Cell to Cell Communication

The three stages of cell signalling are

• paracrine, local, and synaptic
• reception, transduction, and response
• transcription, translation, and folding
• alpha, beta, and gamma

Each of the following numbered processes are involved in signal transduction pathways:  
 I.  Response  
II.  Amplification  
 III.  Reception  
IV.  Transduction
Which of the following represents the sequence of events in a typical signal transduction pathway?

• I, II, III, IV
• III, I, IV, II
• II, IV, I, III
• III, IV, II, I

G proteins are a family of proteins involved in transmitting chemical signals originating from outside a cell into the inside of the cell. G proteins function as molecular switches.
Which of the following best describes the role in which the G protein is most intimately involved in the process shown above?

• Production of the ligand molecule.
• Reception of the signal.
• Transduction of the signal.
• Production of response to signal.

All of the following statements about ligand-receptor complexes are true EXCEPT

• A.  Most receptors exhibit ligand specificity.
• Ligand–receptor interactions are reversible
• Ligand–receptor interactions are reversible
• Ligand-receptor complexes are most often formed in cell communication pathways in which participating cells are in direct contact

When epinephrine binds to cardiac (heart) muscle cells, it speeds their contraction. When it binds to muscle cells of the small intestine, it inhibits their contraction. Which of the following best accounts for the fact that the same hormone can have different effects on muscle cells?

• Cardiac cells have more receptors for epinephrine than do intestinal cells
• Epinephrine circulates to the heart first and thus is in higher concentration around cardiac cells
• The two types of muscle cells have different signal transduction pathways for epinephrine and thus have different cellular responses
• Cardiac muscle is stronger than intestinal muscle and thus has a stronger response to epinephrine

Which of the following can activate a protein by transferring a phosphate group to it?

• cAMP
• G Protein
• protein kinase
• protein phosphatase

What do second messengers do?

• transport a signal molecule through the lipid bilayer and into the cytoplasm
• relay a message from the receptor of the first messenger throughout the cytoplasm
• transmit a message from the outside of the membrane to the extracellular fluid
• produce a cellular response  such as the production of a protein

Signal amplification is most often achieved by

• an enzyme cascade
• binding of multiple signals
• branching pathways
• action of adenylyl cyclase

Which of the following is an example of a second messenger?

• cAMP
• GTP
• insulin
• epinephrine

Cell signaling involves converting extracellular signals to specific responses inside the target cell. Which of the following best describes how a cell initially responds to a signal?

• The cell experiences a change in receptor conformation
• The cell experiences an influx of ions
• The cell experiences an increase in protein kinase activity
• The cell experiences G protein activation