• UNIT 1. INORGANIC CHEMISTRY
  • UNIT 2. INTERMOLECULAR FORCES, WATER, AND ACIDS AND BASES
  • UNIT 3. CARBOHYDRATES
  • UNIT 4. LIPIDS, NUCLEIC ACIDS, AND PROTEINS
  • UNIT 5. CELL MEMBRANES-STRUCTURE AND CELL FUNCTION
  • UNIT 6. PROKARYOTES AND VIRUSES
  • UNIT 7. ENERGY BALANCE
  • UNIT 8. GLYCOLYSIS AND CITRIC ACID CYCLE
  • UNIT 9. ELECTRON TRANSPORT CHAIN
  • UNIT 10. PHOTOSYSNTHESIS
  • UNIT 11. CELLULAR TRANSPORT AND CELLULAR SIGNALING
  • UNIT 12. CELL DIVISION AND CANCER
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  • 3.2

    Functional Groups

    The term functional group refers to the groupings of atoms within molecules. Functional groups determine the specific chemical properties of the molecules and as explained above, the rotation of light. The understanding of functional groups is pivotal to being able to understand the functions of the four major macromolecules: carbohydrates, lipids, proteins, and nucleic acids. Functional groups in macromolecules are usually attached to carbon backbones in different places, and each macromolecule group has unique sets of functional groups. Some of the most important functional groups are identified below in the table.

    Functional Group Name

    Structure

    Polarity

    Properties and Features

    Compound names

    Macromolecule example

    Alkyl

    Nonpolar

    Hydrophobic, Vander Waals interactions

    Hydrocarbons

    Lipids

    Hydroxyl

    Polar

    Soluble in water

    Alcohols

    Carbohydrates

    Carbonyl

    Polar

    Soluble in water

    Aldehydes or ketones

    Nucleic acids, carbohydrates

    Carboxyl

    Ionic

    Soluble in water, acidic

    Carboxylic acids

    Lipids, amino acids

    Amino

    Ionic

    Soluble, basic

    Amines

    Amino acids, nucleic acids

    Sulfhydryl

    Weak polar

    Disulfide bonds

    Thiols

    Amino acids

    Phosphate

    Ionic

    Soluble in water, acidic, energetic

    Phosphoric acids

    Lipids, nucleic acids

    Amide

    Polar

    Soluble in water, peptide bonds, not acidic

    Amides

    Amino acids

    Polymers

    In addition to the formation of isomers, functional groups also allow for similar molecules called monomers to bond together and form more complex structures called polymers. Some of the important macromolecules in biology that are polymer carbohydrates such as glycogen and starch, nucleic acids, and proteins. Lipids are not considered polymers. The synthesis or breakdown of polymers occurs through dehydration reactions or hydration reactions (hydrolysis) respectively. As polymers are synthesized from monomers, specific functional groups from one monomer will lose a -H and a corresponding functional group on another monomer will lose an -OH. As H+ and OH- ions are lost, they will combine to form water (H2O) and their loss is replaced with a new covalent bond between the two monomers. For this reason, this synthesis reaction is called dehydration synthesis. In contrast, when polymers are broken down, water molecules are split to yield a -H and an -OH and those ions are “put back on” each specific monomer which acts to replace the covalent bond between the two monomers which causes them to break apart. This process is called hydrolysis.

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