ap biology unit 4

• cell to cell communication is critical for the ____ and ____ of the cell

  function and survival
• cell to cell communication is responsible for


  the growth and development for multicellular organisms
• how do cells communicate (3 general ways)

  1.direct contact

  2.local signaling

  3.long-distance signaling
• direct contact


  communication through cell junctions
• signaling substances and other material dissolved in the cytoplasm can pass ____ between ___ cells

  freely between adjacent cells
• direct contact in animal cells

  gap junctions
• direct contact in plant cells

  plasmodesmata
• local regulators 


  a secreting cell will release chemical messages (local regulators/ligands) that travel a short distance through the extra cellular fluid
• the chemical messages will cause a ____ in a ____ cell

  response in a target cell
• two examples of local regulators

  1.paracrine signaling

  2.synaptic signaling
• paracrine signaling


  secretory cells release local regulators via exocytosis to an adjacent cell
• synaptic signaling


  occurs in animal nervous systems between the axon terminal and dendrite of two neurons
• long distance signaling


  animals and plants use hormones for long distance signaling
• long distance signaling in plants

  release hormones that travel in the plant vascular tissue or through the air to reach target tissues
• long distance signaling in animals


  use endocrine signaling

  -specialized cells release hormones into the circulatory system where they reach target cells and affect change
• cell to cell signaling can be divided into 3 stages

  1.reception

  2.transduction

  3.response
• reception


  the detection and receiving of a ligand by a receptor in the target cell
• receptor


  macromolecule that binds to a signal molecule (ligand)
• all receptors have an area that ____ with the ligand and an area that ____ a signal to another protein

  interacts, transmits
• binding between ____ and ____ is highly ____

  ligand and receptor is highly specific
• when the ligand binds to the receptor, the receptor ____ via a _____ change

  activates, conformational
• receptors can be in the _____ or ____

  plasma membrane (extracellular) or intracellular
• plasma membrane (extra cellular) receptors


  -most common type of receptor involved in signal pathways

  -bind to ligands that are: hydrophilic, polar, large
• intracellular receptors


  -found in the cytoplasm or nucleus of target cells

  -binds to ligands that can pass through the plasma membrane

  -no 2nd messenger needed
• on the ap exam hydrophobic molecules will be known as

  steroid hormones
• transduction


  the conversion of an extra cellular signal to an intracellular signal that will bring about a cellular response
• transduction requires


  a sequence of changes in a series of molecules known as a signal transduction pathway
• the signal transduction pathway regulates protein activity through


  -phosphorylation

  -dephosphorylation
• phosphorylation


  -by the enzyme protein kinase

  -relays signal inside the cell
• dephosphorylation


  by the enzyme protein phosphatase

  -shuts off pathways
• during transduction the signal is _____

  amplified
• second messengers


  small, non protein molecules and ions help relay the message and amplify the response
• response


  the final molecule in the signaling pathway converts the signal to a response that will alter a cellular process
• examples of responses


  1.protein that can alter membrane permeability

  2.enzyme that will change a metabolic process

  3.protein that turns genes on or off (transcription factors)
• transcription


  uses a strand of dna as a template to build a molecule called rna
• translation


  uses this strand of mrna to translate that nucleotide pattern into amino acids and eventually proteins
• signal transduction pathways can influence


  how a cell responds to its environment
• two main categories of cell membrane receptors

  1.g protein coupled receptors

  2.ligand gated ion channels
• g protein coupled receptors 


  -largest category of cell surface receptors

  -important in animal sensory systems

  -binds to a g protein that can bind to gtp
• ligand gated ion channels


  -located in the plasma membrane

  -important in the nervous system

  -receptors that act as a gate for ions