BIO 201 EXAM 2
The last product in a reaction pathway often regulates the activity of the first enzyme in the branch of the pathway that is unique to its production when the concentration of the product gets very high. Because the structure of the product is very likely to differ substantially from that of the the enzyme's normal substrate, this type of regulation is most likely:
Allosteric inhibition
Which adaptation specific to becoming multicellular compensates for the destabilizing effect of increased size? (Think carefully about answer choices!)
Both ECM and tight junctions
Which of the following is a DISADVANTAGE of endocrine signaling?
By the time it reaches the target cell, the ligand concentration is likely to be low.
Which of the following is/are required in order for an endosome to be transported from the plasma membrane to the Golgi complex? (Select all that apply!)
Microtubules GTP Dynein Actin Myosin ATP Kinesin
Which of the following is/are found in bacteria but not eukaryotes? Peptidoglycan Mitochondria Single-stranded DNA All of the above
Peptidoglycan
True or False: The concentration of K+ inside the cell is higher than it is outside.
true
Consider the reaction: A <=> B. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, and [B] = 1.1 M. Keq' for this reaction is ____ and ∆G°' is _____. (You do not need a calculator for this.)
> 1; < 0
If it were injected directly into liver cells, cAMP would have the effect of:
Activating Protein Kinase A and, therefore, glycogen breakdown
Protons (H+) are moved up their concentration gradients into the lysosome in order to activate lysosomal enzymes. This is an example of:
Active transport
Based on our model for the evolution of the nucleus, which of the following organelles is likely evolved from plasma membrane infoldings?: Rough ER Smooth ER Golgi complex All of the above
All the above
The active and inactive forms of a hypothetical enzyme are shown below. (The polypeptide is represented by the colored rectangles and grey lines holding them together.) The middle rectangle is the catalytic domain, and the reaction it is catalyzing is also shown. This form of enzyme regulation is _______.
Allosteric activation
The enzyme phosphofructokinase-1 (PFK-1) catalyzes the reaction F6P + ATP --> F1,6BP + ADP during glycolysis. When ATP concentrations get very high, ATP also binds to a location on PFK-1 outside of the active site, preventing it from catalysis. This is an example of:
Allosteric inhibition
The H+ ATPase (a.k.a. "proton pump") creates electrochemical gradients across the membranes of many protists. This is an example of:
Direct active transport.
After you eat, insulin is secreted by pancreatic Beta cells into the bloodstream, where it diffuses throughout the body to bind to receptors on target cells, telling them to take up glucose. This mode of signaling is referred to as:
Endocrine
The reaction shown above is: ends with OH
Exergonic
What type of transport brings glucose into cells soon after eating a large meal?
Facilitated diffusion
True or False: The concentration of Ca++ inside the cell is higher than it is outside.
False
True or false: if ΔS > 0, the reaction is definitely exergonic.
False
Which of the following is a disadvantage of being multicellular?
More difficult to absorb nutrients Greater energy needs More difficult to absorb nutrients Reproduction more complicated
If you wanted to decrease liver cell responses to epinephrine, which of the following classes of enzymes would you want to increase in activity?
Protein phosphatase (catalyzes dephosphorylation)
What would likely happen to a cell treated with a compound that causes lysis (breakage) of peroxisomal membranes?
Proteins in the cytoplasm would be damaged.
Specific inhibitors of dyneins have yet to be discovered. When they are discovered, how would they most likely affect cells?
Reduce retrograde transport of endosomes
What is the second messenger in the receptor tyrosine kinase signaling pathway?The enzyme MAPK that gets transported into the nucleus to activate gene transcription
The enzyme MAPK that gets transported into the nucleus to activate gene transcription The kinase The small GTPase ras The enzyme MAPK that gets transported into the nucleus to activate gene transcription None of the above(this is the answer)
Which of the following is NOT consistent with the fluid mosaic model of cell membranes? Membrane-spanning proteins are always oriented in the same way in the membrane. The phospholipid content of the inner and outer leaflets of the membrane are similar. Some proteins are unable to diffuse laterally in the membrane. Cell membranes are lipid bilayers
The phospholipid content of the inner and outer leaflets of the membrane are similar
Which of the following is true of steroid hormones but not a signaling molecule such as a ligand for G-protein coupled receptors?
Their receptors regulate gene transcription.
Which of the following is true for all enzymes?
They alter the transition state.
A major function of the epithelium in animals is to prevent entry of pathogens and toxins from the environment. Which of the following is common to all epithelial cells?
They are held together by tight junctions.
Which of the following is true for all enzymes? They decrease ΔG. They increase the reaction rate. They provide the energy to get over the activation energy barrier. All of the above
They increase the reaction rate.
Which of the following is true of both GPCR signaling and steroid hormone signaling?
They may result from endocrine signals.
True or False: The concentration of Na+ outside the cell is higher than it is inside.
True
Fill in the blank: The name of the cytoskeleton fiber that polymerizes to form pseudopods during amoeboid cell migration is called ___. (one word; spelling matters!)
actin
What is the second messenger in the receptor tyrosine kinase signaling pathway? The kinase The small GTPase ras The enzyme MAPK that gets transported into the nucleus to activate gene transcription None of the above
none of the above
What do microtubules and actin have in common?
they are both an enzyme
Cell adhesion molecules are important components of:
tight junctions
The name of the protein dimer that multimerizes to form the cytoskeleton "railroad tracks" in the cell is ___. (one word; spelling matters!)
tubulin
Bacteria are approximately _____ in diameter; eukaryotic cells are typically at least _____ times this size.
1µm; 10x
Loss of peptidoglycan, combined with increased cell size during evolution of eukaryotes led to a less stable cell. Which of the following evolutionary adaptations compensated for this decreased structural stability?
Cytoskeleton
Which of the following is an advantage of multicellularity?
Greater mobility
Which of the following is least likely to diffuse through a cell's plasma membrane?
H+
Differential centrifugation separates particles based on _______ by applying different _______.
Mass; Spin speeds
Fill in the blank: The cytoskeleton "railroad tracks" used by motor proteins to transport vesicles and other organelles to and from the plasma membrane is called ___. (one word; spelling matters!)
microtubule
What is ∆G°' for the hydrolysis of ATP?
-7.3 kcal/mol
Consider the reaction: A + B <=> C + D. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, [B] = 0.1 M, [C] = 1.9 M, and [D] = 1.9 M; and the pH is 7.0. Keq for the reaction is _____ and the reaction is _____. (you do not need a calculator for this!)
361; exergonic
Protein makes up what percentage of the mass of the plasma membrane in a typical cell (e.g. red blood cells)?
50%
G-protein coupled receptors have ____ transmembrane domains.
7
The enzyme phenylalanine hydroxylase (PAH) catalyzes the conversion of the amino acid phenylalanine to tyrosine. If for this reaction, Keq' = 18.1, ∆G°' is ____ and the reaction is ____.
<0; Exergonic
Consider the reaction: A <=> B. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 1.5 M, and [B] = 0.5 M. Keq' for this reaction is ____ and ∆G°' is _____. (You should not need a calculator for this.)
<1; >0
The Krebs cycle involves the aerobic breakdown of glucose for energy. In the first reaction of the Krebs Cycle, the enzyme Aconitase converts Citric acid to its isomer, the molecule isocitrate. The Keq' for this reaction is approximately 0.1. ∆G°' for this reaction is therefore ____ and the reaction is ____.
>0; Endergonic
Imagine you are a drug developer aiming to inhibit epinephrine responses specifically in liver cells. Which of the following would accomplish this?
A kinase inhibitor
Collagen, an extremely important extracellular matrix protein, is constitutively secreted by fibroblast cells, a type of connective tissue cell. If you had a patient in which collagen is synthesized normally, but fails to be secreted into the extracellular matrix, which of the following would you examine as the likely cause of this problem? (Think very carefully before answering this question!)
A kinesin disorder
Which of the following correctly describes a second messenger?
A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.
Shown below is a branched reaction pathway, in which either D or E can be made from C, depending on which enzyme(s) are active. Imagine that D is necessary for the cell, but that it is beneficial to stop production of D when it reaches a certain threshold concentration in order to preserve A and C for other things (e.g. production of E). Which of the following is the best way to ensure this? E1-E4 are the enzymes that catalyze each of the reactions.
Allosteric inhibition of Enzyme 3 by D
Why did Palade and his colleagues use pancreatic acinar cells in their original Pulse-Chase experiment?
Almost all of the proteins produced by pancreatic acinar cells are secreted.
If you were attempting to identify natural product inhibitors of kinesin activity, which of the following would be a good assay for screening them?
Anterograde transport in cells
Liver cells respond to epinephrine by __________.
Breaking down glycogen.
Consuming very large amounts of certain foods/drinks can affect the digestive system in profound ways. Which of the following would LEAST likely cause some sort of osmotic shock to your stomach and intestinal cells if you consumed a very large amount of it in a short period of time?
Butter
As we learned in class, protein phosphatases catalyze removal of phosphate groups from proteins. How would the activity of a protein phosphatase affect liver cell responses to epinephrine?
Decrease glucose production
Which of the following is a disadvantage of being a multicellular organism?
Decreased structural stability
White blood cells migrate to a source of infection using amoeboid migration along the surfaces of endothelial cells. Imagine you have discovered a toxin that suppresses the immune system by specifically inhibiting pseudopod formation in white blood cells. Which of the following is your toxin's most likely mechanism of action?
Depleting the cell of ATP
Pancreatic acinar cells produce and secrete digestive enzymes into the duodenum. What would happen if pancreatic acinar cells were treated with a toxin that causes lysis (breakage) of smooth ER membranes?
Digestive enzymes would be immediately secreted into the duodenum.
"He was awakened in the middle of the night by a low growling that sounded as if it was coming from just outside his tent. In response, the cells of his adrenal medulla began to secrete epinephrine, causing his palms to sweat, his heart to race, and his hair to stand on end." Epinephrine is involved in what type of signaling as described in this passage?
Endocrine
One of the main differences between growth factor signaling (receptor tyrosine kinase receptors) and epinephrine signaling (G-protein coupled receptors) is that:
Epinephrine signaling is more likely to have a short-term, reversible effect.
ATP hydrolysis is highly _____ because it involves _____.
Exergonic; separation of negatively charged phosphate groups
The hormone glucagon is secreted by the pancreas in response to low blood sugar. Liver cells respond to glucagon by breaking down glycogen to form glucose, which is then release into the bloodstream for the other tissues. Based on this information, what mechanism is most likely used to transport glucose out of the cell into the bloodstream?
Facilitated diffusion
Which of the following is an enzyme? epinephrine G-alpha ATP All of the above None of the above
G-alpha
ras, a small GTPase, hydrolyzes GTP slowly on its own, but its enzymatic activity is increased significantly in the presence of GTPase activating proteins (GAPs). Imagine you discovered a novel mutation that prevents GAP from binding to ras. This mutation would have the effect of:
Increasing cell proliferation
A mutation that causes a decrease in the GTPase activity of G-alpha in liver cells would have the effect of:
Increasing the activity of Protein Kinase A Increasing the production of glucose Increasing the activity of Glycogen phosphorylase
Even though the blood glucose concentration may drop below the intracellular glucose concentration - for example, during a long fast - brain cells can still absorb glucose from the bloodstream. Under these circumstances, how does glucose get into the cells?
Indirect active transport
Unlike in animals, in which the Na+ gradient is used, it is the H+ gradient in some other species that fuels transport of other compounds up their concentration gradients. This type of transport is:
Indirect active transport
Cells shrink when you place them in a solution with a high concentration of the amino acid glycine. This indicates that the cell membrane:
Is NOT permeable to glycine but IS permeable to water
Which of the following is an advantage of endocrine signaling?
It affects large numbers of cells.
What happens to GTP in response to epinephrine binding to its receptor on liver cells?
It binds to G-alpha
Which of the following may be true for an enzyme?
It may chemically interact with its substrate.
Whooping cough, also known as pertussis, is caused by the bacterium Bordetella pertussis. Some of its effects result from production of Pertussis toxin, which prevents Gα from binding to G-protein coupled receptors, and thereby "locking" Gα in the GDP-bound state. If you treated liver cells with Pertussis toxin, how would it affect liver cell responses to epinephrine?
It would decrease glucose production.
Dr. Hutson really likes coffee. Despite that, this is not a question about caffeine. How does a compound that inhibits the GTPase activity of Gα affect liver cell responses to epinephrine?
It would increase glucose production.
G-alpha is not only an activator of Adenylate cyclase, but it is a GTPase. How does mutation in G-alpha that decreases its GTPase activity affect liver cell responses to epinephrine?
It would increase glycogen phosphorylase activity.
What would happen to the cytoskeleton if you replaced all of the normal GTP in cells with a chemical variant of GTP that acts like normal GTP but cannot be hydrolyzed (broken down) to GDP?
It would prevent microtubule depolymerization.
Which of the following enzymes catalyzes phosphorylation of proteins using a phosphate group from ATP?
Kinases
All living organisms, including both bacteria and Eukaryotes have: (Select all that apply; you may want to review Lecture 7 in addition to the current material for this one)
L-amino acids the ability to extract energy from the environment to do work D-monosaccharides Plasma membranes made of phospholipids double stranded DNA Ribosomes
Which of the following is a disadvantage of being a multicellular organism specifically as opposed to unicellular? (read and think carefully!)
More difficult to absorb nutrients
ATP hydrolysis provides the energy for the endergonic reaction: X + Y <=> Z . The mechanism by which this occurs is that compound X is phosphorylated using the phosphate group from ATP. dephosphorylation of X, which itself is exergonic, makes it possible for X and Y to combine to form Z. In this scheme X-P can be considered the transition state. The entire reaction, including ATP is as follows: X + Y + ATP <=> X-P + Y + ADP <=> Z + ADP + Pi
No, because it is irreversibly altered by the reaction
If you did a Pulse-Chase experiment using pancreatic acinar cells, but used radioactively-labeled ribonucleotides instead of proteins, what structure would contain radioactivity immediately after the Chase?
Nuclei
Which of the following do eukaryotes have that bacteria do not?
Nuclei
Which of the following can diffuse most easily through the cell membrane?
O2
Production of antibiotics is an arms race, given the speed with which bacteria can evolve antibiotic resistance. Antibiotics that ____ are most likely to be effective against bacteria without causing side effects to their human (or animal) patient.
Prevent synthesis of peptidoglycan
In the original Pulse-Chase experiment of Palade and colleagues, what can we conclude from the fact that radioactivity in the Golgi complex is initially very low, increases to its highest levels in 15 minutes, and then the radioactivity in Golgi decreases again to near zero by two hours?
Proteins are not made in the Golgi complex, but are transported in after they are synthesized and then eventually exit.
Where in the cell would you expect to see a Ca++ ATPase?
Smooth ER
Extracellular chloride ion (Cl-) concentrations are much higher than intracellular. This gradient is maintained in part by co-transport of K+ and Cl- out of the cell using indirect active transport. Maintenance of the Cl- concentration gradient using this mechanism is therefore dependent on:
The Na+/K+ ATPase
Imagine you walk into lab after spring break, and your TA hands you a beaker containing a solution of A, B, and C in water represented by the equilibrium shown below. If the solution has reached equilibrium, and the beaker is at pH 7.0, 25°C, and 1 atm pressure, what other information do you need to obtain in order to calculate ∆G°' for this reaction? A + B <=> C The concentrations of A, B, and C The molecular weights of A, B, and C The mechanism of the reaction The density of the solution All of the above
The concentrations of A, B, and C
Which of the following is NOT consistent with the fluid mosaic model of cell membranes?
The phospholipid content of the inner and outer leaflets of the membrane are similar.
Which of the following statements is TRUE? Some cytoskeletal elements are carbohydrates. Microtubules are static, but actin is dynamic. Actin is static, microtubules are dynamic. Tubulin and actin are both enzymes. All of the above
Tubulin and actin are both enzymes.
The Na+/K+ ATPase transports Na+ up its concentration gradient and K + ______ its concentration gradient. This is an example of ______ .
Up; Direct active transport
Chloride ion (Cl-) concentrations are approximately 10x higher outside of cells than inside. Imagine you discovered a novel protein that is required in liver cells for transporting Cl- out of the cell up its concentration gradient, and further found that this protein only functions if the Na+/K+ ATPase is active. Which of the following might you reasonably conclude about the Cl- transport protein?
a Na+/Cl- antiporter
Fill in the blank: The motor protein responsible for transporting endosomes from the plasma membrane to the interior of the cell is named ___. (spelling matters!)
dynein
Factors that increase membrane fluidity have the effect of _______ membrane permeability:
increase
Which of the following is an advantage of juxtacrine signaling?
it is fast
Fill in the blank: The motor protein responsible for transporting vesicles to the plasma membrane is named ___. (spelling matters!)
kinesin
