last energy level (AKA Valence Number) Lewis Structure Skip transition metals

  15. Chemical Compounds • Substance formed by the chemical combination of 2 or more elements in a definite proportion • Represented by chemical formulas • Ex: Water = H2O • Compounds do not maintain the properties of elements

  16. Chemical Bonds • Compounds are formed by chemical bonds • Chemical bonds are formed in an attempt to make atoms stable (AKA. Last energy level full) • Main Chemical Bonds: Ionic Bonds and Covalent Bonds

  17. Ionic Bonds • Transfer of electrons (give and take) • Metal (loses) + Nonmetal (gains)

  18. Figure 2-3 Ionic Bonding Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-) Transfer of electron Protons +11 Electrons -11 Charge 0 Protons +17 Electrons -17 Charge 0 Protons +11 Electrons -10 Charge +1 Protons +17 Electrons -18 Charge -1

  19. Writing Formulas for Ionic Compounds • Steps • 1. Write the symbols for each element • 2. Write the oxidation number as superscript • 3. Then crisscross the numbers as subscripts and drop the + and – • 4. reduce when possible

  20. Covalent Bonds • Formed when 2 atoms (nonmetals) share an electron(s) in order to become stable • Results in the formation of molecules

  21. When the electrons are shared equally it is called a non-polar covalent bond

  22. -Electronegativity: ability to attract electrons • Not always equal • - results in a polar covalent bond • -Ex: water

  23. Van der Waals Forces • -Weak forces but they can hold 2 molecules together • How? • -Ex: Geckos

  24. Properties of Water 2.2 • Hydrogen bonds • Form between 2 water molecules • Different from covalent bonds! • Weak bonds

  25. Cohesion: Responsible for surface tension of water Adhesion:

  26. Cohesion + Adhesion = Capillary Action

  27. Liquid water expands when it freezes making it less dense in solid form • Ice floats • Found in all 3 states • Video

  28. Water has a high specific heat • Can absorb a large amount of heat without changing temperature • Important for regulating our climate and body temperature

  29. Water is often involved in mixtures • Material composed of 2 or mores elements or compounds that are physically not chemically mixed together • Ex: Earth’s atmosphere is a mixture of gases

  30. Solutions Involve a substance (solute) being dissolved in water (solvent) Water is the universal solvent due to its polarity Suspension Mixture of water and non-dissolved particles Ex: blood 2 types of mixtures

  31. Water Cycle

  32. Acids, Bases and pH • Water can react to form ions

  33. The pH scale measures the concentration of Hydrogen ions in a solution • Acids have more Hydrogen ions • pH 0-6 • Bases have more Hydroxide ions • pH 8-14 • Neutral ? • Each number = 10 fold increase in acidity or alkalinity

  34. Buffers • The pH of most fluids in most cells in our bodies must be regulated by homeostasis • Buffers are weak acids or bases that can react with strong acids or bases to prevent changes in pH • How?

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