Chapter 9

Which of the following molecules are used as second messengers in signal transduction pathways?

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At any given time, there is an array of signaling molecules in a cell's environment. How does a cell "know" which signaling molecules to respond to?

-A cell responds to a signaling molecule only if the cell has the appropriate receptor.

Which of the following are examples of cell signaling? Choose all that apply.

-A neuron releases neurotransmitters into a synapse, triggering a target nerve cell. -As a response to increasing densities, bacteria coordinate behaviors and form biofilms. -Thyroid hormone stimulates body cells to increase metabolic activity.

Which of the following describes the way in which phosphorylation directly contributes to signal transduction?

-Addition of phosphate groups alters the three-dimensional protein structure, which allows the protein to interact with new binding partners.

Which of the following are ways that apoptosis can be triggered in cells?

-An apoptotic signal is generated within a cell due to excessive DNA damage. -A neighboring cell releases a signal that induces another cell to begin apoptosis.

The cells that make up multicellular organisms send, receive, and respond to a variety of signals. Which of the following is an example of synaptic signaling?

-Changes in a neuron's membrane voltage releases neurotransmitters, which travel to nearby neurons.

The cells that make up multicellular organims send, receive, and respond to a variety of signals. Which of the following is an example of paracrine signaling?

-During wound healing, platelet cells produce a growth factor that induces nearby cells to divide.

The cells that make up multicellular organims send, receive, and respond to a variety of signals. Which of the following is an example of direct signaling?

-Junctions between adjacent plant cells connect their cytoplasms and allow them to share molecules.

The cells that make up multicellular organims send, receive, and respond to a variety of signals. Which of the following is an example of endocrine signaling?

-Pancreas cells produce and release insulin into the bloodstream to induce liver cells to uptake and use glucose.

Ligands bind reversibly to their receptors. Select the statements that describe what would happen if ligands bound irreversibly with their receptors.

-The cell cannot receive new signals. -Pathway will be permanently active.

Which of the following best describes a ligand?

-a small molecule that binds to a protein and affects the protein's function

Which of the following are mechanisms that a cell uses to relay an external signal during signal transduction?

-protein phosphorylation -second messengers

Small molecules and proteins can act as cellular communication signals by binding to cell receptors. A protein binds to its receptor on a cell surface and starts a biochemical chain reaction within the cell. What is the general term for this type of pathway?

-signal transduction

What is the role of second messengers in signal-transduction pathways?

-small molecules or ions that relay a signal from the cell's surface to the cell's interior

How can cells of different tissues respond differently to the same signal molecule?

-variations in the set of proteins that the cell possesses

Intracellular receptors are located in either the cytoplasm or the nucleus. Which type of ligands binds to intracellular receptors?

small lipid-soluble molecules