Untitled Note

Chapter 8: Cell Structure & Function

1. Cell Theory

  • Fundamentals:

    • All living things are composed of cells.

    • Cells are the basic unit of structure and function.

    • New cells arise from existing cells.

2. Scale of Cells and Microscopy

2.2 Types of Microscopes

  • Light Microscopes:

    • Samples can be alive.

    • Uses light and lenses to magnify images.

    • Requires dyes or fluorescent labels for visibility.

  • Electron Microscopes:

    • Samples must be dead and chemically fixed.

    • Uses electrons for high magnification.

    • Two types:

      • Scanning Electron Microscopy (SEM): Surface examination.

      • Transmission Electron Microscopy (TEM): Examines thin cross-sections.

3. Basic Cell Structure

  • General Features:

    • Enclosed by a membrane.

    • Contains cytoplasm, which includes water, salts, ions, macromolecules, and organelles.

  • Organelles:

    • Specialized components that perform specific functions.

    • Can be membrane-bound or non-bound.

  • Types of Cells:

    • Prokaryotes: Smaller, lack a nucleus.

    • Eukaryotes: Larger, possess a nucleus.

4. Key Organelles and Their Functions

  • Cell Wall: Provides structure and protection (plants).

  • Chloroplast: Site of photosynthesis (plants).

  • Central Vacuole: Stores materials and helps maintain cell structure (plants).

  • Nucleus: Contains DNA; controls cellular activity.

  • Ribosomes: Sites of protein synthesis.

  • Endoplasmic Reticulum (ER):

    • Rough ER: Synthesizes proteins.

    • Smooth ER: Synthesizes lipids; detoxifies.

  • Mitochondrion: Produces ATP through cellular respiration.

  • Golgi Body: Modifies and sorts proteins and lipids for secretion.

  • Lysosomes: Digest waste materials.

5. Cell Transport Mechanisms

5.1 Importance of Transport

  • Maintenance of homeostasis through selective permeability.

  • Transport proteins and vesicles are used for materials that cannot pass freely.

5.2 Types of Transport

  • Passive Transport:

    • Does not use energy; moves substances down the concentration gradient.

    • Diffusion: Movement from high to low concentration.

    • Facilitated Diffusion: Requires special proteins for larger molecules.

    • Osmosis: Diffusion of water through selectively permeable membranes.

  • Active Transport:

    • Uses energy; moves substances against their concentration gradient.

    • Protein Pumps: Transport ions using ATP.

    • Bulk Transport: Vesicles move large molecules in/out of cells;

      • Endocytosis: Materials into the cell.

      • Exocytosis: Materials out of the cell.

6. Homeostasis in Living Organisms

  • Organisms maintain a relatively stable internal environment.

  • Unicellular Organisms: Grow, respond to stimuli, and reproduce independently.

  • Multicellular Organisms: Specialized cells that communicate and collaborate for overall organism function.

7. Biological Organization

  • Levels of Organization:

    • Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

8. Cell Communication

  • Chemical Signals: Cells communicate through chemical signals and proteins.

  • Cell Junctions: Physical connections facilitating communication between cells.

  • Receptor Proteins: Translate external signals into cellular responses, altering cellular activity based on the stimulus.