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BIOB10 - Lecture 2.docx

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Biological Sciences
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Rene Harrison

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Lecture 2 BIOB10 Lecture 2 Slide 1 Slide 2  At rest there are the same number of protons and electrons (no charge and neutral)  Slide 3  Key atoms in organic chemistry  At rest does not mean they are most stable  Atoms want to have 2 or 8 electrons – which leads to most stable configuration Slide 4: The Nature of Biological Molecules  organic molecules: called biochemical  biochemistry centers around carbon  - binds to up to four other atoms since it has only 4 outer electrons (8 needed to fill shell) Slide 5  atoms becoming molecules is trying to get that configuration Slide 6: Types of Molecular Bonds in biochemistry I. Covalent Bonds a. Strongest bonds  Electron pairs are shared between atoms to make molecules  Atoms are most stable with a full outer electron shel  The number of covalent bonds formed is determined by the number of electrons needed to fill outer shell Slide 7 Slide 8  Covalent bonds can lead to o Polar molecules o Non polar molecules o Ionized atoms Slide 9:  Polar molecules o Unequal sharing of electrons  if nucleus more positively charged on one atom – will attract electrons more  atoms will become relatively electronegative compared to other atom Lecture 2 BIOB10  leads to an asymmetric distribution…. Slide 10  Polar molecules o Eg. – Water  O-H bonds in water are polarized  [O] partially negative  [H] partially positive  biologically important polar molecules have one or more electronegative atoms – usually O,N,S and/or P Slide 11  Non-Polar Molecules o Equal sharing of electrons  Molecules without electronegative atoms and polar bonds (those consisting of C and H) are nonpolar o hydrocarbons Slide 12  Ionized atoms o An atoms is so strongly electronegative that it can capture electrons from another atom  Become an anion  Atom which lost electron is a cation Slide 13 II. Non-covalent Bonds  Govern interactions between molecules or different parts of a large biological molecule i. Ionic Bonds ii. Hydrogen Bonds iii. Hydrophobic interactions  Dictate interactions within macromolecules Slide 14  Ionic Bonds o Atoms/molecules with positive and negative charges that attract each other o Can hold macromolecules together (DNA  protein)  Figure 2.3 o DNA Interacting with proteins with non-covalent ionic bond o Use a macromolecule with a positive charge on the end to connect to negative charge on DNA Lecture 2 BIOB10 Slide 15  ii) Hydrogen Bonds o occurs between polar molecules o eg. Water  -the partially positive H on one water molecule interacts with the negatively charged O on the second water molecule  polar molecules interact with other polar molecules including water – called hydrophilic Slide 17  DNA backbone is covalent  DNA strands are held together by hydrogen bonds  Protein and DNA are held together by non-covalent bond Slide 18  Hydrophobic interaction o Non-polar molecues are not charged and cannot interact with water (first figure) o Form aggregates to minimize exposure to polar surroundings (second figure) Slide 19 Slide 21  Macromolecules: build around carbon  Hydrocarbons – contain only hydrogen and carbon atoms o Form carbon-containing backbones which may be linear, branched or cyclic o Hydrogen often replaced by functional groups Slide 22 – Functional Groups LOOK AT Slide 23 – Ester bond Slide 24 – Amide/peptide bond Slide 25 – Importance of Functional Groups  Generally have one or more electronegative atoms (N,P,O and/or S)  Makes oranic molecules more polar, and more reactive  Many are capable of ionization and may be +ve or –ve in charge Slide 26 – Four Types of Biological Macromolecules Lecture 2 BIOB10 Slide 27 – Formation of Macromolecules  Monomers are joined by condensation reaction o where a water molecule is removed  Polymers are broken down by hydrolosis o A water is added  Enzymes are constantly assisting with this Slide 28 –  DIAGRAM LOOK AT Slide 29 – Four Types of Biological Macromolecules  Carbohydrates – monosaccharides Slide 30 – Carbohydrates/Sugars  Stores chemical energy  Structural function – exoskeleton of insects, plant cell wall  Attaches to plasma membrane lipids and proteins o Glycocalyx  Important for cell recognition/cell identity  Eg. Blood types, A,B,O, etc  Most have general formula (CH2O)n  Sugars with 5 or more carbons convert inot closed, ring-containing molecule o Lining sugars together – from covalent bond between C1 of one sugar and OH of another  Called glycosidic linkage  Important sugars in cell metabolism have fro 3-7 carbons o Energy stored in hydrogen atoms (used in mitochondria) Slide 32 – Image CARB IMAGE  Glucose has a glycosidic linkange  When two glucose come together it becomes maltose and water Slide 34  Disaccharide – 2 monosa
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