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🦠 Bacterial Cell Parts and Their
Functions (Detailed)
1. Cell Wall (Peptidoglycan Layer)
● Function :
○ Gives the bacterium its shape (coccus = round, bacillus = rod, spirillum = spiral).
○ Protects against mechanical damage.
○ Prevents bursting from osmotic pressure (important in hypotonic environments).
○ Helps distinguish between Gram-positive (thick wall) and Gram-negative (thin wall + outer membrane) bacteria.
2. Plasma (Cell) Membrane
● Function :
○ Regulates transport of nutrients and wastes.
○ Site of cellular respiration (instead of mitochondria).
○ Holds enzymes and pigments for photosynthesis (in photosynthetic bacteria).
○ Anchors flagella and pili.
○ Acts as a selective barrier, maintaining homeostasis.
3. Cytoplasm
● Function :
○ Medium where metabolic reactions occur (glycolysis, fermentation, biosynthesis).
○ Contains enzymes, ions, and nutrients.
○ Provides internal support for cell structures.
○ Stores reserve materials (glycogen granules, lipids).
4. Nucleoid (Bacterial Chromosome)
● Function :
○ Contains the essential genetic information (genes for survival and reproduction).
○ Controls protein synthesis and cell activities.
○ DNA is “naked” (not wrapped in histones).
○ Allows quick copying and cell division since DNA is not separated by a nuclear membrane.
5. Plasmids
● Function :
○ Carry extra genes not essential for survival, but useful (e.g., antibiotic resistance, toxin production, ability to digest unusual nutrients).
○ Can be exchanged between bacteria by conjugation (sex pili) → spreads resistance genes.
○ Contribute to bacterial evolution and adaptability.
6. Ribosomes (70S)
● Function :
○ Help bacteria attach to surfaces, host tissues, and other bacteria.
○ Sex pili transfer plasmids during conjugation → spreads genetic diversity.
○ Contribute to virulence (ability to cause disease) by allowing colonization of host cells.
10. Endospore (in some bacteria like Bacillus, Clostridium)
● Function :
○ Dormant, tough, non-reproductive structure.
○ Protects DNA and cytoplasm from heat, UV radiation, chemicals, and starvation.
○ Can survive for centuries in extreme conditions.
○ Germinates into an active bacterium when conditions improve.
🦠 Bacterial Cells vs. Plant & Animal Cells
🔹 1. Nucleus & DNA
● Bacteria :
○ ❌ No nucleus → DNA is in a nucleoid.
○ DNA is circular , not wrapped in histones.
○ Can have plasmids (extra DNA).
● Plant & Animal Cells :
○ ✅ True nucleus with a membrane.
○ DNA is linear , wrapped in histones, and organized into chromosomes.
○ ❌ No plasmids (except rarely in labs/genetic engineering).
🔹 2. Organelles
● Bacteria :
○ ❌ No membrane-bound organelles.
○ Respiration and photosynthesis happen in the cell membrane.
● Plant Cells :
○ ✅ Have mitochondria (energy) and chloroplasts (photosynthesis).
● Animal Cells :
○ ✅ Have mitochondria for energy.
○ ❌ No chloroplasts.
🔹 3. Ribosomes
● Bacteria :
○ 70S ribosomes (smaller).
○ Site of protein synthesis.
● Plant & Animal Cells :
○ 80S ribosomes (larger, more complex).
○ Usually immobile (except for sperm cells in some plants).
🔹 7. Energy Production
● Bacteria :
○ Use the cell membrane for respiration or photosynthesis.
● Plant Cells :
○ Use mitochondria (respiration) and chloroplasts (photosynthesis).
● Animal Cells :
○ Use mitochondria only.
