Lecture Notes: Macromolecules and Their Structures

Introduction

• Review of macromolecules, their structure, function, subunits.
• Interactive style: pause video to answer questions, play to check.

Types of Macromolecules

1. Carbohydrates
   • Empirical formula: CH2O
2. Lipids
   • Types include triglycerides, fatty acids, steroids, phospholipids.
3. Proteins
4. Nucleic Acids

Carbohydrates

Monosaccharides

• Glucose
  • Six-carbon sugar, forms a six-membered ring, an aldohexose.
  • Aldehyde functional group in straight-chain structure.
• Fructose
  • Isomer of glucose, six carbons, forms a five-membered ring.
  • Ketone functional group, known as D-fructose.
• Galactose
  • Stereoisomer of glucose, differs at carbon 4.
• Ribose
  • Five-carbon sugar, aldopentose.

Disaccharides

• Sucrose: Glucose + Fructose, a disaccharide.

Polysaccharides

• Starch
  • Found in plants, stores energy, consists of amylose (straight) and amylopectin (branched).
• Glycogen
  • Found in animals, highly branched, stores energy.
• Chitin
  • Structural material for insects.
• Cellulose
  • Found in plant cell walls, structural function.

Proteins

Monomers of Proteins

• Amino Acids: Monomers that form polypeptides, which fold into proteins.

Structure of Amino Acids

• Components: Chiral carbon, carboxyl group, amino group, hydrogen, and variable R group.
• Example: Alanine when R group is methyl (CH3).

Aromatic Amino Acids

• Nonpolar Aromatic: Phenylalanine (F), identified by benzene ring.

Formation of Peptide Bonds

• Dehydration Synthesis: Formation by loss of water.

Protein Functions

• Structural Proteins: Keratin, collagen.
• Transport Proteins: Hemoglobin, myoglobin.
• Hormones: Insulin (peptide hormone), Testosterone (steroid hormone).

Enzymes

• Proteins that speed up chemical reactions.
• Identified by suffix -ase (e.g., lactase, protease).

Lipids

Types of Lipids

• Fatty Acids: Saturated (no double bonds) vs. unsaturated (one or more double bonds).
• Triglycerides: Composed of glycerol and three fatty acids.
• Steroids: Identified by four fused rings (e.g., cholesterol).
• Phospholipids: Form cell membranes, have polar head and nonpolar tails.

Functions

• Long-term Energy Storage
• Membrane Structure
• Thermal Insulation

Nucleic Acids

• Components of Nucleotides: Phosphate group, ribose sugar, nitrogenous base.

Important Concepts

• Dehydration vs. Hydrolysis: Building by losing water vs. breaking by adding water.
• Primary vs. Tertiary Structure: Amino acid sequence vs. 3D folding and function.

Review Questions and Key Points

• Various questions on macromolecules, their structures, and functions were discussed thoroughly.
• Importance of understanding molecular structures and functional groups in biology and chemistry.