Chapter 6 Chemistry in Biology

2. Chapter 6 Chemistry in Biology Section 1: Atoms, Elements, and Compounds Section2: Chemical Reactions Section 3: Water and Solutions Section 4: The Building Blocks of Life

3. Identify the particles that makeup atoms. Diagram the particles that make up an atom. Objective:

4. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds Atoms • Chemistry is the study of matter. • Matter is anything that has mass and occupies space. • Atoms are the building blocks of matter. • Neutrons and protons are located at the center of the atom in the nucleus. • Protons are positively charged particles. • Neutrons are particles that have no charge.

6. The first energy level holds 2 electrons. 2nd energy level holds 8 electrons

7. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds • Electrons are negatively charged particles that are located outside the nucleus.

8. The number of neutrons is calculated by subtracting the atomic number from the atomic mass of the element. Ex. Carbon has the atomic number of 6 and an atomic mass of 12. Therefore, it has 6 neutrons (12-6=6).

9. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds Elements • An element is a pure substance that cannot be broken down into other substances by physical or chemical means. • There are over 100 known elements, 92 of which occur naturally. • Each element has a unique name and symbol.

10. The elements are arranged on the periodic table by their atomic number which is the number of protons for that element.

11. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds The Periodic Table of Elements • Horizontal rows are called periods. • Vertical columns are called groups. • Elements in a group have similar properties.

13. Element Hydrogen 1 H 1.008 Atomic number Symbol Atomic mass

14. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds Isotopes • Isotopes are atoms of the same element that have the same number of protons and electrons but have a different number of neutrons.

15. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds Radioactive Isotopes • Radioisotopes give off radiation when the nucleus splits. This radiation can be detected and used for many applications.

16. “SPONCH” – common elements of human body - www.chem.ufl.edu

17. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds Compounds • A compound is formed when two or more different elements combine. • The combination of elements will be in a fixed ratio. Ex. water – H2O • Compounds cannot be broken down into simpler compounds or elements by physical means.

18. Compare and contrast covalent bonds and ionic bonds. Objective

19. Chemistry in Biology A molecule is a compound in which the atoms are held together by covalent bonds. Chapter 6 6.1 Atoms, Elements, and Compounds Chemical Bonds • Covalent bonds • Covalent bonds form when electrons are shared. A molecule is formed.

20. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds Ionic Bonds • Ionic bonds form when two oppositely charged atoms are attracted to each other. Electrons are transferred.

21. Metals donate electrons. Nonmetals accept electrons. Anion is an atom that has lost or gained one or more electrons.

22. Chemistry in Biology Chapter 6

23. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds • Most ionic compounds are crystalline at room temperature and have higher melting points than molecular compounds formed by covalent bonds. • Ionic liquids are more environmentally friendly.

24. Chemistry in Biology Chapter 6 6.1 Atoms, Elements, and Compounds van der Waals Forces • van der Waals forces are attractive forces between molecules. When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together. • The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons.

25. Chemistry in Biology Chapter 6 6.2 Chemical Reactions Reactants and Products • A chemical reaction is the process by which atoms or groups of atoms in substances are reorganized into different substances by breaking or forming chemical bonds. Ex. rust Chemical reaction • Clues that a chemical reaction has taken place include the production of heat or light, and formation of a gas, liquid, or solid. Physical reaction

26. A physical change alters the substance’s appearance notcomposition. A chemical change involves a change in composition of a substance.

27. Chemistry in Biology Chapter 6 6.2 Chemical Reactions Chemical Equations • Chemical formulas describe the substances in the reaction and arrows indicate the process of change. • Reactants are the starting substances, on the left side of the arrow. • Products are the substances formed during the reaction, on the right side of the arrow. • The arrow means yields.

28. Chemistry in Biology Chapter 6 6.2 Chemical Reactions • Glucose and oxygen react to form carbon dioxide and water.

29. Chemistry in Biology Chapter 6 6.2 Chemical Reactions Balanced Equations • The law of conservation of mass states matter cannot be created or destroyed. • All chemical reactions must balance. The number of atoms of each element on the reactant side must equalthe number of atoms of the same element on the product side.

30. The coefficient is the number in front of the reactant or product. The subscript is the number of atoms. The coefficient times the subscript equals the total number of atoms.

31. Chemistry in Biology Chapter 6 6.2 Chemical Reactions Energy of Reactions • Theactivation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.

32. Chemistry in Biology Chapter 6 6.2 Chemical Reactions • An exothermic reaction releases energy in the form of heat. • The energy of the product is lower than the energy of the reactants.

33. Chemistry in Biology Chapter 6 6.2 Chemical Reactions • An endothermic absorbs heat energy. • The energy of the products is higher than the energy of the reactants.

34. Endothermic or Exothermic?

35. Chemistry in Biology • It does not increase how much product is made and it does not get used up in the reaction. Chapter 6 6.2 Chemical Reactions Enzymes • A catalyst is a substance that lowers the activation energy needed to start a chemical reaction. • Catalysts are not used up in a reaction • Enzymes are biological catalysts.

36. Chemistry in Biology Chapter 6 6.2 Chemical Reactions • The reactants that bind to the enzyme are called substrates. • The specific location where a substrate binds on an enzyme is called the active site.

37. Chemistry in Biology Chapter 6 6.2 Chemical Reactions • The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form. • Factors such as pH, temperature, and othersubstances affect enzyme activity.

38. Chemistry in Biology Chapter 6

39. Chemistry in Biology Chapter 6 6.3 Water and Solutions Water’s Polarity • Molecules that have an unequal distribution of charges are called polar molecules. • Polarity is the property of having two opposite poles. Water is a polar compound. • A hydrogen bond is a weak interaction involving a hydrogen atom and a fluorine, oxygen, or nitrogen atom. (#3)

40. Chemistry in Biology Chapter 6 6.3 Water and Solutions Enzyme-Controlled Reactions Visualizing Properties of Water

41. A mixtureis a combination of two or more substances in which each substance retains its individual characteristics. There are two types: Heterogeneous mixtures Homogeneous mixtures Mixtures

42. Chemistry in Biology Chapter 6 6.3 Water and Solutions Homogenous Mixtures • A homogenous mixture has a uniform composition throughout the mixture. Ex. food coloring in water • Solvent + solute = solution • A solvent is a substance in which another substance is dissolved. Food coloring dissolved in water forms a homogenous mixture. • A solute is the substance that is dissolved in the solvent. #10

43. Water is the universal solvent because many substances dissolve in it. (#7) Water is adhesive (sticks to surfaces) which allows it to travel up the stem of a plant. (#8) Water is cohesive (molecules stick together) which causes water to form droplets. (#9) • A solute is the substance that is dissolved in the solvent. (#10)

44. Chemistry in Biology Chapter 6 6.3 Water and Solutions Heterogeneous Mixtures • In a heterogeneous mixture, the components remain distinct. Ex. _________ A salad is a heterogeneous mixture.

45. A suspension is a heterogeneous mixture in which the particles settle out over time. Ex. sand and water

46. A colloid is a heterogeneous mixture in which the particles do not settle out over time. Ex. milk, mayonnaise, paint, blood.

47. Chemistry in Biology Chapter 6 6.3 Water and Solutions Acids and Bases • Substances that release hydrogen ions (H+) when dissolved in water are called acids. • Substances that release hydroxide ions (OH–) when dissolved in water are called bases.

48. Chemistry in Biology Chapter 6 6.3 Water and Solutions pH and Buffers • The measure of concentration of H+ in a solution is called pH. • Acidic solutions have pH values lower than 7. • Basic solutions have pH values higher than 7.

49. Chemistry in Biology Chapter 6 6.3 Water and Solutions • Buffers are mixtures that can react with acids or bases to keep the pH within a particular range.

50. Chemistry in Biology Chapter 6 6.4 The Building Blocks of Life Organic Chemistry • The element carbon is a component of almost all biological molecules.