WEEK TWO BIOLOGY NOTES
WEEK TWO BIOLOGY NOTES biology 1305
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This 7 page Class Notes was uploaded by Lillian Scott on Thursday September 3, 2015. The Class Notes belongs to biology 1305 at University of Texas at El Paso taught by Apodaca, Jennifer in Summer 2015. Since its upload, it has received 83 views. For similar materials see General Biology in Biological Sciences at University of Texas at El Paso.
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Date Created: 09/03/15
Biology 1305 Jennifer Apodaca Week Two Biology Notes 9969 a A hypothesis that fails our test is rejected and considered disproven A hypothesis that passes is supported but not proven Why not An alternative hypothesis might be the real explanation A null hypothesis expresses the alternative possibility that the explanation offered by the hypothesis does not apply Five stages i Observations are made regarding natural phenomena ii These observations lead to a hypothesis that tries to explain the phenomena As mentioned a useful hypothesis is one that is testable because it makes specific predictions iii Experimentation is conducted to determine if the predictions are correct iv The data from the experiment are analyzed v The hypothesis is accepted or rejected a 0906 Atoms are composed of i Protons positively charged particles ii Neutrons neutral particles iii Electrons negatively charged particles Protons and neutrons are located in the nucleus Electrons are found in orbitals surrounding the nucleus Entire atom as no set electric charge Electrons move around atomic nuclei in specific regions called orbitals i Each orbital can hold up to two electrons Orbitals are grouped into levels called electron shells i Electron shells are numbered with smaller number closer to the nucleus ii The electrons in the outermost shell are called valence electrons Elements commonly found in organism have at least one unpaired valence electron The number of unpaired electrons in an atom is it valence i Mass number number of protons and neutrons ii Atomic number number of protons Energy levels and oribtals are different Energy level i Represented by rings ii Show an electron s energy Nitrogen Example i An atom of nitrogen has seven protons and seven electrons ii 2 electrons fill 1St Shell iii 5 electrons in the 2quot l shell 1 2 fill 2s orbital 2 1 each in the 3 p orbitals Biology 1305 Jennifer Apodaca iv Outer 2ncl shell is not full Multiple forms of an element that differ in the number of neutrons 12C contains 6 protons and 6 neutrons 14C contains 6 protons and 8 neutrons Atomic masses are averages of the weight of different isotopes of an element Radioactive Isotopes have unstable nuclei that emit particles of radiation energy to form new daughter isotopes This is known as radioactive decay Each radioactive isotope decays at a constant rate quantified as its halflife Radiometric dating can be used to estimate the age of the Earth and when life first appeared a Organized by atomic number b Rows correspond to number of electron shells c Columns from left to right indicate the numbers of electrons in the outer shell 09969 7h Biology 1305 Jennifer Apodaca Atomic Number or Proton Niumbeer v Elemeniml H 1 Symbol Atomic Mass in emu a Make up about 95 of the atoms in living organisms i Hydrogen and oxygen occur primarily in water ii Nitrogen is found in proteins iii Carbon is the building block of all living matter b Mineral elements less than 1 c Trace elements less than 001 i Essential for normal growth and function a Octet rule Atoms tend to establish completelyfull outer energy levels i Atoms are stable when their outer shell is full ii For many atoms the outer shell fills with 8 electrons iii One exception is hydrogen which fills its outer shell with 2 electrons b Atoms with full energy levels are less reactive than atoms with unfilled energy levels c Molecule 2 or more atoms bonded together i Contains chemical symbols of elements found in a molecule ii Subscript indicates how many of each atom are present iii The molecular formula states the numbers and types of atoms in a molecule d Compound molecule composed of 2 or more elements Biology 1305 Jennifer Apodaca a Atoms share a pair of electrons b Occurs between atoms whose other electron shells are not full Covalent bonds are often the strongest of all chemical bonds because the shared electrons behave as if they belong to each atom d Can share i 1 pair of electrons singe bond HF ii 2 pairs of electrons double bond OO iii 3 pairs of electrons triple bond NN Shared Electron Pairs Oxygen 02 Molecule a When two atoms with different electronegativity s form a covalent bond the shared electrons are more likely to be in the outer shell of the atoms of higher electronegativity rather than the atom of lower electronegativity b One molecule is more electronegative and holds the electrons around its nucleus more frequently than around the nuclei of other atoms Biology 1305 Jennifer Apodaca a An atom in a molecule with a high electronegativity will hold the electrons more tightly and have a partial negative charge whereas the other atom will have a partial positive charge a Weak polar covalent bonds b Represented as dashed or dotted lines c Collectively can form strong bond overall i Holds DNA strands together d Individually weak bonds can form and break easily i Substrate and enzyme bonding a An atom or molecule that carries a charge is called an ion i Cation An atom that loses an electron and becomes positively charged ii Anion An atom that gains an electron and becomes negatively charged iii The resulting attraction between oppositely charged ions is an ionic bond Ionic Bonding positive ion negative ion Biology 1305 Jennifer Apodaca a Electrons can be transferred from one atom to another while still retaining the energy of their position in the atom i Oxidation loss of an electron ii Reduction gain of an electron a Two structure with an identical molecular formula but different structures and characteristics i Structural isomers contain the same atoms but in different bonding relationships ii Stereoisomers identical bonding relationships but the spatial positioning of the atoms differs in the two isomers 1 Geometric isomers positioning around double bond 2 Enantiomers mirror image of another molecule a Occur when i One substance is combined with another 1 Atoms are rearranged in molecules or small molecules combine to form larger molecules ii One substance is broken down into another substance 1 Molecules are split into atoms or smaller molecules b Temperature heat increases the reaction rate because the reactants collide more often c Concentration of reactants and products i More reactants faster reaction ii More products slower reaction may speed reverse d Availability of a catalyst increases rate of reaction by lower amount of energy to get reaction going 2Ca O gt 2CaO Biology 1305 Jennifer Apodaca a The Molecular weight of a molecule is the sum of the mass numbers of all the atoms in the molecule b One mole or 6022 x 1023 molecules has a mass equal to the molecular weight expressed in grams c The concentration of a substance in a solution is typically expressed as molarity M which is the number of moles per liter