Lecture 6 - MACROMOLECULES (I)

Page 2: Overview of Macromolecules

• Key Topics Covered:

  • Introduction to Macromolecules

  • Carbohydrates (Macromolecules I)

  • Lipids (Macromolecules I)

  • Proteins (Macromolecules II)

  • Nucleic Acids (Macromolecules III)

Page 3: Learning Outcomes

• LO1: Broad definition of "macromolecule"

• LO2: Explain synthesis and breakdown of macromolecules by organisms

• LO3: Describe structural features of the four major classes of macromolecules

• LO4: List examples of members of each macromolecule class

• LO5: Describe key functions of members of each macromolecule class

Page 5: Definition and Structure of Macromolecules

• Macromolecules, besides some lipids, are polymers:

  • Polymers: Long chain-like molecules made of many similar or identical subunits (monomers) linked by covalent bonds

• Monomers: Smaller molecules that serve as building blocks of polymers

Page 6: Major Elements and Classes of Macromolecules

• Macromolecule Classes:

  • Carbohydrates

  • Lipids

  • Proteins

  • Nucleic Acids

Page 7: Structural Features: Monomers of Macromolecules

Page 8: Synthesis and Breakdown of Polymers

• Polymer Synthesis:

  • Involves dehydration reaction (loss of water) forming new covalent bonds

• Polymer Breakdown:

  • Involves hydrolysis (addition of water) to split covalent bonds

• Enzyme-Catalyzed Reactions: Both processes are catalyzed by enzymes

Page 9: Carbohydrates - Structural Features

• Carbohydrates: Monosaccharides can be classified as aldoses (e.g., glucose) or ketoses (e.g., fructose) based on the carbonyl group location

• Diversity in monosaccharides comes from spatial arrangements around asymmetric carbons (e.g., glucose vs. galactose)

Page 10: Types of Carbohydrates

• Monosaccharides: E.g. Glucose

• Disaccharides: E.g. Maltose (formed by two monosaccharides linked by a glycosidic bond)

• Polysaccharides: E.g. Starch (polymers of many monosaccharides linked by glycosidic bonds)

Page 11: Storage and Structural Polysaccharides

• Storage Polysaccharides:

  • Starch: Polymer of glucose, stored in plants as granules for energy

  • Glycogen: Highly branched polymer of glucose stored mainly in liver and muscle in animals, hydrolyzed for energy when needed

• Structural Polysaccharides:

  • Cellulose: Major component of plant cell walls

  • Chitin: Polymer of glucose found in the exoskeletons of arthropods

Page 12: Summary of Carbohydrates

• Summary:

  • Types of polysaccharides include starch, glycogen, cellulose, and chitin, serving various functions such as energy storage and structural roles

Page 14: Functional Context of Carbohydrates

• Showcasing chitin in real-life applications such as in cicadas and other exoskeletons of arthropods

Page 16: Overview of Lipids

• Characteristics of Lipids:

  • Generally hydrophobic (non-polar) and poorly mix with water

  • Functions include:

    • Energy storage and transport (e.g., fats)

    • Structural components (e.g., phospholipids)

    • Chemical messengers (e.g., steroids)

    • Photoreceptors (e.g., carotenoids)

    • Protective coverings (e.g., waxes)

  • Note: Lipids are not true polymers

Page 17: Formation of Fats

• Fats (Triacylglycerols/TAGs):

  • Formed by joining three fatty acids to glycerol via ester bonds through dehydration reactions

Page 18: Saturated vs. Unsaturated Fats

• Fatty Acids:

  • Saturated: No double bonds between carbon atoms

  • Unsaturated: One or more double bonds, causing kinks in the hydrocarbon chain

Page 19: Phospholipids

• Phospholipids:

  • Essential for cell membranes

  • Structure: Composed of a hydrophilic (polar) head and two hydrophobic tails

  • Similar to TAG, but contains phosphate and a polar group replacing one fatty acid

Page 20: Steroids

• Steroids:

  • Defined by a carbon skeleton consisting of four fused rings

  • Cholesterol is a key example, found in animal cell membranes and a precursor to other steroids