Cell Communication

In yeast (Saccharomyces cerevisiae), the two sexes are called
1. S plus and S minus.
2. a and alpha.
3. a and b.
4. b and beta.
5. male and female.
Which of the following is true of the mating signal-transduction pathway in yeast?
1. The pathway carries an electrialc signal between mating cell types.
2. Mating type "a" secretes a signal called a-factor.
3. The moleculrar details of the pathway in yeast and in animals are very different.
4. Scientists think the pathway evolved long after multicellular creatures appeared on Earth.
In the yeast signal-transduction pathway, after both types of mating cells have released the mating factors and the factors have bound to specific receptors on the correct cells,
1. binding induces changes in the cells that lead to cell fusion.
2. the cells then produce the a-factor and the alpha-factor.
3. one cell nucleus binds the mating factors and procudes a new nucleus in the opposite cell.
4. the cell membranes fall apart, releasing the mating factors that lead to new yeast cells.
Which of the following responses would be expected in myxobacteria when nutrients are scare?
1. Cells would cannibalize each other unless they secrete a chemical signal telling the other myxobacteris they are alike.
2. Cells secrete an a-factor and an alpha-factor signal that releases new nutrients.
3. Starving cells secrete a chemical signal that simulates other cells to aggregate in the soil and form spores.
4. The starved cells secrete a signal to other cells that it is time to move to another environment.
5. Both C and D are expected responses.
Target cells in an animal that lack receptors for local regulators
1. could compensate by receiving nutrients via an a-factor.
2. could develop normally in response to neurotransmitters instead.
3. would divide but could never reach full size.
4. would not be expected to multiply in response to growth factors from nearby cells.
5. All of these are expected outcomes of cells missing these receptors.
Paracrine signaling
1. involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.
2. requires nerve cells to release a neurotransmitter into synapse.
3. occurs only in paracrine yeast cells.
4. has been found in plants but not animals.
5. involves mating factors attaching to target cells and causing production of new paracrine cells.
Which of the following is TRUE of synaptic signaling and hormone signaling?
1. Hormone signaling occurs in animals only.
2. Hormone signaling is important between cells that are at greater distances apart than in synaptic signaling.
3. Both use neurotransmitters, but hormone signaling is for adjacent cells in animals only.
4. Both are forms of paracrine signaling.
The old saying "one rotten apple spoils the whole barrel" comes from chemical signaling in plants
1. by an increased uptake of carbon dioxide during repiration in target cells.
2. via a local regulatro for apple development.
3. by release of ethylene gas as a plant hormone for ripening.
4. via an a/alpha cell-signal system in the rotten apple.
5. None of these explains the saying.
From the perspective of the cell receiving the message, the three stages of cell signaling are
1. paracrine, local, and synaptic stages.
2. signal reception, signal transduction, and cellular response.
3. signal reception, nucleus disintegration, and new cell generation.
4. called the alpha, beta, and gamma stages.
5. signal reception, cellular response, and cell division.
The signal-transduction pathway in animals that use epinephrine
1. involves activation of glycogen breakdown in liver and skeletal muscle cells.
2. is a classic example of synaptic signaling.
3. is a classic example of paracrine signaling.
4. operates independently of hormone receptors on target cells.
5. None of these describes the epinephrine system.
An animal is born without a fully functional adrenal gland. Of the following, the most likely consequence would be
1. poor production of insulin.
2. inability of the cells to divide in the gland
3. poor mobilization of energy reserves during mental stress
4. loss of ability to transmit signals through a synapse
5. overproduction of blood glucose.
Sutherland discovered that epinephrine
1. signals bypass the plasma membrane of cells
2. lowers blood glucose by binding to liver cells
3. interacts with insulin inside muscle cells.
4. does not interact directly with glycogen phosphorylase
Chemical signal
1. pathways operate in animals, but few operate in plants.
2. systems are absent in bacteria, but are plentiful in yeast.
3. pathways in nature involve the release of hormones into the blood.
4. systems usually involve detection by binding to a target cell survace protein.
The process of transduction usually begins
1. when the chemical signal is released from the alpha cell.
2. when the signal molecule changes the receptor protein in some way.
3. after the target cell divides.
4. after the third stage of cell signaling is completed.
5. when the hormone is released from the gland into the blood
A selective advantage of cell signaling is
1. it allows some organism to evolve without a nervous system.
2. to ensure timing of communication between cells in different parts of an organism
3. to ensure that crucial activities occur in the right cells at the right time.
4. All of these are selective adbantages of cell signaling.
5. None of these are selective advantages of cell signaling.
Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to
1. a specific catalytic site of an enzyme binding to a substrate.
2. DNA encoding a message into RNA
3. a particular metabolic pathway operating within a specific organelle.
4. an enzyme with an optimum pH and temperature for activity.
5. genes making up a chromosome
A small molecule that specifically binds to a larger one
1. is called a signal transducer.
2. is a ligand.
3. is a ploymer.
4. seldom is involved in hormone signaling.
5. usually terminates a signal reception.
Most signal molecules
1. never enter the cytosol of a target cell
2. are water soluble
3. can pass through the plasma membrane.
4. None of these apply to most signal molecules.
5. All of these apply to most signal moleclues.
Which of the following signal systems does NOT use G-protein-linked receptors?
1. yeast mating factors
2. epinephrine
3. neurotransmitters
4. None of these use G-protein-linked receptors.
5. All of these use G-protein-linked receptors
The signaling system in an animal cell lacking the ability to produce GTP
1. would not be able to activiate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
2. could activate only the epinephrine system.
3. was discovered by Sutherland, who won the Nobel Prize for this work.
4. would be able to carry out reception and transduction, but would not be able to respond to a signal
G proteins and G-protein receptors
1. are found only in animal cells.
2. are found only in bacterial cells.
3. are thought to have evolved very early, possibly as sensory receptors in ancient bacteria.
4. probably evolved from an adaptation of the Krebs cycle.
Cholera is a widespread, serious disease of humans. Scientists have been studing ways to control the disease. Effective controls would require researh on
1. the effect of the cholera toxin on synaptic signaling in humans.
2. mating factors in the disease-causing bacteria.
3. the structure and function of the bacteria's tyrosine-kinase receptors.
4. the effect of the cholera toxin on G-pathway proteins.
Membrane receptors that attach phosphates to specific amino acids in proteins are
1. not found in humans.
2. called tyrosine-kinase receptors
3. a class of GTP G-protein signal receptors.
4. associated with several bacterial diseases in humans.
5. important in yeast mating factors that contain amino acids.
The ability of a single ligand binding to a receptor protein to trigger several pathways
1. is characteristic of the synaptic signal system.
2. is unique to the yeast mating system.
3. does not occur in animals, but is common in bacteria.
4. is a key difference between tyrosine-kinase and G-protein-linked receptor systems.
5. is common to all plasma membrane receptor proteins.
Ligand-gated ion channels
1. are important in the nervous system.
2. lead to changes in sodium and calcium concentrations in cells.
3. open or close in response to a chemical signal.
4. None of these describe ligand-gated ion channels.
5. All of these describe ligand-gated ion channels.
The general name for an enzyme that transfers phosphate groups from ATP to a protein is
1. phosphorylase
2. phosphatase
3. protein kinase
4. ATPase
5. There is no general name for such an enzyme
In general, a signal transmitted via phosphorylation of a series of proteins
1. brings a conformational change to each protein.
2. requires binding of a hormone to a cytosol receptor.
3. cannot occur in yeasts because they lack protein phosphatases.
4. always results in enzyme activation inside the target cell.
5. allows target cells to change their shape and therefore their activity.
The activity of a protein regulated by phosphorylation
1. depends mostly on the concentration of inorganic phosphate inside the cell.
2. depends on the balance in the cell between active kinase and active phosphatase enzymes.
3. is dependent on the site of attachment of the protein to the plasma membrane.
4. is independent of kinase activity, but directly dependent on phosphatase activity inside the cell.
5. None of these describe the activity of a protein regulated by phosphorylation.
A plant deficient in calcium could experience several problem, including
1. poor response to signals of stress, drought, or cold
2. decreased response to epinephrine.
3. overactive cyclic AMP responses.
4. stimulated G-protein signals, resulting in abnormal growth.
5. All of these could be responses to low calcium in a plant.
An animal deficient in adenyl cyclase
1. would not be able to transmit nerve impluses via a synapse.
2. could not convert GTP to ATP.
3. would lack plasma membrane-bound receptors.
4. would not respond properly to epinephrine.
5. would be unable to carry out all of the above activities.
Which of the following is NOT considered a secondary messenger?
1. cAMP
2. GTP
3. calcium ions
4. diacylglycerol
5. inositol triphosphate
Which of the following is NOT true of calmodulin?
1. It is a calcium ion binding protein.
2. It is present in high levels in eukaryotic cells.
3. It mediates many calcium-regulated processes in cells.
4. All of the above are ture of calmodulin.
5. None of the above are ture of calmodulin.
Transcription factors
1. regulate the synthesis of DNA in response to a signal.
2. transcribe ATP into cAMP
3. initiate the epinephrine response in animal cells.
4. None of the above is true of transcription factors.
The response of a particular cell to a specific chemical signal
1. depends on its particular collection of receptor proteins.
2. depends on its particular collection of relay proteins.
3. depends on its particular collection of proteins needed to carry out the response.
4. The response of a particular cell to a specific chemical signal depends on all of the above.
5. The response of a particular cell to a specific chemical signal depends on none of these.
Which of the following is NOT true of cell signaling?
1. The key to a cell's continuing receptiveness to regulation is the reversibility of the changes that signals produce
2. Ligand binding is critical to a signal response.
3. Cell signaling has been shown to be important in animals, fungi, and bacteria but less so in plants.
4. Animal cells communicate with nearby cells by secreting local regulators or neurotransmitters at synapses.
5. All of the above are true of cell signaling.
Which of the following is NOT part of the phosphorylation cascade model?
1. A signal molecule binds to a membrane receptor protein.
2. Protein kinase is activated.
3. GTP donates a phophate group to an inactive protein kinase.
4. A specific protein is activated via phosphorylation.
5. A cellular response is initiated.
Which of the following is the best explanation for the inability of an animal cell to reduce the calcium ion concentration in its cytosol compared to the extracellular fluid?
1. blockage of the synaptic signal.
2. loss of the transcription factors.
3. a plasma membrane impervious to calcium ions.
4. low oxygen concentration around the cell.
Which of the following is NOT true of cell communication system?
1. Cell signaling was an early event in the evolution of life.
2. Communication cells may be far a part or close together.
3. Most signal receptors are bound to the outer membrane of the nuclear envelope
4. Protein phosphorylation is a major mechanism of signal transduction.
5. In response to a signal, the cell may alter activities by changes in cytosol activity or in transcription of RNA.