The Chemistry of Life

1. The Chemistry of Life Chapter 2

2. The Nature of Matter • Introduction to “Baby Chemistry” • Life depends on chemistry • We need to be able to understand the chemistry before we move on to understand the rest of body

3. Atoms • Atom - the basic unit of matter • Atoms are made of 3 subatomic particles • Protons - positive charge • Neutrons – neutral charge • Electrons – negative charge

4. Location of Subatomic Particles • Protons and neutrons are found in the atoms nucleus - The center of the cell • Electrons are found outside the nucleus • Electron cloud • They are in constant motion • Are attracted to positive charge of nucleus but remain outside due to energy of motion

5. Why are atoms neutral? • What is the overall charge of the nucleus? • What is the overall charge of the electron cloud? • Nucleus (+) & Electron Cloud (-) • Therefore, atoms are neutral from equal numbers of protons and electrons

6. Elements • Elements – pure substances that consist of entirely 1 type of atom • They are represented by 1, 2 or 3 letters • There are 117 elements (periodic table in back of book) • Based on certain characteristics of each element

7. Elements • Periodic table includes information on atomic mass and atomic number • Atomic Number – number of protons (and therefore electrons) • Atomic Mass – sum of protons and neutrons

8. Elements of the Human Body

9. Isotopes • How are isotopes different?

10. Isotopes • How are isotopes different? • They have a different number of neutrons • Isotopes are identified by their atomic mass number (protons + neutrons) • All isotopes still have the same chemical properties (because neutrons are neutral)

11. Radioactive Isotopes • Have nuclei that are unstable and break down at constant rates over time Important Uses • Determine age of rocks • Treat cancer and kill bacteria that cause food to spoil • Used as “tracers” to follow substances in the body

12. Chemical Compounds *In nature, most elements are found combined with other elements in compounds • Compound – substances formed by the chemical combination of 2 or more elements

13. Chemical Formulas • What information is contained in a chemical formula? • Type of atoms • How many of those atoms • Example) • What’s in H20? A) 2 hydrogen and 1 oxygen

14. Unique Characteristics • Physical and chemical properties of a compound are usually different from those of elements from which they are formed • Example – NaCl • Sodium Chloride : Table Salt • Sodium (Na) – silver colored metal • Chlorine (Cl) – greenish gas + =

15. Chemical Bonds • Hold compounds together • Involves the outer electrons (valence electrons) that surround each atom’s nucleus • 3 types of bonds • Ionic (strongest) • Covalent • Van Der Waals Forces (weakest)

16. Ionic Bonds • One or more electron is “transferred” from one atom to another • An atom that loses an electron has a positive charge • An atom that gains an electron has a negative charge • Positively or negatively charged atoms are called ions

17. Ionic Bonds

18. Covalent Bonds • When electrons are “shared” instead of being “transferred” • How do they share electrons? • The electron travels in the orbits of both atoms • Single bond – 2 electrons shared • Double bond – 4 electrons shared • Triple bond – 6 electrons shared

19. Covalent Bonds • Atoms joined by covalent bonds are called molecules • Water Molecule

20. Van Der Waals Forces • Atoms in covalent bond don’t always share equally • Rapid movement of electrons creates “+” and “-” charges • When molecules are close together, an attraction can occur between oppositely charges region • Creates intermolecular “Vander Waals Forces”

21. Van Der Waals and Geckos • How does the gecko’s foot function similarly to Van Der Waals Forces?

22. Properties of Water • The water molecule – H2O (think mickey mouse)

23. Characteristics/properties of water • Water is a polar molecule • What is polarity? • The uneven distribution of electrons which causes the molecule to have regions with a positive and negative • Allows water to attract to other molecules

24. Characteristics/properties of water • Most abundant compound in living things • Naturally occurring and found at any temperature on the earth • Water expands when it freezes, SO WHAT?? • How does that affect us?

25. Characteristics/properties of water • Held together by hydrogen bonds (not as strong as ionic or covalent) which form between the hydrogen and oxygen • Why would this be important? • How many bonds are there per water molecule?

26. Importance of hydrogen bonds • Allows 4 bonds to form • This bonding pattern is what makes water responsible for it’s many special properties

27. Water properties • Cohesion • An attraction between water molecules • Why can a spider walk on water • How does water come out of a faucet? Surface tension

28. Water Properties • Adhesion • An attraction of water to other molecules • How does a tree get water from its roots to its leaves? • Why does the water level in a graduated cylinder look curved? Capillary action

29. MIxtures • Mixture – a material composed of 2 or more elements or compounds that are physically combined, but not chemically combined • Examples: • Chocolate Chip Cookie • Earths Atmosphere • 2 types of Mixtures • Solution • Suspension

30. Solution & Suspensions • Solution - is a mixture of 2 or more substances in which the molecules are evenly distributed • Example) Salt dissolving in water • (the NaCl and H2O combine by the Cl- being attracted to the H and the Na+ being attracted to the O) • Suspension - mixture of water and non-dissolvedmaterial • Example) Gravel in water

31. solution • 2 important terms to know • Solute – substance being dissolved • Solvent – substance doing the dissolving Q) Why is water considered the greatest solvent in the world? A) Polarity allows it to pull other molecules apart

32. Acids, Bases and pH • Concentrations for hydrogen (H +) and hydroxide (OH-) ions are important indicators of the properties of a solution • A measurement system was created to indicate the concentration of the H + ions in the solution called the pH scale • pH – potential of hydrogen • A pH of 7 = equal number of H + and OH- ions

33. Acids, Bases and pH • A pH of 7 = equal number of H + and OH- ions H + + OH- = H2O • Solutions with a pH < 7 are called acids • Because more hydrogen ions (H +) • The lower the pH, the greater the acidity

34. Acids, Bases and pH • Solutions with a pH > 7 are called alkaline or basic • Because more hydroxide (OH-)ions • The higher the pH, the more basic the solution

35. Acids, Bases and pH • Each step of the pH scale represents a factor of 10 • Ex) pH of 4 has 10x as many H + ions as a solution with a pH of 5 Acids Bases I-------------------------I-------------------------I 1 H + > OH- 7 H + < OH- 14 H + = OH-

36. Buffers • Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH • Why are buffers important? • The pH of fluids within most cells of the human body must generally be kept between 6.5 and 7.5 • If pH is higher/lower – it will affect the chemical reactions that take place • Controlling the pH of cells is important for maintaining homeostasis