prokaryotes eukaryotes

• All cells have:

  • Cell or plasma membrane (separates the cell from the outer environment)
  • Genetic material (DNA)
  • Cytoplasm
• Prokaryotic cells:

  • Lack a membrane-bound nucleus & membrane-bound organelles
  • Have a cell wall with peptidoglycan as the primary component
  • Are much smaller than eukaryotic cells (about 10 times smaller)
  • Grow faster & multiply more rapidly than eukaryotic cells
  • Include all bacteria
• Eukaryotic cells:

  • Have a membrane-bound nucleus & membrane-bound organelles
  • Cell walls are sometimes present, composed of cellulose or chitin
  • Include fungi, algae, protozoa, plants, & animals
• Appendages in prokaryotic cells:

  • Pili:
  • Function to attach bacteria to other bacteria, cells, or surfaces
  • Sex pili allow genetic material exchange between bacterial cells
  • Flagella:
  • Long, thin structures for locomotion
  • Bacteria with flagella are motile
  • Axial Filaments:
  • Bundles of flagella found in spirochetes for corkscrew-like movement
• Cell Envelope in prokaryotic cells:

  • Glycocalyx:
  • Slimy or gummy substance for protection and adherence
  • Outer Membrane:
  • Found in gram-negative bacteria
  • Composed of lipopolysaccharides (LPS's) for protection
  • Cell Wall:
  • Composed of peptidoglycan
  • Maintains shape and withstands turgor pressure
• Cytoplasm in prokaryotic cells:

  • Nucleoid: mass of DNA not surrounded by a membrane
  • Ribosomes: site of protein synthesis
  • Endospores: resting structures produced by some bacteria through sporulation
• Eukaryotic Cell Structure:
• Other species of Clostridium genus cause botulism and gas gangrene
• Staining bacteria allows observation of spores
• Clostridium tetani causes tetanus
• Bacillus is a genus of bacteria that forms spores
• Appendages:

  • Cilia: short, hairlike, motile cellular extensions found on certain cells like some protozoa (Ciliates)
  • Flagella: single, long, hairlike cellular extension in humans, used in sperm cells for motility; some protozoans use flagella for motility
• Cell Wall:

  • Animal cells: no cell wall
  • Plant cells: made of cellulose
  • Fungi: mostly made of cellulose, some made of chitin and cellulose
  • Algae: made of cellulose
  • Protozoans: no cell wall
• Glycocalyx: may exist outside the plasma membrane, composed of carbohydrate chains from glycoproteins in the cell membrane
• Plasma Membrane:

  • Proteins involved in electron transport chain and photosynthesis are found in cytoplasmic organelles in eukaryotes
  • Cell membrane contains cholesterol, only mycoplasmas have cholesterol in their cell membrane
• Cytoplasm:

  • Cytoskeleton: network of filamentous protein structures; functions include giving cell shape, anchoring organelles, transporting substances, involved in cell division and motility
• Nucleus:

  • Nuclear envelope: double membrane with nuclear pores surrounding the nucleus
  • Chromosomes: genetic material composed of DNA; linear
  • Functions: carrier of hereditary information, control center of the cell, isolates DNA in eukaryotic cells
• Ribosomes:

  • Structure: not membrane-bound, made of RNA & protein
  • Function: sites of protein synthesis
• Membrane-bound Organelles:

  • Eukaryotic cells have specialized membrane-bound organelles for specific functions like photosynthesis, ATP production, lipid & protein synthesis, cellular digestion, and transport
• Endoplasmic Reticulum:

  • Structure: interconnecting flattened sacs, tubes, & channels
  • Types & Functions:
  • Rough E.R.: initial modification of proteins
  • Smooth E.R.: main site of lipid synthesis
• Golgi Complex:

  • Structure: 4 to 8 flattened, membrane-bound sacs loosely stacked on top of one another
  • Function: final modification of proteins & lipids
• Vesicles:

  • Structure: membrane-bound sacs
  • Function: transport material within the cell & into & out of the cell
• Mitochondria:

  • Structure: oval shaped, double membrane
  • Function: break down energy-containing organic molecules & repackage energy into ATP
• Cytoskeleton:

  • Structure: network of filamentous protein structures
  • Functions: give cell shape, anchor organelles, transport substances, involved in cell division
• Centrioles:

  • Structure: paired cylindrical structures composed of protein filaments
  • Function: organize a microtubule network during cell division
• Cell Membrane Transport:
• Passive Types of Transport:

  • Diffusion: net movement of particles from greater to lower concentration; passive process
  • Simple Diffusion: lipid interior of cell membrane is a barrier; small, nonpolar, lipid-soluble molecules move easily
  • Osmosis: movement of water across a semipermeable membrane
  • Facilitated Diffusion: carrier proteins move molecules from high to low concentration
• Active Types of Transport:

  • Active Transport: carrier proteins move molecules from low to high concentration; requires ATP
  • Vesicle Mediated Transport by Eukaryotes: endocytosis is a type of vesicle-mediated transport where substances are imported into the cell