Biological Molecules and Their Functions

Quiz and Homework

  • Quiz today - Have a piece of paper ready.
  • Homework 2 (Chapter 2) - Due tonight.
  • Exam 1 Wiki available on Blackboard in Unit 1.
  • Exam 1 scheduled for next Friday.

Lecture Topics Today

  • Chapters: 3.1-3.3, 2.5.
  • Isomers and Macromolecules:
    • Difference between monomers and polymers.
    • Dehydration synthesis vs. Hydrolysis.

Carbohydrates

  • Composition: CHO (carbon, hydrogen, oxygen) with a ratio of 1:2:1.
  • Functions: Carbohydrates are important energy storage molecules.
    • Breaking bonds releases energy (into water and CO2).

Isomers

  • Cis-Trans Isomers:

    • Atoms differ in spatial arrangement due to rigidity of double bonds.
    • Can drastically affect molecule properties.

  • Enantiomers:

    • Isomers that are mirror images of each other (like left and right hands).
    • Typically, only one form is biologically active.
    • E.g., Amino acids are often left-handed, while monosaccharides are predominantly right-handed.

Functional Groups

  • Importance: Functional groups influence the chemical reactions of molecules. Each group reacts in a characteristic way.
  • Key Functional Groups:
    • Hydroxyl group (−OH): Alcohols, e.g., Ethanol.
    • Carbonyl group (C=O): Within ketones and aldehydes, e.g., Acetone and Propanal.
    • Carboxyl group (−COOH): Acts as an acid (e.g., Acetic acid).
    • Amino group (−NH2): Amines (e.g., Glycine).
    • Sulfhydryl group (−SH): Thiols (e.g., Cysteine).
    • Phosphate group (−OPO3²−): Organic phosphates (e.g., Glycerol phosphate).
    • Methyl group (−CH3): Methylated compounds (e.g., 5-Methyl cytosine).

Energy Storage: ATP

  • Adenosine Triphosphate (ATP):
    • Composed of an organic molecule called adenosine attached to three phosphate groups.
    • Function: Stores potential energy by reacting with water, releasing this energy for cellular functions.

Monomers and Polymers

  • Biological macromolecules are formed through the process of dehydration synthesis which removes water to form bonds, making polymers from monomers.
  • Exceptions: Lipids, such as triglycerides, challenge the typical monomer/polymer model.

Dehydration and Hydrolysis Reactions

  • Dehydration Synthesis:

    • A water molecule is removed to bond two monomers into a polymer.

  • Hydrolysis:

    • Involves adding a water molecule to break a bond in a polymer, resulting in two monomers.

Types of Biological Molecules

  • Carbohydrates:

    • Composed of monosaccharides.
    • Examples include starch (plants) and glycogen (animals).

  • Proteins:

    • Formed from amino acids; exhibit structure and function variability dependent on the sequence of amino acids.

  • Nucleic Acids:

    • Composed of nucleotides, function in storing and transmitting genetic information.
    • Examples: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

Nucleic Acids Structure and Function

  • DNA vs. RNA:
    • DNA is double-stranded with deoxyribose sugar.
    • RNA is typically single-stranded with ribose sugar.
  • Building Blocks of Nucleic Acids:
    • Nucleotides consist of a sugar, phosphate group, and nitrogenous base (A, T, C, G for DNA; A, U, C, G for RNA).

Nitrogenous Bases in Nucleic Acids

  • Pyrimidines: Single-ring bases, include
    • Cytosine (C), Thymine (T, in DNA), Uracil (U, in RNA).
  • Purines: Double-ring bases, include
    • Adenine (A) and Guanine (G).

Conclusion

  • Basic understanding of macromolecules and their functional importance is critical to cell biology.
  • Applications in genomics and proteomics are transforming biological research, allowing rapid sequencing and analysis of genetic information.