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Biochemistry. Chapter 4 Functional Groups. Carbon—The Backbone of Biological Molecules All living organisms are made up of chemicals based mostly on carbon due to its bonding ability. Chapter 4. Organic chemistry the study of carbon compounds

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Chapter 4

Functional Groups


Carbon—The Backbone of Biological Molecules

  • All living organisms are made up of chemicals based mostly on carbon due to its bonding ability

Chapter 4
Chapter 4

  • Organic chemistry

    • the study of carbon compounds

  • Organic compoundshave carbon in them (& usually H)

    • Exception: CO2 is considered INORGANIC

    • Range from simple (ie. methane, CH4) to complex molecules (ie. proteins)

Stanley miller s experiment
Stanley Miller’s Experiment

  • Gave support against the concept ofvitalism

    • idea that organic compounds arise only within living organisms

      • disproved when chemists (such as Miller) synthesized carbon compounds in lab

    • Thoughts shifted from vitalism to mechanism

      • the view that all natural phenomena are governed by physical and chemical laws.


Stanley Miller’s Experiment


CH4, NH3, H2O, H2

(thought to be found in the primitive atmosphere)

Simulated lightning

Formation of bonds w carbon
Formation of Bonds w/ Carbon

  • Carbon atoms

    • have 4valence electrons which can bond to 4 other atoms, forming diverse molecules

      • Carbon has bonding versatility

        • It can bond with four other atoms to form diverse molecules, including with hydrogen to form hydrocarbon chains

    • can form 4 covalent bonds with itself or other atoms  very important in living things!



(valence = 1)


(valence = 2))


(valence = 3)


(valence = 4))





Figure 4.4

  • The electron configuration of carbon gives it covalent compatibilitywith many different elements

    • Carbon often bonds covalently to the following molecules, forming an organic molecule:

(Valence= # of covalent bonds an atom can form)

Molecular diversity arising from carbon skeleton variation
Molecular Diversity Arising from Carbon Skeleton Variation

  • Carbon chains

    • Form the skeletons of most organic molecules

    • Vary in length and shape

      • Straight

      • Branched

      • Rings


  • Organic molecules consisting of only C and H

    • Ex: petroleum

  • Found in many of a cell’s organic molecules

    • Ex: phospholipid molecules in cell membranes

  • The covalent bonding btwn C-H is nonpolar (hydrophobic) fats and petroleum will not dissolve in water

  • High energy storage  release a lot of energy when broken down

Example of a hydrocarbon

Fat droplets (stained red)

100 µm

(b) Mammalian adipose cells

(a) A fat molecule

Figure 4.6 A, B

Example of a Hydrocarbon



  • Compounds with the same molecular formula, but different structure & properties

    • Have same # of atoms arranged differently

      3 types of isomers

  • structural~ differ in covalent arrangements of their atoms

    Both of the above molecules are pentane (C5H12)

  • Biochemistry

    2. geometric~ differ in spatial arrangement

    • Arise from inflexibility of double C bond

    • cis (“X’s” same side of double C bond) vs. trans (“X’s” opposite sides of doube C bond)

    • X’s represents an atom or group of atoms

    Cis vs. trans


    • 3. enantiomers~ mirror images of each other

      • used in pharmacological industry

      • The “asymmetrical carbon” is the middle carbon attached to four different atoms or groups of atoms

    1 usually active; other inactive

    Asymmetrical Carbon



    (effective against Parkinson’s disease)


    (biologically inactive)

    Figure 4.8

    Functional groups
    Functional Groups

    • Functional groups

      • parts of organic molecules involved in chemical rxns (chemically reactive groups)

      • replace a hydrogen bonded to a hydrocarbon

      • A given functional group will behave the same way regardless of which organic molecule it is bonded to. (display consistent behavior)