Bio Chapter 2: Chemical Basis of Life
Bio Chapter 2: Chemical Basis of Life Bio 103-003
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This 7 page Class Notes was uploaded by Hibaq Ahmed on Wednesday October 5, 2016. The Class Notes belongs to Bio 103-003 at George Mason University taught by Professor Hermoso in Fall 2016. Since its upload, it has received 5 views.
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Date Created: 10/05/16
Biology Chapter 2: Chemical Basis of Life Chemicals o The stuff that make up our bodies, other organisms, and the environment Matter o Living organisms are composed of it o Anything that occupies space and has a mass (weight) o Composed of chemical elements Element: substance that can’t be broken down to other substance Molecule: one element CHON: (carbon, hydrogen, oxygen, nitrogen) 4 major elements in human body Forms many of the compounds in living organisms (ex. DNA) Compounds o A substance consisting of two or more different elements combined in a fixed trio o Ex. (Sodium + Chlorine = Sodium Chloride) Atoms: smallest unit of matter o Protons: positive charge o Electrons: negative charge gives atom its chemical properties o Neutrons: neutron charge o Protons and neutrons give mass to atoms packed in the atom’s nucleus How to calculate o atomic mass sum of protons and neutron o atomic number number of protons o number of electrons equal to number of protons Electron shells (orbital shell) 2 o Electrons occur in energy levels here 1 shell will only hold 2 max 2 ndshell will only hold 8 max rd 3 shell will only hold 8 max o Valence electrons: the outer most electrons shell: the outer most shell o Elements with same chemical properties have the same valence electrons o Chemically active elements don’t have full shells (not happy) If the shells are full then they are NOT chemically active (happy) o Atoms want to fill their outer electrons shell To do this the atoms share, donate or receive lectrons Chemical bonds: attractions between atoms Covalent: sharing electrons Ionic: receive or give o Ion An atom or molecule with an electrical charge resulting from gain or loss of electrons When electron is lost = positive charge When electron is gained = negative charge Ionic bond 3 Two ions with opposite charges attract each other When the attaction hold the ioins together o Formation of ionic bonds o Covalent bonds Results when atoms share outer-shell electrons Molecule: formed when atoms are held together by covalent bonds Joins atoms into molecule through electron sharing o Electronegativity (see electronegativity notes) The attraction for shared electrons Atoms in a covalently bonded molecule always compete for shared electrons Ex. Water has atoms with different electronegativity’s Oxygen attracts shared electrons more strongly than hydrogen o Oxygen = slight negative charge o Hydrogen = slight positive charge 4 Shared electrons spend more time near oxygen o Hydrogen bond Electrically attracted to opposite charged regions on neighboring molecules o Cohesion A property in which hydrogen bonding causes molecules to stick together o Waters hydrogen bonds moderate temperature Water has a greater ability to resist temperature change than other liquids because of hydrogen bonding Heat o The energy associated with movement of atoms and molecules in matter Temperature o Measures the intensity of heat Heat must be absorbed to break hydrogen bonds Heat must be released to form hydrogen bonds o Liquid water in denser than ice Ice hydrogen bonds are stable Liquid water hydrogen bonds constantly break and re-form o Water is the solvent of life Solution 5 A liquid consisting of a uniform mixture of two or more substance Solvent The dissolving agent Solute The substance that is dissolved o A few water molecules can break apart into ions Hydrogen ions (H+) Hydroxide ions (OH-) Both are extremely reactive A balance b/w the two is critical for chemical process to occur in a living organism Acids Chemicals other than water can contribute to H+ to a solution An acidic solution has a higher concentration of H+ pH scale 0-6: acidic 7: neutral 8-14: basic o Chemical reaction Ex. The formation of water from hydrogen and oxygen Reactants 6 Molecules in the beginning Product Molecules in the ending 7