Unit 4 Cell Communiaction and Cell Cycle

• All cells in our body communicate with each other and this is necessary for our well being
• Humans are multicellular organisms, and we are healthy due to cell communication
• How cells form tissues, organs and organ systems

  1. Cells of similar structure form tissues

  2. Similar tissues group together to make organs

  3. Organs group together to make organ systems
• Cells from different organs have to communicate together with other cells
• Ligands


  Chemical messengers that send messages
• Receptors


  Something used to accept a message
• Types of ligands


  • Protein based ligands
  • Lipid based ligands
• Protein based ligands


  • Cannot go through the cell membrane, their receptors are on the cell membrane
• Lipid based ligands


  • Can easily go through the cell membrane, their receptors are inside the cell membrane
• Types of receptors


  • Protein based receptors
  • Lipid based receptors
  • Transmembrane receptors

  
• Protein based receptors


  Found on the top of the cell membrane (extracellular), used by hydrophilic ligands

  
• Lipid based receptors


  Found on the inside of the cell membrane, used by hydrophobic ligands, produce a transcription factor to synthesize a new protein

  
• Transmembrane receptors


  Span the cell membrane, have an extracellular domain, transmembrane domain, and intracellular domain
• Types of cell communication

  • Autocrine signaling
  • Cell to cell contact (direct contact/Juxtacrine Signaling)
  • Paracrine signaling
  • Quorum sensing
  • Nerve
• Autocrine signaling


  Cell sends chemical messages to itself
• Cell to cell contact (direct contact/Juxtacrine Signaling)


  Cells next to each other communicate with each other
• Animal cell to cell contact

  • Cells are held together by tight junctions, sometimes have gap junctions to exchange substances
• Plant cell to cell contact

  • Cells have plasmodesmata allowing cells next to each other to easily exchange water and solutes
• Paracrine signaling


  Cells send out signals to nearby cells causing a change in behavior
• Paracrine signaling examples


  • Muscle cells - chemical signals from nerves cause muscle contraction
  • Immune system cells - use cell-to-cell contact and short-distance communications to destroy bacteria
• Quorum sensing


  Unicellular organisms (bacteria) talk to others to understand how many of them there are, allowing them to evolve
• Ligands


  Chemical messengers used to communicate
• Intracellular change


  The changes inside of a cell
• Local regulators


  Ligands that communicate closer to each other
• Target cells


  Particular cells messages are sent to
• Lysis


  Holes are poked into the cell and the cell dies
• Quorum


  The minimum/certain amount needed to be successful
• Homeostasis


  The tendency to resist change in order to maintain a stable, relatively constant internal environment
• Osmolarity


  The number of solute in a solution
• Types of receptors


  • G-Protein Linked Receptors
  • Receptor tyrosine kinase
  • Ligand-gated ion channel receptor

  
• Signal transduction pathways


  • Evolved from a common ancestor, series of small steps that make up one large response called a cascade effect, all use second messengers
• Steps of signal transduction pathways

  1. Reception - Binding onto the receptor to initiate signaling

  2. Transduction - Chemical changes caused by the reception, transmitting signal from area of receptor to the end location

  3. Respond - How the cell responds to the chemical changes

  
• Mitosis involves four stages: prophase, metaphase, anaphase, and telophase.
• Interphase is the longest phase of the cell cycle where DNA replication occurs during the S phase.
• The cell cycle consists of interphase (G1, S, G2) and mitosis.
• Prophase is characterized by chromatin condensing into visible chromosomes, nuclear envelope breaking down, centrioles moving apart, spindle fibers forming between them, and formation of mitotic spindles.
• Metaphase is when chromosomes line up at the equator of the cell.
• Metaphase is marked by chromosomes lining up along the equatorial plane of the cell, with their centromeres attached to microtubules of the mitotic spindle.
• During mitosis, chromosomes condense into visible structures, spindle fibers form, sister chromatids separate, and two daughter cells are formed.
• Prophase is characterized by chromatin condensing into visible chromosomes, nuclear envelope breaks down, centrioles move apart, spindle fibers form between them, and mitotic spindles begin forming.