Macromolecules and Cells Summary

Chapter 5: Macromolecules

Overview of Macromolecules

• Definition: Large biological molecules essential for life.
• Types:
  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic Acids

Macromolecules & Their Monomers

• Carbohydrates → Monosaccharides (e.g., glucose)
• Proteins → Amino acids
• Nucleic Acids (DNA & RNA) → Nucleotides
• Lipids → Fatty acids & glycerol (not true polymers)

Polymer Formation & Breakdown

• Dehydration Synthesis:
  • Joins monomers by removing water, forming covalent bonds.
• Hydrolysis:
  • Breaks down polymers into monomers by adding water.

Carbohydrates

• Function: Provide energy & structure.
• Types:
  • Monosaccharides (simple sugars): Glucose, fructose.
  • Disaccharides: Two monosaccharides joined (e.g., sucrose = glucose + fructose).
  • Polysaccharides:
  • Starch: Plants, energy storage.
  • Glycogen: Animals, energy storage.
  • Cellulose: Plants, structural component of cell walls, indigestible by humans.

Lipids

• Function: Energy storage, membrane structure, hormones.
• Types:
  • Fats (Triglycerides): Made of glycerol + 3 fatty acids.
  • Saturated fats: No double bonds, solid at room temp (e.g., butter).
  • Unsaturated fats: Double bonds, liquid at room temp (e.g., oils).
  • Phospholipids: Make up cell membranes (hydrophilic head + hydrophobic tails).
  • Steroids: Four-ring structures (e.g., cholesterol, hormones).

Proteins

• Function: Structure, enzymes, signaling, defense.
• Composition: Made of amino acids linked by peptide bonds.
• Protein Structure:
  1. Primary: Amino acid sequence.
  2. Secondary: Alpha-helices & beta-sheets (hydrogen bonds).
  3. Tertiary: 3D shape (R-group interactions).
  4. Quaternary: Multiple polypeptides joined (not all proteins have this).
• Denaturation: Loss of function due to changes in pH, temperature, or environment.

Nucleic Acids

• Function: Store & transmit genetic information.
• Types:
  • DNA: Stores genetic info.
  • RNA: Helps in protein synthesis.
• Structure: Sugar-phosphate backbone with nitrogenous bases.
• Base Pairing (Hydrogen Bonds):
  • A-T (2 bonds)
  • C-G (3 bonds)
• Differences:
  • DNA: Double-stranded, deoxyribose, contains thymine (T).
  • RNA: Single-stranded, ribose, contains uracil (U).

Chapter 6: The Cell

Types of Cells

• Prokaryotic Cells: (Bacteria, archaea)
  • No nucleus, simpler structure.
• Eukaryotic Cells: (Plants, animals, fungi, protists)
  • Nucleus & organelles.

Cell Organelles & Functions

Cell Membrane & Transport

• Phospholipid Bilayer: Selectively permeable.
• Transport Mechanisms:
  • Passive Transport (No energy required):
  • Diffusion: Molecules move from high to low concentration.
  • Osmosis: Water moves across membrane.
  • Facilitated Diffusion: Transport proteins help molecules cross.
  • Active Transport (Uses ATP):
  • Moves substances against their concentration gradient.

Cell Junctions & Communication

• Tight Junctions: Seal cells together.
• Desmosomes: Provide structural support.
• Gap Junctions: Allow communication between animal cells.
• Plasmodesmata: Allow communication between plant cells.

Summary Cheat Sheet