AP Bio-Chapter 11

Multiple Choice

What is the best explanation for the disappearance of cells between segments of a palm leaf?

• action of a G protein

• amplification

• apoptosis

• a steroid receptor

• none of the above

Multiple Choice

Which best describes what a plasma membrane-spanning receptor does when it binds a signal?

• The receptor binds an extracellular signal molecule and passes it into the cell.

• Activated receptors directly produce a response to the signal.

• It uses the energy from the signal to power its transduction.

• Binding of the signal molecule alters the receptor's other binding sites and activities.

• It amplifies the signal, increasing its influence in the cell.

Multiple Choice

Which would cause the most problems for a cell-signaling pathway involving a G protein-coupled receptor?

• very low cytoplasmic pH

• lack of Ca²⁺

• not enough GTP in the cell

• excess DAG

Multiple Choice

Which correctly describes the use of ligand-gated ion channel receptors?

• Ligand binding is irreversible, resulting in a permanent change in this ion channel's activity.

• The binding site of this type of receptor is most often in the middle of the membrane.

• Once activated, this receptor will cause G proteins to bind with GTP.

• Once the ligand is bound, the ion channel activity can alter the local membrane potential and cytostolic concentration of the ion.

• The ligand involved is often a phosphate group that is covalently added to the cytostolic side of this ion channel.

Multiple Choice

A steriod hormone is bound by an intracellular receptor. The resulting complex is most likely to do what?

• open channels in the membrane for other substances to enter

• open channels in the nuclear envelope for cytoplasmic molecules to enter

• mediate the transfer of phosphate groups to/from ATP

• act as a transcription factor in the nucleus

• enable water-soluble molecules to diffuse across membranes

Multiple Choice

Which would cause the most problems for a cell-signaling pathway involving a steroid molecule?

• very low cytoplasmic pH

• lack of Ca²⁺

• not enough phosphate in the cell

• excess DAG

Multiple Choice

Which gives the most complete and correct description of a signal transduction pathway?

• binding of a signal molecule to a cell protein

• catalysis mediated by an enzyme

• sequence of changes in a series of molecules resulting in a response

• binding of a ligand on one side of a membrane that results in a change on the other side

• the cell's detection of a chemical or mechanical stimulus

Multiple Choice

Which correctly describes what happens during signal transduction inside a cell?

• Some fraction of the original signal is converted into something else and passed through the cell.

• Changes in protein activies and in other items in the cell are induced by an activated receptor.

• The original signal is amplified as it is passed through the cell.

• Energy from the signal is used to power the changes needed in the cell for a response.

• Some phenotypic feature of the cell is altered.

Multiple Choice

Phosphorylation of proteins in a kinase cascade does what?

• makes functional ATP

• distorts a protein from one functional state to another

• activates phosphatases to remove the phosphate group

• alters the permeability of the cell's membrane

• produces an increase in the cell's store of inorganic phosphates

Multiple Choice

Which can be second messengers?

• Ca²⁺

• cAMP

• DAG

• Ca²⁺ and cAMP

• Ca²⁺, cAMP, & DAG

Multiple Choice

Of the following events, which might typically occur third as a cell receives and responds to a signal?

• An enzyme cascade occurs, increasing the number of activated proteins.

• A signal molecule is bound by a transmembrane tyrosine kinase receptor protein.

• The receptor protein complex phosphorylates other proteins.

• A reconfigured protein binds to DNA, altering gene expression.

• Tyrosine kinase receptor subunits dimerize.

Multiple Choice

You have discoverd a drug that will prevent Ca²⁺ from acting as a second messenger. Your drug is targeted to the

• plasma membrane

• nuclear membrane

• endoplasmic reticulum

• plasma membrane and ER

• plasma/nuclear membrane and ER

Multiple Choice

If you wanted to block signaling involving a steroid molecule, which should you destroy?

• plasma membrane

• nuclear pores

• endoplasmic reticulum

• ribosomes

• none of the above

Multiple Choice

Which incorrectly describes a step in a signal transduction pathway?

• The second messenger can diffuse rapidly through the cytosol.

• After the rise in the concentration of the second messenger, it is often removed quickly by degradation or export from the cytosol.

• The proteins that will bind the second messenger are already present before there is a rise in its concentration.

• Synthesis of the enzyme that creates the second messenger occurs right after the signal is received.

• When the cell does not receive the signal, the second messenger is kept at a low concentration.

Multiple Choice

Which is the best example of amplification of signal?

• production of many molecules by many signal molecules

• activation of 100 molecules by a single signal binding event

• activation of a specific gene by a transcription factor

• conversion of the signal into many other types of molecules

• activation of a receptor by a hormone

Multiple Choice

A cell in C. elegans carrying out apoptosis properly depends in part on

• a protein that normally inhibits the process being turned off.

• the creation of a "death signal" by this cell.

• properly resetting all the transductive elements from the last use of this process.

• the receptor moving the "death signal" into the nucleus of the cell.

• turning off various nucleases and proteases in the cell.