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Flashcards in Chapter 7 Deck (57):

Which of the following statements about cyclic AMP is false?

A. It can bind to, and thus open, ion channels in some sensory cells.
B. In some circumstances it can bind to a protein kinase int eh cytoplasm.
C. The enzyme adenylyl cyclase catalyzes its formation from ATP.
D. It is a second messenger.
E. It has enzymatic activity.



A benefit of the many steps involved in protein kinase cascades is that they allow for

A. some specificity of the reponse.
B. amplification of the signal.
C. information to eb communicated to the nucleus.
D. variation in the response.
E. All of the above



The signals that bind to receptors fo the same cell taht made them are known as 

A. paracrine signals.
B. parasitic signals.
C. autocrine signals.
D. hormones.
E. responders.



Which of the following are specialized cell junctions that allow neighboring cells to communicate directly?

A. Tight juncions
B. Gap junctions
C. Desmosomes
D. Ion channels
E. G proteins



The G protein-mediated cascade stimulated by epinephrine results in the phosphorylation of two key enzymes. The eventual results of this phosphorylation are the ___ of glycogen synthase and the ___ of glycogen phosphorylase.

A. stimulation; stimulation
B. stimulation; inhibition
C. inhibition; stimulation
D. inhibition; inhibition
E. inhibition; introversion



The membrane-lined bridges spanning the cell walls between plant cells are known as

A. gap junctions.
B. tight junction.
C. plasmodia.
D. plasmodesmata.
E. G protein receptors.



Which of the following is true?

A. Direct transduction is more common than indirect transduction.
B. In indirect transduction, second messengers mediate the interaction between the receptor and the cell's response.
C. Amplification never occurs via second messengers.
D. Indirect transduction occurs at the plasma membrane.
E. All of the above



Which of the following statements is true?

A. Some mammals have over 1000 genes for odor signal receptors.
B. The signal transduction pathway triggered by odorant molecules results int he opening of ion channels.
C. Each of the thousands of neurons int he nose expresses one of the odor signal receptors.
D. Odorant receptors are G protein-linked.
E. All of the above



The conformational change in EnvZ causes it to become a(n)

A. autocrine receptor.
B. responder.
C. ligand.
D. protein kinase.
E. phosphate group.



For a G protein to play its part in moving events forward in a signal pathway,

A. GDP must be release, and a GTP must occupy the nucleotide-bidning site.
B. GTP must be released, and a GDP must occupy the nucleotide-binding site.
C. cGMP must occupy the otherwise empty nucleotide-binding site.
D. cGMP must leave the otherwise occupied nucleotide-binding site.
E. None of the above



Which of the following is false?

A. Cells are bombarded with numerous signals, but they respond to only a few.
B. A cwell's receptors determine whether or not the cell will respond to a signal.
C. Receptor proteins are very specific.
D. There are only a few kinds of signal receptor proteins.
E. None of the above



To respond to a signal, a cell must have a(n) ___ molecule that can detect the signal.

A. paracrine
B. receptor
C. autocrine
D. responder
E. All of the above



The receptor of estrogen

A. is an ion channel receptor.
B. is a protein kinase receptor.
C. exists within the plasma membrane.
D. exists within the cytoplasm.
E. None of the above



What is the correct order for the following events in the interaction of a cell with a signal? (1) Alteration of cell function; (2) signal binds to receptor; (3) signal released from source; (4) signal transduction.

A. 1234
B. 2314
C. 3214
D. 3241
E. 3421



The major difference between a cell that responds to a signal and one that does not is the presence of a

A. DNA sequence that binds to the signal.
B. nearby blood vessel.
C. receptor.
D. second messenger.
E. transduction pathway.



Which of the following is not a consequence of a signal binding to a receptor?

A. Activation of receptor enzyme activity
B. Diffusion of the receptor in the plasma membrane
C. Change in conformation of the receptor protein
D. Breakdown of the receptor to amino acids
E. Release of the signal from the receptor



Steroid hormones such as estrogen act on target cells by

A. initiating second messenger activity.
B. binding to membrane proteins.
C. initiating gene expression.
D. activating enzymes.
E. binding to membrane lipids.



A nonpolar molecule such as a steroid hormone usually binds to a

A. cytoplasmic receptor.
B. protein kinase.
C. ion channel.
D. phospholipid.
E. second messenger.



Which of the following is not a common type of receptor?

A. Ion channel
B. Protein kinase
C. G protein–linked receptor
D. Cytoplasmic receptor
E. Adenylyl cyclase



Which of the following is not true of a protein kinase cascade?

A. The signal is amplified.
B. A second messenger is formed.
C. Target proteins are phosphorylated.
D. The cascade ends up at the mitochondrion.
E. The cascade begins at the plasma membrane.



Why do some signals (“first messengers”) trigger “second messengers” to activate target cells?

A. The first messenger requires activation by ATP.
B. The first messenger is not water soluble.
C. The first messenger binds to many types of cells.
D. The first messenger cannot cross the plasma membrane.
E. There are no receptors for the first messenger.



Which of the following is not a second messenger?

A. Calcium ion
B. Inositol trisphosphate
D. Cyclic AMP
E. Diacylglycerol



Plasmodesmata and gap junctions

A. allow small molecules and ions to pass rapidly between cells.
B. are both membrane-lined channels.
C. are channels about 1 mm in diameter.
D. are present only once per cell.
E. are involved in cell recognition.



Which of the following statements regarding chemical signaling systems (shown) is false?

A. Autocrine signals have an effect on the cells that secrete them.
B. Paracrine signals have an effect on nearby cells.
C. In larger organisms, circulating signals are carried from the environment to internal cells.
D. In a larger organism, most signals received by cells are chemical in nature.
E. The cells of our body can respond to a diverse array of chemical signals.



Consider the accompanying figure shown depicting the signal transduction mechanism in E. coli responsible for responding to increased solute concentration in the intermembrane space. Complete the following sentence: The _______ acts as a signal transducer in this system, while production of _______ is the cellular response.

A. phosphate; EnvZ
B. . OmpR protein; OmpF protein
C. EnvZ; OmpC protein
D. EnvZ; phosphate
E. EnvZ; OmpR protein



The acetylcholine (Ach) receptor shown here would be considered which of the following types?

A. Ion channel receptor
B. Protein kinase receptor
C. G protein-linked receptor
D. Cytoplasmic receptor
E. Nonpolar signal receptor



The insulin receptor shown is considered which of the following receptor types?

A. Ion channel receptor
B. Protein kinase receptor
C. G protein-linked receptor
D. Cytoplasmic receptor
E. Nonpolar signal receptor



In this figure, part of the signal transduction mechanism common to G protein-linked receptors is shown. Of the following steps in this pathway, select the step that would occur third in the sequence.

A. Activated G protein activates cellular enzymes.
B. Activated receptor binds to membrane-bound G protein.
C. Extracellular hormone (signal) binds to the receptor.
D. GDP bound to the G protein is exchanged for GTP, completing activation of the G protein.
E. Activated cellular enzymes catalyze the formation of products, effectively amplifying the signal inside the cell.



Which of the following statements regarding the signal amplification pathway shown is false?

A. In this cascade, Ras is a G protein.
B. In this cascade MAP kinase is responsible for stimulating cell division.
C. The cascade shown transmits an extracellular signal to the nucleus.
D. In this cascade, a single signal is capable of stimulating a single final effector molecule (MAP kinase).
E. In this cascade, a defect in Ras can result in cancer.



In the phosphorylase activation experiments conducted by Sutherland, Krebs, and Fischer, investigators incubated liver cell membranes with epinephrine. Following incubation, the investigators found that they could remove the membrane components and mix what was left with liver cell cytoplasm, resulting in activation of phosphorylase enzyme. What critical component was present in their membrane-depleted mixture that caused the activation of the phosphorylase enzyme?

A. Glycogen
B. Glucose
D. Adenylyl cyclase
E. Epinephrine



Which of the following statements regarding IP3 and DAG second messenger systems (shown) is false?

A. Protein kinase C requires DAG and Ca2+ to be activated.
B. Activation of phospholipase C requires the activity of activated G protein.
C. Phosphatidyl inositol (PTI) is produced by the activity of phospholipase C and stimulates the release of Ca2+ from the smooth endoplasmic reticulum.
D. IP3 is produced from PTI as an activity of phospholipase C.
E. Activated protein kinase C elicits a cellular response by phosphorylating target enzymes in the cell.



Many signaling pathways in cells make use of the calcium ion (shown). Cells often store large amounts of calcium intracellularly—for example, in the smooth endoplasmic reticulum. Cells store Ca2+ intracellularly because

A. calcium is much more effective as a signaling molecule than any other compound.
B. the cell cannot easily produce calcium.
C. facilitated diffusion channels in the endoplasmic reticulum membrane quickly remove Ca2+ from the cytoplasm, turning the signal off.
D. excessive calcium concentrations outside the cell are lethal to the it, therefore the cell must store large amounts of intracellular Ca2+ to counteract the external calcium levels.
E. calcium is the only second messenger molecule available to eukaryotic cells.



In the study conducted by Robert Furchgott on blood vessel constriction, a gaseous signal molecule (nitric oxide) was identified. This pathway revealed why nitroglycerin is an effective drug for treating angina (insufficient blood flow in the heart). Which of the following statements describes why this drug is effective?

A. Nitroglycerine directly stimulates the opening of Ca2+ channels.
B. Nitroglycerin binds to guanylyl cyclase enzymes, stimulating the production of cGMP.
C. Nitroglycerin blocks nitric oxide synthase activity, resulting in activation of guanylyl cyclase.
D. Nitroglycerin promotes the diffusion of nitric oxide across the membrane of smooth muscle cells.
E. Nitroglycerin releases nitric oxide, which then activates the signaling pathway without nitric oxide synthase activity.



Which of the following molecules is not involved in the signal transduction pathway used in the sense of smell (shown)?

A. Sodium channels
B. Receptor proteins
C. G proteins
E. Nitric oxide



Which of the following statements regarding the cascade of reactions leading to altered enzyme activity (shown) is false?

A. Glycogen synthase is inhibited in the cascade shown.
B. Phosphorylase kinase is inhibited in the cascade shown.
C. The binding of epinephrine results in the release of stored glucose in the cascade shown.
D. The binding of epinephrine results in the inhibition of glycogen synthesis in the cascade shown.
E. The cascade shown results in both the inhibition and activation of different enzymes.



Which of the following statements regarding gap junctions (shown) is false?

A. Gap junctions are channels that appear between adjacent cells.
B. Gap junctions allow molecules such as ATP to be shared between linked cells.
C. Since gap junctions allow sharing of compounds between linked cells, only a few gap junctions appear between linked cells.
D. Signal molecules can move through gap junctions.
E. Gap junctions function to allow metabolic cooperation between linked cells.



One of the most important functions of plasmodesmata in plant cells is to

A. allow rapid diffusion of small signaling molecules, such as hormones, between cells.
B. provide a mechanism to transport endoplasmic reticulum from cell to cell.
C. prevent viral infection between adjacent plant cells.
D. allow the transport of large molecules between adjacent plant cells.
E. allow the exchange of chloroplast organelles between adjacent plant cells.




(spelled out)


diacylglycerol (DAG)

in hormone action, second messenger produced by hydrolytic removal of the head group of certain phospholipids


indirect transduction

cell signaling mechanism in which second messenger mediates interation between receptor binding and cellular response



cytoplasmic strand connecting two adjacent plant cells; allows passage of some molecules



membrate extension traversing the plasmodesma, connecting ER of two plant cells


cyclic AMP

(long form)


cAMP (cyclic AMP)

second messenger formed from ATP


nitric oxide



nitric oxide (NO)

second messenger used in relaxation of muscles

neurotransmitter in nervous system


second messenger

compound released within a target cell following hormone binding to surface receptor; triggers further rxns  within a cell



chemical signal (e.g. hormone) that acts locally, near site of secretion


G protein

membrane protein involved in signal transduction

bound using GDP (inactive state) or GTP (active state)


protein kinase cascade

series of rxns in response to molecular signal in which series of protein kinases are activated in sequence; initial signal is amplified


ionsitol trisphosphate

intracellular second messenger derived from membrane phospholipids



protein channel linking adjacent animal cells in a gap junction


direct transduction

cell signaling mechanism in which receptor acts as the effector in the cellular response


signal transduction pathway

series of biochemical steps in which cell stimuli is translated into a cellular response


effector protein

protein responsible for cellular response to a signal transduction pathway in cell signaling



chemical signal that is binds to and affects the cell that secretes it


protein kinase

enzyme that catalyzes addition of a phosphate group from ATP to a target protein