The Chemistry of Life

The Chemistry of Life Chapter 2 Mr. Scott

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

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

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

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

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.

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

_ 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.

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

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

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

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.

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

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

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

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

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

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.

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

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.

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.

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.

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

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

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

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

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

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

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.

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.

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

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

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

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.

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.

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

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.

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.

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

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

The Chemistry of Life