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BIO206H5 (60)
Chapter 2

detailed chapter 2 notes

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George S Espie

Chapter 2 text notes Chapter 2 (review) Chemical components of cell  Stable vs unstable elements. Unstable elements decay.  C,H,N,O : make up 96.5% of an organism’s weight  Outer most electrons determine how atoms interact  In living tissues, only e of an atom undergoes rearrangements.  Atoms with more than 4 shells are rare in biological molecules  2 types of bonds  Ionic: electrons are transferred from 1 atom to another o Type of electrostatic attraction- force of attraction between 2 oppositely charged ions. o i.e NaCl.  Covalent: sharing of electrons ( are shared unequally) o A molecule is cluster of atoms held together by covalent bond. o Shared electrons form cloud of negative charge. o Nuclei held together by opposing like charges. o Attractive and repulsion forces are in balance when nuclei are Separated by bond length  Elements found with in human body.  Covalent bonds vary in strength  Bond strength is the amount of energy required to break a bond.  Making and breaking covalent bonds in living cells are controlled by enzymes.  There are different types of covalent bonds  Single bond vs double  Single bond allows rotation about axis  Double bond is shorter and more stronger than single  Intermediate bonds between double and single. i.e benzene  Polar structure: one with positive charge concentrated on one end and negative charge concentrated on the other end.  Polar covalent bonds  Electrostatic attractions help bring molecules together in cell  Covalent bonds are very strong in aqueous solution  Strong vs weak electrostatic attraction  Strong: when atoms involved are fully charged i.e nacl  Weak: when polar covalent bonds occur Chapter 2 text notes  Importance of polar covalent bond in biology: they allow molecules to interact through electrical forces.  i.e Large molecules, such as proteins can bind to one another through complimentary charges on their surface  The electrostatic attraction resembles ionic bond but is weaker than ionic.  Water is held together by H bonds  H2O: 70% of cells’s weight  H2O: highly polar covalent bond  Weaker than covalent bonds  When H binds to O or N or F  Hydrophilic: “water loving” molecules with + or – charges dissolve readily in water  i.e sugar, DNA, RNA and most of the proteins  Hydrophobic: Water fearing molecules  Are uncharged and form few or no H bonds. Don’t dissolve in water.  i.e hydrocarbons. They form hydrophobic thin membrane around the cell.  Some polar molecules form acids and bases in water  Acids ^  Strong vs weak acid  Strong acid lose their proton quickly  Weak acid holds on to the proton  Base: any molecule capa
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