Chapter 27 (study review)

Characteristics of Prokaryotes

• Unicellular organisms without a nucleus.

• Two domains: Bacteria and Archaea.

• Major features distinguishing Bacteria and Archaea include cell wall composition, membrane structure, and ribosomal RNA sequences.

Prokaryotic Structure

• General structure includes: nucleoid, plasmids, cell membrane, and cell wall.

• Cell wall types:

  • Gram-positive: thick peptidoglycan layer.

  • Gram-negative: thin peptidoglycan layer with outer membrane.

Structures in Prokaryotes

• Flagella: motility structures.

• Fimbriae: adherence structures.

• Sex pili: for conjugation.

• Capsule/Slime layer: protects from desiccation and immune response.

• Endospores: resistant structures for survival in harsh conditions.

Prokaryotic Shapes

• Shapes: cocci (spherical), bacilli (rod-shaped), spirilla (spiral).

Reproduction and Genetic Variation

• Reproduction: binary fission (asexual).

• Genetic variation processes:

  • Transformation: uptake of foreign DNA.

  • Transduction: DNA transfer via bacteriophages.

  • Conjugation: DNA transfer between bacteria via direct contact.

Autotrophic Prokaryotes

• Photoautotrophs: use sunlight for energy.

• Chemoautotrophs: obtain energy from inorganic molecules.

• Photosynthesis vs. chemosynthesis: light vs. chemical energy used for carbon fixation.

Heterotrophic Prokaryotes

• Photoheterotrophs: use light for energy but require organic compounds.

• Chemoheterotrophs: acquire both energy and carbon from organic sources.

Oxygen Requirements

• Obligate aerobes: require oxygen.

• Obligate anaerobes: are poisoned by oxygen.

• Facultative anaerobes: can use oxygen or anaerobic respiration.

Pathogens and Antibiotics

• Pathogen: harmful microorganisms, e.g., certain bacteria causing disease.

• Antibiotics: substances produced by prokaryotes to inhibit or kill other microbes, essential for competition in the environment.