lecture 5

Question 1

termination

Answer 1

• binding of signaling molecules is reversible
• as the signal in extracellular fluid walls, fewer receptors are bound
• unbound receptors revert to inactive form
• cellular response occurs only when number of bound receptors is above threshold

Question 2

apoptosis

Answer 2

• integrates multiple cell-signalling pathways
• SP components interact in number of ways
• cellular proteins integrate multiple signals to elicit proper responses
• programmed cell death (apoptosis): cells infected/damaged/reached end of functional life span
• DNA/organelles/cytoplasmic components broken down by cellular agents
• cell shrinks in blebbing
• cell componenets engulfed and digested by scavender cells
• protection of neighbouring cells from damage

Question 3

apoptosis triggers

Answer 3

• extracellular /intracellular signals
• extracellular:
  – initiate transduction pathways that activate genes/proteins responsible for death
• intracellular:
  – cell whose DNA is irrevocably damaged
  – signal passed along protein-protein interactions
• signals close to those of C. elegans

Question 4

mechanisms

Answer 4

• essential fo development/maintenance in animals
• failure can result in irregular growth (cancer)
• activatio of certain proteins may lead to neuro-degenerative disease