Unit 2:Chemistry of Life

1. Unit 2:Chemistry of Life Atoms, Ions and Molecules Properties of Water Acids and Bases Organic Molecules Chemical Reactions Enzymes

2. Atoms, Ions and Molecules • This topic looks at some Chemistry basics that are essential for understanding life. • It defines and explains the roles of atoms, ions and molecules.

3. Atoms, Ions and Molecules • element - substance that cannot be broken down chemically into any other substances • atom - matter that cannot be subdivided any further without losing its essential properties

4. Subatomic particles • Particles smaller than an atom • 1940: protons, neutrons, electrons, neutrinos, positrons • Protons, neutrons, electrons – building blocks from which atoms are made • protons and neutrons in nuclei • electrons in orbit around nuclei • Neutrinos and positrons were somewhat peculiar particles discovered outside Earth's atmosphere and of uncertain origin or significance.

6. “CHONPS” + 4

7. “CHONPS”

10. Atoms, Ions and Molecules • Molecule: 2 or more atoms join together chemically • Compound: molecule that contains 2 or more different elements • All compounds are molecules but not all molecules are compounds.

11. Chemical BONDS • Covalent • Ionic • Polar Covalent • Hydrogen

14. Polar Covalent Bonds • electrons shared by the atoms spend a greater amount of time, on average, closer to one nucleus than the other • due to geometry of molecule and electronegativity differences • result is a charge separation in the molecule, where one part of the molecule has a partial negative charge and one part has a partial positive charge

15. Polar Covalent Bonds • molecule is not an ion (no excess of protons or electrons) • water is the most common but not the only molecule that can have polar covalent bonds • other molecules that have polar covalent bonds are peptide bonds and amines • the biological consequence of polar covalent bonds is that these kinds of bonds can lead to the formation of a weak bond called a hydrogen bond

16. Polar Covalent Bonds

17. Hydrogen Bonds • formed when a charged part of a molecule having polar covalent bonds forms an electrostatic interaction with a substance of opposite charge • molecules that have nonpolar covalent bonds do not form hydrogen bonds • classified as weak bonds because they are easily and rapidly formed and broken under normal biological conditions • under the right environmental conditions, any compound that has polar covalent bonds can form hydrogen bonds

18. Hydrogen Bonds • important in biological systems • explains many of the properties of water • used to stabilize and determine the structure of large macromolecules like proteins and nucleic acids • involved in the mechanism of enzyme catalysis

20. What characteristic of an atom gives it its chemical properties? • the number of protons • the number of neutrons • the number of electrons • the number of electrons in its outer orbital

21. All life on earth depends on water; organisms are made up mostly from water and require it more than any other molecule. • Hydrogen bonding among water molecules gives water several important properties that contribute to its important role in the biology of all organisms.

22. States of Matter

23. Cohesion & Adhesion • Cohesion – wateris attracted to other water molecules • Adhesion – wateris attracted to other materials • oxygen end of water has a negative charge • hydrogen end has a positive charge • hydrogens of one water molecule are attracted to oxygen of another water molecule • this attractive force is what gives water its cohesive and adhesive properties

24. Surface Tension • cohesion of water molecules at the surface of a body of water • all the water molecules on the surface of a quantity of water (a bead, cup, pond, etc.) are 'holding' each other together, creating surface tension

25. Cohesion & Adhesion • Surface tension allows water striders to 'skate' across the top of a pond. • Many objects are heavier than water, but because of surface tension, the water is able to hold up the metal. • Surface tension is not the force that keeps boats floating.

27. Capillary Attraction • related to adhesive properties of water • click here for demonstration • water 'climbs' up the straw as the water molecules are attracted to the straw molecules • when one water molecule moves closer to the straw molecules the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw.

31. Why don’t oceans freeze as easily as fresh water lakes? • Cohesion • Heat capacity • Ice floats • Water is a good solvent

32. Fish live in water. What property of water is important for the survival of fish during the winter? • Cohesion • Heat capacity • Ice floats • Water is a good solvent

33. Summary – Properties of Water • Cohesion • Adhesion • Surface tension • Capillary Attraction • High heat capacity • Low density as a solid

34. Acids & Bases • Acid: substance that increases the hydrogen ion (H+) concentration in a solution • Base: substance that removes hydrogen ions from a solution, resulting in an increase in the hydroxide ion (OH-) concentration.

35. Acid • H+ very reactive • Example: H+ can bind with atoms in metals, causing them to corrode • Acids can donate H+ to other chemicals • Stomach acid • helps to kill most bacteria that you ingest • enhances breakdown of chemicals in food • enhances efficiency of digestion and absorption

36. Bases • Low H+; High OH • Baking soda, Alka-seltzer, milk of magnesia • Antacids • OH ions bind with excess H+ ions, neutralizing the acid • Household cleaners

37. Acids & Bases • Acidity of a liquid is measured as its concentration of hydrogen ions • pH scale expresses this concentration in logarithmic units • very acidic = pH 0 • neutral value = pH 7 • very alkaline (basic) = pH 14

38. pH scale

39. Organic Compounds • Substances that contain carbon • Carbon occurs in almost every chemical compound found in living things • Four main types of organic compounds in living things: • carbohydrates • proteins • lipids • nucleic acids

40. Organic Compounds • Combination of carbon and almost any other element • Unique atomic structure allows a carbon atom to link up with as many as four other atoms of another • Also links up with other carbon atoms to form long, stable chains, variety of combinations carbon can form with other elements is almost limitless • FYI…scientists have already identified more than ten million organic compounds.