Exam 1
Which of the following best describes the biochemical role of coenzyme A? A) It activates acyl groups for group transfer. B) It assists in the transport of metabolic intermediates across membranes. C) It shuttles electrons within the electron transport chain. D) It introduces adenine nucleotides into metabolic products. E) It introduces thiol groups into metabolic products.
A) It activates acyl groups for group transfer. Remember that the CoA is a good leaving group and that this allows for an energetically favorable reaction to occur (hydrolysis). In other words, it gives it a push through.
Rotenone, a toxic natural product from plants, strongly inhibits the transfer of electrons from iron-sulfur centers in Complex I to ubiquinone in insect and fish mitochondria. Antimycin A, a toxic antibiotic, strongly inhibits the oxidation of ubiquinol. (a) Explain why rotenone ingestion is lethal to some insect and fish species. (b) Explain why antimycin A is a poison. (c) Given that rotenone and antimycin A are equally effective in blocking their respective sites in the electron transfer system, which would be a more potent poison? Explain.
A) electrons will be halted from complex I and there would be a build up of NADH, but the ubiquinol can still take electrons from complex II (FADH2 driven) B) stops ubiquinol from working all together and therefore halting all ability to carry any electrons forward in the chain and build up of both NADH and FADH2
Choose the correct path taken by a pair of electrons as it travels down the electron-transport chain. A) FADH2 → complex I → CoQ → Complex III → Cyt c → complex IV → O2 B) NADH → complex I → CoQ → Complex III → Cyt c → complex IV → O2 C) FADH2 → complex II → Succinate → Complex III → Cyt c → complex IV → O2 D) NADH → complex II → CoQ → Complex III → Cyt c → complex IV → O2 E) NADH → complex I → complex II→ Complex III → Cyt c → complex IV → O
B) NADH → complex I → CoQ → Complex III → Cyt c → complex IV → O2 Remember that the complex are not in numerical order.
The net result of the Electron Transport System that links it to ATP synthesis is the: A) production of NADPH B) generation of a proton gradient C) generation of superoxide D) conversion of CoQ to QH2 E) translocation of ADP
B) generation of a proton gradient The H+ gradient drives the ATP syntheses turbine There was an experiment that bypassed this by using magnets
Draw the fatty acids named here: A) 16:0 n-hexadecanoate B) 16:1 cis-∆9 hexadecanoate C) 18:1 cis-∆9 octadecanoate D) 18:1 trans-∆9 octadecanoate E) an omega (ω)-3 fatty acid
C) 18:1 cis-∆9 octadecanoate # of Carbons:# of double bonds. Cis/Trans- where the double bond is located
Which of the following statements regarding the reaction below is false? CH3CH2OH + NAD+ ----------------------------------> alcohol dehydrogenase CH3CHO + NADH + H+ A) Ethanol (CH3CH2OH) is the reducing agent B) Ethanol is oxidized C) Alcohol dehydrogenase is the oxidizing agent D) NAD+ is the oxidizing agent E) NADH is oxidized
C) Alcohol dehydrogenase is the oxidizing agent Remember that an oxidized molecule is losing an electron and that a reduced molecule is gaining an electron Ethanol is being oxidized NAD+ is being reduced So, NAD+ is the oxidizing agent and ethanol is the reducing agent
Which of the following conditions will activate pyruvate dehydrogenase kinase, which catalyzes the phorphorylation and inactivation of E1 in the pyruvate dehydrogenase complex? A) Elevated concentrations of acetyl-CoA B) Elevated concentrations of NAD+ and ADP C) Elevated concentrations of NADH and ATP D) Elevated concentrations of OAA E) Elevated concentrations of NADPH
C) Elevated concentrations of NADH and ATP Remember what each enzyme does: Kinase- phosphorylates Dehydrogenase- redox Synthase- builds Because if you have higher NADH and ATP levels you already have the energy and do not need to make more
All the dehydrogenases of glycolysis and the citric acid cycle use NAD+ as the electron acceptor except succinate dehydrogenase, which uses covalently bound FAD. Explain why FAD is a more appropriate electron acceptor than NAD+ in the dehydrogenation of succinate, based on the Eo' values of the fumarate/succinate, NAD+/NADH, and succinate dehydrogenase FAD/FADH2 redox pairs (Eo' for FAD/FADH2 in this enzyme is +0.050V).
Delta G = -nF(delta E) Where a -delta G = a spontaneous reaction NAD+: -(2)(96.5 kJ/molv)(-0.32v-0.03v) = 68 kJ/mold FAD: -(2)(96.5 kJ/molv)(+0.05v-0.03v) (+0.05 is a given) = -3.7 kJ/mold Because FAD is more negative it is more spontaneous/favorable
Sphingolipids: A) have a sphingosine backbone instead of glycerol. B) have a fatty acid linked to the backbone via an amide as opposed to an ester bond. C) include gangliosides. D) include cerebrosides. E) all of the above.
E) all of the above. Sphingolipids are any class of compounds that are fatty acid derivatives of shingosine and occur chiefly in the cell membranes of the brain and nervous tissue. Another characteristic is the sphingosine backbone instead of glycerol
Olestra® is a noncaloric fat substitute that is synthesized from sucrose and six to eight 12-carbon fatty acids. Because the fatty acids are linked to the sucrose via ester bonds, Olestra® is not absorbed or metabolized. Why does Olestra® cause depletion of fat-soluble vitamins (A, D, E, and K)? A) These vitamins are used to break down Olestra®. B) Olestra® blocks the absorption of these vitamins by coating the intestinal walls. C) Olestra® can dissolve these vitamins and because Olestra® is not absorbed, they are excreted. D) These vitamins react with Olestra®. E) All of the above.
Here is a great example of picking out the needed info question... - it is a fat substitute - synthesized by a sugar and a fatty acid (sugar = hydrophilic/fatty acid = hydrophobic) - Fat soluble vitamins (KADE) are not absorbed Why is there a depletion in KADE? Like dissolves like... The hydrophobic portion is dissolving the fat-soluble vitamins and excreting them. C) Olestra® can dissolve these vitamins and because Olestra® is not absorbed, they are excreted.
There are many cases of human disease in which one or another enzyme activity is lacking due to genetic mutation. However, cases in which individuals lack one of the enzymes of the citric acid cycle are extremely rare. Why?
No ATP formed and the organism would die.
During the preparation of Bearnaise sauce, egg yolks are incorporated into melted butter to stabilize the sauce and avoid separation. The stabilizing agent in the egg yolks is phosphatidylcholine (lecithin, shown below). Suggest why this work
Phosphatylcholine has long hydrocarbon chains (hydrophobic) and oxygen (hydrophilic). By having both of these qualities this is amphipathic - which provides the stability in the sauce.
Catalytic hydrogenation, used in the food industry, converts double bonds in the fatty acids of the oil triacylglycerols to -CH2-CH2-. How does this affect the physical properties of the oils?
Saturated = no double bonds Unsaturated = double bond(s) The more saturated, the higher the melting point
Briefly explain how a hydropathy plot can help to distinguish between alpha-helical and beta-barrel transmembrane domains.
The beta barrel will have alternating hydrophobic and hydrophilic portions close to the 0. (Alternate due to the direction of the beta sheets) The alpha helices spanning a membrane will have spikes . (ie: a 7-transmembrane domain protein will have 7 peaks in a row with small spaces in between)
Which of the following situations or phrases most accurately describes the citric acid cycle? a. a chaotic, unregulated traffic circle b. "all roads lead to Rome" c. The shortest distance between two points is a straight line
The greater the solubility in a nonpolar medium, the more rapidly a molecule crosses a lipid bilayer. In many ways, the citric acid cycle can be considered as the centerpiece of cellular metabolism, with a variety of catabolic and anabolic pathways leading to and from it.
Individuals with a thiamine-deficient diet have relatively high levels of pyruvate in their blood. Explain this observation in biochemical terms.
Thiamine is part of the TPP that is used with PDH to take private (from glycolysis) to Acetyl-CoA (for CAC). Without thiamine this cannot occur and the private would build up.
In the last reaction of the citric acid cycle, malate is dehydrogenated to regenerate oxaloacetate: L-Malate + NAD+ → oxaloacetate + NADH + H+ ∆Go'"= 29.7 kJ/mol (a) Calculate the equilibrium constant for this reaction at 25°C. (b) Because ∆Go' assumes a standard pH of 7, the equilibrium constant calculated in (a) corresponds to Keq' = [oxaloacetate] [NADH]/ [L - Malate][NAD+] The measured concentration of L-malate in rat liver mitochondria is about 0.20 mM when [NAD+]/[NADH] is 10. Calculate the concentration of oxaloacetate in these mitochondria. (c) To appreciate the magnitude of the mitochondrial oxaloacetate concentration, calculate the number of oxaloacetate molecules in a single rat liver mitochondrion. Assume the mitochondrion is a sphere of diameter 2.0 µm.
This is a unit conversion problem... A) relate delta G to K Delta G = -2.3RT log(K) K(eq) = 6.18X10^-6 B) K = [products]/[reactants] Since it is given that the [NAD+]/[NADH] = 10/1 you can substitute these number respectively into the equation. [oxaloacetate] = 1.24X10^-8 C)1cm^3 = 1mL and V = 4/3*pi*r^3 Remember that you want to cancel out all units to end up with the # of oxaloacetate molecules/1 mitochondria 4.2X10^-15 oxaloacetate molecules per mitochondria
Using the standard reduction potential table and other information given on the additional sheet, calculate the ∆Go' for the overall reaction of Complex I of the ETS. State any assumptions you need to make. The explicit overall reaction of Complex 1: NADH + CoQ + 5H+(matrix) --> NAD+ + CoQH2 + 4H+(cytoplasm)
This is where half reactions come in... NAD+ + 2H+ + 2e- --> NADH + H+ (E found on chart is +0.32) --we switch the - to + because of the direction the reaction is going compared to the chart is opposite CoA + 2H+ + 2e- --> CoQH2 (E found on chart is +0.1) Add these together --> .32+.1= 0.42 (This is your delta E) Relate this to delta Ga... Delta G = -nF(delta E) = -(2)(96.5 kJ/molv)(0.42 v) = 81.06 kJ/mol (n is in the table) --note that if n is different for the two half equations add a cofactor to the lesser of the two in order to balance it out
The two products of the "light reactions" needed in order for the Calvin Cycle to function are a. ATP and NADPH b. NAHPH and oxygen c. ATP and oxygen
a. ATP and NADPH Both high-energy phosphate bonds of ATP and reducing equivalents in the form of NADPH are needed by the enzymes of the Calvin Cycle.
The uncoupler dinitrophenol (DNP) prevents ATP synthesis while allowing electron transport to proceed because a. DNP is capable of transporting protons across the membrane, dissipating the proton gradient b. DNP prevents the buildup of a proton gradient by altering the electron transfer complexes such that they no longer pump protons c. DNP binds to the ATP synthase and acts as an inhibitor of the enzyme
a. DNP is capable of transporting protons across the membrane, dissipating the proton gradient DNP effectively "short circuits" the proton motive force such that it is dissipated before it can be used to drive ATP production.
Which of the following is not a mobile or diffusible electron carrier in the mitochondrial electron transport chain? a. FAD b. ubiquinone c. cytochrome c
a. FAD FAD is a component of Complex II or succinate dehydrogenase. It feeds electrons directly into the electron transport chain.
Which of the following is NOT a difference of archaeal membrane lipids relative to those of other organisms? a. a backbone other than glycerol is used b. fatty acid esters are replaced with long chain alcohol esters to the glycerol c. the long hydrophobic tails are branched rather than being linear
a. a backbone other than glycerol is used This is NOT a difference. Glycerol is used as the backbone although it has an inverted stereochemistry relative to that used in other organisms
The most common way in which integral membrane proteins span the membrane is in a. alpha helical segments b. beta sheet structures c. single strands with no secondary structure
a. alpha helical segments Alpha helices offer an energetically favorable way for a protein to span the membrane in terms of having hydrophobic R-groups on the outside and the polar peptide bonds hydrogen bonded together on the inside.
Which of the following describes the direction of proton movement relative to electron transfer and phosphorylation? a. electron transfer pumps protons out of the matrix. As the protons reenter through the ATP synthase, ATP is produced in the matrix b. electron transfer pumps protons into the matrix. As the protons leave the matrix through ATP synthase, ATP is produced on the opposite side of the membrane c. electron transfer pumps protons into the matrix. As the protons leave the matrix through the ATP synthase, ATP is produced in the matrix
a. electron transfer pumps protons out of the matrix. As the protons reenter through the ATP synthase, ATP is produced in the matrix All directions are correct with respect to both electron transfer and phosphorylation.
In addition ot the CO2 used as a substrate, a second CO2 is also required for activity of rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase). This second CO2 function to a. form a part of the binding site for a metal ion involved in the binding of ribulose 1,5-bisphosphate b. stabilize the interaction between the large and small subunits of the enzyme c. replace the Co2 used as a substrate so the reaction can proceed again
a. form a part of the binding site for a metal ion involved in the binding of ribulose 1,5-bisphosphate The CO2 binds to a lysine amino group, producing a negatively charged carbamate that binds to a magnesium ion.
In phosphoglycerides, fatty acids are esterfied at a. glycerol carbons 1 and 2 b. glycerol carbons 1 and 3 c. any two of the three glycerol
a. glycerol carbons 1 and 2 The third carbon is the site at which phosphate is esterified.
Although the glyoxylate cycle is not present in animals, many plants and animals can use this modified form of the citric acid cycle. The glyoxylate cycle is beneficial in that a. it allows the organisms which possess it to grow on acetate b. it provides a source of glyoxylate which is an essential molecule in biosynthetic pathways in these organisms c. it does not release CO2 which is toxic to these organisms
a. it allows the organisms which possess it to grow on acetate The ability to use alternate carbon sources provides a metabolic versatility.
Although the pyruvate dehydrogenase complex is subject to allosteric control, especially inhibition by reaction products, the main regulatory process controlling the enzymes activity in eukaryotes is a. phosphorylation by ATP that turns off the complex and dephosphorylation that turns it on b. phosphorylation by ATP that turns on the complex and dephosphorylation that turns it off c. exchange of ADP and ATP on the pyruvate dehydrogenase complex
a. phosphorylation by ATP that turns off the complex and dephosphorylation that turns it on High levels of ATP are indicative of a situation in which no further ATP is needed and thus the enzyme is turned off by phosphorylation.
In order for an electron transfer reaction to be energetically spontaneous, which of the following must be true? a. the change in reduction potential must be positive b. the change in reduction potential must be negative c. the two groups involved in the electron transfer must be in direct contact
a. the change in reduction potential must be positive A positive value for ΔEo will give a negative value for ΔGo.
Although salts of fatty acids form micelles, phospholipids and glycolipids form bimolecular sheets because of a. the presence of two fatty acyl chains b. the differing interaction between polar head groups with one another c. the differing interaction between polar head groups and water
a. the presence of two fatty acyl chains The two fatty acyl chains are too bulky to be accommodated in a micelle structure making a sheet structure more favorable.
Glucose-6-phosphate can be utilized by either the glycolytic or the pentose phosphate pathway. What is the major factor regulating how the use of glucose-6-phosphate is distributed between these two pathways? a. the relative levels of NADP+ and NADPH b. the different location of the two pathways within the cell c. allosteric inhibition of the glucose-6-phosphate dehydrogenase enzyme by ATP
a. the relative levels of NADP+ and NADPH The glucose-6-phosphate dehydrogenase enzyme needs NADP+ as a substrate and is competitively inhibited by NADPH.
In the reaction catalyzed by succinyl-CoA synthetase a. a phosphohitidyl residue is used to displace the CoA from succinate b. a succinylphosphate transfers its phosphate to a histidyl residue c. GDP is phophorylated by a succinyl phosphate
b. a succinylphosphate transfers its phosphate to a histidyl residue The succinylphosphate generated in the first step of the reaction transfers its phosphate to a histidine in the next step.
Which enzyme of the citric acid cycle most resembles the pyruvate dehydrogenase complex in terms of its structure, organization, and the reaction it performs? a. isocitrate dehydrogenase b. alpha - ketoglutarate dehydrogenase c. succinate dehydrogenase
b. alpha - ketoglutarate dehydrogenase The α-ketoglutarate dehydrogenase enzyme is structurally and functionally homologous to the pyruvate dehydrogenase complex.
Under conditions in which NADPH is NOT needed, how are five-carbon sugare, such as ribose-5-phosphate, generated? a. through the normal pentose phosphate pathway b. by withdrawing 3-carbon units from the glycolytic pathway and convering them into 5-carbon sugars via the nonoxidative branch of the pentose phosphate pathway c. it is not possible to produce 5-carbon sugars under these circumstances
b. by withdrawing 3-carbon units from the glycolytic pathway and convering them into 5-carbon sugars via the nonoxidative branch of the pentose phosphate pathway Glyceraldehyde-3-phosphate and dihydroxyacetone phosphate can serve as starting points for generation of 5-carbon sugars in a series of reactions involving transketolase and transaldolase.
The main use of hydropathy plots is to a. identify regions of peripheral membrane proteins capable of interacting with the membrane surface b. identify membrane-spanning helical regions in integral membrane proteins c. determine the number of lipids which must be displaced when an integral membrane protein is incorporated into the membrane
b. identify membrane-spanning helical regions in integral membrane proteins The method is based on identification of regions of a protein that would be compatible with placement spanning a lipid bilayer.
The presence of uncoupling proteins allows ______ energy from the mitochondrial electron transport chain to be used for ATP synthesis and _______ for the production of heat. a. more, less b. less, more c. all, none
b. less, more Regulated uncoupling can balance the needs of the organism for ATP and heat.
The rubisco enzyme also catalyzes a wasteful reaction in which ribulose 1-5-bisphosphate is broken into 3-phosphoglycerate and phosphoglycolate. In this reaction (which is the first of the process called photorespiration), the enzyme utilizes what as a substrate instead of Co2? a. phosphate b. oxygen c. ammonia
b. oxygen The reaction with oxygen produces a peroxy intermediate that is broken down to yield the products.
Which of the following would be expected to lower the Tm for a phospholipid bilayer? a. replacing a lipid containing unsaturated fatty acids with one containing saturated fatty acids b. replacing a lipid containing 18-C fatty acid with one containing 16-C fatty acid c. adding ions to bind to charged groups in the polar head groups
b. replacing a lipid containing 18-C fatty acid with one containing 16-C fatty acid Longer fatty acids interact more strongly than do shorter fatty acids. The weakened interaction should lower the Tm.
proton flow through the ATP synthase enzyme a. provides the energy for adding a phosphate to ADP to make ATP b. results in the release of ATP from its tightly bound state in the active site c. produces local pH changes in the active site which alter the equilibrium constant for the reaction
b. results in the release of ATP from its tightly bound state in the active site Although readily produced in the active site, ATP is only released when protons flow through the enzyme.
Of the enzymes of the citric acid cycle, which is not a freely soluble enzyme? a. citrate synthase b. succinate dehydrogenase c. malate dehydrogenase
b. succinate dehydrogenase Succinate dehydrogenase in associated with the inner mitochondrial membrane with one of its products (FADH2) directly entering the electron transport chain.
Many tropical plants use a C4 pathway of carbon fixation. In these types of plants a. the Calvin cycle is absent and not used in the CO2 fixation process b. the Calvin cycle is localized in specific types of cells where the CO2 concentration is increased by the C4 pathway c. the Calvin cycle is present but only used as a backup when the C4 pathway cannot meet the needs of the plant
b. the Calvin cycle is localized in specific types of cells where the CO2 concentration is increased by the C4 pathway The purpose of the C4 pathway (localized in the mesophyll cells) is to increase the concentration of CO2 in the cells where the Calvin Cycle is located (the bundle sheath cells).
The reactions of the photosynthetic carbon fixation via the Calvin cycle are often referred to as the "dark reactions" because a. they occur only in darkness and not in light b. the reactions involved do not depend directly on the presence of light c. we remain largely "in the dark" as to the reaction of the Calvin Cycle
b. the reactions involved do not depend directly on the presence of light Although the Calvin cycle utilizes products of the "light reactions", light itself is not involved in the reactions of the cycle.
Lipid molecules are said to be amphipathic, meaning that a. they have asymmetric carbons and can exist in left- and right-handed forms b. they have a dual nature with part of the molecule being hydrophobic and the other part hydrophilic c. they are capable of moving rapidly from one side of a lipid bilayer to the other
b. they have a dual nature with part of the molecule being hydrophobic and the other part hydrophilic This dual nature is the key feature in understanding the role of lipids in membranes.
Transketolase is an enzyme involved in the interconversion of 3-, 4-, 5-, 6-, and 7-carbon sugars in the nonoxidative branch of the pentose phosphate pathway. What cofactor does this enzyme use to stabilize a carbanionic intermediate in the reaction mechanism? a. a Schiff's base b. thiamine pyrophosphate c. a divalent cation
b. thiamine pyrophosphate A covalent addition product involving the substrate and thiamine pyrophosphate is formed during the mechanism.
In the reaction catalyzed by the pyruvate dehydrogenase complex, the two carbons constituting the acetyl group are a. the transferred directly to the lipoamide cofactor b. transferred to the lipoamide by an earlier intermediate in the process c. oxidized by NAD while attached to the lipoamide
b. transferred to the lipoamide by an earlier intermediate in the process The two carbons are first attached to thiamine pyrophosphate and then transferred to the lipoamide.
What is the source of electrons at Complex II (Succinate-Q-reductase)? a. NADH from the citric acid cycle and glycolysis b. NAD+ from conversion of pyruvate to lactate c. FADH2 from the citric acid cycle
c. FADH2 from the citric acid cycle FADH2 is generated in the citric acid cycle (in the succinate dehydrogenase-catalyzed conversion of succinate to fumarate) and it enters the electron transport chain at Complex II (succinate-Q-reductase).
Unsaturated fatty acids have double bonds that are in the cis, rather than the trans, configuration. One of the consequences of this is a. an alteration in the charge of the molecule b. an alteration in the number of carbons in the molecule c. a bend in the molecule
c. a bend in the molecule A cis double bond produces a bend in the molecule while a trans double bond does not.
Of the three major types of membrane lipids, which is not found in prokaryotes? a. phospholipids b. glycolipids c. cholesterol
c. cholesterol Cholesterol is not present in prokaryotic membrane lipids. Even within eukaryotes, it is mainly limited to mammalian systems.
Assuming that pyruvate was labeled with radioactive 14C in its middle (keto) carbon, where would the radiolabel appear after one turn of the citric acid cycle? a. as CO2 b. in one carboxyl group of oxaloacetate c. equally divided between the two carboxyl groups of oxaloacetate
c. equally divided between the two carboxyl groups of oxaloacetate The "randomization" of label between the two carboxyl groups results from the reaction catalyzed by fumarase.
Which of the following is NOT part of the Mitchell chemiosmotic hypothesis? a. a proton of the energy from electron transport is used in generation of a proton-motive force that in turn provides the energy for ATP synthesis b. the use of electron transfer to provide the energy for ATP synthesis requires an intact membrane c. high-energy phosphorylated intermediates that serve as phosphate donors to ADP are generated as a result of electron-transfer reaction
c. high-energy phosphorylated intermediates that serve as phosphate donors to ADP are generated as a result of electron-transfer reaction High energy phosphorylated intermediates are not a part of Mitchell's chemiosmotic hypothesis.
The process of glycolysis occurs in the cytoplasm. The electrons from the NADH generated during glycolysis a. enter the mitochondrial electron chain directly as NADH freely enters the mitochondria b. cannot be used by the mitochondrial electron transport chain as NADH cannot enter the mitochondria c. may enter the electron transport chain either at the level of NADH or FADH2, depending on the shuttle system used to transport them into the mitochondria
c. may enter the electron transport chain either at the level of NADH or FADH2, depending on the shuttle system used to transport them into the mitochondria The glycerol-3-phosphate shuttle allows electrons from cytoplasmic NADH to enter the mitochondrial electron transport chain at the level of FADH2 and the malate-aspartate shuttle at the level of NADH.
The first reaction of the Calvin Cycle involves the reaction of CO2 with ______ to give two molecules of __________. a. ribose 1,5-bisphosphate, glyceraldehyde 3-phosphate b. ribulose 1,5-bisphosphate, glyceraldehyde 3-phosphate c. ribulose 1,5-bisphophate, 3-phosphoglycerate
c. ribulose 1,5-bisphophate, 3-phosphoglycerate Both ribulose 1,5-bisphosphate and 3-phosphoglycerate are involved in the reaction with CO2 that produces the latter.
The major use of NADPH generated by the pentose pathway is a. serving as a replacement for NADPH generated by photosynthesis in carbon fixation b. linking the oxidation of sugars to the mitochondrial electron transport chain c. serving as a reductant in biosynthetic pathways
c. serving as a reductant in biosynthetic pathways The NADPH generated in the pentose phosphate pathway serves as a reductant in a variety of biosynthetic pathways.
Of the electron transfer complexes associated with the inner mitochondrial membrane, which is not involved in generation of a proton gradient? a. cytochrome oxidase (complex IV) b. cytochrome bc1 (complex III) c. succinate-Q reductase (complex II)
c. succinate-Q reductase (complex II) The passage of electrons through Complex II does not contribute to the proton gradient
In going from acetyl-CoA to succinate, two carbons have entered the cycle and two have been released as CO2. Why is the cycle not considered as complete at this point? a. not enough NADH has been generated b. the cell requires FADH2 produced in subsequent reactions of the cycle c. the oxaloacetate used to initiate the cycle must be regenerated
c. the oxaloacetate used to initiate the cycle must be regenerated One must replace what one used to start the cycle (oxaloacetate) in order to keep it going.
The purpose of anaplerotic reactions is a. to divert materials out of the citric acid cycle for use in biosynthesis b. to produce pyruvate to initiate the cycle when glucose is not occurring c. the replenish the citric acids cycle if it becomes depleted of intermediates by biosynthetic demands
c. the replenish the citric acids cycle if it becomes depleted of intermediates by biosynthetic demands One must have some oxaloacetate present in order to start the cycle. If it is depleted, it must be replenished before the cycle can operate.
In considering the movement of small molecules across a lipid bilayer, the permeability coefficient can be correlated with a. the size of the molecule b. the interaction of the molecule with the polar head groups c. the solubility of the molecule in a nonpolar solvent
c. the solubility of the molecule in a nonpolar solvent The greater the solubility in a nonpolar medium, the more rapidly a molecule crosses a lipid bilayer.
