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Transcript
Chapter 2 Chemistry of Life Section 2.1 – Atoms, Ions and Molecules Section 2.2 – Properties of water Section 2.3 – Carbon-based Molecules Section 2.4 – Chemical Reactions Section 2.5 - Enzymes 1 Atoms, Ions and Molecules Living things and non-living things are made of matter - Matter – anything that occupies space and has mass - Mass – the amount of matter in an object 2 Matter is made up of atoms. - Atom – smallest particle of matter that can exist and still have the properties of that particular kind of matter. - 3 Parts make up an atom 1. proton – positive charged particle Affects the IDENTITY of element 2. electron – negative charged particle affects reactivity 3. neutron – neutral/ no charge affects mass - Atoms make up elements 3 Atoms make up elements - Element – substance consisting entirely of one type of atom. - Cannot be broken down into simpler substances. - Just 4 elements make up 96% of the human body’s mass - - Carbon (C) Oxygen (O) Nitrogen (N) Hydrogen (H) Elements are found on the periodic table. 4 Sodium, reacts violently with water http://ruminatingdude.blogspot.com/2005/08/justifying-what-we-teach-in-hs.html Video Chlorine gas used in chemical warfare is Deadly stuff! 5 But chemically combined… NaCl = Table salt! Compound – two or more elements that are chemically combined - Can be broken down into smaller substances Ex: water – made up of hydrogen and oxygen = H2O NaCl - table salt (sodium and chlorine) 6 Ion - Is an atom that has gained or lost an electron, - Anion – The atom gains an electron - Cation – the atom loses an electron Ex. Li+ Ex. F Ex. Ca+ Ex. O- 7 Compounds Ionic bond: Metal + Non metal (transferred electrons) Strongest bond Covalent bond: Nonmetal + nonmetal (shared electrons) Second strongest bond Molecule - The smallest part of a covalent compound that still has all the properties of the compound Example: the smallest unit possible of water 8 Checkpoint What distinguished one element from another? Describe how an ionic compound is formed and how a covalent compound is formed. What is the difference between and ionic bond and a covalent bond? 9 2.2 Properties of Water KEY CONCEPT Water’s unique properties allow life to exist on Earth. Life depends on hydrogen bonds in water. • Water is a polar molecule. – Polar molecules have slightly charged regions. + H O H + – Nonpolar molecules do not have charged regions. _ + H O H _ - Hydrogen bonds form between slightly positive hydrogen atoms and slightly negative atoms. 10 + Properties of water 1. High Specific Heat- water resists changes in temperature. Example: Ocean Temp 2. Cohesion – Attraction of molecules of the same substance. 1 molecule of water sticking to another molecule of water (droplets) 3. Adhesion – Attraction of molecules of different substances. Water molecules sticking to other things. Water sticking to glass. Water sticking to the inside stem of a plant. 11 • Hydrogen bonds are responsible for four important properties of water. 1. Polarity 2. High specific heat 3. Cohesion 4. Adhesion Two additional properties of water: 5. Capillary Action - the ability to move upward against gravity. Due to the combined properties of adhesion and cohesion. 6. Surface Tension - because water is polar and bonds with other water molecules it creates hydrogen bonds that create a small amount of tension on the surface. Properties of water video 12 Many compounds dissolve in water. • A solution - when one substance dissolves in another. – homogeneous mixture. – Solvents dissolve other substances. – Solutes dissolve in a solvent. solution • “Like dissolves like.” – Polar solvents dissolve polar solutes. – Nonpolar solvents dissolve nonpolar solutes. – Polar substances and nonpolar substances generally remain separate. 13 Some compounds form acids or bases. • An acid releases a hydrogen ion when it dissolves in water. – high H+ concentration – pH less than 7 stomach acid pH between 1 and 3 more acidic • A base removes hydrogen ions from a solution. – low H+ concentration – pH greater than 7 bile pH between 8 and 9 more basic 14 • A neutral solution has a pH of 7. pure water pH 7 15 Check Point How do polar molecules form hydrogen bonds? What determines whether or not a compound will dissolve in water? Compare acids and bases Name one example, from everyday life, of adhesion and cohesion. Hank water video 16 2-3 Carbon Based Molecules- Organic 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 or rings 17 Carbon-Based Molecules • Most Living things are made up of Carbon. (Organic) • Many carbon-based molecules are made of many small subunits bonded together. • Monomer = 1 molecule. • Polymer = many monomers bonded together. 18 Four Main types of carbon based molecules 1. Carbohydrates 2. Lipids Fats and oils 3. Nucleic Acids Sugars and starches DNA and RNA 4. Proteins Amino acids 19 1. Carbohydrates Molecules made of C, H, O (1:2:1) Broken down into usable chemical energy that the body can use. Include sugars and starches Monosaccharides include simple sugars (C6H12O6) – glucose, fructose, galactose Polysaccaharides Glycogen, starches, and cellulose 20 Carbohydrates - Function Carbohydrates can be broken down to provide energy for cells. Some carbohydrates are part of cell structure. Polymer (starch) Starch is a polymer of glucose monomers that often has a branched structure. Polymer (cellulose) monomer Cellulose is a polymer of glucose monomers that has a straight, rigid structure 21 Carbohydrates Polysaccharides: – storage in animals (glucose/sugar) Starches – made and stored by plants. Cellulose – makes up the cell wall of a plant - structure Glycogen 22 Biochemical Reactions - • Dehydration Synthesis –anabolic reaction polymers are formed monomer + monomer polymer + water • Example: • • monosaccharide + monosaccharide disaccharide + water Hydrolysis –large molecules ( polymers) broken into simpler ones (monomers) polymer + water monomer + monomer Example disaccharide + water monosaccharide +monosaccharide 2. Lipids Molecules made of C, H, O no fixed ratio Store large amounts of chemical energy in organisms. Include fats, oils, waxes and cholesterol Fats – found in foods such as meat and butter. Oil – olive oil, peanut oil Cholesterol – your body needs a certain amount to function but too much can cause problems. 24 Lipids Lipids are nonpolar molecules -fats, oils, and cholesterol. – contain carbon chains called fatty acids. – fatty acids bonded to glycerol. Triglyceride 25 Lipids: structure • Fats and oils have different types of fatty acids. – saturated fatty acids (single bonds) – unsaturated fatty acids (at least one double bond 26 Lipids: Functions – broken down as a source of energy – make up cell membranes – used to make hormones 27 • Phospholipids make up all cell membranes. – Polar phosphate “head” – Nonpolar fatty acid “tails” Phospholipid 28 3. Protein Molecules made of C, H, O and N A protein is a polymer made of monomers called amino acids. Organisms use 20 different amino acids to build proteins. Your body makes 12 of the 20 amino acids. The rest come from foods you eat such as meat, beans and nuts. Proteins differ in the number and order of amino acids. 29 Proteins – 20 different amino acids are used to build proteins in organisms. – differ in side groups, or R groups. – linked by peptide bonds. 30 Protein Protein is required by the body for the growth, maintenance and repair of all cells. Protein is a major component of all muscles, tissues and organs. Needed for metabolism, digestion and the transportation of nutrients and oxygen in the blood. The main nutrient that keeps our hair shiny and healthy, our nails strong, our skin fresh and glowing and our bones strong and healthy. 31 4. Nucleic Acids Molecules made of C, H, O, N and P Nucleic acids are polymers of monomers called nucleotides. – Nucleotides are made of a sugar, phosphate group, and a nitrogen base. A phosphate group deoxyribose (sugar) nitrogen-containing molecule, called a base 32 Nucleic Acids There are 2 types DNA and RNA DNA - stores the information for putting amino acids together to make proteins. Deoxyribo Nucleic Acid RNA – helps to build proteins. Ribo Nucleic Acid 33 Nucleic Acids – DNA stores genetic information. – RNA builds proteins. DNA RNA 34 Check Point What is the relationship between a monomer and a polymer? How are nucleic acids and proteins polymers? How are carbohydrates and lipids similar? Different? How does the property of carbon account for the variety of organic compounds? 35 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: changed during a chemical reaction. – Products: made by a chemical reaction. • Bond energy - the amount of energy that it takes to break 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 36 Chemical reactions release or absorb energy. • Activation energy - amount of energy needed to start a chemical reaction. 37 • Exothermic reactions release more energy than they absorb. – Reactants have higher bond energies than products. – Excess energy is released by the reaction. 38 • 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. 39 Check point Hydrogen peroxide breaks down into water and hydrogen gas. Explain why this is a chemical reaction. What are the reactants? What are the products? How do endothermic and exothermic reactions differ? 40 2.5 Enzymes A catalyst lowers activation energy. Catalysts are substances that speed up chemical reactions. decrease activation energy increase reaction rate 41 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. 42 Enzymes • An enzyme’s structure allows only certain reactants to bind to the enzyme. – Substrates - reactant substrates (reactants) – active site enzyme Substrates bind to an enzyme at certain places called active sites. 43 Enzymes • The lock-and-key model helps show how enzymes work. – substrates brought together – bonds in substrates weakened Substrates bind to an enzyme at certain places called active sites. The enzyme brings substrates together and weakens their bonds. The catalyzed reaction forms a product that is released from the enzyme. 44 Check Point How does a catalyst affect the activation energy of a chemical reaction? Describe how the interaction between an enzyme and a substrate changes a chemical reaction Some organisms live in very hot or acidic environments. Would their enzymes work in a person’s cells? 45