Quiz 9

A drug designed to inhibit the response of cells to the steroid testosterone would almost certainly result in which of the answer choices?

A decrease in the transcription of certain genes

Which of the answer choices are responsible for the amplification of an intracellular signal? Select all that apply

Adenylyl cyclase activity and protein kinase activity

When a ligand binds to a G protein-coupled receptor, which of the answer choices would you expect to happen before any of the others?

Adenylyl cyclase activity increases.

Which of the events are listed in the correct order of G protein-coupled signaling?

Adenylyl cyclase catalyzes the formation of cAMP, which activates protein kinase A (PKA).

Which statement is true about G proteins?

All of these choices are correct: Some G proteins are composed of three subunits, G proteins release GDP and bind GTP when associated with an activated receptor, G proteins can deactivate themselves by catalyzing the hydrolysis of bound GTP to produce GDP and inorganic phosphate, and G proteins are a component of the signal-transduction pathways associate with a G protein-coupled receptor.

The extent and duration of a cellular response to a signal depend on the:

All: Binding affinity of the receptor to the signaling molecule, concentration of the signaling molecule in the vicinity of the receptor, level of expression of the genes encoding the signal transduction proteins, and level of expression of the genes encoding the proteins that terminate the response

The high variability in the cell-specific expression of different types of G protein-coupled receptors, each with a distinct affinity for specific signaling molecules allows:

All: Signaling cells to activate only certain other cell types, amplification of signal response when multiple signals are present, and specific cell types to respond to multiple different signals

Which statement is true about the Delta protein?

All: delta is produced by embryonic stem cells as they differentiate into neurons in the brain, directly signals to a Notch transmembrane protein in adjacent cells, and directs adjacent cells to differentiate into glial cells

A cellular response to a signal can be terminated by:

All: inactivation of intracellular signal transduction proteins, inactivation of proteins in the signal pathway over time, depletion of a second messenger, and depletion of the signal that activates the receptor

Defects in cell signaling can lead to a cancerous cell as a result of:

All: overproduction of signals that trigger cell division, overproduction of a receptor that triggers cell division, a defective receptor that stays in the activated state and triggers cell division continuously, and a defective signal transduction protein that stays in the activated state and triggers cell division continuously.

Which type of receptor undergoes a conformational change upon activation?

All: receptor kinase, ligand-gated ion channel, intracellular receptor, and G protein-coupled receptor

To have communication between cells, you must have a

All: signaling molecule, responding cell and receptor

The type of cellular response to a signal depends on:

All: the activity of terminator proteins expressed in the cell, the type of signal transduction proteins expressed in the cell, the activity of other signaling pathways in the cell, and the type of receptor being expressed in the cell

In which of the statements is cell signaling prevented?

Allergy medicines, which are called antihistamines, bind to and block histamine receptors to keep fluids in capillaries that would normally be released and cause stuffy noses and watery eyes

When T cells in your immune system recognize a pathogen, they release Interleukin 6 (IL6), which binds back to receptors on the T cell surface. Which of the answer choices best describes this kind of IL6 signaling?

Autocrine Signaling

Despite their differences, steroid hormones

Bind intracellular receptors to form complexes that enter the nucleus

How are steroid hormone receptors and cell-surface receptors similar?

Both types undergo a conformational change when they bind to their ligand

what is a key difference between cell signaling by a cell-surface receptor and cell signaling by an intracellular receptor?

Cell-surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules

Which type of cell signaling does not rely on the diffusion of a chemical signal molecule?

Contact-dependent signaling

An increased heart rate caused by the release of adrenaline from the adrenal glands, which are located just above the kidney, is an example of _____ signaling.

Endocrine

Which type of receptor is membrane-associated? Select all that apply

G protein-coupled receptor, receptor kinase, and ligand-gated ion channel

Which type of receptor requires a set of accessory proteins to signal?

G protein-coupled receptors

Which of the answer choices is part of the general response of cells during cellular communication?

Receptors on the outside of the cell bind to specific signal molecules, A cell-surface receptor molecule becomes activated by binding to a molecular signal, An activated cell-surface receptor transfers the signal to the interior of the cell, and The signal is transmitted inside the cell and amplified as a series of proteins are activated in sequence, affecting cellular activities according to the type of signal involved.

Of the answer choices, what is the most likely reason that paracrine signaling does not activate the cell that is producing the signaling molecule?

The cell does not have the proper receptor.

You strip off all proteins on the cell surface by using a protease (an enzyme that destroys proteins). Now, when you add a specific signaling molecule, the cell still responds. What is the most reasonable explanation of this?

The receptor for this signal is inside the cell, and the signaling molecule is non-polar and can diffuse into the cell.

Why do the functions of many receptor kinases depend on the fluid nature of the plasma membrane?

The receptor monomers must move together and dimerize to be activated.

What would happen to a signaling pathway if phosphatases had reduced levels of function?

The response to the signal would persist longer after activation.

How would signaling be affected if a mutation caused a G protein to replace GDP with GTP on its own without needing to be activated by the G protein-coupled receptor?

The signaling pathway would be activated even when no ligand was present.

Which of the answer choices would be considered a cell-surface receptor?

a protein that forms a channel that allows ions to enter the cell when a ligand binds

A protein on a cell surface that binds to a signaling molecule is an example of which element of cellular communication?

a receptor protein

Which of the answer choices would be found in the cytoplasm and not on the cell surface?

a receptor that binds a nonpolar steroid hormone and activates transcription

You observe a cell that has a receptor protein that binds a signaling molecule that is produced by the same cell. What kind of signaling is occurring in this cell?

autocrine signaling

A bacterium releases a toxin that binds to and activates a G protein-coupled receptor in the mammalian gut. The result is high levels of cAMP in these cells. This toxin might work by:

binding to and activating the G protein-coupled receptor in these cells.

Which is a step in cell signaling?

cellular response, signal transduction, receptor activation, and signal termination

Which type of signaling regulates the differentiation of cells in the nervous system into neurons or glial cells?

contact-dependent signaling

Which type of receptor is involved in rapid responses of muscle cells and neurons?

ligand-gated ion channel

Communication between neurons is an example of which type of cell signaling?

paracrine signaling

Which of the answer choices correctly pair enzymes that activate and terminate the same step in a signaling event? Select all that apply.

protein kinase (activates) and phosphatase (terminates) and adenylyl cyclase (activates) and phosphodiesterase (terminates)

phosphate groups play a key role in receptor kinase activation by:

providing binding sites to recruit and activate signal-transduction proteins.

Which type of receptor activates a signaling transduction pathway by transferring phosphate groups to a substrate?

receptor kinase

Which one of the answer choices could be found bound to the regulatory region of a gene?

steroid hormone receptor

Ion channels can be involved in cell signaling because:

they receive signals from other cells and lead to a cellular response.