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MACROMOLECULES

Study Guide / Objectives

• Objective 1: Explain why carbon is an important element for life on earth.
• Objective 2: State how carbon skeletons can vary in organic molecules.
• Objective 3: Recognize and name biologically important chemical groups (functional groups).
• Objective 4: Describe how chemical groups affect organic molecules.
• Objective 5: State (1) the basic structure, (2) the biological importance, and (3) examples of carbohydrates, lipids, proteins, and nucleic acids.

Carbon: The Basis for Biological Molecules

• Key Properties of Carbon:
  • Can form four bonds.
  • Can bond to other carbons, creating carbon skeletons.
  • Commonly bonds with hydrogen (H), oxygen (O), and nitrogen (N).

Carbon Skeletons and Chemical Groups

• Molecule properties depend on:
  • Carbon Skeleton.
  • Chemical Groups.
• Example: Dopamine promotes mother-infant bonding.

Variations of Carbon Skeletons

1. Length

• Examples of hydrocarbons with differing lengths:
  • Ethane: C₂H₆
  • Propane: C₃H₈

2. Branching

• Example: Butane vs. 2-Methylpropane (isobutane)

3. Double Bond Position

• Examples:
  • 1-Butene: C₄H₈
  • 2-Butene: C₄H₈

4. Presence of Rings

• Examples:
  • Cyclohexane: C₆H₁₂
  • Benzene: C₆H₆

Isomers

• Definition: Isomers are compounds with the same molecular formula but different structures and properties.
  • Structural Isomers: Different covalent arrangements of atoms.
  • Cis-Trans Isomers: Same covalent bonds, different spatial arrangements.
  • Enantiomers: Isomers that are mirror images of each other.

Examples of Isomers

• Structural Isomers: Pentane vs. 2-Methylbutane
• Cis-Trans Isomers:
  • Cis isomer: Two functional groups on the same side.
  • Trans isomer: Two functional groups on opposite sides.
• Enantiomers in Drug Effects:
  • Example: S-Ibuprofen reduces inflammation; R-Ibuprofen helps asthma patients.

Chemical Groups and Molecular Functions

• Importance of Functional Groups:
  • Key components in organic molecules engaged in reactions.
  • Arrangement of functional groups leads to unique properties.

The Seven Key Functional Groups

1. Hydroxyl Group (—OH)
   • Properties: Alcohols
   • Example: Ethanol
2. Carbonyl Group (C=O)
   • Subdivided into Ketones and Aldehydes.
   • Examples: Acetone (ketone), Propanal (aldehyde)
3. Carboxyl Group (—COOH)
   • Acts as an acid.
   • Example: Acetic acid
4. Amino Group (—NH₂)
   • Acts as a base, makes amines.
   • Example: Glycine
5. Sulfhydryl Group (—SH)
   • Properties: Thiols
   • Example: Cysteine
6. Phosphate Group (—OPO₃²⁻)
   • Organic phosphate
   • Example: Glycerol phosphate
7. Methyl Group (—CH₃)
   • Methylated compound.
   • Example: 5-Methylcytosine

Building Large Biological Molecules

• Four classes:
  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic Acids
• Macromolecules are large molecules made of covalently bonded atoms.

Monomers & Polymers

• Monomer: Single subunit.
• Polymer: Chain of linked monomers.
• Examples:
  • Carbohydrates, Nucleic Acids, Proteins: Often found as monomers and long polymers.
  • Lipids: Not true polymers or composed of repeated subunits.

Synthesis and Breakdown of Polymers

• Dehydration Synthesis: Process of assembling polymers by removing water.
  • Example: Formation of glycogen.
• Hydrolysis: Reverse process that breaks down polymers by adding water.

Carbohydrates

• Key Polysaccharides:
  • Starch: Energy storage in plants (e.g., potatoes).
  • Cellulose: Structural material in plant cell walls.
  • Chitin: Component in arthropods' exoskeletons and fungal cell walls.
• Monosaccharides molecular formula: Typically multiples of CH₂O.
  • Example: Glucose (C₆H₁₂O₆)
  • Classified by carbonyl location (aldose vs ketose).

Polysaccharides Structure and Function

• Polysaccharides have storage and structural functions;
  • Their architecture is determined by sugar monomers and glycosidic linkages.

Lipids

• Characteristics: Hydrophobic molecules; not true polymers.
• Types: Fats, Phospholipids, and Steroids
• Fats: Composed of glycerol and fatty acids.
  • Ester Linkage: Formed during dehydration reactions.
• Phospholipids: Form cell membranes; hydrophilic heads and hydrophobic tails.
• Steroids: Lipids with a structure of four fused rings; cholesterol is a key steroid in cell membranes.

Proteins

• Functions: Structural support, transport, defense, cellular communication, movement, etc.
• Made from Amino Acids: 20 different types linked by peptide bonds.
  • Polypeptides: Chains of amino acids.
• Four Levels of Structure:
  1. Primary Structure: Sequence of amino acids.
  2. Secondary Structure: Coils and folds (e.g., α-helices, β-sheets).
  3. Tertiary Structure: Overall 3D shape formed by interactions of side chains.
  4. Quaternary Structure: Polypeptide subunits join to form a functional protein.

Enzymes in Proteins

• Catalysts: Speed up chemical reactions by lowering activation energy.
  • Bind substrates at active sites, forming an enzyme-substrate complex.

Nucleic Acids

• Types: DNA and RNA, which store and transmit genetic information.
• Composed of Nucleotides (monomers) forming long chains (polymers).
• Function of ATP: High-energy carrier; hydrolysis releases energy for cellular processes.

DNA to Protein Flow of Information

• Process includes:
  • Transcription: DNA to RNA
  • Translation: RNA to Protein

Miller-Urey Experiment

• Demonstrated synthesis of organic compounds under prebiotic conditions.

Summary of Key Relationships

• The unique shape of macromolecules is crucial for their function.
• Changes in the chemical structure of proteins can significantly affect their behavior and the physiological implications (e.g., sickle-cell disease).

Quiz Questions from Lecture Material

• Which functional groups donate hydrogen and behave as acids?
• What is the relevance of structural isomers in drug efficacy?
• How do temperature changes affect protein functionality?
• The role of ATP in energy transfer within cells.