learning catalytics questions for cell exam 3
This graph is an example of what?
transporting one kind of ion across a membrane down its concentration gradient
Are all transmembrane proteins integral proteins?
yes All transmembrane proteins are integral membrane proteins. Not all integral membrane proteins are transmembrane proteins.
The researchers conduct an experiment described in the figure below. Oxygen is added after one minute and the pH of the solution the mitochondria are in is being measured throughout the experiment. Succinate is an intermediate in the ETC. What is happening with the mitochondria that causes the pH to stay the same for the first minute?
The ETC won't pump any H+ without oxygen present as a final electron donor.
PC -- phosphatidylcholine
The most abundant glycerophospholipid in cell membranes
A researcher feeds a mouse the biomolecules below. These biomolecules have been produced to be isotopically labled on all their carbons with the less abundant 13C isotope. This allows her to track where these carbons end up after the molecules are digested. Which of the following molecules could produce acetyl CoA containing a 13C label? a) 13C Glucose b) 13C fatty acid chains c) 13C amino acids
a) 13C Glucose b) 13C fatty acid chains c) 13C amino acids We specifically worked through how fatty acids and glucose are made into acetyl CoA (beta oxidation and glycolysis, respectively). For amino acids we simply covered that some enter as glycolysis intermediates, some are converted to acetyl CoA through another pathway, and some enter as TCA cycle intermediates.
A researcher feeds a hamster isotopically labeled biomolecules so that all the carbons are the less abundant 13C isotope. This allows him to track where these carbons end up. Which of the following molecules could produce carbon dioxide with a 13C label? Think about what steps would occur for this to take place. a) 13C glucose b) 13C fatty acids c) 13C amino acids d) None of these would produce CO2 in mice.
a) 13C glucose b) 13C fatty acids c) 13C amino acids The acetyl CoA they all produce (see last question) would enter into the citric acid cycle which produces CO2.
The sodium-hydrogen exchanger imports one Na+ into the cell and simultaneously exports one H+ out of the cell in order to maintain cellular pH. This exchanger can even pump H+ from the cell when the extracellular environment is at low pH. The sodium-hydrogen exchanger is then an example of which of the following: (select all that apply) a) Antiport b) Secondary active transport c) Ion Channel d) P-type Pump
a) Antiport b) Secondary active transport It is an anti-porter because the ions are going in opposite directions across the membrane. It is secondary active transport because the Na++ is going down its concentration gradient and driving H+ against its gradient. It isn't an ion channel because channels only allow ions to go DOWN their concentration gradient. No ATP is being hydrolyzed so it isn't a p-type pump.
Which of the following would produce 2 NADH molecules? (Select all that apply) a) Break down of one glucose to pyruvate molecules. b) Breakdown of two pyruvate molecules into acetyl CoA. c) Breakdown of 2 acetyl CoA into CO2
a) Break down of one glucose to pyruvate molecules. b) Breakdown of two pyruvate molecules into acetyl CoA. Breakdown of 2 acetyl CoA into CO2 would make 6 total NADH molecules (not 2). The others each produce 2 NADH.
Which of the following would produce 2 ATP (or GTP) molecules? (select all that apply) a) Breakdown of one glucose molecule into pyruvate molecules. b) Breakdown of 2 pyruvate molecules into Acetyl CoA. c) Breakdown of 2 acetyl CoA molecules into CO2.
a) Breakdown of one glucose molecule into pyruvate molecules. c) Breakdown of 2 acetyl CoA molecules into CO2. The reaction that converts pyruvate into Acetyl CoA does not produce ATP directly (it does make 2 NADH molecules for every 2 acetyl CoA though that can dump electrons into the ETC). The breakdown of acetyl CoA into CO2 is the TCA cycle which makes 1 ATP or GTP per cycle (thus 2 produced for 2 acetyl CoA molecules).
Which of the following methods do cells use to conduct reactions with positive delta G at standard state? Select all that apply. a) Couple it with a reaction with a negative delta G. b) Catalyze it with an enzyme c) Capture energy from sunlight d) Increase the reactant concentrations so they are much higher than the product concentrations
a) Couple it with a reaction with a negative delta G. c) Capture energy from sunlight d) Increase the reactant concentrations so they are much higher than the product concentrations The lecture provides examples of all of these except catalyzing the reaction with an enzyme. Enzymes do not make reactions more favorable or change delta G, they just speed up reactions that are already favorable.
Which of the following statements is FALSE regarding enzyme regulation? a) Feedback inhibition is defined as a mechanism of down-regulating enzyme activity by the accumulation of a product earlier in the pathway. b) If an enzyme's allosteric binding site is occupied, the enzyme may adopt an alternative conformation that is not optimal for catalysis. c) Protein phosphorylation is a way to alter the conformation of an enzyme to either increase OR decrease enzyme activity. d) Cleavage of peptide bonds in an enzyme can either activate or inactivate its catalytic activity.
a) Feedback inhibition is defined as a mechanism of down-regulating enzyme activity by the accumulation of a product earlier in the pathway. Negative feedback inhibitors are typically products of reactions later in the pathway.
Which of the following statements is definately FALSE if phosphatidylserine is found at higher percentages in the outer leaflet than in the inner leaflet of the plasma membrane? a) Flippases are functioning b) Floppases are not functioning c) The cell will undergo cell death d) Scramblases are not functioning in the plasma membrane e) More than one answer is false
a) Flippases are functioning If PS is higher in the outer leaflet than in the inner, flippase is definitely not working. If scramblease was also on then you would expect similiar concentrations of PS on both sides of the membrane. Floppase could still be functional (moving lipids to outside leaflet), or not... we can't tell from the information in this question. PS in the outer leaflet signals apoptosis.
Which processes generate NADH? (select all that apply) a) Glycolysis b) Conversion of pyruvate into ethanol c) Conversion of pyruvate into acetyl CoA d) Conversion of pyruvate into lactic acid e) The electron transport chain f) The TCA cycle
a) Glycolysis c) Conversion of pyruvate into acetyl CoA f) The TCA cycle The conversion of pyruvate into ethanol or lactic acid regenerates NAD+ (uses NADH) so that glycolysis can continue without the oxygen needed for the ETC to do this job.
Pyruvate is produced in the cytoplasm and needs to enter the mitochondria for the cell to make most of its energy. To find the transporter, scientists looked for mitochondrial genes that made which type of protein? a) Integral membrane protein b) Peripheral membrane protein c) Transporters aren't considered membrane proteins
a) Integral membrane protein Since the molecules need to pass through both layers of the phospholipid bilayer, all carriers, channels, and transporters are integral membrane proteins.
Which of the following is (are) responsible for maintaining the resting membrane potential? Select all that apply. a) Ion gradients across the plasma membrane b) Impermeability of the plasma membrane to various ions c) The Na+/K+ ATPase d) Sodium/Glucose Linked transporters
a) Ion gradients across the plasma membrane b) Impermeability of the plasma membrane to various ions d) Sodium/Glucose Linked transporters
Increased [Ca++] in the cytoplasm causes muscle contraction. Given what you now know about the sodium/calcium exchanger and the Na+/K+ ATPase, which of the following best describes how Digoxin helps congestive heart failure patients? a) It indirectly causes an increase in intracellular Ca++, which leads to stronger heart muscle contractions. b) It indirectly causes a decrease in intracellular Ca++, which leads to stronger heart muscle contractions. c) It must also bind to the Na/Ca exchanger and lead to increased Ca++ in the cell, thus causing stronger heart muscle contractions. d) It causes higher rates of Ca++ export, which leads to stronger heart muscle contractions
a) It indirectly causes an increase in intracellular Ca++, which leads to stronger heart muscle contractions.
Predict the function of the enzyme below: a) It synthesizes a precursor needed for CTP anabolism. b) It hydrolyzes CTP into CDP and inorganic phosphate. c) It is an RNA polymerase that synthesizes RNA from CTP, UTP, GTP, and ATP. d) It is impossible to hypothesize the enzyme's function because CTP is binding to a regulatory site.
a) It synthesizes a precursor needed for CTP anabolism. Since CTP binds an allosteric site and inhibits activity it is acting as an allosteric inhibitor of this enzyme. Allosteric inhibitors are often negative feedback regulators.
What can you tell about the movement of this molecule across membranes from only its structure shown below? Select all that apply. a) It will require a transport protein to cross a membrane. b) It will require energy to transport. c) It can pass through a phospholipid bilayer via diffusion. d) It could pass through a membrane via facilitated diffusion.
a) It will require a transport protein to cross a membrane. d) It could pass through a membrane via facilitated diffusion. It is charged and large so it will require a transport protein to cross the membrane or phospholipid bilayer. It will not require energy to transport as long as it is moving down its concentration gradient. Facilitated diffusion is when a molecule moves down its concentration gradient through a transporter or channel protein.
Which of the following are types of lipids that are covalently attached to proteins to generate lipid-linked proteins? (select all that apply) a) Prenyl b) Cholesterol c) Fatty acyl d) glycosylphosphatidylinositol (GPI) e) Phosphatidylethanolamine (PE)
a) Prenyl c) Fatty acyl d) glycosylphosphatidylinositol (GPI)
Which of the following uses hydrolysis of UTP to make the reaction favorable? (select all that apply) a) Storing glucose in the form of glycogen chains. b) Adding a uracil base to an RNA chain during transcription. c) Cholesterol synthesis d) Protein synthesis
a) Storing glucose in the form of glycogen chains. b) Adding a uracil base to an RNA chain during transcription. Cholesterol synthesis uses hydrolysis of acetyl CoA and oxidation of NADPH, while protein synthesis uses hydrolysis of ATP and GTP.
Consider now the reverse reaction: Y going to X. It may help to sketch out a new reaction progress curve. Which of the following would be true? (select all that apply) a) The reaction would have a positive delta G. b) The free energy of the products would be higher on the y-axis than the reactants. c) The reaction would proceed spontaneously in these conditions. d) The enzyme would still lower the activation energy.
a) The reaction would have a positive delta G. b) The free energy of the products would be higher on the y-axis than the reactants. d) The enzyme would still lower the activation energy.
Study this diagram that describes the ion gradient across the inner membrane of bacterial cells. How does this compare to the eukaryotic cell membrane potential? (select all that apply) a) They both have a resting membrane potenial b) They both have a concentration gradient c) They both have an voltage gradient d) They both have mechanisms to drive Na out of the cell against its concentration gradient e) They both use ATP to pump ions across the membrane
a) They both have a resting membrane potenial b) They both have a concentration gradient c) They both have an voltage gradient d) They both have mechanisms to drive Na out of the cell against its concentration gradient This diagram shows ATP being GENERATED by ion concentration differences in bacteria, while in Eukaryotes ATP is used by the Na+/K+-ATPase to maintain the action potential. The others are all true!
Which of the following contain a glycerol backbone? (select all that apply) a) Triacylglycerol b) Glycolipids c) Sphingolipids d) Phosphatidylcholine
a) Triacylglycerol d) Phosphatidylcholine Glycolipids and sphingolipids contain a Sphingosine backbone not glycerol. Phosphatidylcholine (PC) is the most abundant glycerophospholipid in cell membranes. Triacylglycerol is the storage from of fats (glycerol with 3 fatty acid chains attached).
The study of enzymes includes an examination of how the activity is regulated. Which variable or variables used to describe enzyme activity will remain the same in the presence and absence of a competitive inhibitor? a) Vmax b) initial velocity at a low substrate concentrations c) Km d) Km and Vmax
a) Vmax
The presence of which type of lipid increases membrane rigidity at 37 degree Celsius? a) phospholipids with saturated fatty acid tails b) cholesterol c) phospholipids with cis-fatty acid tail d) phospholipids with short fatty acid tails
a) phospholipids with saturated fatty acid tails b) cholesterol Long saturated fatty acid tails on phospholipids leads to increased hydrophobic intereaction surface between chains, thus increasing lipid packing and increasing rigidity. At higher temperatures (such as body temperature 37C), cholesterol promotes rigidity. Other options increase fluidity by disrupting the packing between chains (cis-fatty acids) or having less surface to interact with (short tails).
What is the proper order and location of the following two events in glucose metabolism: a) pyruvate is made in the cytoplasm, then acetyl CoA is made in the mitochondria b) acetyl CoA is made in the cytoplasm, then pyruvate is made in the cytoplasm c) pyruvate is made in the cytoplasm, then acetyl CoA is made in the cytoplasm d) acetyl CoA is made in the mitochondria, then pyruvate is made in the mitochondria e) These are unrelated events so they can happen in either order.
a) pyruvate is made in the cytoplasm, then acetyl CoA is made in the mitochondria Pyruvate is a final product of glycolysis and since glycolysis happens in the cytoplasm, pyruvate must first be produced in the cytoplasm. Then that pyruvate enters the mitochondria where it is converted to acetyl CoA and can enter the citric acid cycle.
Eukaryotic cells have membrane bound organelles. What is NOT TRUE about the membranes of these organelles? a) They are all lipid bilayers b) All contain the same phospholipid components c) All contain lipids that are synthesized in the ER d) All of the presented answers are true
b) All contain the same phospholipid components There are a myriad of phospholipid types and the locations of the different types vary based on which organelle and which leaflet of the membrane.
You generated your vessicles for the experiment in buffer with pH 6 and then transfered them to buffer with pH 8. Now you see ATP synthesis even in the dark! What happened? a) bacteriarhodopsin unfolded due to the pH change and is now allowing H+ through without light. b) Bacteriarhodopsin is no longer needed to generate the H+ gradient. c) Your labmate must have messed with your samples! No way this could happen. d) ATP synthase must have flipped around in the membrane due to the change in pH.
b) Bacteriarhodopsin is no longer needed to generate the H+ gradient. Since the only thing light is doing is setting up the H+ gradient, you don't need light if the gradient is already set up (different pH's = different [H+]). If bacteriarhodopisin unfolded and allowed H+ to flow through freely then the gradient would be equilibrate and ATP would not be generated. Membrane proteins can't change orientation in the membrane after they are synthesized.
You have generated antibodies that recognize the extracellular domain of the Ca2+-pump. Adding these antibodies to animal cells blocks the active transport of Ca2+ from the cytosol into the extracellular environment. What do you expect to observe with respect to intracellular Ca2+? a) Ca2+ pumps in vesicle membranes will keep cytosolic calcium levels low. b) Ca2+ pumps in the endoplasmic reticulum membrane will keep cytosolic calcium levels low. c) Ca2+ concentrations in the cytosol will become higher than outside the cell. d) Ca2+ concentrations in the cytosol will decrease at a steady rate.
b) Ca2+ pumps in the endoplasmic reticulum membrane will keep cytosolic calcium levels low. In addition to the Ca2+-pumps in the plasma membrane, Ca2+-pumps are also found in the membrane of the endoplasmic reticulum (ER). This how Ca++ is released from the ER into the cytoplasm during PLC signalling. The transporters in the ER membrane will continue to remove calcium ions from the cytosol, keeping calcium levels low.
Which of the following is enriched in lipid rafts? (Select all that apply) a) polyunsaturated fatty acids b) Cholesterol c) Signaling proteins d) Glycolipids
b) Cholesterol c) Signaling proteins d) Glycolipids These are all found in high quantities in lipid rafts except for poly unsaturated fatty acids which tend to be located in MORE fluid areas of the membrane not less fluid ones as is the case in lipid rafts. Remember the double bond puts a kink in the tail and decreases the packing in the fatty acid tails.
Which of the following generate carbon dioxide? (select all that apply) a) Glycolysis followed by lactic acid fermentation b) Glycolysis followed by ethanol fermentation c) Glycolysis followed by the TCA cycle
b) Glycolysis followed by ethanol fermentation c) Glycolysis followed by the TCA cycle Glycolysis doesn't produce CO2... 6 carbon sugar goes in, two 3 carbon sugars come out. Convertion of pyruvate into lactic acid (another 3 carbon sugar) does not involve loss of carbon, but conversion to ethanol (a 2 carbon sugar) does.
If Na+ channels are opened in a cell that was previously at rest, how will the membrane potential be affected? a) It will not be affected. b) It becomes more positive c) It becomes more negative d) it will be reset
b) It becomes more positive As Na+ ions move into the cell, the net charge becomes more positive (less negative) and the membrane potential changes to reflect both Na+ and K+ ions being inside the cell.
Which of the following is a characteristic feature of a transport protein? a) It has a few, if any, hydrophobic amino acids b) It exhibits a specificity for a particular type of molecule c) It always requires the expenditure of cellular energy to function d) It can only move molecules against their concentration gradient e) More than one answer is correct
b) It exhibits a specificity for a particular type of molecule
Which of the following best describes the behavior of a gated channel? a) Once stimulated, it will stay open continuously. b) It opens more frequently in response to a given stimulus. c) It opens more widely as the stimulus becomes stronger. d) Once open it will move ions selectively against their concentration gradient.
b) It opens more frequently in response to a given stimulus. Gated ion channels are more likely to be found in the open state when stimulated, and more likely to be found in the closed position when not stimulated. They do not open wider to more stimulus as this would mess up the selectivity filter. They only allow ions to move down their concentration gradient (facilitated diffusion).
If you inhibited SGLT2, what would happen to the sodium concentration INSIDE of an epithelial cell? a) It would increase b) It would decrease c) It would stay the same
b) It would decrease Since SGLT2 uses Na+ going down its concentration gradient (outside to inside) to drive glucose import, the inhibition would lead to decreased sodium inside of the cell. It would also lead to decreased glucose levels inside of the cell.
What is true about membrane 1 when compared to membrane 2? a) Membrane 1 is more permeable b) Membrane 1 may contain phospholipids with more saturated fatty acid tails. c) Membrane 1 is more rigid d) Membrane 1 may be at lower temperature
b) Membrane 1 may contain phospholipids with more saturated fatty acid tails. c) Membrane 1 is more rigid d) Membrane 1 may be at lower temperature
When the net charge on either side of the plasma membrane is zero, what else must be true? a) The cell is probably below the threshhold level. b) The electrical potential across the membrane is zero. c) The membrane potential is between −20 mV and −200 mV. d) K+ concentrations are the same on both sides of the membrane. e) Ions can't move across the membrane without addition of ATP.
b) The electrical potential across the membrane is zero. The electrical potential is dependent on the charge difference. Ions could still move across the membrane based on their concentration difference (which could generate a charge difference), but the cell wouldn't be considered to have electrical potential at that moment (0 mV). K+ could have differing concentrations on the different sides of the membrane and the charge be zero if it was balanced by higher Na+ on the other side. The threshold level for most cells is negative, so zero would be above the threshold.
Think about the meaning of Vmax and Km. If you conducted a michaelis mention experiment and plotted substrate concentration versus initial velocity using a lower concentration of enzyme, how would Vmax and Km be affected? a) Vmax would go up b) Vmax would go down c) Km would go up d) Km would go down e) Vmax and Km would be uneffected by enzyme concentration.
b) Vmax would go down Vmax is the maximum rate at which product can be formed. If we increase enzyme concentration, we'll increase the rate at which product can be made at any given concentration of substrate.
Digoxin is a drug used to treat congestive heart failure. Digoxin inhibits the Na+/K+ ATPase pump in cardiac muscle cells (cardiomyocytes). What effect will digoxin have on intracellular sodium and potassium concentrations? a) [Na] will go down, [K] will go up b) [Na] will go up, [K] will go down c) Both [Na] and [K] will decrease d) Digoxin won't affect the intracellular concentration of either ion.
b) [Na] will go up, [K] will go down
If you wanted to generate galactose quickly (a product of the Nagalase cleavage reaction), which would you use in high concentrations? a) beta galactose glycolsylated protein b) alpha galactose glycolsylated protein
b) alpha galactose glycolsylated protein The alpha oriented product has a higher Vmax and thus will form product at a higher rate when substrate is supplied at high concentrations.
Enzymes facilitate reactions in living systems. Figure 3-21 presents an energy diagram for the reaction X→Y. The solid line in the energy diagram represents changes in energy as the reactant is converted to product under standard conditions. The dashed line shows changes observed when the same reaction takes place in the presence of a dedicated enzyme. Which equation below indicates how the presence of an enzyme affects the activation energy of the reaction (catalyzed versus uncatalyzed)? a) d − c versus b − c b) d − a versus b − a c) a + d versus a + b d) d − c versus b − a
b) d − a versus b − a The activation energy is the difference in energy between the reactants (point a in the graphy) and the transition state (point b in the uncatylzed reaction and point d for the catalyzed reaction). This difference in activation energies is often referred to as delta delta G double dagger, which sounds like a fun trophy at the end of video game level.
Plant cells contain which of the following? (select all that apply) a) peptidoglycan cell wall b) grana c) mitochondria d) ATP synthase
b) grana c) mitochondria d) ATP synthase The cell walls of plants are made from cellulose... bacterial cell walls are made of peptidoglycan. Grana are the stacks of thlakoid membranes found in chloroplasts. ATP synthase is found both in the mitochondria and in chloroplasts of plant cells.
Enzymes do not "stabilize reactant molecules". If they did, which of the following would happen to the thermodynamics of the reaction they catalyze? a) Vmax would change. b)Delta G would become more negative. c) Activation energy would increase. d) The reaction would work even better.
c) Activation energy would increase. Stabilizing reactants would lower their energy (G). This would cause activation energy to go up (transition state energy minus reactant energy). Since delta G is the energy of the products minus the energy of the reactants this would cause delta G to increase (become less negative if favorable, or become more positive if unfavorable). Both of these would hinder the reaction from proceeding in the forward direction! Vmax and Km are KINETICS of an enzyme and would not effect the thermodynamics of the reaction.
Each year, the U.S. forest industry harvests millions of cords of wood to build homes, make furniture, paper, and other products. Which of the following processes contributes the most to the increase in timber biomass? a) Absorption of mineral substances from the soil via the roots b) Absorption of organic substances from the soil via the roots c) Incorporation of CO2 gas from the atmosphere into molecules by leaves d) Incorporation of H2O from the soil into molecules by green leaves e) Absorption of solar radiation into the leaf
c) Incorporation of CO2 gas from the atmosphere into molecules by leaves Wood is mostly made up of cellulose, which is a polysaccharide consisting of a linear chain of several hundred to many thousands of linked D-glucose units. Both water and carbon dioxide are reactants for photosynthsis that generates this glucose, but water is used to supply electrons and generate oxygen, while CO2 is used directly in the Calvin Cycle to make glucose. Light and minerals are important components that allow for the biomass to be generated, but don't contribute any weight themselves to the biomass.
What is true about this lipid? a) It is a phospholipid b) It is a trans-fatty acid c) It is an unsaturated fatty acid d) It will be solid at room temperature e) More than one answer is correct
c) It is an unsaturated fatty acid The lipid shown is an unsaturated fatty acid with a single cis bond (not trans). The unsaturation means it will be liquid at room temperature. It does not have a phosphate head group so it is not a phospholipid.
If the TCA cycle doesn't require O2 as a reactant, why does the TCA cycle stop in the absence of oxygen? a) There's no oxygen to add to pyruvate to make acetyl CoA. b) The cell uses the O2 to generate the CO2 product made by the TCA cycle. c) NAD+ and FAD cannot be regenerated in the absence of O2 d) Without O2 the ETC will oxidize the acetyl CoA directly bypassing the TCA e) It doesn't stop in the absence of oxygen
c) NAD+ and FAD cannot be regenerated in the absence of O2
Which arrow indicates the Km of the enzyme represented on this Michaelis-Menten plot? a) Blue Arrow b) Red Arrow c) Purple Arrow d) Green Arrow
c) Purple Arrow
Which of the following best describes why type II diabetics don't take SGLT1 inhibitors? a) SGLT1 is not located in the kidneys so the drugs wouldn't block glucose re-absorption. b) SGLT1 has too high of an affinity for glucose so it would be too hard to block. c) SGLT1 only absorbs a minor amount of the glucose from the kidneys so it wouldn't make much of a difference in blood glucose levels. d) SGLT1 is a passive transporter so it can't be inhibited with a drug.
c) SGLT1 only absorbs a minor amount of the glucose from the kidneys so it wouldn't make much of a difference in blood glucose levels. Because of its low capacity for glucose transport SGLT1 only absorbs 10% of glucose in the kidneys, while SGLT2 absorbs 90%. SGLT2 inhibition has a much larger impact over blood glucose levels than inhibiting SGLT1. SGLT1 and SGLT2 are both secondary active transporters and both are found in the kidneys. While it is true that SGLT1 does have higher affinity for glucose than SGLT2 (lower Km), drugs usually have incredibly high affinities (often in the nM range compared to glucose affinities in the mM range) so if it were effective to inhibit SGLT1 it would be possible to design drugs that target it.
The sodium/calcium exchanger lets in three sodium ions for every calcium ion it exports. What do you predict drives the export of Ca++ from the cytoplasm (against it's concentration gradient)? a) The Sodium/Calcium exchanger must hydrolyze ATP b) Potassium ions moving against their concentration gradient c) Sodium ions moving down their concentration gradient d) Nothing needs to drive calcium export; it occurs passively via the exchanger.
c) Sodium ions moving down their concentration gradient
Nagalase catalyzes the deglycosylation of the vitamin D3-binding protein which prevents them from being able to activate macrophages. Interestingly, the effeciency of the enzyme depends on the stoichemetry of the terminal galactose sugar it removes (alpha versus beta orientation of the sugar's -OH group). Which substrate does the enzyme bind more tightly? How do you know? a) beta, because it has a lower Vmax b) beta, because it has a higher Km c) beta, because it has a lower Km d) alpha, because it has a higher Vmax e) alpha, because it has a higher Km
c) beta, because it has a lower Km Km is associated with affinity. You want to first estimate Vmax of each and then go to 1/2 vmax. From there you go horizontally until you get to that sugars activity curve and then drop verticly to determine the Km.
What is the expression for the free energy change (delta G) for the conversion of X to Y? Use the points a, b, c, and d on the graph to describe which free energy values you use. a) b-d b) b-a c) c-a d) a-c e) It depends on if we are talking about the catalyzed or non-catalyzed reaction.
c) c-a
Biological enzymes work by: a) Increasing the temperature of the reaction b) Increasing the entropy of the reaction c) Increasing the activation energy of the reaction d) Decreasing the activation energy of the reaction e) Decreasing delta G
d) Decreasing the activation energy of the reaction Enzyme decrease the activation energy so that they occur faster. They do not effect delta G, so therefore they also don't change entropy or enthalpy (these are all properties inherent to the products and reactant molecules). Enzymes also can't change reaction temperature.
The picture shown is of a receptor protein. Which of the following is incorrect: a) It is synthesized at the rough ER. b) It is an integral membrane protein. c) It is a transmembrane protein. d) The majority of the protein must be made up of hydrophobic amino acids.
d) The majority of the protein must be made up of hydrophobic amino acids. All of the protein except for the 22 amino acids close to the C-terminal end that form the transmembrane helix is located in extracellular space which is an aqueous environment and would not necessarily be hydrophobic. It is a transmembrane protein and would permanently associated with the membrane (thus an integral membrane protein). Proteins with transmembrane helices are all synthesized at the rough ER.
Which of the following is not true concerning integral membrane proteins? a) Detergent is required to remove them from the membrane. b) They are important players in signalling pathways. c) Integral membrane proteins are synthesized at the ER. d) They could be made up entirely of hydrophilic amino acids. e) They can be made up of either alpha helices or beta sheets.
d) They could be made up entirely of hydrophilic amino acids. All integral membrane proteins associate with the hydrophobic interior of the lipid bilayer and therefore contain hydrophobic amino acids. This statement could be true of peripheral membrane proteins though!
Electron transport is coupled to ATP synthesis in mitochondria, in chloroplasts, and in the thermophilic bacterium Methanococcus (a bacteria that uses methane as the final electron acceptor for energy generation). Which of the following is likely to affect the coupling of electron transport to ATP synthesis in ALL of these systems? a) a potent inhibitor of ferredoxin b) the removal of oxygen c) the absence of light d) an ADP analog that inhibits ATP synthase
d) an ADP analog that inhibits ATP synthase All three systems use ATP synthase. Ferredoxin is an electron transport carrier in chloroplasts but not mitochondria which use Coenzyme Q and cytochrome C instead. Oxygen is required only in mitochondria. Light would only affect chloroplasts.
Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential? a) by closing Na+ channels b) by preventing the secretion of excitatory neurotransmitters c) by opening K+ channels d) by opening Cl− channels
d) by opening Cl− channels Inhibitory neurons release inhibitory neurotransmitters such as GABA and glycine. They bind to and open ligand-gated Cl− channels. This lowers the membrane potential making it harder to reach the threshold where Na+ channels will be activated. If Na+ channels are open, Cl− ions will rush into the cell as well, neutralizing the positive charges carried by Na+.
Inside an active mitochondrion, MOST electrons follow which pathway? a) citric acid cycle → NADH2 → electron transport chain → ATP b) pyruvate → citric acid cycle → ATP → NADH → oxygen c) glycolysis → NADH → ETC → ATP d) citric acid cycle → NADH → electron transport chain → oxygen
d) citric acid cycle → NADH → electron transport chain → oxygen
Which of these lipids would you be LEAST likely to find on the outer leaflet of an endocytic vesicle? a) phosphatidylcholine b) cholesterol c) phosphatidylserine d) galactocerebroside e) glycerophospholipid
d) galactocerebroside Galactocerebroside is a glycolipid: "galacto" refers to the sugar galactose. Glycolipids face AWAY from the cytoplasm. Therefore, they may be found on the inner leaflet of a vesicle, but NOT on the outer leaflet facing the cytoplasm.
Lysozyme is an enzyme that specifically recognizes and cleaves bacterial polysaccharides, which renders it an effective antibacterial agent. Into what classification of enzymes does lysozyme fall? a) isomerase b) protease c) nuclease d) hydrolase
d) hydrolase From the lecture you should know the reaction lysozyme catlyzes and the details how it adds water to break the bonds between the sugar subunits. From the chart of enzyme types you need to study you know this type of reaction is a hydrolase.
You conduct an experiment where you put purified bacteriarhodopsin (a light driven H+ pump) in lipid liposomes with ATP synthase you purified from heart mitochondria. Which components do you need to add to your experiment to generate ATP? (select all that apply) a) NADH b) NADP+ c) oxygen d) light e) ADP + inorganic phosphate
d) light e) ADP + inorganic phosphate Light is used by bacteriarhodopsin to generate the H+ gradient. The gradient and ADP and Pi are all that are needed for ATP synthase to make ATP. Electron carriers aren't needed in this experiment because light is being used to power the proton pump, not electron transport.
Which are the net products of glycolysis for one molecule of glucose that enters? a) 4 ATP + 2 pyruvate + 2 NADH b) 4 ATP + 2 pyruvate + 2 NAD+ c) 2 ATP + pyruvate + NADH d) 2 ATP + pyruvate + NAD+ e) 2 ATP + 2 pyruvate + 2 NADH
e) 2 ATP + 2 pyruvate + 2 NADH Throughout glycolysis you actually make 4 ATPs + 2 pyruvates + 2 NADH. However, the process uses 2 ATPs in the early stages. Therefore, the net result is: 2 ATP + 2 pyruvate + 2 NADH
Which of the following reactions would occur spontaneously? a) NADPH oxidized to form NADP+ b) sucrose broken down into glucose and fructose c) ATP hydrolyzed to ADP and inorganic phosphate d) Acetyl-CoA transfers two carbons and releases Coenzyme A. e) All of the above would be spontaneous.
e) All of the above would be spontaneous. NADPH, ATP, and acetyl CoA are all energy carrier molecules we looked at examples for in the lecture/ your text book. This means that breakdown of these molecules is very negative delta G (spontaneous) that can be used to catalyze reactions with a positive delta G. We also know sucrose breakdown is spontaneous because A) it a catabolic process and B) we looked at synthesis of sucrose as an example of a non-spontaneous reaction that required coupling in order to make it spontaneous... this means that the reverse would be a spontaneous reaction and not require coupling. So the answer is all of the above.
ΔG measures the change of free energy in a system as it converts reactant (Y) into product (X). ΔG is equal to... a) ΔG° + RT b) ln [X]/[Y] c) - TΔS d) free energy of the reactants minus the free energy of the products e) none of the above
e) none of the above from our three delta G equations we know: ΔG = ΔG° + RT ln [X]/[Y], because Q= [X]/[Y]. Also, ΔG = ΔH- TΔS also, ΔG = G of X - G of Y None of these correspond to the answer above.
true or false: glycolysis requires oxygen
false Glycolysis is an independent metabolic process that involves the break down of glucose. Glycolysis is an anaerobic process, oxygen is not required for glycolysis to take place. Oxygen is not used in glycolysis in any shape or form. O2 is required if the pyruvate produced in glycolysis is to be broken down any further.
all carriers, channels, and transporters are what kind of membrane proteins?
integral membrane proteins
Triacylglycerol
the storage form of fats glycerol with 3 fatty acid chains attached
