Bio Test 2 (Symula)
For one molecule of Acetyl-CoA, the citric acid cycle produces... a) 3NADH b) 2FADH2 c) 4CO2 d) 2ATP or GTP e) 2H2O
A) 3NADH Why? One turn of the citric acid cycle releases two carbon dioxide molecules and produces three NADH, one FADH2, and one ATP or GTP
The dissociation constant of a ligand is... a) a measure of the affinity of the receptor for its ligand. b) higher when ligand-receptor binding occurs at low ligand concentrations. c) The rate at which a ligand binds its receptors. d) The dose at which drugs can act as ligands. e) Lower when ligand-receptor binding occurs at high ligand concentrations.
A) A measure of the affinity of the receptor for its ligand. Why? - Dissociation Constant: A mathematical constant that describes the tendency of a large molecule to dissociate reversibly into smaller components. - Affinity: The resemblances in structure between two organisms or between biological populations implicating that they are of a common origin
Which of the following processes is best matched with where it occurs in the cell? a) ATP synthesis; mitochondrial matrix b) Glycolysis; mitochondria c) Chemiosmosis; cytoplasm d) citric acid cycle; intermembrane space in mitochondria e) Electron transport chain; cytoplasm
A) ATP synthesis; mitochondrial matrix Why? ATP is synthesized in the electron transport chain which takes place in the matrix of the mitochondria
Which of the following statements about calcium is true? a) Active transport maintains the concentration difference of calcium ions between the cytoplasm of a cell and its extracellular compartment. b) Calcium ions are usually more concentrated in the cytoplasm than outside the cell. c) IP3 is a signal that causes calcium channels to close. d) A cell can increase intracellular concentrations of calcium by making more calcium. e) In a fertilized egg, an increase in intracellular calcium leads to decreased activity of protein kinase C.
A) Active transport maintains the concentration difference of calcium ions between the cytoplasm of a cell and its extracellular compartment Why? Since in the normal state of a cell, large concentration differences in K+, Na+ and Ca2+ are maintained, it is evident that active transport mechanisms are at work.
Which of the following compounds listed below link(s) glycolysis and the citric acid cycle to the electron transport chain? a) Both b and d b) NADH c) ADP and Pi d) ATP e) FADH2
A) Both b and d
During the citric acid cycle, the oxidation of _________ occurs at the same time as the reduction of _________. a) Carbons from the original glucose molecule; NAD+ b) Carbon dioxide; NADH c) NAD+ ; carbons from the original glucose molecule d) NADH; carbon dioxide
A) Carbons from the original glucose molecule; NAD+ Why? - isocitrate is oxidized, producing a five-carbon molecule, α-ketoglutarate, together with a molecule of CO2 and two electrons, which reduce NAD+ to NADH. - The hydroxyethyl group is oxidized to an acetyl group, and the electrons are picked up by NAD+, forming NADH
The synthesis of ATP from ADP and Pi is an _______ reaction. In mitochondria, ATP synthesis is driven by the flow of _______ down the concentration and electrical gradient established by _______. a) Endergonic; protons; electron transport b) Exergonic; Na+ ions; glycolysis c) Exergonc; protons; glycolysis d) Endergonic; Na+ ions; electron transport e) Endergonic; protons; citric acid cycle
A) Endergonic; protons; electron transport
Which of the following best describes the reaction Glucose + 6O2 ----> 6CO2 +6H2O Delta G = -686kcal/mol a) It is exergonic, so it releases energy b) It is exergonic, so it uses energy c) It is endergonic, so it releases energy d) It is endergonic, so it uses energy
A) It is exergonic, so it releases energy
In photosynthesis, the production of NADP+ does what to the carbons from CO2? a) It reduces them b) It oxidizes them c) It forms covalent bonds between them d) It has no effect on CO2 e) It changes them into a sugar
A) It reduces them Why? pg. 196 the Calvin cycle uses the ATP and NADPH to produce carbohydrate. Therefore the production of NADP+ reduces (Adds phosphate) to the Carbons from CO2.
Which of the following statements about membrane receptors in a signal transduction pathway is true? a) Ligands bind to the extracellular binding domain and do not enter the cell. b) Ligands enter the cell and bind to the cytoplasmic side of the receptor. c) They are embedded in the cell membrane but do not span its width. d) Ligands bind irreversibly to the membrane receptor. e) Ligands bind to the extracellular binding domain and then enter the cell.
A) Ligands bind to the extracellular binding domain and do not enter the cell. Why? Signal Transduction Pathway: cell converts extracellular signals into intracellular events
Most of the ATP made during the complete oxidation of glucose to CO2 and water is a) Made by the mitochondrial ATP synthase. b) Synthesized by the sodium-potassium ATPase. c) Synthesized in the cytosol. d) Made from substrate-level phosphorylation. e) Made directly by the citric acid cycle.
A) Made by the mitochondrial ATP synthase.
The binding of a substrate to an enzyme a) May involve hydrogen bonds and van der Waals interactions. b) Is always covalent. c) Is nonspecific. d) Is irreversible. e) Does not induce shape changes in the enzyme.
A) May involve hydrogen bonds and van der waals interactions
Which part of photosynthesis occurs outside of the chloroplast? a) None of the photosynthesis occurs outside of the chloroplast b) The light reactions c) Cyclic electron transport d) Noncyclic electron transport e) The Calvin cycle
A) None of the photosynthesis occurs outside of the chloroplast Why? Photosynthesis takes place inside plant cells in small things called chloroplasts. Chloroplasts (mostly found in the mesophyll layer) contain a green substance called chlorophyll.
Triglycerides are major energy storage molecules. Which of the following, about the complete oxidation of triglycerides to CO2 and water and the oxidation of glucose to two molecules of pyruvate, is correct? a) Only glucose oxidation uses the glycolytic pathway. b) Catabolism of both triglycerides and glucose to pyruvate involves the production of Acetyl CoA as an intermediate. c) Catabolism of both triglycerides and glucose is endergonic. d) Catabolism of both triglycerides and glucose to pyruvate involves the citric acid cycle. e) Catabolism of triglycerides and catabolism of glucose to pyruvate involves the electron transportation chain.
A) Only glucose oxidation uses the glycolytic pathway. Why? because Pyruvate is made in Glycolysis.
If an inhibitor was bound to mitochondrial ATP synthase, it would prevent the a) Production of ATP at the expense of the proton gradient established by electron transport. b) Rotation of the membrane component of ATP synthase. c) Rotation of ATP synthase F1 in the mitochondrial inner membrane space. d) Coupling of the synthesis of ATP to the flow of protons from the mitochondrial matrix to the mitochondrial intermembrane space. e) Both a and b
A) Production of ATP at the expense of the proton gradient established by electron transport.
CO2 is fixed using the enzyme ________ and is used during the _________. a) Rubisco; the Calvin cycle b) RuBP; the Clavin cycle c) NADPH; the light reactions d) NADPH; the Calvin cycle e) Rubisco; the citric acid cycle
A) Rubisco; the Calvin cycle
When a message from outside a cell is transferred to the inside of a cell, what process has occurred? a) Signal transduction b) Signal amplification c) Depolarization d) Signal Recognition e) Signal phosphorylation
A) Signal Transduction Why? Signal Transduction is the transmission of molecular signals from a cell's exterior to its interior. Signals received by cells must be transmitted effectively into the cell to ensure an appropriate response. This step is initiated by cell-surface receptors.
Which of the following statements about gap junctions is true? a) They permit signal movement among linked cells. b) They occur mainly in plants. c) They are made of structural G proteins. d) They generally occupy a small percent (less than 1%) of the area of the plasma membrane. e) Their structure allows communication within a cell.
A) They permit signal movement among linked cells Why? - Gap Junctions: are a specialized intercellular connection between a multitude of animal cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between the linked cells.
In the citric acid cycle, electrons are transferred a) To NAD+ b) To NADH c) From NAD+ d) From NADH e) To ATP
A) To NAD+
Which of the following is a role of both NADH and NADPH? a) To carry and transfer energy from electrons b) To increase the reaction rate c) To activate ATP synthase directly d) To become reduced e) To act as enzymes that build ATP
A) To carry and transfer energy from electrons
In the experiment used to identify the source of oxygen waste from photosynthesis researchers.... a) Used an isotope of oxygen b) Inhibited redox reactions with leaves c) Used isotopes of hydrogen d) Used an isotope of carbon in CO2 e) Found CO2 was the source of oxygen
A) Used and isotope of oxygen Why? - Plants watered with water containing 18O atoms release oxygen gas containing 18O atoms - Plants supplied with carbon dioxide containing 18O atoms do not release oxygen gas containing 18O atoms - This shows that the oxygen gas produced by photosynthesis comes from water and not carbon dioxide.
To be metabolized, glucose must be converted to glucose 6-phosphate. However, at equilibrium, a mixture of glucose and phosphate at concentrations that exist in cells would contain little glucose 6-phosphate. How do cells circumvent this problem? a) Phosphate from the hydrolysis of ADP is used to phosphorylate glucose. b) ATP is used as the donor of the phosphate group, and thus the formation of glucose 6-phosphate is exergonic. c) An enzyme raises the activation energy barrier to favor glucose 6-phosphate formation. d) An enzyme changes the equilibrium constant for the reaction to favor glucose 6-phosphate formation. e) ATP is used as the donor of the phosphate group, and the formation of glucose 6-phosphate is endergonic.
B) ATP is used as the donor of the phosphate group, and thus the formation of glucose 6-phosphate is exergonic
The synthesis of ATP from ADP and Pi by substrate-level phosphorylation a) Takes place in the absence of oxygen. b) Accounts for a minor fraction of all ATPs made by cells. c) Is an oxidative phosphorylation reaction. d) Occurs in the cytochrome c oxidase complex. e) Creates a proton gradient.
B) Accounts for a minor fraction of all ATPs made by cells.
The _______ of photosynthesis overlaps the _______ of chlorophyll a and b. a) Action spectrum; fluorescence spectrum b) Action spectrum; absorption spectrum c) Absorption spectrum; fluorescence spectrum d) None of the above e) Absorption spectrum; action spectrum
B) Action spectrum; absorption spectrum Why? -Action Spectrum: A plot of the rate of photosynthesis carried out by an organism against the wavelengths of light ot which it is exposed. -Absorbtion Spectrum: A plot of light absorbed by a purified pigment against wavelength.
A protein kinase cascade can amplify an intracellular signal by a) Activating a G protein which then binds and activates a second protein, amplifying the signal. b) Activating one kinase molecule that can then trigger the activation of many proteins. c) Using transcription factors to increase gene expression. d) Opening gap junctions to allow diffusion of signals from neighboring cells. e) Using nitric oxide to quickly diffuse into cells, amplifying the response.
B) Activating one kinase molecule that can trigger the activation of many proteins
If cell A has 20 receptors for a signal and cell B has 40 receptors for that signal and both cells are exposed to the same amount of signal ... a) Only cell A will generate a response b) Cell B will be more sensitive than cell A c) Cell A will be more sensitive than cell B d) Only cell B will generate a response e) Both cells are equally sensitive
B) Cell B will be more sensitive than cell A Why? Cell B has more receptors
CO2 is produced during which of the steps of cellular respiration? a) Glycolysis b) Citric acid cycle c) Electron transport d) Chemiosmosis e) A and C
B) Citric acid cycle Why? CO2 is released in the Citric Acid Cycle
If an enzyme requires a biotin molecule in order to function, that molecule is probably a(n) _________. a) Cofactor b) Coenzyme c) Prosthetic Group d) Second messenger e) Allosteric activator
B) Coenzyme Why? From table 8.2 in the book: Coenzymes **-Biotin** -Coenzyme A -NAD -ATP
Gap junctions allow passage of ions and small proteins from one cell to the next through small channels called... a) Plasmodesmata b) Connexons c) Receptor proteins d) Desmosomes e) Desmotubules
B) Connexions Why? Connexions: A protein that forms tunnels across gap junctions, enabling ions or small molecules, such as glucose, to pass from one cell to another.
What is the metabolic fate of pyruvate in anaerobic muscle? a) It is decarboxylated. b) It is reduced to lactate. c) It is oxidized. d) It is converted to ethanol. e) It is converted to acetyl CoA.
B) It is reduced to lactate.
An enzyme, which is a component of a metabolic pathway, is allosterically regulated by a downstream intermediate of that particular metabolic pathway. Which of the following is a likely role for this particular enzyme? a) It acts by degrading other enzymes in the pathway. b) It regulates the pathway through a feedback inhibition mechanism. c) It irreversibly binds to the product of its pathway step, reducing product concentration. d) It is inhibited by upstream intermediates of the pathway. e) It senses the optimal temperature for the pathway by denaturing at excessively high temperature.
B) It regulates the pathway through a feedback inhibition mechanism Why? A cellular control mechanism in which an enzyme that catalyzes the production of a particular substance in the cell is inhibited when that substance has accumulated to a certain level, thereby balancing the amount provided with the amount needed.
The molecule that binds to a specific three-dimensional site on a cellular receptor is referred to as a(n) a) Regulator. b) Ligand. c) Ion channel. d) Receptor. e) Chaperone.
B) Ligand Why? Ligand: Molecule that binds to a receptor site on another molecule by fitting into a 3D site on the cellular receptor
The products of noncyclic electron transport are a) NADP+, O2, and ATP. b) NADPH, O2, and ATP. c) ATP. d) NADPH and ATP. e) NADP+ and ATP.
B) NADPH, O2, and ATP. http://image.slidesharecdn.com/photosynthesis-130329125857-phpapp02/95/photosynthesis-24-638.jpg?cb=1364562002
The electron carries NAD+ , FAD, NADP+ all belong to _________, are _________ and are _______by electron transport. a) Nucleic acids; coenzymes; oxidized b) Nucleic acids; coenzymes; reduced c) Nucleic acids; cofacotors, reduced d) Proteins; cofactors; oxidized e) Proteins; coenzymes; reduced
B) Nucleic acids; coenzymes; reduced
The end product(s) of glycolysis is/are a) Acetyl CoA, ATP, and NADH. b) Pyruvate, ATP, and NADH. c) Pyruvate, ATP, and NAD+. d) Acetyl CoA, ATP, and NAD+. e) Pyruvate.
B) Pyruvate, ATP, and NADH.
The major product of photosynthesis that is exported from the leaves to the rest of the plant is a) Glucose. b) Sucrose. c) Amino acids. d) Nucleotides. e) Starch.
B) Sucrose Why? Book pg 195 Glucose and Fructose may be converted into Sucrose which is transported out of the leaf to other organs in the plant. The organs hydrolyze the sucrose to its constituent monosaccharides, which can be used as sources of energy or as building blocks for other molecules.
Which of the following statements disagrees with the second law of thermodynamics? a) Chemical energy may be converted to light energy. b) The disorder of a system decreases overall with time. c) Only a portion of the total energy of a system is available to do work. d) Potential energy may be used to do work. e) During energy conversion some energy can be lost as heat.
B) The disorder or a system decreases overall with time Why? The second law of thermodynamics states that the total entropy of an isolated system always increases over time, or remains constant in ideal cases where the system is in a steady state or undergoing a reversible process.
Which of the following is not a characteristic of C4 plants? a) C4 plants use the Calvin cycle. b) The first product of photosynthesis in C4 plants is a 3 carbon molecule. c) C4 plants have less ancient origins than C3 plants. d) C4 plants contain RuBP carboxylase and PEP carboxylase. e) C4 plants are better adapted to hot climates than C3 plants.
B) The first product of photosynthesis in C4 plants is a 3 carbon molecule.
The concentration of CO2 in Earth's atmosphere has increased over the past 200 years. If this trend continues, what could happen to photosynthesis, assuming the concentration of oxygen in the atmosphere will not change? a) The net yield of C3-driven photosynthesis should decrease; C4-driven photosynthesis should be unaffected. b) The net yield of C3-driven photosynthesis should increase; C4-driven photosynthesis should be unaffected. c) The net yield of C3-driven photosynthesis should stay the same; C4-driven photosynthesis should increase. d) Both the net yield of C3-driven photosynthesis and C4-driven photosynthesis should not change. e) None of the above
B) The net yield of C3-driven photosynthesis should increase; C4-driven photosynthesis should be unaffected.
Which of the following statements about ATP is false? a) The phosphate bond energy of ATP may be transformed into light. b) The phosphate bond energy of ATP cannot be harnessed for work. c) ATP is a building block of RNA. d) The synthesis of ATP is an endergonic reaction. e) The hydrolysis of ATP to ADP and Pi is an exergonic reaction.
B) The phosphate bond energy of ATP cannot be harnessed for work Why? The hydrolysis of ATP yields free energy
During signal transduction, signal amplification occurs when a) The signal binds to a receptor b) The signal activates many cellular processes c) The signal causes an ion channel to open d) The signal binds to a receptor more than once
B) The signal activates many cellular processes. Why? Signal Amplification: The binding of one or a few neurotransmitter molecules can enable the entry of millions of ions.
Which of the following statements about intracellular receptors is false? a) They may be bound to chaperone proteins. b) Their ligands are usually hydrophilic. c) They may respond to light. d) They may move into the nucleus. e) Some are transcription factors.
B) Their ligands are usually hydrophilic
Plants that carry out crassulacean acid metabolism (CAM) differ from C4 plants in that a) They do not carry out the Calvin cycle. b) Their stomata are open at night. c) They do not need ATP for photosynthesis. d) They do not contain PEP carboxylase. e) They do not contain rubisco.
B) Their stomata are open at night.
Which of the following is not true about enzymes? a) They bind specific substrates at their active sites b) They cannot be used again after binding their substrates c) They can cause physical strain on a chemical bond d) They speed up the rate of the reaction e) They have no effect of the delta G of a reaction
B) They cannot be used again after binding their substrates Why? They can bind rebind and bind again
Which of the following is required for a cell to respond to a peptide signal like oxytocin? a) A signal cascade b) A second messenger c) A membrane-bound receptor d) It is catabolic e) It can be coupled with ATP hydrolysis
C) A membrane-bound receptor
Which statement given below best characterizes the properties of a photosystem? a) A photosystem consists of pigments and proteins but not a reaction center chlorophyll. b) A photosystem consists of pigments such as chlorophyll but not proteins. c) A photosystem is a complex of pigments, proteins, and a reaction center chlorophyll. d) A photosystem consists of a reaction center chlorophyll but not light-harvesting pigments and proteins. e) A photosystem consists of light-harvesting pigments but no reaction center chlorophyll.
C) A photosystem is a complex of pigments, proteins, and a reaction center chlorophyll.
In response to a chemical signal, the receptor on an intestinal cell have phosphates transferred to it, the type of receptor is probably a) A gated ion channel b) A voltage channel c) A protein kinase receptor d) A g-protein receptor
C) A protein kinase receptor Why? The role of a kinase is to complete phosphorylation
In an experiment on cellular respiration, Edith was examining the effect of starving rats of the rate of cellular respiration. After 2 days of starvation, Edith found a high level of ADP and NAD+ in rat muscle tissue compared to well-fed rat groups. If she were to measure the enzyme isocitrate dehydrogenase (ICDH) from the citric acid cycle, you could predict that ICDH would be a) At the same levels in starved and well-fed rats b) Active and at high levels only in the well-fed rats. c) Active in both groups and at higher levels only in the starved rats d) At the same levels, but in the active form in well-fed rats and in the deactivated form in starved rats
C) Active in both groups and at higher levels only in the starved rats.
The correct order of the four derivatives of ATP from the least number of attached phosphate groups to most number of attached phosphate groups is a) AMP, ADP, ATP, and adenosine. b) ADP, ATP, adenosine, and AMP. c) Adenosine, AMP, ADP, and ATP. d) ATP, ADP, AMP, and adenosine. e) Adenosine, ATP, ADP, and AMP.
C) Adenosine, AMP, ADP, and ATP
The membrane-lined bridges called plamodesmata that span the cell walls between plant cells a) Have a large space for diffusion of cytoplasmic components between cells. b) Have central tubes derived from the Golgi apparatus. c) Allow as much flow between cells as do gap junctions in animal cells. d) Function primarily as tight junctions between cells. e) Contain channels made by connexons.
C) Allows as much flow between cells as do gap junctions in animal cells Why? They permit the intercellular passage of molecules and signals and play a central role in plant physiology and development. Evidence suggests that small molecules can pass from cell to cell by passive diffusion and that this is controlled by regulation of the pore itself. This contributes to processes such as the transport of sugars between cells and tissues.
The signal transduction pathway leading to the perception in the brain of an odorant molecule starts with.... a) Opening of gated calcium ion channels, resulting in changes in cytoplasmic ion concentrations b) Diffusion of the odorant molecule into neurons c) Binding of the odorant molecule to a transmembrane receptor and activation of a G protein d) Activation of a G protein, which in turn activates adenylyl cyclase causing synthesis of cAMP e) Activation of phosphodiesterase, resulting in a lowering of cAMP levels.
C) Binding of the odorant molecule to a transmembrane receptor and activation of a G protein Why? - Binding of odorant molecules to receptors triggers a signal transduction pathway, sending action potentials to the brain
Protein kinase receptors phosphorylate themselves and/or other proteins when activated, resulting in a(n) a) Decrease in ligand-receptor binding. b) Change in the dissociation constant. c) Change in shape and function of the proteins. d) Inhibition of further transduction of the signal. e) Increase in production of ATP.
C) Change in shape and function of proteins Why? - Phosphorylation: Phosphorylation is a chemical reaction that adds a phosphate group consisting of one phosphorus atom and four oxygen atoms to an organic molecule such as a protein. -The strong negative charge on a phosphate group changes the way a protein is shaped
NADH is made during the _______ and used during the _________. a) Energy-harvesting reactions; citric acid cycle b) Energy-investing reactions; citric acid cycle c) Citiric acid cycle; electron transport chain d) Energy-investing reactions; electron transport chain
C) Citric acid cycle; electron transport chain Why? The outputs of the Citric acid cycle are carbon dioxide, reduced electron carriers (NADH and FADH2), and a small amount of GTP The electron transport chain in cellular respiration will take the energy stored in NADH and FADH2 during the citric acid cycle and convert it to chemical bond energy in the form of ATP.
When cyanide was found in the Tylenol taken by several people, the victims NAD+ levels were very low and NADH levels were very high. This was because? a) Glycolysis produced excess NADH b) Citric acid cycle enzymes were inhibited so could not reduce NAD+ c) Cyanide blocked the electron transport chain d) Citric acid cycle enzymes were over-activated by NAD+
C) Cyanide blocked the electron transport chain
Based on the second law of thermodynamics, which must also be true about a catabolic reaction? a) Delta H Increases b) Delta H Decreases c) Delta S is positive d) Delta S is negative
C) Delta S is positive Why? - Second Law of Thermodynamics: The second law of thermodynamics states that the total entropy of an isolated system always increases over time, or remains constant in ideal cases where the system is in a steady state or undergoing a reversible process. - Catabolic Reaction: Catabolic reactions give out energy. They are exergonic. In a catabolic reaction large molecules are broken down into smaller ones.
The synthesis of complex molecules is _______, whereas their degradation is _______. Synthesis occurs with _______ in entropy. a) Exergonic; endergonic; an increase b) Endergonic; exergonic; no change c) Endergonic; exergonic; a decrease d) Exergonic; endergonic; no change e) Endergonic; exergonic; an increase
C) Endergonic; exergonic; a decrease Why? Synthesis of a complex molecule is Endergonic because it takes energy to build a molecule. When that molecule is broken, the reaction is exergonic. And synthesis occurs with a decrease in entropy because it loses disorder, it becomes less free.
In biology, energy cannot be captured from which of the following? a) Redox reactions b) Ion gradients c) Entropy d) ATP hydrolysis e) Breaking covalent bonds
C) Entropy Why? Entropy is a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.
The light-independent reactions ______ While the light-dependent reactions _______. a) Make O2; split water b) Split H2O; make ATP c) Fix CO2; make ATP d) Fix CO2; use ATP e) Make ATP; split water
C) Fix CO2; make ATP Why? Light independent reactions use ATP and do carbon fixation, but in order for this to happen Light depend reactions must make the ATP (Book pg 188)
C4 plants differ from C3 plants because C3 plants _______ while C4 plants _______. a) Gain CO2 via photorespiration; lose CO2 via photorespiration b) Can concentrate the CO2 by regulating the stomata closure; can concentrate CO2 at night c) Have mesophyll cells that fix CO2 and contain the Calvin cycle; have mesophyll cells that fix CO2 and bundle sheath cells that contain the Calvin cycle d) Produce a four-carbon intermediate after CO2 fixation; produce a three-carbon intermediate after CO2 fixation e) Concentrate CO2 near rubisco; cannot concentrate CO2 near rubisco
C) Have mesophyll cells that fix CO2 and contain the Calvin cycle; have mesophyll cells that fix CO2 and bundle sheath cells that contain the Calvin cycle
When citric acid (citrate) levels are very high, which of the following is unlikely to continue to occur? a) Allosteric inhibition of glycolysis enzymes like PFK b) Increased fatty acid synthesis c) Increased G3P production d) To become reduced e) To act as enzymes that build ATP
C) Increased G3P production Why: Because Citric Acid (Citrate) Inhibits the enzyme PFK. PFK catalyzes the important steps of glycolysis. PFK is an enzyme that functions in carbohydrate metabolism and especially in glycolysis by catalyzing the transfer of a second phosphate (as from ATP) to fructose. If Citrate inhibits PFK it stops Pyruvate oxidation, citric acid cycle, and ETC.
In addition to driving the synthesis of ATP and the reduction of NADP+ to NADPH, light stimulates the Calvin cycle by _______ and _______. a) Increasing the pH of the stroma; oxidation of some enzymes b) None of the above c) Increasing the pH of the stroma; reduction of some enzymes d) Decreasing the pH of the stroma; reduction of some enzymes e) Decreasing the pH of the stroma; oxidation of some enzymes
C) Increasing the pH of the stroma; reduction of some enzymes Why? -Proton transfer from the stroma into the thylakoid lumen causes an increase in the pH of the stroma. (Book pg 196) - Because ATP and NADPH are oxidized to form ADP and NADP+... The H+ they each lost is transferred to the Enzyme.
The G protein-mediated cascade stimulated by epinephrine results in the phosphorylation of two key liver enzymes which eventually results in the _______ of glycogen synthase and the _______ of glycogen phosphorylase, leading to the release of glucose. a) Stimulation; transcription b) Stimulation; inhibition c) Inhibition; stimulation d) Inhibition; inhibition e) Inhibition; transcription
C) Inhibition; stimulation Why? Epinephrine activates glycogen phosphorylase in liver cells
Crosstalk in cell signaling refers to the... a) inactivation of multiple signal transduction pathways. b) convergence of enzymes and transcription factors. c) interaction of signal transduction pathways d) activation and inactivation of enzymes. e) activation of a signal transduction pathway.
C) Interaction of signal transduction pathways Why? -cell signaling pathways may operate independently, or communicate with one another to integrate their response to cellular signals coming from different controlling cells -interpathway interaction=crosstalk
If ΔG for a reaction is positive, the reaction a) Would proceed quickly. b) Could drive an energy-requiring process. c) Is endergonic. d) Would have a positive ΔH. e) Is spontaneous.
C) Is endergonic Why? Positive Delta G indicates: - Non spontaneous - Endothermic - Endergonic - Negative Entropy
The chemical reaction NAD+ +2e- + 2H ----> NADH has a Delta G of 52.4 Kcal/mol. Which of the following is true about this reaction? a) It releases free energy b) It is exergonic c) It has a negative Delta S d) It is catabolic e) It can be coupled with ATP hydrolysis
C) It has a negative Delta S Why? It looses disorder. It becomes one piece instead of multiple pieces.
Which of the following, about the citric acid cycle, is false? a) It does not operate under anaerobic conditions. b) It requires NAD+ and FAD. c) It releases less energy than glycolysis. d) CO2 is released during operation of the cycle. e) It takes place in the mitochondrial matrix.
C) It releases less energy than glycolysis. Why? Glycolysis releases: 2ATP and 2NADH Citric Acid Cycle releases: 1 ATP, 3NADH, and 1FADH2
To make ATP, substrate-level phosphorylation requires a(n) ________ and oxidative phosphorylation requires_________. a) Enzyme; oxygen b) Phosphates; oxygen c) Kinase; proton gradient d) Proton gradient; enzymes
C) Kinase; proton gradient Why? - A protein kinase is a kinase enzyme that modifies other proteins by chemically adding phosphate groups to them (phosphorylation) - Oxidative phosphorylation (or OXPHOS in short) is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing energy which is used to reform ATP. In most eukaryotes, this takes place inside mitochondria.... and.....a proton gradient is a higher concentration of protons outside the inner membrane of the mitochondria than inside the membrane is the driving force behind ATP synthesis.
CO2 enters a plant via the _______ and H2O enters a plant via the _______. a) Leaves; leaves b) Stems; leaves c) Leaves; roots d) Roots; leaves e) Roots; roots
C) Leaves; roots Why? - Plants get carbon dioxide from the air through their leaves. - Water is taken up by the roots of a plant.
The ultimate source of energy for ATP synthesis in chloroplasts is a) The electrochemical proton gradient across the chloroplast outer membrane. b) Energized chlorophylls. c) Light. d) The electrochemical proton gradient across the thylakoid membrane. e) Electron transport.
C) Light
Which of the following statements about the role of chlorophyll in photosynthesis is false? a) Chlorophyll contains Mg2+. b) Chlorophyll appears green because it reflects green light. c) Most of the chlorophyll in a plant participates in an oxidation/reduction reaction. d) Most of the chlorophyll in a plant functions to gather light. e) Chlorophyll is present in light-harvesting complexes also known as antenna systems.
C) Most of the chlorophyll in a plant participates in an oxidation/reduction reaction.
The role of NADP+ in photosynthesis is most like the role of which molecule in cellular respiration? a) CO2 b) NADH c) O2 d) Glucose e) G3P
C) O2 Why? NADP+ is the final electron receptor in photosynthesis
The electron transport chain a) Oxidizes water to O2 and 2 H+. b) Pumps protons into the mitochondrial matrix during electron transport. c) Oxidizes the intermediate electron carriers, NADH and FADH2. d) Is the site of most reactions of the citric acid cycle. e) Synthesizes ATP.
C) Oxidizes the intermediate electron carriers, NADH and FADH2.
Which of the following is not a way that enzymes increase a rate of a reaction? a) Donating a proton to the substrate b) Inducing strain on the substrate c) Permanently binding the substrate d) Orienting substrates e) Reacting chemically with the substrate
C) Permanently binding the substrate Why? Enzymes increase the rate of a reaction by: - orienting substrates - inducing strain in the substrate - temporarily add chemical groups to substrates ex: transfer H+ to the substrate, functional groups form temporary substrates, and metal ions that are firmly bound to side chains of enzymes can lose or gain electrons
Which of the following reactions is not an oxidation-reduction reaction? a) FAD + H2O ↔ FADH2 + ½ O2 b) NADH + acetaldehyde ↔ NAD+ + ethanol c) R—CH = CH—CH3 + H2O ↔ RCH2—CH (OH)—CH3 d) NADH + ½ O2 + H+ ↔ NAD+ + H2O e) AH2 + B ↔ A + BH2
C) R—CH = CH—CH3 + H2O ↔ RCH2—CH (OH)—CH3
Guichard et al. (2013) investigated the process of cell signaling in the presence of cholera toxin (CTX). Specifically, they investigated a molecule that is known to intensify diarrhea in the presence of CTX, but also found that this molecule disrupted the formation of cell-cell junctions. Since this molecule triggers many different reactions, it probably functions as a(n) _______. a) Receptor b) Juxtacrine signal c) Second messenger d) Effector e) G-protein
C) Second Messenger Why? Secondary Messengers activate Kinase cascades (The product of one reaction starts another reaction).
PIP2 is a phospholipid in cell membranes that produces two lipid-derived _______ when hydrolyzed by phospholipase C. a) Receptors b) Targets c) Second messengers d) Kinase receptors e) Enzymes
C) Second Messengers Why? A variety of hormones and growth factors stimulate the hydrolysis of PIP2 by phospholipase C -- a reaction that produces two distinct second messengers, diacylglycerol and inositol 1,4,5-trisphosphate (IP3)
Which of the following is the correct ordering of the steps in a generalized signal transduction pathway? a) Signal molecule enters the nucleus; signal molecule binds to DNA; transcription of specific genes occurs b) Signal molecule binds to the extracellular region of the receptor; signal molecule diffuses through cell membrane; signal is transduced to the nucleus where specific genes are turned on or off. c) Signal molecule binds to receptor; molecules within the cell transduce the signal; cell responds d) Signal molecule activates a target cell; target cell binds to a receptor; receptor is activated e) Signal molecule is secreted by a nearby cell; signal molecule enters the cell; signal activates receptor
C) Signal molecule binds to receptor; molecules within the cell transduce the signal; cell responds
Which of the following parameters is indicative of how far and in what direction a reaction will progress? a) The change in enthalpy of the reaction (ΔH) b) The concentration of products c) The change in free energy of the reaction (ΔG) d) The concentration of reactants e) The overall size of the system in which the reaction occurs
C) The change in free energy of the reaction (ΔG)
In cellular respiration, the energy used to make ATP from ADP + Pi comes directly from which of the following? a) ATP synthase b) Oxidation of NADH c) The proton gradient d) Light e) Another ATP molecule
C) The proton gradient Why? Proton Gradient - A higher concentration of protons outside the inner membrane of the mitochondria than inside the membrane is the driving force behind ATP synthesis.
Of the choices below, which best describes the organization of chloroplast membranes? a) Inside a single phospholipid bilayer is a membrane that surrounds the thylakoid b) The thylakoid membrane is outside the stroma c) The stroma is outside the thylakoid membrane, but inside the other 2 membranes d) The stroma is between the two membranes of the chloroplast
C) The stroma is outside the thylakoid membrane but inside the other two membranes.
Which of the following statements is true about photosystems? a) They contain only a single chlorophyll molecule b) Their protons are excited by photons c) They convert light energy to chemical energy d) Protons break covalent bonds in chlorophyll
C) They convert light energy to chemical energy Why? Photosystems - photosystems are the protein structures in plant chloroplasts that absorb light energy and convert the light energy to chemical energy
The best description of the energy-investing reactions of glycolysis would not include _______. a) They use ATP b) They are endergonic c) They produce pyruvate d) They make G3P e) They split glucose into 2 molecule
C) They produce pyruvate Tip: Endergonic = investing +delta G -Delta S Exergonic= harvesting, -delta G +Delta S
In the complete oxidation of glucose, 6 CO2 molecules are formed per glucose molecule. The number of CO2 molecules released by glycolysis is _______, by pyruvate oxidation is ______, and by the citric acid cycle is _______. a) 1; 1; 4 b) 0; 0; 6 c) 1; 2; 3 d) 0; 2; 4 e) 2; 2; 2
D) 0; 2; 4
The chemical energy stored from photosynthesis represents _______ percent of the total energy of the sunlight hitting a green leaf. a) 100 b) 10 c) 50 d) 5 e) 30
D) 5
The products of cyclic electron transport are a) NADP+ and ATP. b) NADP+, O2, and ATP. c) NADPH and ATP. d) ATP. e) NADPH, O2, and ATP.
D) ATP.
If you were to grow a green plant in a lighted chamber in the presence of radioactive carbon dioxide for several days, which of the following types of compounds in the plant would be radioactive? a) Amino acids and nucleotides. b) Fatty acids and membrane lipids. c) Nucleotides and nucleic acids. d) All of the above e) Carbohydrates, including Calvin cycle intermediates, starch and sucrose.
D) All of the above
Protein kinase receptors can be regulated. If a molecule binds to a site other than the active site and makes the active site available to a signal, the regulation of the protein kinase is done by a(n) __________? a) Competitive inhibitor b) Non-competitive inhibitor c) Allosteric inhibitor d) Allosteric activator e) Irreversible activator
D) Allosteric activator Why? An allosteric activator is an activator that occurs when the binding of one ligand enhances the attraction between substrate molecules and other binding sites.
Reaction center chlorophylls a) Become oxidized in the dark. b) Are not involved in electron transport in photosynthesis. c) Undergo reduction when in the excited state. d) Are oxidized when in the excited state. e) Have a different structure from most of the antennae chlorophylls.
D) Are oxidized when in the excited state.
In which process is oxygen reduced in cellular respiration? a) Glycolysis b) Citric acid cycle c) At the start of the electron transport chain d) At the end of the electron transport chain e) During ATP synthesis through ATP synthase
D) At the end of the electron transport chain Why? Oxygen is the final electron receptor. It is reduced to create water.
The product of photosynthesis... a) Is always a 6-Carbon sugar b) Is always a 3-Carbon sugar c) Is only used to fuel cellular respiration d) Can be used to synthesize many macromolecules e) Is always glucose
D) Can be used to synthesize many macromolecules.
In order to decrease the sensitivity of a cell to a particular signal, the cell could... a) Increase the concentration of the signal b) Decrease the concentration of the signal c) Increase the number receptors d) Decrease the number of receptors e) A cell cannot change its sensitivity
D) Decrease the number of receptors Why? sensititivity depends on how many receptors a cell has, therefore, if you have fewer receptors then the sensitivity will be decreased.
Photorespiration a) Is a metabolic pathway that results from carboxylation of RuBP. b) Is a metabolic pathway that takes place entirely within chloroplasts. c) Is a metabolic pathway that is insensitive to the CO2 to O2 concentration ratio. d) Decreases the efficiency of photosynthesis in C3 plants. e) Increases the efficiency of photosynthesis in C4 plants.
D) Decreases the efficiency of photosynthesis in C3 plants.
The first law of thermodynamics states that a) Energy can be created from chemical bonds b) Energy available for work increases c) Spontaneous reactions release energy d) Energy can be transferred, but not created e) Entropy increases following a chemical reaction
D) Energy can be transferred, but not created
Which of the following does not represent a way that living things store potential energy? a) Covalent bonds b) Reduced electron carriers c) Electrochemical gradients d) Entropy
D) Entropy Why? Entropy is disorder or randomness. There is no stored energy within it
Acetyl CoA is a) Formed in the cytosol during the complete oxidation of glucose. b) Used for the synthesis of sugars. c) Formed within mitochondria by the reduction of pyruvate. d) Formed within mitochondria by the oxidation of fatty acids. e) Formed in the cytoplasm by the oxidation of glucose.
D) Formed within mitochondria by the oxidation of fatty acids. Why? Chart 9.13 pg 179.
Which of the following reactions can be coupled with the hydrolysis of a single ATP (Delta G = -7.3kcal/mol) molecule? (DG = Delta G) a) Glucose 1-phosphate ----> glucose 6-phosphate (DG = -1.7kcal/mol) b) ADP + Pi ---> ATP (DG = 7.3kcal/mol) c) Glucose + 6O2 ---> 6CO2 + 6H2O (DG = -686kcal/mol) d) Glucose + Pi ---> Glucose 6-Phosphate +H2O (DG = 3.3kcal/mol) e) All of these, but B
D) Glucose + Pi ---> Glucose 6-Phosphate + H2O (DG = 3.3kcal/mol)
______ is an example of a prosthetic group. a) Iron ions b) Biotin c) Coenzyme A d) Heme e) ATP
D) Heme Why? Table 8.2 Prosthetic Groups: **- Heme** - FAD - Retinal
In cellular respiration, the H+ gradient is formed in the ______ and in photosynthesis the H+ gradient is formed in the _________. a) Intermembrane space; stroma b) Matrix; thylakoid interior c) Matrix; stroma d) Intermembrane space; thylakoid interior e) Cytoplasm; thylakoid interior
D) Intermembrane space; thylakoid interior Why? ETC's H+ gradient forms in the intermembrane space of the Mitochondria.
A reaction that has a negative ΔG a) Is endergonic. b) Must have a negative change in enthalpy. c) Cannot be used to drive a reaction with a positive ΔG. d) Is spontaneous. e) Proceeds more rapidly than a reaction with a neutral ΔG.
D) Is spontaneous Why? A negative Delta G means: - exergonic - exothermic - + entropy - Spontaneous
Entropy a) Tends to increase in a spontaneous reaction. b) Tends to decrease the total energy in the universe. c) Is represented in equations by the letter "H." d) Is the total energy in a system. e) When multiplied times the absolute temperature is the useable energy in a system.
D) Is the total energy in a system Why? What entropy measures is how much energy is spread out in a process OR how spread out the initial energy of a system becomes in that system (at constant temperature).
What is the best description of a spontaneous reaction? a) It requires and enzyme to proceed b) The products have a lower entropy than the reactants c) Once started, it will proceed quickly d) It is exergonic e) It uses free energy
D) It is exergonic Why? An exergonic reaction refers to a reaction where energy is released. Because the reactants lose energy (G decreases), Gibbs free energy (ΔG) is negative under constant temperature and pressure. These reactions usually do not require energy to proceed, and therefore occur spontaneously.
When PIP2 is hydrolyzed, IP3 is released into the cytoplasm where it a) closes Ca2+ channels in the cell membrane, decreasing cytosolic Ca2+. b) activates nitric oxide synthase. c) binds with DAG, which then activates protein kinase C (PKC). d) opens Ca2+ channels in the smooth endoplasmic reticulum, increasing cytosolic Ca2+. e) directly stimulates G protein activation of phospholipase C.
D) Opens Ca2+ channels in the smooth endoplasmic reticulum, increasing cytosolic Ca2+ Why? - Book pg 135 there are many signals that can cause calcium channels to open including IP3. IP3 is the hydrophylic protion of PIP2 and projects into the cytoplasm.
In plants, the citric acid cycle must remake which of the following? a) RuBP following G3P b) RuBP following oxidation of Acetyl CoA c) Citic acid following G3P production d) Oxaloacetate following the oxidation of Acetyl CoA e) None of these. Plants don't use the citric acid cycle.
D) Oxaloacetate following the oxidation of Acetyl CoA Why? Oxaloacetate is remade because the freshly produced oxaloacetate, in turn, reacts with yet another molecule of acetyl CoA, and the cycle begins again.
The majority of ATP is formed during... a) Photosynthesis b) Glycolysis c) The citric acid cycle d) Oxidative phosphorylation e) Substrate-level phosphorylation
D) Oxidative Phosphorylation Why? Oxidative phosphorylation, the process where electron transport from the energy precursors from the citric acid cycle (step 3) leads to the phosphorylation of ADP, producing ATP. This also occurs in the mitochondria.
If lactic acid fermentation occurs, which of the following does not place? a) Glycolysis b) Production of Pyruvate c) Reducing of NAD+ d) Pyruvate oxidation e) ATP synthesis
D) Pyruvate Oxidation Why? Pyruvate oxidation, which follows glycolysis, is essentially the conversion of pyruvate molecules to carbon dioxide, acetyl coenzyme A, and NADH.
For a cell to respond to a signal, the cell must have a specific _______ molecule that can detect the signal. a) Paracrine b) Response c) Autocrine d) Receptor e) Recognition
D) Receptor Why? Receptor: Recognizes its signal very specifically to ensure that only those cells that make a specific receptor will respond to a given signal
In the energy-investing reactions of glycolysis, kinases a) Attach phosphates to ADP b) Rearrange carbon in sugars c) Remove carbons from sugars d) Remove phosphates from ATP
D) Remove phosphates from ATP Why? Kinase: an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule.
If you eat Chick-fil-A for lunch, part of your lunch will contain fats. In which process would your body use the fatty acids from the fats in your lunch to generate ATP? a) Fermentation b) Glycolysis c) Pyruvate Oxidation d) The citric acid cycle e) Electron transport
D) The citric acid cycle
Cyanide inhibits the enzyme in the mitochondrial electron transport chain that reduces O2 to water. Suppose that you add cyanide to a suspension of muscle cells from a rat. Which statement given below is the most accurate with respect to the effects of cyanide on glucose catabolism? a) Both the citric acid cycle and glycolysis would be stimulated. b) The citric acid cycle and glycolysis would be inhibited. c) The citric acid cycle would be inhibited, but glycolysis would not—ethanol accumulates. d) The citric acid cycle would be inhibited, but glycolysis would not—lactic acid accumulates. e) The citric acid cycle would not be inhibited, but glycolysis would.
D) The citric acid cycle would be inhibited, but glycolysis would not—lactic acid accumulates.
The immediate source of energy for ATP synthesis in chloroplasts is a) Electron transport. b) The electrochemical proton gradient across the chloroplast outer membrane. c) Light. d) The electrochemical proton gradient across the thylakoid membrane. e) NADPH.
D) The electrochemical proton gradient across the thylakoid membrane. Why? Ions also carry an electric charge that forms an electric potential across a membrane. If there is an unequal distribution of charges across the membrane, then the difference in electric potential generates a force that drives ion diffusion until the charges are balanced on both sides of the membrane.
Which of the following about the light-independent reactions of photosynthesis is false? a) NADPH is consumed by light-independent reactions. b) The light-independent reactions refer to the pathways by which CO2 is reduced to carbohydrates. c) The light-independent reactions take place in the chloroplast stroma. d) The light-independent reactions operate in the dark. e) ATP is consumed by light-independent reactions.
D) The light-independent reactions operate in the dark. Why? Light-indepent reactions do not directly require light energy; however, in most plants the light independ reactions STOP in the dark because ATP synthesis and NADP+ reduction require light. They dont operate in the dark, they just stop in the dark. They are called dark reactions because they don't require light, not because they occur in the dark.
If an enzyme that normally functions at a pH 7 is exposed to an environment with pH 4, what would you expect to occur? a) The enzyme would function normally b) The enzyme's covalent bonds would break c) The enzyme would no longer be necessary d) The shape of the enzyme's active site would change e) The enzyme would increase the rate of a reaction
D) The shape of the enzyme's active site would change Why? pH denatures proteins and can cause them to change shape and lose their function.
The ultimate source of energy for all living things is... a) Photosynthesis b) Covalent bonds c) Cellular respiration d) The sun e) Glycolysis
D) The sun
The first step of the Calvin Cycle produces a 6-carbon sugar. If the goal is to make 2 3-carbon sugars, why do we need to use more than one CO2 molecule in photosynthesis? a) To balance the equation b) 6CO2 are necessary to make the 6-carbon sugar c) Some CO2 are necessary to make Rubisco d) To remake the RuBP molecule that forms the first 6 carbon sugar e) Many CO2 are reduced by NADPH to make the sugar.
D) To remake the RuBP molecule that forms the first 6 carbon sugars
Rubisco a) Is an enzyme b) Fixes carbon to RuBP c) Converts RuMP to RuBP d) Only binds to CO2 e) A and B
E) A and B Why? Rubisco: An enzyme that catalyzes the reaction that incorporates (fixes) carbon dioxide into the Calvin cycle.
In the energy-harvesting reactions of glycolysis, an enzyme called hexokinase is used. Therefore you know which of the following must be true? a) A phosphate was added to ATP b) A redox reaction took place c) A phosphate was added to sugar d) Water was removed from sugar e) A phosphate was removed from ATP
E) A phosphate was removed to ATP Why? because Energy-harvesting removes a phosphate. While Energy-INVESTING adds phosphates
Earl Sutherland and colleagues conducted experiments that showed epinephrine binds to a receptor in the cell membrane of liver cells and that a second messenger is involved in transducing the signal for the breakdown of glycogen into glucose. This second messenger was later identified as cyclic AMP. Knowing this, what would you expect to occur if you broke liver cells open, separated the membrane fragments from the cytoplasm, and then incubated the membrane fragments with epinephrine, glycogen, and ATP? a) Glycogen would not be broken down into glucose because the second messenger would not be present. b) A second messenger would be generated, which would then activate the enzyme that breaks down glycogen into glucose. c) Glycogen would be broken down into glucose because the second messenger would be present. d) Epinephrine would stimulate the receptor to break down glycogen into glucose. e) A second messenger would be generated, but no breakdown of glycogen would occur since the second messenger acts upon a cytoplasmic enzyme.
E) A second messenger would be generated, but no breakdown of glycogen would occur since the second messenger acts upon a cytoplasmic enzyme Why? The second messenger cyclic AMP is made from ATP adenylyl cyclase, an enzyme embedded in the plasma membrane which would be produced if you were to separate the membrane fragments from the cytoplasm, and the incubate them with epinephrine, glycogen, and ATP.
Signal transduction pathways are important in multicellular organisms because they allow.... a) Cells producing a signal to be at a distance from the target cells. b) An organism to respond to external signals. c) Cells deep within an organism to respond to signals transmitted by cells nearby. d) Signals in micromolar (µm) amounts to have effects on cells. e) All of the above
E) All of the above
Which of the following is a reason that photosynthesis is essential for living things? a) It produces sugars that consumers can use for energy b) It alters CO2 levels and O2 levels in the atmosphere c) It changes the climate on earth d) It converts light energy into chemical energy e) All of these are reasons that photosynthesis is essential
E) All of these are reasons that photosynthesis is essential
Plants and animals all use the molecule G3P. Plants use G3P to do which of the following? a) Energy-investing reactions of cellular respiration b) Produce glycogen c) Make fatty acids d) Lactic acid fermentation e) Any of the above
E) Any of the above Why? G3P is used in the Citric Acid Cycle G3P is a product of the Calvin Cycle that is used to form glucose, amino acids, or fatty acids.
The conversion of malate to oxaloacetate in the citric acid cycle takes place with the conversion of NAD+ to NADH. In this reaction, NAD+ is a) Oxidized. b) The reducing agent. c) The oxidizing agent. d) reduced. e) Both b and c
E) Both b and c
A suspension of yeast supplied with glucose as its source of energy was transferred from an aerobic environment to an anaerobic one. Which of the following would you predict for the rate of glucose utilization and the rate of ethanol production after the transfer? a) Glucose usage would not change and ethanol production would increase. b) Glucose usage would decrease and ethanol production would increase. c) Both glucose usage and ethanol production would not change. d) Glucose usage would increase and ethanol production would decrease. e) Both glucose usage and ethanol production would increase.
E) Both glucose usage and ethanol production would increase.
Which of the following is not a way that a single signal can generate different responses in two different cells? a) Use a protein kinase receptor in one cell and a g-protein receptor in another b) Use different second messengers in each cell. c) Use a direct response in one cell and an indirect response in another d) Use different effectors in each cell e) Change the shape of the receptor binding site
E) Change the shape of the receptor binding site
The electron transport chain a) Is present in the outer membrane of the mitochondrion. b) Generates a proton-motive force by hydrolyzing ATP. c) Reduces FAD. d) Reduces NAD+. e) Contains cytochromes.
E) Contains cytochromes. Why? pg.173 figure 9.8 - Chytochromes: any of a number of compounds consisting of heme bonded to a protein. Cytochromes function as electron transfer agents in many metabolic pathways, especially cellular respiration.
You are given two reactions; reaction A has a ΔG of -7.3 and reaction B has a ΔG of +4.0. The overall coupled reaction would be _______ with an overall ΔG of _______. a) endergonic; -3.3 b) exergonic; -10.3 c) endergonic; +3.3 d) exergonic; +10.3 e) exergonic; -3.3
E) Exergonic; -3.3
Suppose the reaction A→B has a large, negative ΔG. The reaction would proceed _______, at equilibrium _______ would be present, and _______. a) From A to B; mostly B would be present; the reaction would be fast b) From A to B; mostly B would be present; the reaction would be slow c) Not enough information is provided. d) From B to A; mostly A would be present; the reaction would be slow e) From A to B; mostly B would be present; insufficient information is given to predict the rate of the reaction.
E) From A to B; mostly B would be present; insufficient information is given to predict the rate of the reaction
Oxytocin binds to a G protein-linked receptor. In response to the hormone binding, the G protein that is linked to the receptor becomes activated and binds to which of the following three types of molecules to initiate a cellular response? a) Hormone, G protein-linked receptor, and GTP b) GTP, cytoplasmic receptor, and transcription factor c) G protein-linked receptor, ATP, and enzyme d) Ligand, GDP, and GTP e) G protein-linked receptor, GTP, and effector protein
E) G protein-linked receptor, GTP, and effector protein
After being excited by a photon, photosystem II is reduced by electrons from a) Photosystem I b) Itself c) O2 d) CO2 e) H2O
E) H2O
Reagents, such as dinitrophenol, increase the permeability of the mitochondrial inner membrane to protons. The addition of dinitrophenol to a suspension of animal cells should a) Decrease the rate of oxidation of NADH. b) Increase lactic acid production. c) Decrease the rate of pyruvate oxidation. d) Stimulate ATP synthesis by mitochondria. e) Inhibit mitochondrial ATP synthesis.
E) Inhibit mitochondrial ATP synthesis.
Which of the following effectors of enzyme activity is least likely to be utilized by cells? a) Allosteric inhibitors b) Competitive inhibitors c) Noncompetitive inhibitors d) Allosteric activators e) Irreversible inhibitors
E) Irreversible inhibitors Why? Irreversible inhibitors are not common in the cell because the enzyme is permanently inactivated and cannot be recycled. Cells prefer to use reversible inhibition.
Glycolysis a) Is an endergonic reaction. b) Cannot occur in the absence of oxygen. c) Is a reaction that follows pyruvate oxidation. d) Is the conversion of glucose to two molecules of lactate. e) Is an oxidation-reduction process.
E) Is an oxidation-reduction process.
A competitive inhibitor of an enzyme-catalyzed reaction a) Inhibits to the same extent at all substrate concentrations. b) Binds to an allosteric site. c) Cannot bind to the active site. d) Always interferes with product release. e) Is usually structurally similar to the substrate.
E) Is usually structurally similar to the substrate Why? Competitive Inhibitor: AN inhibitor is similar enough to a particular enzyme's natural substrate to bind non-covalently to its active site, yet different enough that the enzyme catalyzes no chemical reaction.
Why is the statement, "ATP creates energy for life," incorrect? a) Energy is required to make ATP. b) Life produces ATP. c) It is a violation of the first law of kinetics. d) It is a violation of the second law of thermodynamics. e) It is a violation of the first law of thermodynamics.
E) It is a violation of the first law of thermodynamics Why? First law of thermodynamics: is a version of the law of conservation of energy, adapted for thermodynamic systems. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed.
In photosynthesis RuBP is used in the _______ and is a(n)________. a) Light reactions; electron carrier b) Light reactions; 5-C molecule c) Calvin cycle; electron carrier d) Light-independent reactions; enzyme e) Light-independent reactions; 5-C molecules
E) Light-independent reactions; 5-C molecules Why? In the Calvin cycle RuBP is the 5-carbon organic compound that attaches to CO2 producing two molecules of 3-PGA and therefore the process of photosynthesis continues.
In green plant photosynthesis, water is a) Oxidized to oxygen gas (O2) in the dark. b) Reduced to hydrogen gas (H2) in the light. c) Reduced to oxygen gas (O2) in the light. d) Reduced to hydrogen gas (H2) in the dark. e) Oxidized to oxygen gas (O2) in the light.
E) Oxidized to oxygen gas (O2) in the light.
In C3 photosynthesis, NADPH is used for the a) The regeneration phase of the Calvin cycle. b) Synthesis of ATP. c) Formation of 3-phosphoglycerate (3-PG). d) Fixation of carbon dioxide (CO2). e) Reduction of 3-phosphoglycerate (3-PG) to form glyceraldehyde-3-phosphate (G3P).
E) Reduction of 3-phosphoglycerate (3-PG) to form glyceraldehyde-3-phosphate (G3P).
A prosthetic group of an enzyme is a) Permanently altered by the reaction catalyzed by the enzyme. b) Consumed in the enzymatic reaction. c) Easily dissociated from the enzyme. d) An organic molecule usually made up of amino acids. e) Required by some enzymes in order to function as a catalyst.
E) Required by some enzymes in order to function as a catalysts
Fermentation a) Completely oxidizes glucose to CO2 and H2O. b) Is endergonic. c) Occurs under aerobic conditions in yeasts. d) Is not coupled to substrate-level ADP synthesis. e) Results in the formation of lactic acid or ethanol.
E) Results in the formation of lactic acid or ethanol.
The reason that you need oxygen is... a) So you can breath b) To transport electrons to the electron transport chain c) To make water d) To oxidize carbon in glycolysis e) That it accepts the final electron from the electron transport chain
E) That it accepts the final electron from the electron transport chain
Why is the citric acid cycle only used when oxygen is present? a) Oxygen is required to oxidized carbon b) Oxygen is required to make oxaloacetate c) Oxygen accepts electrons in the citric acid cycle d) The citric acid cycle requires Acetyl CoA to be oxidized by oxygen e) The citric acid cycle requires NAD+ produced by electron transport
E) The citric acid cycle requires NAD+ produced by electron transport Why? Oxygen is needed to recycle the NAD+ from the NADH produced in the citric acid cycle
In a reaction catalyzed by an enzyme, a) Substrate binding is nonspecific. b) The enzyme's structure is permanently modified. c) The rate of the reaction is unaffected by temperature. d) The rate of the reaction is linearly dependent on the substrate concentration. e) The enzyme does not affect the equilibrium constant for the reaction.
E) The enzyme does not affect the equilibrium constant for the reaction
When a cell responds to its own chemical signal, the chemical signal is called a(n) __________ signal. a) Juxtacrine b) Paracrine c) Autocrine d) endocrine e) It could be any of these
c. Autocrine Why? Autocrine: Secretes a hormone that binds to autocrine receptors on the same cell (simulates itself)
