CELL COMMUNICATION

Consider this pathway:



epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP



The second messenger in this pathway is ________.

cAMP

What does it mean to say that a signal is transduced?

The physical form of the signal changes as it passes from the cell membrane to the ultimate intracellular target.

One of the major categories of receptors in the plasma membrane functions by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

receptor tyrosine kinases

A signal transmitted via phosphorylation of a series of proteins is generally associated with which of the following events?

activation of a ligand-gated ion channel

Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?

paracrine signaling

Put the steps of the process of signal transduction in the order they occur.



1. A conformational change in the signal-receptor complex activates an enzyme.

2. Protein kinases are activated.

3. A signal molecule binds to a receptor.

4. Target proteins are phosphorylated.

5. Second messenger molecules are released.

3, 1, 5, 2, 4

Which of the following is true during a typical cAMP-mediated signal transduction event?

Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

What role do phosphatases play in signal transduction pathways?

they inactivate protein kinases to turn off signal transduction

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. Which of the following conditions is required for the target organ to respond to a particular hormone?

The target organ must have receptors that recognize and bind the hormone molecule.

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

signal molecule

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

ligand-gated ion channel

What is a primary function of transcription factors?

They control gene expression.

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

aggregation of bacteria that can cause cavities

Why does testosterone, a lipid-soluble signaling molecule that crosses the membranes of all cells, affect only target cells?

intracellular receptors for testosterone are present only in target cells

Which of the following statements about a G protein signaling pathway is true?

A G protein bound to GTP is in its active state