Lecture 7

Question 1

Cell Signaling

Answer 1

• Extracellular signaling molecules: any molecule that can transmit signals between cells
• Receptor: Binds a signaling molecule
• Ligand: A signaling molecule that can be bound by a receptor
• Intracellular Signaling Molecules: any molecule that can transmit a signal within a cell
• Effectors: Receive signals to change cell behavior

Question 2

Signaling

Answer 2

• Contact dependent: two cells must be very close to connect membrane-bound signal in signaling cell to membrane-bound receptor in target cell
• Paracrine: Signaling cell releases diffusible signal to target cells
• Autocrine: A cell secretes a diffusible signal for itself
• Synaptic: Neuron extends an axon to reach distant target cell
• Endocrine: Endocrine cell secretes hormones into bloodstream for long range distribution

Question 3

GTP Binding Proteins

Answer 3

• GEFs: Helps exchange GDP for GTP
• GAPs: Activate GTPase activity to hydrolyze GTP to GDP
  -GTP-binding turns signaling pathway on

Question 4

Signaling Speed

Answer 4

• Synaptic signaling is very fast
• Endocrine is slow
• Changes to transcription are slow
• Changes to protein function are fast
• Changes in membrane potential are fast

Question 5

Scaffold Proteins

Answer 5

• Bind intracellular signaling proteins
• Ensure signals passed in order
• Perception of signal modifies membrane lipids(phosphorylation of PIs)
• Intracellular signaling moelcules bind to new PIPs

Question 6

Protein Interaction

Answer 6

• SH3 domains bind proline rich sequences: do not require phosphorylation
• SH2 and PTB domains bind phosphorylated tyrosines
• PH domains bind PIs
• Coincidence detectors require multiple signals