SHS General Biology 1: Types of Cells

Key Concepts:

• Cells as the basic units of life
• Prokaryotic cells (bacteria and archaea)
• Eukaryotic cells (animal, plant, fungi, protists)
• Cellular components: plasma membrane, cytoplasm, DNA, ribosomes
• Organelles: nucleus, mitochondria, Golgi body, endoplasmic reticulum, chloroplasts
• Cell wall, capsule, flagella, pili
• Cell division: conjugation, transformation, transduction, mitosis/meiosis
• Transcription and translation

1. Cells as Building Blocks of Life

• A cell is the smallest unit of a living thing.
• Organisms can be unicellular (e.g., bacteria) or multicellular (e.g., humans).
• Cells form tissues, tissues form organs, organs form organ systems, and organ systems form an organism.
• Example: A brick wall is analogous to the body, with cells being the individual bricks.

2. Prokaryotic Cells

• Classified under domains Bacteria and Archaea.
• "Pro" means before, "karyon" means nucleus.
• Simple, unicellular organisms lacking a nucleus or other membrane-bound organelles.
• DNA is located in a central region called the nucleoid.
• Bacteria have a cell wall made of peptidoglycan (sugar and amino acids).
• Many have a polysaccharide capsule for protection, shape maintenance, and preventing dehydration, and attachment to surfaces.
• Some have flagella for locomotion and pili for exchanging genetic material during conjugation.
• Example: Bacterial cells.

3. Eukaryotic Cells

• Found in animals, plants, fungi, and protists.
• "Eu" means true, "karyon" means nucleus.
• Cells with a membrane-bound nucleus and other membrane-bound organelles (compartments or sacs with specialized functions).
• Organelles are like "little organs" within the cell.
• Example: Animal cells, plant cells, fungi cells.

4. Common Components of All Cells

• Plasma Membrane: Outer covering separating the cell's interior from the environment.
• Cytoplasm: Jelly-like region within the cell where cellular components are found.
• DNA: Genetic material of the cell.
• Ribosomes: Particles that synthesize proteins.

5. Key Differences Between Prokaryotic and Eukaryotic Cells

| Feature | Prokaryotic Cells | Eukaryotic Cells | | ------------------- | ---------------------------------------------- | ---------------------------------------------- | | Size | 0.5 to 3 micrometers | 2 to 100 micrometers | | Organisms | Single-celled | Multicellular | | Organelles | Absent (mitochondria, Golgi body, ER, etc.) | Present (mitochondria, Golgi body, ER, etc.) | | Nucleus | Not well-defined, no membrane | Well-structured, compartmentalized, functional | | Cell Division | Conjugation, transformation, transduction | Mitosis/Meiosis | | Replication Origin | Single | Multiple | | Transcription/Translation | Occur together | Transcription in nucleus, translation in cytosol | | Genetic Material | Circular, double-stranded | Linear, double-stranded |

6. Coronavirus Attack Mechanism (Example of Cell Interaction)

• Virus infects the body by entering healthy cells.
• Virus makes copies of itself and multiplies.
• Coronavirus latches onto healthy cells (especially lung cells) via spiky surface proteins binding to ACE2 receptors.
• Virus hijacks healthy cells and takes command, eventually killing some of them.

7. Self-Evaluation Questions

• What is a cell?
• Why is the cell the basic unit of life?
• What is a prokaryotic cell?
• What is a eukaryotic cell?
• What are the similarities and differences between prokaryotic and eukaryotic cells?
• What is the importance of these lessons to our lives?

8. Synthesis/Conclusion

The lesson highlights the fundamental nature of cells as the building blocks of all living organisms. It emphasizes the distinction between prokaryotic and eukaryotic cells, focusing on their structural differences, particularly the presence or absence of a nucleus and other organelles. Understanding these differences is crucial for comprehending the complexity and diversity of life, as well as how viruses interact with cells to cause disease. The self-evaluation questions encourage critical thinking about the concepts learned and their relevance to real-world applications.