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CSU LIFE 102 - Lecture Notes Section 8

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LSCC102 LECTURE NOTES by ©E. PILON-SMITSTEXT: BIOLOGY, 7TH EDITION, BY CAMPBELL_____________________________________________________________CHAPTER 1Question => Hypothesis => Experiment => Accept or reject hypothesisCHAPTER 2SUB-ATOMIC PARTICLESNEUTRON PROTON ELECTRONCHAPTER 3CHAPTER 4OTHER ORGANELLESLSCC102 LECTURE NOTES by ©E. PILON-SMITSTEXT: BIOLOGY, 7TH EDITION, BY CAMPBELLThese notes could be a good example of how your own summary, that you use to study foran exam, could look like. Use these notes to complement or check your own lecture notes/summaries. They also give a good idea of the material you should focus on for an exam.Note: since these notes were originally made in 1998 for an earlier edition of Campbell, there may be some things in here that were not presented in class later on, or vice versa. In case of doubt, check with your instructor. But most things are still the same._____________________________________________________________SECTION 1 (CHAPTERS 1-6): THE COMPONENTS OF CELLS CHAPTER 1Biology is the study of life. An organism is alive if it shows:- metabolism - reproduction- growth and development - response to environment• BIOLOGY STUDIES LIFE IN ALL ITS FORMS AND AT ALL LEVELS OF ORGANIZATION AND TIMEOrganization levels: sub-microscopic => global; Time levels: nanoseconds => billions of years• BIOLOGY is a broad, MULTI-DISCIPLINARY science. It has many sub-disciplines, focusing on different organization/time levelsMost scientists use the hypothetico-deductive method (or scientific method):Question => Hypothesis => Experiment => Accept or reject hypothesis• LIFE IS AT THE SAME TIME VERY UNIFORM AND VERY DIVERSE* diversity is exhibited mainly at the organismal level: visible* uniformity is exhibited mostly at the molecular and cellular level: (sub) microscopicUniformity: * all organisms are made up of cells* cellular structures and processes are very similar in all organismsDiversity: * cell structure may differ: Prokaryotes vs. Eukaryotes* number of cells may differ: unicellular vs. multicellular* the way organisms acquire food differs: autotrophs vs. heterotrophs 1CHAPTER 2• LIVING MATTER CONSISTS OF 25 ELEMENTS*96% of living matter is carbon (C), oxygen (O), hydrogen (H) or nitrogen (N) (know these 4)* Most of the other 4% are calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), and magnesium (Mg)*In addition, 14 trace elements are present (and necessary) in very small amounts• THE SMALLEST UNIT OF AN ELEMENT IS THE ATOM. EACH ELEMENT HAS A SPECIFIC ATOMIC STRUCTURE, WHICH DETERMINES ITS PROPERTIESATOMS ARE MADE UP OF PROTONS, NEUTRONS AND ELECTRONSSUB-ATOMIC PARTICLES NEUTRON PROTON ELECTRONLOCATION nucleus nucleus in orbit around nucleusCHARGE 0 +1 -1MASS 1 Dalton 1 Dalton negligibleNUMBER/ATOM variable (isotopes) constant variable (ions)Atomic number: the number of protons. The atomic number determines the element.Examples: the atomic number of hydrogen is 1: 1H. Similarly: 6C, 7N, 8O.Usually, the number of protons, neutrons and electrons are the same. Atomic weight: the number of protons + the number of neutrons.Examples: the atomic weight of hydrogen is 2: 2H. Similarly: 14C, 14N, 16O.Ions: atoms (or molecules) with one or more electrons more (- charge), or fewer (+ charge).Isotopes: atoms with the same number of protons but different numbers of neutrons Some isotopes are unstable and decay, emitting radiation: radioactivity. Examples: 3H, 14CIsotopes can be used: in science (carbon dating, tracers) and medicine (radiation).• ELECTRONS ARE ARRANGED IN SHELLS – with different distances to the nucleusshell 1 can hold 2 electrons; shells 2 and higher hold 8 (or more) electrons.VALENCE SHELL: THE OUTER SHELL THAT HOLDS ELECTRONS2The number of electrons in the valence shell determines an atom’s chemical behavior: it strives to fill its valence shell (make its number of electrons up to 8). It can do so by sharing an electron pair with another atom, thus forming a bond. # electrons in valence shell # electrons needed to fill valence shellHydrogen 1 in shell 1 1Oxygen 6 in shell 2 (+2 in shell 1) 2Nitrogen 5 in shell 2 (+2 in shell 1) 3Carbon 4 in shell 2 (+2 in shell 1) 4=> H can form 1 bond, O two bonds, N three, and C four.Examples: H2O (water), CO2 (carbon dioxide), CH4 (methane), NH3 (ammonia).Biologically relevant noteworthy exceptions: P and S. P can make 5 bonds, S sometimes makes 6.When atoms bond, they form a molecule. Compounds are composed of two or more elements.• THERE ARE DIFFERENT TYPES OF BONDS:A. Covalent bond – Strong bond between two atoms in a molecule, sharing electron pair(s).Single bond: one e- pair shared; double bond: two pairs shared; triple bond: three pairs shared. Covalent bonds can be polar or non-polar: it is polar when one of the atoms attracts the electronpair more strongly than the other (is more electronegative).Example: water is polar; the oxygen atom attracts the electrons more than the hydrogen atoms.B. Ionic bond – Strong bond between atoms when an electron is transferred from one atom to another. Both atoms become charged ions, one positive (cation), one negative (anion). The cations and anions attract each other and form aggregations: salt crystals.Although ionic bonds are strong, many salts dissolve in water.C. Hydrogen bond – Weak bond formed by electrical attraction between a hydrogen atom and a polar other atom (usually O or N). H-bonds are important in biology for temporary associations between molecules (e.g. molecular signaling) or to stabilize large molecules (DNA, proteins).• CHEMICAL REACTIONS: MOLECULES REACT WITH EACH OTHER. THE ATOMIC BONDS IN THE REACTANTS ARE BROKEN AND OTHER BONDS ARE FORMED, REARRANGING THE ATOMS IN NEW MOLECULES (=PRODUCTS)MASS CONSERVATION LAW: all atoms of the reactants are still present in the products3Most reactions are reversible: A + B  C + DThe speed of the forward and reverse reactions depend on the concentrations of the reactants Chemical equilibrium: the forward and reverse reactions occur at equal velocity => the concentrations of the reactants remain constant (but not necessarily equal to each other).CHAPTER 3• LIFE ON EARTH EVOLVED IN WATER70% of the earth’s surface is water. Organisms are 70-95% water.• WATER IS SPECIAL BECAUSE: * IT FORMS HYDROGEN BONDS (4 per molecule) * IT IS POLAR Because of the hydrogen bonds:1) Water is cohesive: the


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CSU LIFE 102 - Lecture Notes Section 8

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