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Transcript
THE CHEMISTRY OF LIFE CHAPTER 2 BEWARE! SECTION 2-1: THE NATURE OF MATTER • REMEMBER from a long, long time ago… • Atoms are made up of electrons (-), neutrons (neutral), and protons (+) • If the number of +s in the nucleus = the number of –s in the electron shells the atom is stable. • If not the atom wants to bond. Bonds • Ionic bond – when electrons are transferred from one atom to another –Example NaCl • Covalent bond – electrons are shared between atoms –Example H2O Bonds • All of what we do in this unit will focus on different types of COVALENT BONDS • Now let’s look at the difference between Polar and NON-Polar Covalent bonds. BEWARE! SECTION 2-2: PROPERTIES OF WATER • Polarity – uneven distribution of electrons between the hydrogen and oxygen atoms – Oxygen is bigger and attracts the electrons more than hydrogen • Hydrogen bonds – slightly positive, polar H atoms are attracted to polar negative atoms like O • Cohesion – attraction between molecules of same substance – Water has high surface tension (allows some bugs to walk on water) • Adhesion - attraction between molecules of different substances – Capillary action (water moves up a straw along the sides) Acids, Bases, and pH H2O Water H+ Proton + OH+ Hydroxide Ion • pH scale – indicates the concentration of H+ • pH = 7 = neutral (H+ = OH-) • Base = pH above 7 (lower H+ than pure water) • Acid = pH below 7 (higher H+ than pure water) • Buffer – weak acids or bases that can prevent sharp, sudden changes in pH – Example: bicarbonate http://www.epa.gov/acidrain/education/site_students/phscale.html LIFE’S BACKBONE • Most of the compounds that make up living things contain carbon. • 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. Carbon Backbone From this guy!!! And why is he called the cigarette snail? SECTION 2-3: CARBON COMPOUNDS • Organic compounds- those compounds that contain carbon • Chemical Formulas - show how many and which atoms are in a compound • Structural Formulas - show the arrangement of the atoms in a compound • Isomers - compounds with the same chemical formula, but different structure (ex. propanol and isopropanol) COVALENT BOND #’S • Atoms want to fill their electron shells. An atom wants to make just enough bonds to fill its shells. • H (white) makes one bond • O (red) makes two bonds • C (black) makes four bonds Important Biological Molecules • What are they? –Carbohydrates –Lipids –Proteins –Nucleic acids • We’ll learn about them one at a time. CARBOHYDRATES • Organic compounds composed of carbon, hydrogen and oxygen with a ratio of two hydrogen atoms to every one oxygen atom • Made up of smaller units called simple sugars (monosaccharides) USE OF CARBOHYDRATES • Source of energy for many living things • Also used to build body structures • Examples: sugar and starch, cellulose and chitin Chitin! TYPES OF CARBOHYDRATES • Monosaccharides • Disaccharides • Polysaccharides MONOSACCHARIDES • Only one sugar molecule • Examples -glucose, fructose, and galactose • All three are C6H12O6, but they are isomers • Draw Glucose DISACCHARIDES • Double sugars (two monosaccharides combined) • Examples: sucrose, lactose, and maltose • All are isomers with the chemical formula C12H22O11 POLYSACCHARIDES • Long chains of monosaccharides joined together • Examples: starch, glycogen, and cellulose • Plants store excess sugar as starch, and break it down for energy Representation of a Polysaccharide • Humans store excess sugar as glycogen, & break it down for energy • Cellulose used by plants for structural purposes. DEHYDRATION SYNTHESIS • Two molecules join together by losing a molecule of water HYDROLYSIS REACTION • Larger molecules broken down into smaller molecules by the addition of water Lipids Aka The Fat Cat Sat on a Flat Mat Section LIPIDS • Include fats, oils, steroids & waxes • Composed of carbon, hydrogen and oxygen, but the # of H atoms per molecule is much greater than the # of O atoms • An example, C57H110O6 Other examples USES OF LIPIDS • Stored for energy • Form basic structure of cell membranes • Protection • Insulation • Waterproof coverings THE STRUCTURE OF SOME IMPORTANT FATS • Built from 2 basic molecules: –Glycerol - an alcohol –Fatty Acids - a long carbon chain with a -COOH (carboxyl group) at one end Triglyceride Structure Phospholipid Structure • http://library.tedankara.k12.tr/chemistry/vol5/polarity%20and%20activity/z247.htm • Different types of fatty acids: –Saturated - all single, covalent bonds in between carbons in chain –Unsaturated - one double bond between carbons in chain –Polyunsaturated - many double bonds between carbons in chain • Cholesterol - another lipid, made by animals, both helpful & harmful Proteins Yaw dis is aboout da Proteens ! PROTEIN • Made up of amino acids linked together • Composed of C, H, & O as well as nitrogen, N, and possibly sulfur USES OF PROTEINS • build living materials like muscle • act as enzymes to help carry out chemical reactions • fight disease • transport particles into or out of cells • act as markers on cells General Structure Alanine Serine There are 20 main amino acids • Each has same basic structure with the only difference being the “R” group • Amino acids are linked by peptide bonds (formed by dehydration synthesis) Essential Amino Acids • Peptide bond is between two amino acids • Polypeptide – (a protein) many amino acids joined Amino acids Nucleic Acids Nucleic Acids • Nucleic Acids are molecules that are used for the storage of energy or information. • Some examples of Nucleic Acids are DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and ATP (adenosine triphosphate) • Nucleic Acids are made of monomers called NUCLEOTIDES. Nucleotides http://dnatesting.biz/nucleotides.png • DNA 3D MATTER AND ENERGY SECTION 2-4: CHEMICAL REACTIONS • Chemical reactions always involve breaking bonds in reactants and making bonds in products • Some reactions release energy and therefore usually occur spontaneously • Other reactions need energy to happen • Activation energy – the minimum amount of energy needed to start a reaction • Enzymes are catalysts which speed up chemical reactions • Enzymes are proteins that lower activation energy and allow reactions to occur at normal temperatures Reaction pathway Activation energy without enzyme without enzyme Activation energy with enzyme Reaction pathway with enzyme • Each enzyme is specific and has a specific shape • Enzymes are not permanently changed and are not used up in the reaction • They are continuously recycled! • Most enzymes end in -ase • Reactants are called substrates Enzymes •The area where the enzyme interacts is called the active site •Think of the substrate as a flexible key that must fit into the active site http://images.google.com/imgres?imgurl=http://www.phschool.com/science/biology_place/labbench/lab2/images/indfit.gif&imgr efurl=http://phschool.com/science/biology_place/labbench/lab2/induced.html&h=160&w=240&sz=39&hl=en&start=5&tbnid=t6Ka sPuPLl37wM:&tbnh=73&tbnw=110&prev=/images%3Fq%3Denzyme%2Bsubstrate%2Banimations%26svnum%3D10%26hl%3Den%2 6lr%3D%26safe%3Dactive Enzyme Substrates Products Active site http://imglib.lbl.gov/ImgLib/COLLECTIONS/BERKELEYLAB/RESEARCH-1991-PRESENT/MATERIALSSCIENCE/images/96703439.lowres.jpeg