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CSU LIFE 102 - Exam 1 Study Guide

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LIFE 102 1st EditionExam # 1Study Guide Chapters:1 – 6CHAPTER 1Biology is the study of life. An organism is alive if it shows:- metabolism - reproduction- growth and development - response to environmentBIOLOGY STUDIES LIFE IN ALL ITS FORMS AND AT ALL LEVELS OF ORGANIZATION AND TIME Organization 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 levels Most 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 DIVERSEdiversity 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 organisms Diversity: * cell structure may differ: Prokaryotes vs. Eukaryotesnumber of cells may differ: unicellular vs. multicellular the way organisms acquire food differs: autotrophs vs. heterotrophs CHAPTER 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 PARTICLESNEUTRONPROTONELECTRONLOCATIONnucleusnucleusin orbit around nucleusCHARGE0+1-1MASS1 Dalton1 DaltonnegligibleNUMBER/ATOMvariable (isotopes)constantvariable (ions)Atomic number: the number of protons. The atomic number determines the element.1Examples: 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 numberof 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 neutronsSome isotopes are unstable and decay, emitting radiation: radioactivity. Examples: 3H, 14C Isotopes can be used: in science (carbon dating, tracers) and medicine (radiation).• ELECTRONS ARE ARRANGED IN SHELLS – with different distances to the nucleus shell 1can hold 2 electrons; shells 2 and higher hold 8 (or more) electrons.VALENCE SHELL: THE OUTER SHELL THAT HOLDS ELECTRONSThe 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 shellHydrogen1 in shell 11Oxygen6 in shell 2 (+2 in shell 1)2Nitrogen5 in shell 2 (+2 in shell 1)3Carbon4 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: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. 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 productsMost 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:Water is cohesive: the molecules stick together => water has a high surface tension Water has a high specific heat: it takes much energy to increase water temperature Water has a high heat of vaporization: it takes much energy to vaporize water Water has its highest density in liquid phase (at 4oC) => ice floats on water Because of the polarity of water, many compounds dissolve in it.Hydrophilic compounds love water and dissolve in it (polar compounds) Hydrophobic compounds do not dissolve in water (apolar compounds like oil, fat)Important properties of solutions:The compounds that dissolve are called the solutes, the liquid is called the solvent Solute concentration : number of solute molecules per unit solvent. Concentration is usually expressed in molar (M) = mole of solute per liter solvent 1 mole = 6.1023 molecules (by approximation).molecular weight (Mw): the weight in grams of 1 mole of a compound (= the weight of its atomsin daltons)Example: glucose, C6H12O6 has a Mw of (6x12)+(12x1)+(6x16)=180 gram/mole=> for a 1M solution, 180 g. of glucose is dissolved


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