Transcript Electrons
Chapter 2 The Chemistry of Life Section 1: The Nature of Matter Objectives • What three subatomic particles make up atoms? • How are all the isotopes of an element similar? • What are the two types of chemical bonds? The Big Idea • Life Depends on chemistry • Chemical reactions keep you alive Atom • Basic unit of matter Democrites Subatomic particles • Protons - Positively charged (+) • Neutrons - Not charged (neutral) • Electrons - Negatively charged (-) Electrons Bind together to form the nucleus Protons Nucleus Neutrons Element • A pure substance that consists of just one type of atom An elements atomic number = number of protons 6 C Carbon 12.011 Atomic number Isotope • Atoms of the same element that differ in the number of neutrons they contain Nonradioactive carbon-12 6 electrons 6 protons 6 neutrons Nonradioactive carbon-13 6 electrons 6 protons 7 neutrons Radioactive carbon-14 6 electrons 6 protons 8 neutrons The Sum of protons and neutrons in the nucleus of an atom is its mass number 6 C Carbon 12.011 Mass number • The weighted average of the masses of an elements isotope is called its atomic mass Radioactive isotopes • Can be dangerous • Can be used practically –Radioactive dating –Treat cancer –Kill bacteria Compounds • A substance formed by the chemical combination of two or more elements in definite proportions • Ex) H2O, NaCl Table Salt Ionic Bonds • Formed when one or more electrons are transferred from one atom to another Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-) Protons +11 Electrons -10 Charge +1 Protons +17 Electrons -18 Charge -1 Transfer of electron Protons +11 Electrons -11 Charge 0 Protons +17 Electrons -17 Charge 0 • If an atom loses an electron it becomes positive • If an atom gains an electron it becomes negative Ions • Positively and negatively charged atoms Covalent Bonds • Forms when electrons are shared between atoms Molecule • The structure that results when atoms are joined together by a covalent bond • Smallest unit of most compounds Van der Waals Forces • A slight attraction that develops between the oppositely charged regions of nearby molecules due to unequal sharing of electrons Section 2: Properties of Water Objectives • Why are water molecules polar? • What are acidic solutions? What are basic solutions? The Big Idea • Much of our planet is covered in water • Water is necessary for life to exist • If life exists on other planets, there most likely is water present • Water has many properties that make life possible Polarity (-) The oxygen atom has a stronger attraction for electrons (+) Hydrogen Bonds • Because of waters partial charges, they can attract each other and create hydrogen bonds • Not as strong as covalent or ionic bonds • Waters ability to create multiple hydrogen bonds gives it many special properties Cohesion • Attraction between molecules of the same substance Adhesion • Attraction molecules of different substances Mixture • Material composed of two or more elements or compounds that are physically mixed but not chemically combined • Ex.) salt & pepper, earths atmosphere Solutions • Mixture of two or more substances in which the molecules are evenly distributed • Ex.) salt water • Settles out over time Solutions Cl- Cl- Na+ Na+ Water Water Solute • Substance that is dissolved • Ex.) salt Solvent • The substance that does the dissolving • Ex.) Water Suspensions • Mixture of water and nondissolved materials • Ex.) sugar solution, blood • Separate into pieces so small, they never settle out The pH scale • Indicated the concentration of hydrogen ions in a solution Acid Neutral Base Acids • Any compound that forms H+ (hydrogen) ions in solution Base • A compound that produces OH(hydroxide) ions in solution Buffers • Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden pH changes Section 3: Carbon Compounds Objective • What are the functions of each group of organic compounds? Interest Grabber Section 2-3 Life’s backbone • Most of the compounds that make up living things contain carbon. In fact, carbon makes up the basic structure, or “backbone,” of these compounds. Each atom of carbon has four electrons in its outer energy level, which makes it possible for each carbon atom to form four bonds with other atoms. • As a result, carbon atoms can form long chains. A huge number of different carbon compounds exist. Each compound has a different structure. For example, carbon chains can be straight or branching. Also, other kinds of atoms can be attached to the carbon chain. Methane Acetylene Butadiene Benzene Isooctane Macromolecules “giant molecules” • Formed by a process called polymerization Monomers • Smaller units Polymers • Linked up monomers Carbohydrates • Compounds made up of carbon, hydrogen, and oxygen atoms usually in a ratio of 1:2:1 • Main source of energy • The monomers of starch are sugars • Single sugar molecules are called monosaccharides • The large macromolecules formed from monosaccharides are known as polysaccharides Starch Glucose Lipids • Made mostly from carbon and hydrogen atoms • Used to store energy Lipid Fatty Acids Glycerol Proteins • Macromolecules that contain nitrogen as well as carbon, hydrogen, and oxygen • Proteins are polymers of molecules called amino acids Amino Acids Carboxyl group General structure Alanine Serine • More than 20 different amino acids, can join to any other amino acid • The instructions for arranging amino acids into many different proteins are stored in DNA • Each protein has a specific role • The shape of proteins can be very important Proteins Amino Acids Nucleic Acids • Macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus Double Helix Nucleotides • Consists of 3 parts: 5-carbon sugar, phosphate group and nitrogen base Nitrogen Base Phosphate group 5-Carbon Sugar 2 kinds of nucleic acids • RNA (ribonucleic acids) – contains sugar ribose • DNA (deoxyribonucleic acid) – contains sugar deoxyribose Section 4: Chemical Reactions and Enzymes Objectives • What happens to chemical bonds during chemical reactions? • How do energy changes affect whether a chemical reaction will occur? • Why are enzymes important to living things? The Big Idea • Living things are made up of chemical compounds • Everything that happens to an organism is based on chemical reactions Chemical Reactions • A process that changes or transforms one set of chemicals into another Reactants • Elements or compounds that enter into a reaction Products • Elements or compounds produced by a chemical reaction Example Reaction: Getting rid of carbon dioxide • In the blood CO2 + H20 H2CO3 (carbonic acid) • In the lungs H2CO3 CO2 + H2O Released as you breathe Energy in reactions Energy-Absorbing Reaction Energy-Releasing Reaction Activation energy Products Activation energy Reactants Reactants Products Activation Energy • The energy that is needed to get a reaction started Enzymes • Some chemical reactions are too slow or have activation energies that are too high to make them practical for living tissue • These chemical reactions are made possible by catalysts Catalyst • Substance that speeds up the rate of chemical reactions • Work by lowering a reactions activation energy Enzyme • • • • • Biological catalysts Speed up reactions in cells Very specific Named for the reaction is catylzes Enzyme names always end in ase Reaction pathway without enzyme Activation energy without enzyme Reactants Reaction pathway with enzyme Activation energy with enzyme Products Substrates • The reactants of enzyme catalyzed reactions • The active site of the enzyme and the substrate have complementary shapes • Fit like a lock and key Enzyme Action Enzyme – substrate complex ADP Enzyme (hexokinase) Glucose Substrates Products ATP Glucose-6phosphate Products are released Active site Enzyme-substrate complex Substrates are converted into products Substrates bind to enzyme Regulation of Enzyme Activity • Enzymes are affected by any variable that affects chemical reactions 1. pH 2. Temperature 3. Concentration of enzyme