bpbio

• Cell theory


  The historic scientific theory, now universally accepted, that living organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells
• Tenets of cell theory

  • All living organisms are composed of one or more cells
  • The cell is the basic unit of structure and organization in organisms
  • Cells arise from pre-existing cells
• There is no universally accepted definition of life. Some biologists consider non-cellular entities such as viruses living organisms, And thus reasonably disagree with the first tenet
• Discovery of cells


  1. Improvements to microscopes over time

  2. Robert Hooke's observations of cork under the microscope

  3. Matthias Schleiden and Theodor Schwann's studies of animal and plant cells
• Microscopes


  Devices that use lenses to magnify small objects, allowing the observation of cells
• Developments in microscope technology

  • Romans' discovery that objects appear larger under glass
  • Salvino D'Armate's eyepiece magnifier
  • Compound microscopes in Europe around 1620
  • Robert Hooke's microscope observations
  • Anton van Leeuwenhoek's single-lens microscope
  • Improvements by Carl Zeiss, Otto Schott, and Ernst Abbe
  • Electron microscope development in the 1920s
• Cell


  The fundamental unit of structure and function in all living organisms
• Components of the cell theory

  • All living organisms are composed of one or more cells
  • The cell is the basic unit of structure and organization in organisms
  • Cells arise from pre-existing cells
• The idea that all cells come from pre-existing cells had already been proposed by Robert Remak, but Rudolf Virchow is credited with adding it as the third tenet of cell theory
• Modern interpretation of cell theory

  • All known living things are made up of one or more cells
  • All living cells arise from pre-existing cells by division
  • The cell is the fundamental unit of structure and function in all living organisms
  • The activity of an organism depends on the total activity of independent cells
  • Energy flow (metabolism and biochemistry) occurs within cells
  • Cells contain DNA in the chromosome and RNA in the nucleus and cytoplasm
  • All cells are basically the same in chemical composition in organisms of similar species
• Cell wall


  A rigid non-living layer found outside the cell membrane that surrounds the cell
• Layers of the cell wall

  • Middle lamella
  • Primary cell wall
  • Secondary cell wall
• Cell wall


  • Protects the inner parts of the plant cell
  • Gives plant cells a more uniform and regular shape
  • Provides support for the plant body
  • Allows distribution of nutrients throughout the plant
• Cell membrane


  A selectively permeable barrier that physically separates the intracellular space from the extracellular environment
• Phospholipids


  The special lipids that compose the cell membrane, with a hydrophilic head and hydrophobic tail
• Cell membrane


  • Controls the movement of substances in and out of the cell
  • Performs functions like osmosis, diffusion, transport of nutrients
  • Provides mechanical support and flexibility to the cell
• Prokaryotic cell


  A type of cell that does not have a true nucleus or membrane-bound organelles
• Organisms with prokaryotic cells

  • Bacteria
  • Archaea
• Organisms with prokaryotic cells are unicellular and are called "prokaryotes"
• Prokaryotic cell


  • Covered in a cell membrane
  • Houses loose DNA and ribosomes (not bound by a plasma membrane)
  • DNA and ribosomes work to produce proteins needed for the cell
• Prokaryotic cells are much smaller than the smallest eukaryotic cells
• Surface-area-to-volume ratio limit


  The size where prokaryotic cells can no longer import the number of nutrients they need for the volume of cytosol they contain
• Bacteria are much larger than viruses because they are actively carrying out the biochemical reactions of life within their cells
• Prokaryotic cell


  • No true nucleus
  • No membrane-bound organelles
  • Nucleoid region contains DNA
  • Cell wall
  • Cytoplasm
  • Cytoskeleton
  • Ribosomes
  • Vacuoles
  • Flagella
  • Pili
  • Capsule
• Prokaryotic cells have no distinct organelles bound by membranes
• Prokaryotic cell


  • Cell membrane
  • DNA (often in a large circular genome)
• Prokaryotic cells can have cilia and flagella to help them move around, with different structure than eukaryotes
• Components of all prokaryotic cells

  • Nucleoid region
  • DNA and RNA as genetic material
  • Ribosomes
  • Cytosol with cytoskeleton
• Prokaryotic cells are usually between 0.1 to 5 micrometers in length, while eukaryotic cells are generally much larger, between 10 and 100 micrometers
• Prokaryotic cells have a higher surface-area-to-volume ratio which allows them to obtain more nutrients
• Prokaryotic cells


  • Bacterial cells
  • Archaeal cells
• Bacterial cells


  • Cell walls can contain peptidoglycan
  • Capsule
  • Flagella
  • Pili
  • Circular chromosome
  • Plasmids
• Archaeal cells


  • Cell walls do not contain peptidoglycan
  • Flagella evolved differently
  • Membranes contain different lipids
  • Circular chromosome
  • Plasmids
• Binary fission


  The process by which prokaryotic cells divide, duplicating DNA and separating into two cells
• Eukaryotic cell


  Contains membrane-bound organelles such as a nucleus, mitochondria, and endoplasmic reticulum
• Organisms based on eukaryotic cells

  • Protozoa
  • Fungi
  • Plants
  • Animals
• Eukaryotic cells are larger and more complex than prokaryotic cells
• Eukaryotic cell


  • Cytoskeleton (microtubules, microfilaments, intermediate filaments)
  • Cytosol
• Quiescence (G0)


  A phase in the eukaryotic cell cycle where the cell is not actively dividing
• Stages of eukaryotic cell interphase

  • Gap 1 (G1)
  • Synthesis (S)
  • Gap 2 (G2)