Biology 1201 08 22 2012 Scientific Method What is Science understanding natural world study of how world works how to apply the understanding What do scientists do make observations attempt to discern patterns the things you learn assume that the future is like the past from the observations something is easier to understand when you look for patterns in Scientific Method What are the basic steps of the method observation generalization or model prediction or hypothesis what will happen in a year test this see what happens What is the outcome of this process and continue through the circle these tests generate a new observation You look at the data you collected Hypothesis prediction for something that has not been tested yet best Terminology guess Theory hypothesis has been tested many times and has been supported has validity very good model Law gain support nothing more than a theory that has continued to be tested and don t see a lot in biology we speak of laws in terms of physics chemistry few in biology because the study is much newer so still developing What is Biology The study of life What is Life This is more difficult we don t know what exactly will happen reproduction requires resources cells evolves adaptable responds to environment made of organic matter organization complex molecules ecosystem a lot of energy goes to maintaining this organization breathing development reproduction growth changes during lifetime as gas exchange organism evolve respond to environment this is what people use to determine weather something is alive What are the characteristics of Life Chapter 2 08 22 2012 approach BASIC CHEMISTRY We are going to begin by using a reductionist Scale of Nature What are the sizes of biologically important structures Log Scale Solubility DEMO Like dissolves Like Sucrose sugar dissolved in water Sucrose sugar did not dissolve in ethanol What determines this Like dissolves like Like in terms of polarity Polar solutes dissolve in polar solvents Non polar solutes dissolve in non polar solvents What determines the polarity of a molecule The type of bond s within a molecule Polarity is important biologically They are the result of electrical attractions between atoms Gaining losing or sharing as a result of valence Electrical attraction are what is holding us together Opposite charges attract ATOMS Smallest unit of matter separable by normal chemical means Smallest unit of an element that retains all of the elements chemistry definition properties An atom is composed of many smaller particles particle mass electric charge proton 1 charge mass of 1 dalton neutron 0 charge neutral mass of 1 dalton electron 1 charge mass of 0 dalton Atomic is the number of protons This determines the characteristics of the element Atomic Mass is the number of protons neutrons sum of the mass of all the subatomic particles Atomic Structure Bohr Model nucleus This model has electrons moving in orbitals or shells around the Not the most accurate model Electrons fill the shell from the inside out The electrons always try to be in the lowest orbital or energy shell that is closest to the nucleus The lowest level K full at 2 least energy the next level L His next observation was that an atom was most stable that is unreactive when the outer most shell M of electrons was full Atoms will try to gain or lose electrons in order to fill their outer shell or valence shell The number of electrons to be gained or lost to fill the outer shell of electrons is called the valence Valence predicts the number of bonds that an atom will form Valence electrons the electrons in the outermost shell STRONG BONDS Bonds which are the result of very strong electrical attraction where electrons are lost or gained are called IONIC BONDS Form when atoms completely gain or lose electrons Strongest bonds when DRY Complete removal of electron o One has too many one has one too few o The two oppositely charged ions now attract one another Bonds which are the result of electrical attractions which are not so strong where the electrons are shared are COVALENT BONDS If shared equally purely covalent o Most common when the two atoms are the same H H C C O O C H an exception o Only C H in the carbon backbone non polar If shared unequally polar covalent charge separation Strongest bond in water important in biology for organic molecules o within cells POLAR COVALENT BONDS Can these bonds can be considered to grade from one to another The force between the atoms holding them together is really the same force On one side you have no sharing have it 100 other has 0 On other side you have covalent sharing perfectly In between you have polar covalent What determines the number and type of bond Number the valence Type electronegativity Electronegativity a measure of the tendency of an atom to attract a bonding pair of electrons table Measure of the attraction an atom has for electrons How much it wants to gain or lose Electronegativity seems to increase from left to right on periodic Electronegativity increases from bottoms to top on periodic table Electronegativity Bonds Ionic when differences are 1 7 or greater the bond is usually ionic Covalent non polar when differences are of less than 5 Polar covalent are between 5 and 1 7 NOTE THE NUMBER IS THE DIFFERENCE BETWEEN THEM How do bonds influence the polarity of the molecule Molecules which contain ionic bonds will be polar o Going to go into solution in water Molecules which contain polar covalent bonds will be polar with just a few exceptions o Also goes into solution in water Molecules which contain pure covalent bonds will be non polar o Will not go into solution in water ElectronegativityWeak Bonds A bond which is the result of very weak electrical attractions between atoms on different molecules or difference parts of a large molecule bearing partial electrical charges are HYDROGEN BONDS One atom involved must be Hydrogen Occur between molecules that have polar covalent to ionic bonds There are so many of them QUANTITY Weak bonds bonds which are not involved in making a substance MOLECULES AND COMPOUNDS A molecule is the smallest unit of a compound with the same properties A compound is a substance consisting of two or more different atoms in specific proportions bonded together in a specific pattern Molecular formula A shorthand way to represent the types and numbers of different atoms present in a molecule H2O CO2 C6H12O6 Isomers molecules of the same molecular
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