Bio 201 exam 2 pract. questions
Which of the following SUPPORTS the endosymbiotic theory for the origins of mitochondria and chloroplasts? Mitochondria and chloroplasts are genetically similar to bacteria. Mitochondria and chloroplasts have double membranes. Mitochondria and chloroplasts divide independently of the cell. All of the above
All of the above
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: Competitive inhibition Covalent modification Zymogen activation Allosteric activation Allosteric inhibition
Allosteric inhibition
What happens to GTP in response to epinephrine binding to its receptor on liver cells? It gets phosphorylated It falls off of G-alpha It is hydrolyzed It binds to G-alpha
It binds to G-alpha
Which of the following is/are found in eukaryotes but not bacteria? Mitochondria Ribosomes Both ribosomes and phospholipids Phospholipids
Mitochondria
Shown here is a transmission electron micrograph (TEM) of the interior of a cell. What structure is circled, and what happens in this structure? Nucleus; Transcription Nucleus; Translation Smooth ER; Calcium storage Smooth ER; Protein processing, e.g. glycosylation Rough ER; Translation
Rough ER; Translation
The lipid:protein ratio in a typical membrane (e.g. red blood cells) is approximately: 10:1 2:1 1:1 1:2
1:1
Protons (H+) are moved up their concentration gradients into the lysosome in order to activate lysosomal enzymes. This is an example of: Ion channels Facilitated diffusion Simple diffusion Active transport
Active transport
The endosymbiotic theory explains the evolution of: Viruses Anaerobic bacteria All bacteria All Eukaryotes
All Eukaryotes
Based on our model for 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 of the above
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: Autocrine Paracrine Juxtacrine Endocrine
Endocrine
Which of the following is a mechanism by which cells ensure a strong response to a small amount of ligand? Receptor-mediated endocytosis GTP hydrolysis by G-proteins Enzyme cascades 2nd messengers All of the above
Enzyme cascades
ATP hydrolysis is highly _____ because it involves _____. Endergonic; removal of a phosphate group forming phosphoric acid, which decreases the pH Exergonic; separation of negatively charged phosphate groups Exergonic; alteration of the transition state Endergonic; breaking of covalent bonds
Exergonic; separation of negatively charged phosphate groups
True or false: Only mutations that alter amino acid residues in the active sites of enzymes affect the function of the enzyme. True False
False
Which of the following is an advantage of multicellularity? Easier to absorb nutrients More stable Increased mobility All of the above
Increased mobility
What do microtubules and actin have in common? They are both enzymes. They are both stable. They are both found in the center of the cell. They both require GTP for polymerization
They are both enzymes.
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 ciliated. They are held together by tight junctions. They secrete digestive enzymes. They are columnar.
They are held together by tight junctions.
Which of the following distinguishes plant cells from animal cells? They arose through endosymbiosis. They have mitochondria. They have circular genomes. They have cell walls and chloroplasts.
They have cell walls and chloroplasts.
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 never true of enzymes? They change the transition state of a reaction. They lower ΔG of a reaction. They interact chemically with the reactants. They are restored to their original form at the end of the reaction.
They lower ΔG of a reaction.
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 Cl- ATPase a K+/Cl- antiporter a Cl- channel. a Na+/Cl- antiporter
a Na+/Cl- antiporter
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
Fill in the blank: The name of the motor protein that uses actin as its cytoskeletal partner is called ___. (one word; spelling matters!)
myosin
In the original Pulse-Chase experiment of Palade and colleagues, what was does the % or # of grains on the y-axis represent? Secretory vesicles Leucine RNA Proteins
proteins
Pancreatic acinar cells were selected for the original original Pulse-Chase experiment of Dr. Palade and his colleagues because almost all of the proteins they produce are: Hormones Similar Secreted Enzymes
secreted
Cell adhesion molecules are important components of: tight junctions plant cell walls Extracellular matrix bacterial cell walls
tight junctions
Fill in the blank: 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 10 µm; 100x 100 µm; 10x 100µm; 100x
1µm; 10x
Protein makes up what percentage of the mass of the plasma membrane in a typical cell (e.g. red blood cells)? 5% 10% 25% 50%
50%
Which of the following correctly describes a second messenger? A protein, such as a G-protein, that is activated upon ligand binding to receptor. An enzyme such as Adenylate Cyclase that is activated upon ligand binding to receptor. An enzyme responsible for the cellular effects of a signal transduction pathway, like Protein Kinase A or Glycogen Phosphorylase. A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.
A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.
The H+ ATPase (a.k.a. "proton pump") creates electrochemical gradients across the membranes of many protists. This is an example of: Indirect active transport Facilitated diffusion Direct active transport. Simple diffusion
Direct active transport.
When doing differential centrifugation, microsomes pellet to the bottom of the tube at faster spin speeds than lysosomes. This indicates that microsomes are ___________ than lysosomes. Larger Smaller Heavier Lighter
Lighter
Differential centrifugation separates particles based on _______ by applying different _______. Charge; Temperatures Density; Solutions Enzyme activity; pH Mass; Spin speeds
Mass; Spin speeds
Which of the following is found in eukaryotes BUT NOT in bacteria? Membrane-bound organelles Phospholipids Cell walls Ribosomes Double-stranded DNA
Membrane-bound organelles
If you wanted to decrease liver cell responses to epinephrine, which of the following classes of enzymes would you want to increase in activity? Adenylate cyclase Protein phosphatase (catalyzes dephosphorylation) cAMP Phosphorylases
Protein phosphatase (catalyzes dephosphorylation)
Which of the following statements is TRUE? Polymerization occurs predominantly at the minus (-) ends of microtubules. Tubulin is an enzyme. Microtubules do not undergo polymerization or depolymerization until the cell receives a signal Polymerization is favored when tubulin is bound to GDP.
Tubulin is an enzyme.
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!)
microtubules
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 0.00277; endergonic 361; endergonic 0.00277; exergonic
361; exergonic
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 <0; Endergonic >0; Endergonic <0; Exergonic
<0; Exergonic
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 >1; > 0 < 1; > 0 > 1; < 0
> 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 >0; Endergonic <0; Exergonic >0; Exergonic
>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 An inhibitor of cAMP Phosphodiesterase, which breaks down cAMP An inhibitor of Protein phosphatase A GTPase inhibitor All of the above
A kinase inhibitor Response Feedback: Make sure to know the difference between the ras pathway straight from the epinephrine pathway. Also remember the GTPase activity counteracts the effect of any pathway involving a G-protein, regardless of the type
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 H+ pump disorder A Ca++ deficiency A failure of the Na+/K+ ATPase A kinesin disorder
A kinesin disorder
If you had a patient in which the lung epithelium was leaking fluids from the bloodstream into the lumen of the lung, which of the following is the most likely cause? A mutation in actin A mutation in a cell adhesion molecule High levels of cholesterol A mutation in an extracellular matrix protein
A mutation in a cell adhesion molecule
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!) ATP Actin Dynein Microtubules Kinesin GTP Myosin
ATP Dynein Microtubules GTP Response Feedback: The "train tracks" and everything required for their polymerization, plus the retrograde motor protein and everything required for its activity
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 with the active site on the right. The reaction it is catalyzing is also shown on the right. The P in the red circle refers to a phosphate group. This enzyme is a/an _______ and it this form of enzyme regulation is _______. Phosphorylase; covalent modfication ATPase; covalent modification ATPase; allosteric inhibition ATPase; allosteric activation GTPase; allosteric activation *The one with the little P on top*
ATPase; covalent modification
Which of the following is an advantage of multicellularity? Larger size Greater mobility Functional specialization of cells/tissues All of the above
All of the above
Which of the following is NOT TRUE of a second messenger in signal transduction? It is diffusible It is produced when the "first messenger" binds to its receptor It may activate enzymes All of the above are TRUE
All of the above are TRUE
The enzyme phosphofructokinase-1 (PFK-1) catalyzes the 3rd reaction in glycolysis. When AMP concentrations are very high, AMP binds to a location outside the active site PFK-1, which promotes catalysis. This is an example of: Competitive inhibition Allosteric activation Allosteric inhibition Covalent modification Zymogen activation
Allosteric activation
Shown below is a branched reaction pathway, in which either D or E can be made from C. Imagine that D must be maintained at or above a minimum threshold concentration, and only when it is above this concentration, it is ok to produce E. Which of the following is the best way to ensure this? E1-E4 are the enzymes that catalyze each of the reactions. Assume that if an enzyme is subject to activation, it is always inactive in the absence of its activator, and if it is subject to inhibition, it is always active in the absence of inhibitor. Allosteric activation of Enzyme E3 by E Allosteric activation of Enzyme E4 by D Allosteric inhibition of Enzyme E3 by D Allosteric inhibition of Enzyme E1 by D
Allosteric activation of Enzyme E4 by D
Pyrimidines are synthesized through a long series of reactions beginning with the amino acid aspartate. The ribonucleotide CTP is the final compound in this pathway, and when there is enough CTP, it binds to and inhibits the enzyme that catalyzes the first reaction in the pathway, aspartate transcarbamoylase (ATCase). Because CTP is structurally and chemically different from the enzyme's natural substrates, this type of regulation must be: Covalent modification Allosteric activation Zymogen activation Competitive inhibition Allosteric inhibition
Allosteric inhibition
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 activation Competitive activation Competitive inhibition Allosteric inhibition Covalent modification
Allosteric inhibition
Imagine you want to get rich by genetically engineering tobacco plants to produce cannabidiol (CBD). To do so, you insert the genes for each of the enzymes in the (hypothetical) CBD synthesis pathway. Let's just say that the first step in the pathway is conversion of Acetyl-CoA to the compound Malonyl-CoA shown below (This is purely hypothetical.) Imagine now that CBD is toxic at very high concentrations. What would be the best way to synthesize CBD, but to turn off its production before it reaches toxic concentrations and so that Acetyl-CoA can be conserved for other processes? Shown below is the hypothetical pathway. I1, I2, and I3 are the intermediates in the pathway. Enzymes 1-5 (E1-E5) catalyze each reaction in the order in which they appear. Allosteric inhibition of Enzyme 1 by Acetyl-CoA Allosteric inhibition of Enzyme 1 by Malonyl-CoA Allosteric inhibition of Enzyme 1 by CBD Allosteric inhibition of Enzyme 5 by CBD Allosteric activation of E1 by Acetyl-CoA
Allosteric inhibition of Enzyme 1 by CBD
Shown below is a branched reaction pathway, in which either D or E can be made from C. Imagine that E is necessary for the cell, but that it is beneficial to stop production of E when it reaches a minimum threshold concentration in order to preserve A and C for other things (e.g. production of D). Which of the following is the best way to ensure this? E1-E4 are the enzymes that catalyze each of the reactions. Always assume that if an enzyme is subject to activation, it is inactive in the absence of activator, and if an enzyme is subject to inhibition, it is always active in the absence of the inhibitor. Allosteric inhibition of Enzyme E4 by E Allosteric activation of Enzyme E4 by D Allosteric inhibition of Enzyme E1 by E Allosteric activation of Enzyme E3 by E
Allosteric inhibition of Enzyme E4 by E
Which of the following IS CONSISTENT with or TRUE regarding the endosymbiotic theory for the origins of mitochondria and chloroplasts? bic cell engulfed photosynthetic bacterium. Plants are not aerobic. An anaerobic cell engulfed an aerobic bacterium. Chloroplasts evolved before mitochondria.
An anaerobic cell engulfed an aerobic bacterium.
Endosymbiosis is most likely to succeed when it involves a/an ______ host and a/an _____ endosymbiont. Aerobic host; anaerobic endosymbiont Photosynthetic host; anaerobic endosymbiont Photosynthetic host; photosynthetic endosymbiont Anaerobic host; photosynthetic endosymbiont
Anaerobic host; photosynthetic endosymbiont
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? Sugar Butter Water Table salt (NaCl) Amino acid supplements for body-building
Butter
Which of the following is a DISADVANTAGE of endocrine signaling? It is so complex that things can easily go wrong. It may involve second messengers, which require an enzyme-catalyzed reaction. By the time it reaches the target cell, the ligand concentration is likely to be low. It usually involves regulated secretion, which requires a signal.
By the time it reaches the target cell, the ligand concentration is likely to be low. Response Feedback: Review advantages and disadvantages of signaling modes from Lecture 14!
The reaction below shows the process by which the protease Chymotrypsin becomes activated. What is the zymogen? None of the above Chymotrypsin Unused fragments Chymotrypsinogen Trypsin *Image with blue squiggly line equation*
Chymotrypsinogen
The enzyme Succinate dehydrogenase (SDH) catalyzes the reaction succinate --> fumarate in the Citric Acid Cycle. The compound malonate, whose structure is just similar enough to succinate (structures shown below), can bind to the active site of SDH, preventing succinate from binding. This is an example of: Competitive inhibition Allosteric activation Zymogen activation Covalent modification Allosteric inhibition
Competitive inhibition
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 Nuclei Mitochondria and chloroplasts Double-stranded DNA
Cytoskeleton
Which of the following is a disadvantage of being a multicellular organism? Decreased mobility Cellular specialization Decreased structural stability All of the above
Decreased structural stability
The reaction shown above is: Endergonic Endothermic Exergonic None of the above *amino/phosphate/sugar base -H2O-> 2phosphate/amino/sugarbase + PO3OH
Exergonic
Shown below are the results of two fluorescence recovery after photobleaching (FRAP) experiments. Which of the following could explain the difference between the data represented by the dashed line as compared to that represented by the solid line? FRAP was performed on the same cell but at a lower temperature. The membrane of the cell indicated by the dashed line is more fluid than the membrane of the cell represented by the solid line. The membrane of the cell indicated by the dashed line has fewer saturated fatty acids in its phospholipids. All of the above
FRAP was performed on the same cell but at a lower temperature.
Ca++ flowing down its concentration gradient through a Ca++ channel is an example of: Simple diffusion. Facilitated diffusion. Direct active transport. Indirect active transport.
Facilitated diffusion.
Which of the following is an enzyme? epinephrine G-alpha ATP All of the above None of the above
G-alpha
Taxol, derived from the Pacific Yew tree, was one of the first effective anti-cancer compounds discovered. It acts by inhibiting microtubule depolymerization. Which of the following is a likely cellular side effect of treatment with Taxol? Increased exocytosis Loss of pseudopod formation in white blood cells Decreased endocytosis Increased cell size
Increased cell size
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 cAMP production Increasing Protein Kinase A activity Increasing glucose production Increasing cell proliferation All of the above None of the above
Increasing cell proliferation. Response Feedback: The ras pathway results in proliferation. The GTPase activity counteracts this effect. So you have to figure out what would happen if you inhibit the GAP that would normally accelerate the GTPase
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? Simple diffusion Facilitated diffusion Direct active transport Indirect active transport It doesn't
Indirect active transport
Which of the following is an advantage of endocrine signaling? It is fast. It affects large numbers of cells. It can be bidirectional. All of the above
It affects large numbers of cells.
Which of the following is a DISadvantage of paracrine signaling? It involves a 2nd messenger. It is bidirectional. It affects only a small number of cells. It is irreversible. All of the above
It affects only a small number of cells.
Which of the following is a DISADVANTAGE of endocrine signaling? It cannot involve hydrophobic, non-polar signaling molecules. It is irreversible. It is relatively slow. It usually involves regulated secretion, which requires a signal.
It is relatively slow.
Dr. Hutson really likes coffee. Caffeine is a xanthine, a class of molecules that are similar to purines. One of the mechanisms by which caffeine acts is to inhibit the enzyme cAMP phosphodiesterase, which converts cAMP to plain old AMP, which is inactive. How does caffeine alter liver cell responses to epinephrine? It would decrease proliferation It would decrease glucose production. It would increase glucose production. It would increase proliferation
It would increase glucose production.
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. Nothing, the cytoskeleton would behave normally It would prevent actin polymerization. It would prevent actin depolymerization It would prevent microtubule polymerization.
It would prevent microtubule depolymerization.
Which of the following is/are required in order for pancreatic acinar vesicles to be transported to the plasma membrane prior to secretion? (Select all that apply!) Kinesin Actin Myosin Dynein Microtubules GTP ATP
Kinesin Microtubules GTP ATP Response Feedback: The "train tracks" and everything required for their polymerization, plus the anterograde motor protein and everything required for its activity
For solutes that cannot diffuse through the membrane, water moves across the membrane from a region of ______ to a region of ______ solute concentration. High to low Low to high
Low to high
Which of the following is a disadvantage of being a multicellular organism specifically as opposed to unicellular? (Read and think carefully!) Increased mobility More difficult to absorb nutrients. Loss of peptidoglycan reduces stability. All of the above
More difficult to absorb nutrients
Based on their differences in cell structure, which of the following would you be more likely to see in bacteria than in Eukaryotes? More proteins with primary structure changes. More time between stimulus and response when the response requires production of new proteins Faster transcription All of the above
More proteins with primary structure changes.
Inhibition of which of the following would prevent indirect active transport of glucose into cells? GluT1 Ca++ ATPase Ligand-gated ion channels Na+/K+ ATPase
Na+/K+ ATPase
Archeological evidence suggests that Neanderthals may have been aware of the medicinal properties of plants over 60,000 years ago. Imagine you are a modern-day ethnobotanist and have identified a compound from fossilized tree pollen that binds to the alpha subunit of the most common G-proteins. To test how the compound affects the activity of Gα, you treat liver cells with the compound alongside epinephrine. You observe that the cells fail to produce glucose. Which of the following could be how the compound acts? It could inhibit the GTPase activity of Gα. It could decrease the affinity of Gα for GDP. It could cause Gα to bind more tightly to adenylate cyclase. None of the above
None of the above
Which of the following correctly describes a second messenger? A protein, such as a G-protein, that is switched 'on' upon ligand binding to receptor. An enzyme that is activated upon ligand binding to receptor. An enzyme responsible for the cellular effects of a signal transduction pathway, like Protein Kinase A or Glycogen Phosphorylase. None of the above
None of the above
Which of the following is/are found in bacteria BUT NOT in eukaryotes? Cell walls Phospholipids DNA genomes None of the above: All are found in bacteria and some or all Eukaryotes
None of the above: All are found in bacteria and some or all Eukaryotes
Which of the following do eukaryotes have that bacteria do not? Double-stranded DNA RNA Nuclei All of the above
Nuclei
Which of the following pellets at the slowest speeds during differential centrifugation? Microsomes Ribosomes Nuclei Vesicles
Nuclei
"During embryonic development red blood cells begin to develop in patches called blood islands. The blood cells secrete growth factors that diffuse only to nearby cells, signaling differentiation into endothelial cells. The endothelial cells eventually form the linings of the blood vessels." The growth factor described in the passage is involved in what type of signaling? Autocrine Paracrine Endocrine Juxtacrine
Paracrine
Which of the following does NOT specifically support of the theory that Eukaryotes evolved through endosymbiosis? (i.e. the Endosymbiotic Theory) Plants have both mitochondria and chloroplasts. Mitochondria and chloroplasts have two membranes. Mitochondria and chloroplasts have circular genomes. Mitochondria and chloroplasts are genetically related to bacteria.
Plants have both mitochondria and chloroplasts.
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 actin polymerization Prevent translation Prevent transcription Prevent synthesis of peptidoglycan
Prevent synthesis of peptidoglycan
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 Prevent translation Prevent actin polymerization Prevent transcription
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 degraded within two hours. Proteins are not made in the Golgi complex, but are transported in after they are synthesized and then eventually exit. It takes about fifteen minutes to synthesize a protein. Proteins are secreted. Proteins are made in the Golgi complex
Proteins are not made in the Golgi complex, but are transported in after they are synthesized and then eventually exit.
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 secreted. It takes about fifteen minutes to synthesize a protein. Proteins are not made in the Golgi complex, but are transported in after they are synthesized and then eventually exit. Proteins are degraded within two hours. Proteins are made in the Golgi complex
Proteins are not made in the Golgi complex, but are transported in after they are synthesized and then eventually exit.
What would likely happen to a cell treated with a compound that causes lysis (breakage) of peroxisomal membranes? Proteins would fail to be secreted. Nothing, because the low pH of the peroxisome would be buffered by the cell. Ca++ would leak out triggering massive exocytosis. Proteins in the cytoplasm would be damaged.
Proteins in the cytoplasm would be damaged.
What would likely happen to a cell treated with a compound that causes lysis (breakage) of ribosomal membranes? Proteins would leak out and fail to be secreted, but cytoplasmic proteins would be unaffected. All protein synthesis would cease. Proteins would not be glycosylated. Ribosomes don't have membranes.
Ribosomes don't have membranes.
Pancreatic acinar cells were selected for the original original Pulse-Chase experiment of Dr. Palade and his colleagues because they wanted to better understand how _________ were transported through the cell. Teeny tiny automobiles Bacteria Peroxisomes Secreted proteins
Secreted Proteins
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 All of the above The density of the solution The concentrations of A, B, and C The molecular weights of A, B, and C The mechanism of the reaction
The concentrations of A, B, and C Response Feedback: Find deltaG from Keq. All you need for Keq is equilibrium concentrations of all components.
Which of the following best explains why we can safely say, "Diamonds are forever"? The conversion of diamonds into charcoal has an extremely high activation energy. The conversion of diamonds into charcoal is highly endergonic. The conversion of diamonds into charcoal is highly exergonic. The conversion of diamonds into charcoal involves an increase in entropy.
The conversion of diamonds into charcoal has an extremely high activation energy.
The reaction below, phosphorylation of glucose, is exergonic because it is coupled to ATP hydrolysis. The enzyme hexokinase catalyzes this reaction. Which of the following best describes how an enzyme for this reaction works? glucose + ATP <=> glucose-6-P + ADP The enzyme makes the reaction exergonic. The enzyme alters the mechanism of the reaction by altering the transition state. The enzyme is not actually necessary as long as ATP is available to provide energy for the reaction. The enzyme is activated by phosphorylation, thereby providing the energy for the reaction.
The enzyme alters the mechanism of the reaction by altering the transition state.
Shown below are the results of two fluorescence recovery after photobleaching (FRAP) experiments. Which of the following could explain the difference between the data represented by the dashed line as compared to the data represented by the solid line? The membrane of the cell indicated by the dashed line contains longer fatty acid chains in its phospholipids. The membrane of the cell indicated by the dashed line contains phospholipids with more unsaturated fatty acids. The membrane of the cell indicated by the dashed line has fewer proteins. The membrane of the cell indicated by the dashed line is more fluid.
The membrane of the cell indicated by the dashed line contains longer fatty acid chains in its phospholipids.
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 ______ . Down; indirect active transport Down; facilitated diffusion Up; Direct active transport Up; Indirect active transport Down; facilitated diffusion
Up; Direct active transport
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 catalyzes is also shown. This form of enzyme regulation is _______. Covalent modification Allosteric activation Allosteric inhibition Competitive inhibition Zymogen activation *The one with the ATP --> ADP + Pi*
Zymogen activation
∆G°' for the hydrolysis of ATP is considered to be: highly endergonic highly exergonic slightly endergonic slightly exergonic
highly exergonic