Notes on Cell Theory and Structure

Introduction

• Personal anecdote about science classroom experiences.
• Importance of hands-on activities in learning (e.g., dissection, experiments).

Modern Cell Theory

1. Smallest Living Unit: The cell is the smallest living unit in all organisms.
2. All Living Things are Made of Cells: Every organism is composed of one or more cells.
   • Example: Amoeba (unicellular) vs. humans (multicellular).
3. Cells Come from Pre-existing Cells: Cells arise from other cells, containing genetic material.

Types of Cells: Prokaryotes vs. Eukaryotes

• Prokaryotes:

  • Examples: Bacteria and Archaea.
  • Characteristics:
    • No nucleus (genetic material not enclosed).
    • No membrane-bound organelles.

• Eukaryotes:

  • Examples: Plants, animals, fungi, protists.
  • Characteristics:
    • Membrane-bound organelles, including a nucleus.

Common Features of Both Types:

• Genetic material (DNA).
• Cytoplasm.
• Ribosomes (make proteins).
• Cell membrane (controls entry/exit of materials).

Inside the Cell

Cell Membrane

• Selectively permeable (maintains homeostasis).

Cytoplasm

• Jelly-like substance surrounding organelles.
• Contains cytoskeleton for support and movement.

Ribosomes

• Not membrane-bound.
• Function: Protein synthesis.
• Can be free in cytoplasm or attached to rough ER.

Eukaryotic Organelles

• Nucleus:

  • Contains genetic material (DNA).
  • Controls cell activities; contains nucleolus for ribosome production.

• Endoplasmic Reticulum (ER):

  • Rough ER: Has ribosomes; involved in protein production/transport.
  • Smooth ER: No ribosomes; involved in detoxification and lipid production.

• Golgi Apparatus:

  • Packaging center for molecules received from ER.
  • Modifies, sorts, and sends materials out (e.g., secretion).

• Mitochondria:

  • Powerhouse of the cell; produces ATP through cellular respiration (requires glucose and oxygen).

Differences Between Plant and Animal Cells

• Plant Cells:

  • Have chloroplasts for photosynthesis (convert light energy to glucose).
  • Large central vacuole for storage.
  • Have a cell wall for protection and structural support.

• Animal Cells:

  • Have several smaller vacuoles.

Exit Path of a Protein

1. Made from DNA instructions in the nucleus.
2. Synthesized by ribosomes on the rough ER.
3. Transported via vesicles to the Golgi apparatus for sorting.
4. Sent out through membrane via vesicle if tagged for secretion.

Conclusion

• Encouragement to explore more about eukaryotic organelles.
• Reminder to stay curious.