Chemical signalling

• What is the function of protein receptors?

  Cell to cell communication and binding sites
• What is quorum sensing in bacteria?

  Cell to cell communication based on density
• What do bacteria produce for quorum sensing?

  Autoinducers
• How does Vibrio fischeri use quorum sensing?

  To express genes for bioluminescence
• What happens to autoinducer concentration as the bacterial population increases?

  Concentration of autoinducers increases
• What do autoinducers bind to in quorum sensing?

  LuxR receptor proteins
• What is synthesized as a result of the LuxR receptor activation?

  Luciferase enzyme
• What role do hormones play in animals?

  Act as chemical messengers in the bloodstream
• What are neurotransmitters?

  Chemical messengers released by neurons
• What are cytokines involved in?

  Immune response through cell communication
• What are calcium ions classified as in signaling?

  Secondary messengers
• What are the three types of hormones?

  1. Amino hormones (e.g., epinephrine)
  2. Protein hormones (e.g., FSH, LH)
  3. Steroid hormones (e.g., estradiol, testosterone)
• What are the types of neurotransmitters?

  1. Individual amino acids (e.g., glutamate)
  2. Peptides (e.g., CCK)
  3. Amines (e.g., dopamine)
  4. Nitrous oxides (NO)
  5. Esters (e.g., acetylcholine)
• Why is there diversity in signaling molecules?

  Natural selection favors advantageous molecules
• How do hormones differ from neurotransmitters in terms of effects?

  Hormones have long-distance effects
• How do neurotransmitters act in the body?

  They act locally in synapses
• What are transmembrane receptor proteins?

  Integral proteins in the plasma membrane
• What is the hydrophobic section of transmembrane proteins?

  Section within the fatty acid tail
• Why can't peptides and protein hormones pass through the plasma membrane?

  They are too large to pass through
• Where are intercellular receptor proteins located?

  In the cytoplasm or nucleus
• What type of chemical signals can bind to intercellular receptors?

  Hydrophobic chemical signals
• What initiates transduction pathways?

  Binding of signaling chemical to receptor
• What happens when a ligand binds to an intracellular protein?

  Changes gene expression
• Where are G-proteins found?

  In the cytoplasm
• What are the subunits of G-proteins?

  Alpha, beta, and gamma subunits
• What happens to GDP when a ligand binds to GPCR?

  GDP is released and replaced by GTP
• What does the alpha subunit of G-proteins do after activation?

  Interacts with secondary messengers
• What are the steps in the action of acetylcholine receptors?

  1. Electrical impulse triggers release
  2. Acetylcholine diffuses across synaptic cleft
  3. Binds to receptors, sodium channels open
  4. Influx of sodium ions occurs
  5. Membrane depolarization in post-synaptic neuron
  6. Electrical impulse continues
  7. Acetylcholine is broken down