The Chemistry of Life

1. The Chemistry of Life Chapter 2 Mr. Scott

2. H O 2-1 Atoms, Ions, and Molecules • Living things consist of atoms of different elements. • An atom is the smallest basic unit of matter. • An element is one type of atom. • Can not be broken down into simpler substance

3. 2-1 Atoms, Ions, and Molecules • Atomic composition • The nucleus has protons and neutrons. • Protons (+) • Neutrons (no charge) • Electrons are in energy levels outside nucleus. • Electrons (-) • Protons = what an atom is • Electrons = what an atom does

4. 2-1 Atoms, Ions, and Molecules • Electrons and energy levels • 2n2 – determines number of electrons for energy level • n = energy level • Rule of 8 or octet rule • Important for bonding

5. _ O H H + + 2-1 Atoms, Ions, and Molecules • A compound is made of atoms of different elements bonded together. • water (H2O) • Salt (NaCl)

6. gained electron ionic bond Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-) 2-1 Atoms, Ions, and Molecules • Ions form when atoms gain or lose electrons. • An ion is an atom that has gained or lost one or more electrons. • positive ions • negative ions • Ionic bonds form between oppositely charged ions.

7. Oxygen atom (O) Carbon atom (C) Oxygen atom (O) 2-1 Atoms, Ions, and Molecules • Atoms share pairs of electrons in covalent bonds. • A covalent bond forms when atoms share a pair of electrons. • Multiple covalent bonds • Diatomic molecules

8. _ O H H + + 2-2 Properties of Water • Life depends on hydrogen bonds in water. • Water is a polar molecule. • Polar molecules have slightly charged regions. • Nonpolar molecules do not have charged regions. • Hydrogen bonds form between slightly positive hydrogen atoms and slightly negative atoms.

9. 2-2 Properties of Water • Polarity is created by the pull of electrons away from hydrogen towards oxygen • This creates partial positive and partial negative regions of the molecule

10. 2-2 Properties of Water • Hydrogen bonds are responsible for three important properties of water. • High specific heat • Cohesion • Adhesion

11. 2-2 Properties of Water • High Specific Heat • Water resists changes temperature so must absorb more to change temperature • Important to cells • Cohesion • Attraction between like molecules • Produces surface tension • Adhesion • Attraction between different molecules • Important in transport of water in plants

12. solution 2-2 Properties of Water • Many compounds dissolve in water. • A solution is formed when one substance dissolves in another. • A solution is a homogeneous mixture. • Solvents dissolve other substances. • Solutes dissolve in a solvent.

13. 2-2 Properties of Water • “Like dissolves like.” • Polar solvents dissolve polar solutes. • Water, blood, plasma, sugars, proteins • Nonpolar solvents dissolve nonpolar solutes. • Oils, fats • Polar substances and nonpolar substances generally remain separate. • Suspension

14. 2-2 Properties of Water • Some compounds form acids or bases. • Break into ions • An acid releases a hydrogen ion when it dissolves in water. • High H+ concentration • pH less than 7

15. bile pH between 8 and 9 more basic 2-2 Properties of Water • A base removes hydrogen ions from a solution. • Low H+ concentration • More OH ions present • pH greater than 7

16. 2-2 Properties of Water • pH and Living Organisms • Most need to keep their pH in a small range • Usually around 7 • Some plants thrive in acidic conditions • Evergreens, azaleas • pH can be regulated by buffers • Can either bind to H+ to raise pH or release them to lower pH

17. 2-3 Carbon-Based Molecules • Carbon atoms have unique bonding properties. • Carbon forms covalent bonds with up to four other atoms, including other carbon atoms. • Carbon-based molecules have three general types of structures. • straight chain • branched chain • ring

18. 2-3 Carbon-Based Molecules • Many carbon-based molecules are made of many small subunits bonded together. • Monomers are the individual subunits. • Polymers are made of many monomers.

19. 2-3 Carbon-Based Molecules • Four main types of carbon-based molecules are found in living things. • Carbohydrates • Lipids • Proteins • Nucleic Acids

20. 2-3 Carbon-Based Molecules • Carbohydrates are made of carbon, hydrogen, and oxygen. • Carbohydrates include sugars and starches. • Monosaccharides are simple sugars. • Polysaccharides include starches, cellulose, and glycogen.

21. Polymer (starch) Starch is a polymer of glucose monomers that often has a branched structure. Polymer (cellulose) Cellulose is a polymer of glucose monomers that has a straight, rigid structure monomer 2-3 Carbon-Based Molecules • Carbohydrates can be broken down to provide energy for cells. • Some carbohydrates are part of cell structure.

22. 2-3 Carbon-Based Molecules • Lipids are nonpolar molecules that include fats, oils, and cholesterol. • Many contain carbon chains called fatty acids. • Fats and oils contain fatty acids bonded to glycerol.

23. 2-3 Carbon-Based Molecules • Lipids have several different functions. • Broken down as a source of energy • Make up cell membranes • Used to make hormones

24. Phospholipid 2-3 Carbon-Based Molecules • Phospholipids make up all cell membranes. • Polar phosphate “head” • Nonpolar fatty acid “tails”

25. 2-3 Carbon-Based Molecules • Fats and oils have different types of fatty acids. • saturated fatty acids • unsaturated fatty acids

26. 2-3 Carbon-Based Molecules • Cholesterol • Ring structured lipid • Found in eggs and other fatty foods • Used to make cell membranes and hormones

27. 2-3 Carbon-Based Molecules • Proteins are polymers of amino acid monomers. • Twenty different amino acids are used to build proteins in organisms. • Amino acids differ in side groups, or R groups. • Amino acids are linked by peptide bonds

28. 2-3 Carbon-Based Molecules • Protein structure • Side groups determine structure • Sulfur in the side group causes the protein to bend • Hydrogen bonds can form between side groups • Causes the protein to fold

29. nitrogen-containing molecule,called a base A phosphate group deoxyribose (sugar) 2-3 Carbon-Based Molecules • Nucleic acids are polymers of monomers called nucleotides. • Nucleotides are made of a sugar, phosphate group, and a nitrogen base.

30. 2-4 Chemical Reactions • Bonds break and form during chemical reactions. • Chemical reactions change substances into different ones by breaking and forming chemical bonds. • Reactants are changed during a chemical reaction. • Products are made by a chemical reaction.

31. 2-4 Chemical Reactions • Bond energy is the amount of energy that breaks a bond. • Energy is added to break bonds. • Energy is released when bonds form. • A reaction is at equilibrium when reactants and products form at the same rate. CO2 + H2O ↔ H2CO3

32. 2-4 Chemical Reactions • Chemical reactions release or absorb energy. • Energy added during reactions breaks bonds • When bonds form, energy is released • During all chemical reactions energy is absorbed and released • Some release more than absorb and visce versa

33. 2-4 Chemical Reactions • Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction.

34. 2-4 Chemical Reactions • Exothermic reactions release more energy than they absorb. • Reactants have higher bond energies than products. • Excess energy is released by the reaction.

35. 2-4 Chemical Reactions • Endothermic reactions absorb more energy than they release. • Reactants have lower bond energies than products. • Energy is absorbed by the reaction to make up the difference.

36. 2-5 Enzymes • A catalyst lowers activation energy. • Catalysts are substances that speed up chemical reactions. • Decrease activation energy • Increase reaction rate

37. 2-5 Enzymes • Enzymes allow chemical reactions to occur under tightly controlled conditions. • Enzymes are catalysts in living things. • Enzymes are needed for almost all processes. • Most enzymes are proteins.

38. 2-5 Enzymes • Disruptions in homeostasis can prevent enzymes from functioning. • Enzymes function best in a small range of conditions. • Changes in temperature and pH can break hydrogen bonds. • An enzyme’s function depends on its structure.

39. substrates (reactants) enzyme Substrates bind to anenzyme at certain places called active sites. 2-5 Enzymes • An enzyme’s structure allows only certain reactants to bind to the enzyme. • substrates • active site

40. Substrates bind to anenzyme at certain places called active sites. The enzyme bringssubstrates together and weakens their bonds. The catalyzed reaction formsa product that is releasedfrom the enzyme. 2-5 Enzymes • The lock-and-key model helps illustrate how enzymes function. • Substrates brought together • Bonds in substrates weakened