Cell structure

• Prokaryotes


  • Smaller
  • No nucleus or membrane bound organelles
  • Circular DNA without histones
  • 70s ribosomes
  • No cytoskeleton
  • Cell division by binary fission
  • Asexual reproduction
  • Unicellular
  • Haploid
  • Archaea and bacteria
• Prokaryote cell structure


  • Peptidoglycan cell wall - encloses and protects, maintains shape, prevents bursting
  • Plasma membrane - controls movement in and out
  • Cytoplasm - site of metabolic reactions
  • Pili - protein filaments for cell adhesion and DNA transfer
  • Flagella - movement
  • 70s ribosomes - site of protein synthesis
  • Nucleoid region - contains cell activity and reproduction, naked DNA, single chromosome
  • Plasmid - circles of DNA that carry genes, used in antibiotic resistance and genetic modification
  • Capsule - polysaccharides that protect and adhere to surfaces
• Eukaryotes


  • Larger
  • Nucleus + membrane bound organelles
  • Linear DNA wrapped around histones
  • Cytoskeleton -> microtubules + movement in cells
  • Divide via mitosis and meiosis
  • Sexual or asexual
  • Plants, fungi, animal cells
  • Multicellular
• Plasma membrane


  • Controls movement in and out, selectively permeable
• Cytoplasm


  • Holds organelles and contains enzymes
• Mitochondria


  • Site of cellular respiration
• 80s ribosomes


  • Site of protein synthesis
• Nucleus


  • Contains cell activity and reproduction of unicellular
• Nucleolus


  • Production of ribosomes
• Smooth ER


  • Produce and store lipids
• Rough ER


  • Transports proteins to the Golgi apparatus
• Golgi


  • Processes and packages proteins to be released in Golgi vesicles
• Vesicle


  • Transports and releases substances by fusing with the plasma membrane
• Lysosomes


  • Hydrolytic enzymes destroy microbes engulfed by red blood cells and old cellular organelles
• Centrioles


  • Establish microtubules during nuclear division
• Vacuole


  • Maintain osmotic balance and storage
• Cell wall


  • Protection, maintain shape, prevent bursting
• Chloroplast


  • Photosynthesis
• Compartmentalization


  1. External and internal conditions can be different

  2. Efficient metabolism due to localized enzymes and substrate

  3. Localized conditions, pH can be kept at optimum levels

  4. Isolate toxic substances such as digestive enzymes in lysosomes

  5. Numbers and locations of organelles can be changed
• Atypical cell structure in eukaryotes

  • One single muscle cell contains many nuclei
  • Red blood cells don't have a nucleus
  • Sieve tubes in plants don't have a nucleus, have little cytoplasm and few organelles to reduce resistance
  • Hyphae have many nuclei
• Unicellular organisms


  • Paramecium - Heterotrophic, Move using cilia
  • Chlamydomonas - Unicellular green algae, Autotrophic
• Gram positive bacteria


  • Bacillus
  • Staphylococcus
• Cell theory


  • All living things are composed of cells
  • Cells only arise from pre-existing cells
  • The cell is the smallest unit of life
• Light microscopes


  • Small and easy to use
  • Cheap
  • Rely on light
  • Resolution limited to 0.2um
• Electron microscope


  • Very expensive
  • Hard to use
  • Uses electrons
  • 0.1nm resolution
• Magnification


  Image size/actual size
• Developments


  • Freeze fracture - Freeze + break, Observed with an electron microscope
  • Cryogenic electron - Freeze to cryogenic temps, More firm and stable, Freezing increases resolution and reduces damage from electron beams
  • Immunofluorescence - Fluorescent tag attached to antibodies specific for antigens, Shows up brightly on a light microscope
  • Fluorescent dye - Used with light microscopes, Makes the sample colorful
• Endosymbiosis


  1. Eukaryotic organisms evolved when a common ancestor endocytosed a prokaryotic cell capable of generating energy from oxygen

  2. Instead of being digested, the cells had a mutualistic relationship

  3. Provides energy -> mitochondria

  4. Also chloroplasts
• Evidence for endosymbiosis


  • Both 80um
  • Transcribe mRNA from DNA and synthesize proteins in their ribosomes like prokaryotes
  • Have double membranes
  • Circular naked DNA
  • Divide by binary fission
  • Susceptible to antibiotics
• How many micrometers are in one millimeter?

  1000 um
• How many nanometers are in one micrometer?

  1000 nm
• What is the relationship between millimeters, micrometers, and nanometers?

  1 mm equals 1000 um and 1 um equals 1000 nm
• If you have 2 mm, how many micrometers do you have?

  2000 um
• If you have 5 um, how many nanometers do you have?

  5000 nm
• How do you convert nanometers to micrometers?


  Divide by 1000