cELL bIO cH 15
Auxin hormones function in plants to __________________________
allow plants to sense light direction
Desensitization __________.
allows a cell to respond to a change in its environment, rather than continuing to fire endlessly in the presence of an unchanging environment
Nitric oxide is involved in which of the following biological processes?
anticoagulation visual perception smooth muscle relaxation all of these are correct answers
What holds Ras at the inner surface of the plasma membrane?
attachment to a lipid group that is embedded in the inner leaflet of the bilayer
What might be the result if cells that you are culturing acquire a mutation in a protein-tyrosine kinase that prevents the protein from being regulated in a normal fashion and keeps it continually in an inactive state?
cessation of cell division
Current Attempt in Progress What stimuli below can change the cytosolic concentrations of Ca2+ ions dramatically within certain plant cells?
changes in light changes in pressure changes in the concentrations of abscisic acid all of these are correct answers
The activation of a common effector by signals from a variety of unrelated receptors, each of which binds to its own ligand, is called _________.
convergence
What is activated by calcium ions entering an egg cell just after fertilization?
cyclin-dependent kinases that drive the zygote toward its first mitotic division
What phrase below is an accurate description of caspases?
cysteine proteases activated at an early stage of apoptosis proteases with a key cysteine residue in their catalytic site all of these answers are correct
Why are G-protein coupled receptors often known as 7TM receptors?
They have 7 transmembrane α-helices.
What allows cells to respond to an extracellular messenger molecule?
They must express receptors that specifically recognize and bind that particular messenger molecule.
Which statement is INCORRECT regarding biosensors? A biosensor should be nonselective in what it detects A biosensor should be able to detect small quantities of molecules of interest A biosensor should provide reproducible results A biosensor should function over a wide temperature range
A biosensor should be nonselective in what it detects
No matter how the signal initiated by the binding of a ligand is transmitted (via a second messenger or by protein recruitment), what is the outcome of that signal?
A protein at the top of an intracellular signaling pathway is activated.
________ is an inorganic gas that has been shown to act as a second messenger that ________. A) NO, induces the relaxation of the smooth muscles of blood vessels B) N2O2, induces the relaxation of the smooth muscles of blood vessels C) Nitric oxide, can induce neurotransmission Answers A and C are correct
Answers A and C are correct
What is the relationship between the formation of IP3 and the elevation of intracellular [Ca2+]?
Binding of IP3 to the smooth ER causes releases of calcium.
Which of these is NOT currently an application for biosensors? Blood glucose monitor for diabetics Environmental pollutant detector Blood cholesterol monitor for heart attack survivors Food contaminant detectors
Blood cholesterol monitor for heart attack survivors
Once the kinase domain of receptor protein-tyrosine kinase has been activated, what does the activated receptor protein-tyrosine kinase do?
Each receptor subunit phosphorylates its partner on tyrosine residues found in regions adjacent to the kinase domain.
What is the largest protein superfamily encoded by animal genomes?
G-protein coupled receptors
Arrestins form a small group of proteins that bind _______ and compete for binding to _______ with ____________.
GPCRs, those GPCRs, heterotrimeric G proteins
Which of the following is true of calmodulin when it is involved in eliciting a response?
It contains four binding sites for calcium. The calcium-calmodulin complex may bind to a protein kinase. The calcium-calmodulin complex can stimulate gene transcription. All of these are correct answers.
By what mechanism does cholera toxin elicit the symptoms of cholera?
It modifies Gα-subunits and inhibits their GTPase activity in the cells of the intestinal epithelium. Adenylyl cyclase molecules remain in the active mode and continue making cAMP when they normally should not. Adenylyl cyclase molecules remain in the active mode, causing intestinal epithelium cells to secrete large volumes of fluid into the intestinal lumen. All of these answers are correct.
An experiment in which acetylcholine, given to cells whose RNA nucleotide triphosphates were previously labeled by exposure to radiolabeled orthophosphate, resulted in the radiolabeling of membrane phospholipids like phosphatidylinositol and their derivatives, the phosphoinositides. What did this suggest to the researchers who performed the experiment?
It suggested that inositol-containing lipids can be phosphorylated by specific lipid kinases that are activated in response to extracellular messenger molecules like acetylcholine.
You homogenize liver tissue forming a broken-cell preparation and treat the preparation with epinephrine and/or glucagon. What happens in the broken-cell preparation?
Phosphorylase activity increases.
What is a function of apoptosis in vertebrates?
Removal of cells with genetic damage. Removal of those neurons that fail to find their way to the target tissue Removal during embryonic development of T lymphocytes that possess receptors capable of binding tightly to proteins present on the surface of normal cells within the body. All of these answers are correct.
Imagine that you are conducting experiments and you have a cell line that responds to an external hormonal signal by entering the apoptotic pathway. How would these cells respond to this hormonal signal if you could instantly and completely inactivate the Bcl-2 protein?
Since Bcl-2 normally protects cells from apoptosis, loss of this protein would cause these cells to go through apoptosis.
Which of the following supports the ligand-mediated model of receptor dimerization?
Some growth and differentiation factors like PDGF or CSF-1 are composed of two similar or identical disulfide-linked subunits, each of which has a binding site for a receptor.
How does the immune system manage to avoid recognizing and attacking normal cells within the body?
T lymphocytes that have the ability to recognize normal cells within the body are eliminated by apoptosis early in the development of the immune system.
How do docking proteins lend versatility to the signaling process mediated by the receptor protein-tyrosine kinase?
The ability of the receptor to turn on signaling molecules can vary with the docking proteins expressed in a particular cell.
If the receptor is degraded along with its ligand after internalization, what is the effect on the cell's ability to respond to a hormone?
The cell has decreased sensitivity to subsequent stimuli.
Where are steroid receptors generally located and where do they bind the steroid hormone once it enters the cell?
They are located and bind the steroids in the cytoplasm.
The IP3 receptor is also a __________.
a calcium channel
What kinds of responses may be initiated when signals traveling down signaling pathways reach their target proteins, which are usually involved in basic cellular processes?
a change in gene expression activation of DNA synthesis a change in ion permeability all of these are correct answers
Perception of sweet, savory and bitter tastes depends upon _________.
a compound interacting with a G protein coupled receptor on the receptor cell surface
What stimulus triggered by the binding of acetylcholine then activates nitric oxide synthase?
a rise in cytoplasmic Ca2+ concentration
Auxin signaling involves the process of _______________________________.
binding promoters to transcription factors of the auxin response factor (ARF) family. dimerizing repressors of the Aux/IAA family which, when bound by AFRs can lower transcription activity initiating a "molecular glue"-like activity which brings Aux/IAA and E3 ubiquitin ligase together to degrade transcriptional repressotrs all statements are correct
The activation of a variety of different effectors by signals from a single receptor binding a single ligand is referred to as ________.
divergence
What cells are responsible for regulating the diameter of the leaf pores or stomata?
guard cells
In which of the following biological processes is nitric oxide NOT involved? hearing neurotransmission smooth muscle relaxation visual perception
hearing
When a foreign antigen binds to its receptor on a mast cell, it activates a ___________, which, in turn, activates an effector called __________.
heterotrimeric G protein, phosphatidylinositol-specific phospholipase C-β
Which of the following is NOT a mechanism that has been proposed to explain receptor dimerization of protein-tyrosine kinases?
inactive receptors possessing binding sites for another receptor
Which type of receptor is directly involved in a change of distribution of ions on opposite sides of the membrane?
ligand-gated ion channel
What role do activated steroid receptors play in the cell?
ligand-regulated transcription factors
Which of the following are natural ligands that bind to G-protein coupled receptors?
odorants and tastants opium derivatives photons all of these are correct answers
Where is the receptor for IP3 located?
on the surface of the SER
Which of the following signaling mechanisms is seen primarily in plants and not in animals?
protein histidine kinases
In which of the following processes do calcium ions play a key role?
synaptic transmission cell movement transcription all of these are correct answers
In autocrine signaling, _________.
the cell producing the messenger expresses receptors on its surface that can respond to that messenger
How were nitroglycerine's therapeutic benefits discovered?
the fact that dynamite factory workers with heart conditions had less angina on days that they worked
Binding of epinephrine and/or glucagon to its specific receptor protruding from the plasma membrane of a target cell results in _________.
the inhibition of glycogen synthase the activation of protein kinase A the release of glucose into the bloodstream all of these are correct answers
In endocrine signaling, _________.
the messenger molecules reach their target cells via passage through bloodstream
Death by apoptosis is a neat, orderly process characterized by _________.
the overall shrinkage in volume of the cell and its nucleus and the dissection of the chromatin into small fragments the loss of adhesion to neighboring cells the rapid engulfment of the "corpse" by phagocytosis all of these answers are correct
Trans-autophosphorylation refers to ___________________.
the protein kinase activity of one receptor-protein tyrosine kinase subunit of a dimer phosphorylating the tyrosine residues in the cytoplasmic domain of the other receptor of the dimer
In cells exposed to stressful stimuli, like X-rays or damaging chemicals, what response does the MAP kinase cascade coordinate?
withdrawal from the cell cycle
