Prokaryotic cell structure

• Prokaryotic cell organelles:

  • Always present: cell wall, cell membrane, circular DNA, cytoplasm, ribosomes
  • Sometimes present: plasmid, pilus, capsule, flagellum
• Plasmids

  • small loops of DNA that are separate from the main circular DNA
  • contains genes for antibiotic resistance, can be passed between prokaryotes
• Slime capsule

  • protects bacteria from attack by cells of the immune system
• Flagellum

  • long, hair-like structure that rotates to help the cell move
• Pili

  • help bacteria attach to surfaces/other substances
• Cell wall

  • prokaryotic: made of murein, which is a glycoprotein
  • eukaryotic: made of cellulose/lignin in plants, chitin in fungi
• Ribosomes

  • prokaryotic: smaller, 70s ribosomes
  • eukaryotic: larger, 80s ribosomes
• Genome

  • prokaryotic: no nucleus, DNA is circular, not attached to any histone proteins
  • eukaryotic: has a nucleus, DNA is linear, tightly bounded to histone proteins to form chromosomes
• • prokaryotic: no membrane-bound organelles
  • eukaryotic: has membrane-bound organelles
• Virus

  • acellular (not made up of cells) and non-living (can’t reproduce independently)
  • structurally they have:
  • core of genetic material: DNA or RNA, single or double stranded
  • a protein coat called a capsid
  • attachment proteins: allow virus to attach to a host cell
• Viral replication

  1. Virus attaches to host cell receptor proteins using attachment proteins
  2. Virus injects its genetic material into the host cell
  3. Host cell produces the viral components, which are assembled into new viral particles
  4. Host cell bursts, releasing the new viral proteins
• Binary fission:

  1. Circular DNA and plasmids replicate
  2. Cell elongates, DNA loops move to opposite poles
  3. Cytoplasm divides, cell membrane forms
  4. 2 identical daughter cells produces, each with 1 copy of circular DNA and a variable number of copies of the plasmid
• Faster growth of bacteria

  • higher temperature: more enzyme activity
  • more oxygen/glucose: more respiration
  • more phosphate: more ATP/DNA/RNA
  • more nucleotides: more DNA synthesis