bibs

What is ∆G°' for the hydrolysis of ATP?

-7.3 kcal/mol

The lipid:protein ratio in a typical membrane (e.g. red blood cells) is approximately:

1:1

The protein:lipid ratio in a typical membrane (e.g. red blood cells) is approximately:

1:1

Bacteria are approximately _____ in diameter; eukaryotic cells are typically at least _____ times this size.

1µm; 10x

Cholesterol generally makes up what percentage of the lipid mass of the plasma membrane?

25%

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

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

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 a cell adhesion molecule

Which of the following correctly describes a second messenger?

A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response

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 _______.

ATPase; covalent modification

Protons (H+) are moved up their concentration gradients into the lysosome in order to activate lysosomal enzymes. This is an example of:

Active transport

Pertussis toxin is produced by Bordetella pertussis, a bacterium that causes whooping cough. Pertussis toxin catalyzes the addition of ADP-ribose (structure below) to Gα, which prevents Gα from binding to GPCRs thus "locking" it in the GDP-bound state. How would pertussis toxin affect liver cell responses to epinephrine?

Adenylate Cyclase activity would decrease

The endosymbiotic theory explains the evolution of:

All Eukaryotes

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

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

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 E4 by D

Imagine you want to get rich by genetically engineering tobacco plants to produce acai berry juice. To do so, you insert the genes for each of the enzymes in this hypothetical pathway, the first step of which is conversion of glucose to fructose. The challenge is that glucose must be maintained at or above a minimum concentration or the plant will die because it can no longer make ATP. For the reaction pathway shown below, what is the best way to achieve this?

Allosteric activation of enzyme E1 by Glucose

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

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 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

Which of the following IS CONSISTENT with or TRUE regarding the endosymbiotic theory for the origins of mitochondria and chloroplasts?

An anaerobic cell engulfed an aerobic bacterium.

The ancestor to all Eukaryotes was likely an _________ that ingested a/an _________ , which led to evolution of mitochondria.

Anaerobic archaeum; Aerobic bacterium

Which adaptation specific to becoming multicellular compensates for the destabilizing effect of increased size? (Think carefully about answer choices!)

Both ECM and tight junctions

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

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.

The enzyme Succinate dehydrogenase (SDH) catalyzes the reaction succinate --> fumarate in the Citric Acid Cycle (structures shown below). If fumarate binds to the active site of SDH, thereby preventing succinate from binding, this is an example of:

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

As we learned in Lecture 15, 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

As we learned in Lecture 15, protein phosphatases catalyze removal of phosphate groups from proteins. How would the activity of a protein phosphatase affect a cell's response to growth factors?

Decrease proliferation

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.

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.

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

The reaction shown above is:

Exergonic

ATP hydrolysis is highly _____ because it involves _____.

Exergonic; separation of negatively charged phosphate groups

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.

Ca++ flowing down its concentration gradient through a Ca++ channel is an example of:

Facilitated diffusion.

True or False: The concentration of Ca++ in the cytoplasm is higher than it is in the smooth ER.

False

True or False: The concentration of Ca++ inside the cell is higher than it is outside.

False

Which of the following is an advantage of multicellularity?

Functional specialization of cells/tissues Larger size Greater mobility

Which of the following is an enzyme?

G-alpha

Shown here is a graph illustrating data from the origial Pulse-Chase experiment analyzing protein secretion in pancreatic acinar cells. Trace C corresponds to radioactivity in which structure?

Golgi complex

Which of the following is a disadvantage of being multicellular?

Greater energy needs More difficult to absorb nutrients Reproduction more complicated

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 a DISadvantage of paracrine signaling?

It affects only a small number of cells.

Which of the following can be considered both an advantage and a disadvantage of juxtacrine signaling?

It affects only one or a very small number of cells.

Which of the following is a DISADVANTAGE of endocrine signaling?

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 increase 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.

Chloride ion (Cl-) concentrations must be maintained much higher outside of cells than inside of cells. How this gradient is maintained is complex, but a key transporter co-transports Cl- along with K+ ions. The name of this transport protein could be ____ and its mode of transport would be ____.

K+/Cl- symporter; indirect active transport

Which of the following enzymes catalyzes phosphorylation of proteins using a phosphate group from ATP?

Kinases

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.

Lighter

Differential centrifugation separates particles based on _______ by applying different _______.

Mass; Spin speeds

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!)

Microtubules Kinesin GTP ATP

Which of the following is/are found in eukaryotes but not bacteria?

Mitochondria

Which of the following does NOT specifically support of the endosymbiotic theory for the origins of mitochondria and chloroplasts?

Mitochondria and chloroplasts are very common.

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

Inhibition of which of the following would prevent indirect active transport of glucose into cells?

Na+/K+ ATPase

What is the second messenger in the receptor tyrosine kinase signaling pathway? 1) the kinase 2) the small GTPase ras 3) the enzyme MAPK that gets transported into the nucleus to activate gene transcription

None of the above

Which of the following pellets at the slowest speeds during differential centrifugation?

Nuclei

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 was does the % or # of grains on the y-axis represent?

Proteins

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.

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 would likely happen to a cell treated with a compound that causes lysis (breakage) of ribosomal membranes?

Ribosomes don't have membranes.

Shown here is a graph illustrating data from the original Pulse-Chase experiment analyzing protein secretion in pancreatic acinar cells. Trace B corresponds to radioactivity in which structure?

Rough ER

Which of the following forms microsomes during differential centrifugation?

Rough ER Smooth ER Golgi Complex

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

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.

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?

The concentrations of A, B, and C

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

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

Which of the following is true for all enzymes?

They alter the transition state.

What do microtubules and actin have in common?

They are both enzymes.

Which of the following distinguishes plant cells from animal cells?

They have cell walls and chloroplasts.

Which of the following is true for all enzymes?

They increase the reaction rate.

Which of the following statements is TRUE?

Tubulin is an enzyme.

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 K+/Cl- symporter.

Which of the following observations constitutes evidence that mitochondria evolved before chloroplasts?

all eukaryotes have mitochondria; only a subset of eukaryotes have chloroplasts

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:

allosteric activation

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

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

Which of the following is a disadvantage of being a multicellular organism?

decreased structural stability

Shown below is a free energy diagram for a chemical reaction. An enzyme that catalyzes this reaction acts by ________ the magnitude of _________:

decreasing; 1

∆G°' for the hydrolysis of ATP is considered to be:

highly exergonic

What happens to GTP in response to epinephrine binding to its receptor on liver cells?

it binds to g-alpha

Which of the following is a DISADVANTAGE of endocrine signaling?

it is relatively slow

Fill in the blank: The motor protein responsible for transporting vesicles to the plasma membrane is named ___. (spelling matters!)

kinesin

Which of the following is found in eukaryotes BUT NOT in bacteria?

membrane-bound organelles

Which of the following correctly describes a second messenger? 1) A protein, such as a G-protein, that is switched 'on' upon ligand binding to receptor. 2) An enzyme that is activated upon ligand binding to receptor. 3) An enzyme responsible for the cellular effects of a signal transduction pathway, like Protein Kinase A or Glycogen Phosphorylase.

none of the above

Which of the following do eukaryotes have that bacteria do not?

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?

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

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

secreted

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 _______.

zymogen activation