🦠 Prokaryotes vs. Eukaryotes

What are the similarities between all cells (prokaryotes and eukaryotes)?

All cells are:

• Surrounded by a cell membrane
• Contain DNA (genetic material)
• Use ribosomes to make proteins
• Contain cytoplasm

Describe the key features of Prokaryotic Cells.

Prokaryotic cells (Bacteria & Archaea) have:

• Nucleoid: region where DNA is located (not membrane-bound)
• Ribosomes: 70S (smaller)
• Cell membrane: selective barrier
• Cell wall: peptidoglycan (in bacteria), pseudopeptidoglycan (in archaea)
• Flagella: movement (rotating)
• Fimbriae/pili: attachment, conjugation (DNA transfer)
• Endospores: survival structures (resistant to heat, chemicals)
• Glycocalyx (capsule/slime layer): protection, adhesion, biofilms
• Granules/inclusions: nutrient storage

Describe the key features of Eukaryotic Cells.

Eukaryotic cells (Protists, Fungi, Plants, Animals) have:

• Nucleus: membrane-bound, contains DNA
• Ribosomes: 80S (larger)
• Mitochondria: energy (ATP production)
• Endoplasmic Reticulum (ER): protein and lipid synthesis
  • Rough ER (with ribosomes)
    \rightarrow
    proteins
  • Smooth ER
    \rightarrow
    lipids, detoxification
• Golgi Apparatus: modifies, sorts, packages proteins/lipids
• Cytoskeleton: structural support, intracellular transport
• Cell membrane: selective barrier
• Cell walls: some have them; plants (cellulose), fungi (chitin)

What are the key differences between Prokaryotes and Eukaryotes?

• Prokaryotes: no nucleus, no membrane-bound organelles, smaller size (\sim
  1 \text{–} 10 \text{ µm})
• Eukaryotes: nucleus, membrane-bound organelles, larger (\sim
  10 \text{–} 100 \text{ µm})

Name and describe the three Domains of Life.

• Bacteria: prokaryotes, peptidoglycan walls, diverse environments
• Archaea: prokaryotes, extreme environments, no peptidoglycan, unique membranes
• Eukarya: all eukaryotes (Protista, Fungi, Plantae, Animalia)

Explain Gram Staining and the difference between Gram-positive and Gram-negative bacteria.

• Gram-positive: thick peptidoglycan wall, purple stain (ex: Staphylococcus spp.)
• Gram-negative: thin peptidoglycan + outer membrane, pink stain (ex: E. coli)

What are some mnemonics for remembering key characteristics of cells and Gram staining?

• Prokaryotes = PRO = NO nucleus.
• Eukaryotes = EU = TRUE nucleus.
• Gram+: Purple = Positive.
• Gram-: Pink = Negative.