BIOL 120 1st Edition Lecture 3 Outline of Last Lecture II Hierarchy of living systems finished III Process of science scientific method a Deductive reasoning Inductive reasoning observation hypothesis prediction IV Cells Cell Theory a Cell Theory Cell V Evolution and Natural Selection a Evolution Phylogenetic tree Natural selection fitness adaptation selective adaptation VI Interpreting the tree of life Taxonomy a Phylogenetic tree Taxonomy phylum genus species VII Summary of chapter 1 Outline of Current Lecture II Basic Atomic Structure a Matter Element Atoms Protons Neutrons Electrons Molecules Energy Chemical Energy Thermodynamics Atomic Number Atomic Mass Isotope III Chemical Bonds a Valence electrons Valence Chemical Reaction Covalent Bond Ion Cation Anion Ionic Bond IV Representing Molecules a Molecular formulas Structural formulas Ball and stick models Space filling models CPK coloring models Current Lecture II Basic Atomic Structure A chemical reactions are happen 24 7 in our bodies to turn food into energy These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 Complex molecules are metabolized to release energy to the body B Matter anything that occupies space and has mass solid liquid or gas 1 i e rocks metals air C Element a substance that can t be broken down into another substance by chemical reactions 1 25 elements are essential for life provide nutrition for bodily functions a Carbon proteins Hydrogen Oxygen Nitrogen DNA 95 of the elements living matter uses b Phosphorus ATP Sulfur amino acids calcium bone structure potassium needed for muscle movement few others last 5 c The body also requires a few trace elements needed for enzyme activity Iron Iodine etc 2 Atomic Number a Atomic number the number of protons in the nucleus i i e Hydrogen has 1 proton Atomic number is 1 b Atomic mass the number of protons and neutrons i isotope an atom with the same number of protons but a different number of neutrons number of electrons are similar in all cases a i e Carbon has 6 p and 6 n At Wt 12 b Carbon has 6 p and 8n At Wt 14 D Atoms 1 Composed of a Protons positively charged particles b Neutrons neutral particles i Protons and neutrons are found in the nucleus c Electrons negatively charged particles i Electrons surround the nucleus in orbitals E Molecules 1 Molecule a substance made from two or more atoms of similar or different types O2 H2O NaCl a form when atoms bond to each other 2 Water is the most important for life a It is highly polar forms hydrogen bonds connects DNA i This makes water an extremely efficient solvent ability to dissolve things F Energy 1 Energy is the capacity to do work or supply heat and can be 1 Stored potential or 2 Active motion a Chemical energy potential energy that is stored in chemical bonds i When ATP breaks down this is what provides the body energy from food ii If these reactions are spontaneous lead to lower potential energy and higher entropy iii If non spontaneous require an input of energy b Most important compounds in organisms contain carbon G Thermodynamics 1 First Law energy cannot be created or destroyed 2 Second Law spontaneous natural processes increase entropy overall H Atomic Number 1 Atomic number the number of protons in the nucleus a i e Hydrogen has 1 proton Atomic number is 1 2 Atomic mass the number of protons and neutrons a isotope an atom with the same number of protons but a different number of neutrons number of electrons are similar in all cases i i e Carbon has 6 p and 6 n At Wt 12 ii Carbon has 6 p and 8n At Wt 14 III Chemical Bonds 1 Atomic mass and atomic number describe how an element will interact with another element will it gain lose or share an electron to be stable a left side of periodic table tends to give up an electron and right side tends to gain one b This electron activity is the basis for organization of materials and flow of energy through living world 2 Electron arrangement around the nucleus a They move in regions called orbitals each orbital can hold up to 2 electrons i these orbitals are grouped in levels called electron shells a i e Shell 1 1 orbital 2 electrons Shell 2 4 orbitals 8 electrons 11 electrons 2 in shell 1 8 in shell 2 1 in shell 3 unbalanced and will gain or lose ii Valance electrons electrons in the outermost shell iii Valance number of unpaired electrons in an atom a determines the number of bonds an element can make carbon has 4 valences therefore it can make 4 bonds 3 Chemical reaction A Chemical reaction when an atom gives up shares or gains one or more electrons with another atom 1 Atoms are most stable when each electron orbital is filled B Covalent Bond each atom s unpaired valence electrons are shared by both nuclei to fill their orbital 1 Known as molecules 2 Electrons are not always shared equally An atom with high electronegativity will hold the electrons closer giving it a partial negative change and the weaker atom a partial positive charge a Non polar covalent bond equal electronegativity b Polar covalent bond unequal electronegativity C Ionic Bond 1 Ion an atom or molecule that carries a charge 2 Cation an atom that loses an electron and becomes positively charged 3 Anion an atom that gains and electron and becomes negatively charged 4 Ionic Bond results from the attraction of a cation and anion IV Representing Molecules A Molecular formulas indicate the numbers and types of atoms in a molecule 1 i e H2O CH4 B Structural formulas indicate which atoms are bonded together and whether the bonds are single double or triple C Ball and stick models and space filling models show 3D geometry D CPK coloring a popular color convention for distinguishing atoms of different chemical elements in molecular models