What role does a transcription factor play in a signal transduction pathway?

What role does a transcription factor play in a signal transduction pathway?

A. By binding a plasma membrane receptor it initiates a cascade
B. It relays a signal from the cytoplasm to the plasma membrane
C. It activates relay proteins
D. By binding to DNA it triggers the transcription of a specific gene
E. It is a plasma membrane protein that binds signal molecules

Answer: D

A toxin that inhibits the production of GTP would interfere with the function of a signal transduction pathway that is initiated by the binding of a signal molecule to _____ receptors.

A toxin that inhibits the production of GTP would interfere with the function of a signal transduction pathway that is initiated by the binding of a signal molecule to _____ receptors.

A- intracellular

B-steroid

C- ion-channel

D- G-protein-linked

E- receptor tyrosine kinase






Answer: D

Lipid-soluble signal molecules, such as testosterone, cross the membranes of all cells but affect only target cells because

Lipid-soluble signal molecules, such as testosterone, cross the membranes of all cells but affect only target cells because 

A)only target cells retain the appropriate DNA segments.
B) intracellular receptors are present only in target cells.
C) most cells lack the Y chromosome required.
D) only target cells possess the cytosolic enzymes that transduce the testosterone.
E) only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor.

Answer: B

Protein phosphorylation is commonly involved with all of the following except

Protein phosphorylation is commonly involved with all of the following except

A) regulation of transcription by extracellular signal molecules.
B) enzyme activation.
C) activation of G protein-coupled receptors.
D) activation of receptor tyrosine kinases.
E) activation of protein kinase molecules.

Answer: C

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells? 

A) Enzymatic activity was proportional to the amount of calcium added to a cell-free extract.
B) Receptor studies indicated that epinephrine was a ligand.
C) Glycogen breakdown was observed only when epinephrine was administered to intact cells.
D) Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined.
E) Epinephrine was known to have different effects on different types of cells.

Answer: C

The activation of receptor tyrosine kinases is characterized by

The activation of receptor tyrosine kinases is characterized by 

A) dimerization and phosphorylation.
B) IP3 binding.
C) a phosphorylation cascade.
D) GTP hydrolysis.
E) channel protein shape change.

Answer: A

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

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

A) receptor tyrosine kinase
B) G protein-coupled receptor
C) phosphorylated receptor tyrosine kinase dimer
D) ligand-gated ion channel
E) intracellular receptor

Answer: D

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because 

A) they are species specific.
B) they always lead to the same cellular response.
C) they amplify the original signal manyfold.
D) they counter the harmful effects of phosphatases.
E) the number of molecules used is small and fixed.

Answer: C

If an adult person has a faulty version of the human-analog to ced-4 ofthe nematode, which of the following might more likely result?

If an adult person has a faulty version of the human-analog to ced-4 ofthe nematode, which of the following might more likely result? 

A) neurodegeneration
B) activation of a developmental pathway found in the worm but not in humans
C) a form of cancer in which there is insufficient apoptosis
D) webbing of fingers or toes
E) excess skin exfoliation

Answer: C

Human caspases can be activated by

Human caspases can be activated by 

A) irreparable DNA damage or protein misfolding.
B) infrequency of cell division.
C) high concentrations of vitamin C.
D) a death-signaling ligand being removed from its receptor.
E) electron transport.

Answer: A

The main proteases involved in apoptosis are

The main proteases involved in apoptosis are 

A) ced-3 and ced-4.
B) inactive.
C) cytochromes.
D) caspases.
E) G proteins.

Answer: D

Why has C. elegans proven to be a useful model for understanding apoptosis?

Why has C. elegans proven to be a useful model for understanding apoptosis? 

A) The animal has very few genes, so that finding those responsible is easier than in a more complex organism.
B) The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.
C) This plant has a long-studied aging mechanism that has made understanding its death just a last stage.
D) While the organism ages, its cells die progressively until the whole organism is dead.
E) All of its genes are constantly being expressed so allof its proteins are available from each cell.

Answer: B

The termination phase of cell signaling requires which of the following?

The termination phase of cell signaling requires which of the following? 

A) removal of the receptor
B) activation of a different set of relay molecules
C) converting ATP to camp
D) reversing the binding of signal molecule to the receptor
E) apoptosis

Answer: D

What are scaffolding proteins?

What are scaffolding proteins? 

A) ladder-like proteins that allow receptor-ligand complexes to climb through cells from one position to another
B) microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores
C) large molecules to which several relay proteins attach to facilitate cascade effects
D) relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing
E) proteins that can reach into the nucleus of a cell to affect transcription

Answer: C

The use of beta 2 antagonist drugs may be useful in asthma because

The use of beta 2 antagonist drugs may be useful in asthma because 

A) they may increase constriction of the skeletal muscle of the chest wall.
B) they may increase heart rate and therefore allow the patient to get more oxygen circulated.
C) they may dilate the bronchioles by relaxing their smooth muscle.
D) they may override the beta blockers that the patient is already taking.
E) they may obstruct all G protein-mediated receptors.

Answer: C

As humans, we have receptors for two kinds of beta adrenergic compounds such as catecholamines. Cardiac muscle cells have beta 1 receptors that promote increased heart rate. Some drugs that slow heart rate are called beta blockers. Smooth muscle cells, however, have beta 2 receptors which mediate muscle relaxation. Blockers of these effects are sometimes used to treat asthma. The description above illustrates which of the following?

As humans, we have receptors for two kinds of beta adrenergic compounds such as catecholamines. Cardiac muscle cells have beta 1 receptors that promote increased heart rate. Some drugs that slow heart rate are called beta blockers. Smooth muscle cells, however, have beta 2 receptors which mediate muscle relaxation. Blockers of these effects are sometimes used to treat asthma. The description above illustrates which of the following? 

A) Just because a drug acts on one type of receptor does not mean that it will act on another type.
B) Beta blockers can be used effectively on any type of muscle.
C) Beta adrenergic receptors must be in the cytosol if they are going to influence contraction and relaxation.
D) The chemical structures of the beta 1 and beta 2 receptors must have the same active sites.

Answer: A

Which of the substances below is a protein that can hold several other relay proteins as it binds to an activated membrane receptor?

Which of the substances below is a protein that can hold several other relay proteins as it binds to an activated membrane receptor? 

A) active transcription factor
B) third messenger
C) ligand
D) scaffolding protein
E) protein kinase





Answer: D

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

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

A) lower cytoplasmic levels of cAMP
B) an increase in receptor tyrosine kinase activity
C) a decrease in transcriptional activity of certain genes
D) an increase in cytosolic calcium concentration
E) a decrease in G-protein activity

Answer: C

One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of blood in the penis, facilitating erection. cGMP is inhibited, therefore the signal is prolonged. The original signal that is now inhibited would have

One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of blood in the penis, facilitating erection. cGMP is inhibited, therefore the signal is prolonged. The original signal that is now inhibited would have 

A) hydrolyzed cGMP to GMP.
B) hydrolyzed GTP to GDP.
C) phosphorylated GDP.
D) dephosphorylated cGMP.
E) removed GMP from the cell.

Answer: A

Which of the following is a correct association?

Which of the following is a correct association? 

A) kinase activity and the addition of a tyrosine
B) phosphodiesterase activity and the removal of phosphate groups
C) GTPase activity and hydrolysis of GTP to GDP
D) phosphorylase activity and the catabolism of glucose
E) adenylyl cyclase activity and the conversion of cAMP to AMP

Answer: C