Eukaryotic Cells: Structure, Function, and Comparison with Prokaryotes

1. Endosymbiotic Theory: Origin of Mitochondria and Chloroplasts

The endosymbiotic theory explains how mitochondria and chloroplasts originated from ancient symbiotic relationships between early eukaryotic cells and prokaryotic organisms.

• Mitochondria likely evolved from engulfed aerobic bacteria.

• Chloroplasts likely evolved from engulfed photosynthetic cyanobacteria.

• These organelles became integral parts of eukaryotic cells through symbiosis.

Example: Modern mitochondria and chloroplasts contain their own DNA, supporting this theory.

2. Differences Between Eukaryotes and Prokaryotes

Eukaryotic cells differ from prokaryotic cells in several fundamental ways:

• Eukaryotes have a true nucleus and organelles.

• Eukaryotic cells are generally larger and more complex than prokaryotic cells.

3. Mitosis vs. Meiosis

Mitosis and meiosis are two types of cell division with distinct outcomes and purposes.

Differences:

• Mitosis: Produces two identical diploid cells.

• Meiosis: Produces four genetically different haploid cells (gametes).

• Meiosis includes crossing over, increasing genetic diversity.

Similarities:

• Both involve DNA replication and similar phases (prophase, metaphase, etc.).

4. Endocytosis & Exocytosis

These are processes by which cells transport materials across their membranes.

• Endocytosis: The cell engulfs materials into vesicles for internalization.

• Exocytosis: Vesicles fuse with the plasma membrane to release materials outside the cell.

5. Eukaryotic Kingdoms

Eukaryotes are classified into several kingdoms based on their characteristics:

• Unicellular: Protista (some Fungi)

• Multicellular: Animalia, Plantae, Fungi

• Photosynthetic: Plantae and some Protista (algae)

6. Ten Main Groupings of Helminths

• Flatworms (Platyhelminths)

• Roundworms (Nematodes)

7. Tubular Extensions of Fungi

• Hyphae: Thread-like structures forming the mycelium of fungi.

8. Sexual and Asexual Fungal Spores

• Asexual spores: Conidia, sporangiospores (produced by mitosis)

• Sexual spores: Zygospores, ascospores, basidiospores (produced by meiosis)

9. Mycosis

A mycosis is a fungal infection.

• Example: Athlete's foot (tinea pedis)

10. Why Protists Are Hard to Classify

Protists are diverse in structure, metabolism, reproduction, and movement, making classification challenging.

11. Animal-like Protists

• Ciliates: Move using cilia.

• Flagellates: Move using flagella.

• Amoeboids: Move using pseudopods.

12. Fungal Plasma Membranes

• Contain ergosterol instead of cholesterol.

13. Eukaryotes with Cell Walls

• Fungi: Chitin

• Algae: Various polysaccharides

14. Eukaryotic Glycocalyx

A carbohydrate coat outside the plasma membrane that aids in cell protection, adhesion, and cell recognition.

15. Differences Between Prokaryotic & Eukaryotic Flagella

• Eukaryotic flagella are larger and have a 9+2 microtubule structure.

• Prokaryotic flagella rotate; eukaryotic flagella whip.

16. Cilia

Cilia are hair-like structures used for movement and moving substances along cell surfaces. Found in some protists and animal cells.

17. Eukaryotic vs. Prokaryotic Ribosomes

• Eukaryotic: 80S

• Prokaryotic: 70S

• In eukaryotes, ribosomes are found in the cytoplasm or bound to rough ER.

18. Cytoskeleton & Centrosome

• Made of microfilaments, intermediate filaments, and microtubules.

• Centrosome organizes microtubules and forms the mitotic spindle.

19. Three Natures of the Nucleus

• Nuclear envelope (double membrane)

• Nucleolus (rRNA synthesis)

• Chromatin (DNA + proteins)

20. Two Functions of the Endoplasmic Reticulum (ER)

• Rough ER: Protein synthesis

• Smooth ER: Lipid synthesis and detoxification

21. Two Functions of the Golgi Apparatus

• Modifies proteins and lipids

• Packages and ships them in vesicles

22. Lysosomes & Secretory Vesicles

• Lysosomes: Contain digestive enzymes; break down waste

• Secretory vesicles: Store and transport materials for exocytosis

23. Mitochondria: Similarities to Bacteria & Function

Similarities:

• Own circular DNA

• Double membrane

• Ribosomes similar to bacterial ones

Mitochondria are called the "powerhouse of the cell" because they produce ATP via cellular respiration.