The water content in the human body is approximately:
A) 90%.
B) 80%.
C) 70%.
D) 60%.
E) 50%.
C) 70%
The four most abundant chemical elements in living systems are:
A) hydrogen, oxygen, sulfur and phosphorus.
B) hydrogen, carbon, nitrogen and oxygen.
C) sodium, potassium, carbon and oxygen.
D) sodium, potassium, nitrogen and sulfur.
E) carbon, nitrogen,
B) Hydrogen, carbon, nutrogen, and oxygen
Nearly all proteins contain:
A) cobalt.
B) phosphorus.
C) selenium.
D) sulfur.
E) none of the above.
D) sulfur.
Which of the following statements is FALSE?
A) Proteins can be structural components of cells.
B) Proteins can transmit signals between cells.
C) Proteins can transport molecules within cells and between cells.
D) Proteins can be both hormones and hormone
E) Proteins are the only biological polymer that can catalyze biochemical reactions.
Which of the following is NOT classed as a lipid?
A) Cholesterol
B) Palmitic acid
C) Glycerol
D) Phosphatidyl serine
E) Triacylglycerol
C) Glycerol
Amino acids and simple organic compounds like carbon dioxide and hydrogen cyanide cannot be produced without the use of enzymes.
False
Oxidation-reduction reactions, which are the basis of many biochemical reactions and pathways, cannot take place in the absence of oxygen.
False
Many biochemical reactions that form biopolymers from monomeric units involve the removal of water.
True
The principle component of a biological membrane is a triglyceride.
False
The chemical element ________ has a role in both transfer of energy as well as in the structure of nucleic acids.
Phosphorous
List the four major classes of biological macromolecules.
lipids, carbohydrates, proteins, nucleic acids
An amphipathic molecule provides the foundation for biological membranes because they have both ________ and ________ functional groups.
hydrophilic, hydrophobic
Genomics is concerned with the entire ________, while ________ is focused on identifying all of the proteins of a cell.
genome, proteomics
Each of the following is a noncovalent interaction EXCEPT:
A) a hydrogen bond.
B) a carbon-hydrogen bond.
C) the interaction between an amino and a carboxylate group.
D) a van der Waals interaction.
E) an interaction between �NH3+ and a water molecule.
B) a carbon-hydrogen bond.
The most important noncovalent interaction in biochemistry is the ________ bond.
hydrogen
Which of the following is FALSE when considering van der Waals interactions?
A) The van der Waals radius represents the most stable distance between two interacting centers.
B) Van der Waals radii can determine molecular surfaces.
C) Molecules that intera
E) They are not important in determining the stability of three-dimensional structures of proteins
Which of the following in biological compounds are sufficiently electronegative to serve as strong donors in a hydrogen bond?
A) Hydrogen and oxygen
B) Oxygen and nitrogen
C) Nitrogen and hydrogen
D) Hydrogen and carbon
E) Nitrogen and carbon
B) Oxygen and nitrogen
Hydrogen bonds share features of both covalent and noncovalent bonds.
True
Which of the following is TRUE of hydrophobic molecules?
A) They have limited solubility in water.
B) Water forms a cage-like structure around them.
C) Dissolving in water decreases the entropy of the mixture.
D) They self-associate by releasing some of t
E) All of the above
Water is both a hydrogen bond donor and acceptor
True
Amphipathic molecules are not able to interact via van der Waals forces
False
Ionic compounds can be readily dissolved in water because the high dielectric constant of water screens and decreases the ________ force between the oppositely charged ions.
electrostatic
The ________ describes the tendency for hydrophobic molecules to aggregate because of the exclusion of water with the consequent increase of entropy of the solvent.
hydrophobic effect
Glycine cannot serve as a buffer because it has two ionizable groups.
False
The average charge on an amino acid below its pI will be positive
True
Calculate the acid dissociation constant Ka of a 0.2 M solution of weak acid that is 0.1% ionized.
2 � 10-7
Calculate the pH of a 0.1 M phosphate buffer (pKa = 6.86) that contains equal amounts of acid and conjugate base
6.86
Calculate the pH of a 0.2 M acetate buffer (pKa = 4.77) that contains twice as much acid as conjugate base
4.47
The pKa of each amino acid residue in a protein will not be influenced by the adjacent residue.
False
Calculate the pH at the end of an enzyme-catalyzed reaction if it were carried out in a 0.1 M phosphate buffer, pH 6.86 and 0.005 M of acid was produced during the reaction?
6.77
If hydroxide is added to an amino acid it will become increasingly ________ charged.
negatively
Calculate the pH of a weak acid that is 0.2% ionized in a 0.2 M solution
3.39
The net charge on an amino acid at its isoelectric point (pI) is ________.
zero
Many proteins interact with DNA at physiological pH because:
A) proteins are naturally attracted to DNA regardless of the pH.
B) the negatively charged DNA is electrostatically attracted to positively charged regions on proteins.
C) the positively charged
B) the negatively charged DNA is electrostatically attracted to positively charged regions on proteins.
Small ions in biological fluids:
A) encourage strong electrostatic interactions between oppositely charged macroions at low ionic strengths.
B) encourage strong electrostatic interactions between oppositely charged macroions at high ionic strengths.
C) ha
A) encourage strong electrostatic interactions between oppositely charged macroions at low ionic strengths.
Which of the following statements is FALSE?
A) Organisms are open systems as they can exchange both energy and materials with their environments.
B) In an open system energy can be converted from one form into another.
C) Organisms are open systems as the
C) Organisms are open systems as they can create energy from their environments.
Which of the following statements is FALSE?
A) Entropy is a measure of disorder.
B) The entropy of an isolated system will tend to increase to a maximum value.
C) Biological systems are highly ordered so entropy changes are not relevant.
D) Biological sys
C) Biological systems are highly ordered so entropy changes are not relevant.
A biochemical reaction will proceed in the direction as written if:
A) ?G = zero.
B) ?G > 0.
C) ?G < 0.
D) ?H > 0.
E) ?H < 0.
C) ?G < 0.
Life is an irreversible process, such that it never comes to equilibrium.
True
The equilibrium constant of a reaction:
A) is not related to the change in free energy of the reaction.
B) is the same as the mass action ratio when the reaction is displaced from equilibrium.
C) can change if the concentration of reactants and products a
D) is related to the change in free energy of the reaction.
The change in enthalpy (?H) for the complete oxidation of a fatty acid is different depending on whether it occurs via a biochemical pathway or combustion to CO2 and H2O
False
A reaction at its lowest energy state for the system and with equal rates in the forward and reverse directions is said to be at ________.
equilibrium
A reaction at equilibrium can be driven in one direction or the other by changing the ________ of reactants or products
concentration
A thermodynamically unfavorable reaction can become favorable if the mass action ratio is ________ than the equilibrium mass action ratio
less
Calculate the equilibrium constant for the enzymatic hydrolysis of 0.1 M glucose-6-phosphate to glucose and inorganic phosphate given that 0.05% of the original glucose-6-phosphate remained after reaching equilibrium and the activity of water is unity
199.8
The ?Go of a reaction:
A) will change if the temperature of the reaction is changed.
B) will change if the concentration of reactants and products are changed.
C) is not related to the equilibrium constant.
D) can be used to calculate whether a reaction i
D) can be used to calculate whether a reaction is thermodynamically favorable under defined non-standard conditions.
Calculate the ?G?' for the reaction
fructose-6-phosphate ? glucose-6-phosphate
given the equilibrium constant is 1.97 and the physiological relevant temperature is 37?C
-1.75kJ/mol
A thermodynamically unfavorable reaction can become favorable when coupled to a highly endergonic reaction
False
A reaction with a large negative free energy of hydrolysis can be coupled to the synthesis of ATP from ADP and Pi
True
In a general redox reaction, the reductant becomes oxidized and the oxidant becomes reduced
True
The standard reduction potential is a measure of the ability of a reductant to ________ an electron
lose
The standard reduction potentials for the following reactions are given below.
Pyruvate + 2H+ + 2e- ? lactate E? = -0.190 V
NAD+ + 2H+ + 2e- ? NADH/H+ E? = -0.320V.
Calculate ?G? for the overall spontaneous reaction making use of the relationship between
-25kJ/mol
Which of the following amino acids would most likely be found on the surface of a protein?
A) Aspartic acid
B) Leucine
C) Proline
D) Valine
E) Phenylalanine
A) Aspartic acid
Protein biosynthesis uses only L-amino acids
True
All amino acids have a chiral ?-carbon EXCEPT ________.
glycine
The side chain of ________ has a pKa in the physiological pH range and is therefore often involved in proton transfer during enzymatic catalysis
histidine
At physiological pH, the carboxylic acid group of an amino acid will be ________, while the amino group will be ________, yielding the zwitterion form
deprotonated, protonated
At pH=0, the net charge on a polypeptide will be negative
False
Which of the following modified amino acids is incorporated during translation rather than being modified post-translationally?
A) Phosphoserine
B) Selenocysteine
C) ?-carboxyglutamate
D) N-?-acetyllysine
E) 4-hydroxyproline
B) Selenocysteine
An amide bond between the ?-carboxylic acid group of one amino acid and the ?-amino group on another is called a ________.
peptide bond
The chemical ________ can cleave amide bonds on the C-terminal side of methionine residues
cyanogen bromide
Which of the following is FALSE when considering the standard genetic code?
A) Three separate codons encode translation stop signals.
B) There are 64 possible codons to represent 20 common amino acids.
C) AUG serves as the translation start codon in most
E) Each of the three stop codons can also encode rare modified amino acids
Which of the following statements about insulin is INCORRECT?
A) In the active form it has two polypeptide chains joined by disulphide bonds.
B) It is synthesized as a random coil single chain on membrane-bound ribosomes.
C) The leader sequence is cleaved
D) The disulphide bonds form after the final proteolytic cleavage to yield mature insulin.
Most proteins have blocked amino and carboxyl terminals
False
Conservative amino acid changes never affect stability or function of a protein
False
When referring to the amino acid sequences of proteins, sequence homology is the same as sequence similarity
False
Several homologous proteins can be aligned to provide a ________ sequence
consensus
Recombinant proteins containing a ________ can be purified using immobilized metal affinity chromatography and eluted by the addition of imidazole, a low pH buffer or a buffer containing EDTA
his-tag, or hexahistidine-tag
Applications of mass spectrometry include:
A) determination of the mass of a protein.
B) determining the primary structure of proteins.
C) detection of post-translational modifications on proteins.
D) A and B.
E) A, B, and C
E) A, B, and C
In size exclusion chromatography, the smallest proteins are eluted last
True
________ chromatography is used to separate proteins based on their surface charge
Ion exchange
In considering protein secondary structure which of the following is INCORRECT?
A) An ? helix repeats after 18 residues and has 3.6 residues per turn.
B) A network of main-chain hydrogen bonds connect ? strands in a ? sheet.
C) The most common structures
D) The 310 helix is right-handed and often contains proline residues
The amino acid side chain residues in an ? helix point outwards away from the center of the helix
True
________ between amide protons and carbonyl oxygens is necessary to stabilize a regular folding of protein secondary structure
Hydrogen bonding
A ________ plot describes which structures in a polypeptide are sterically possible and which are not based on the angles of rotation about the backbone Namide �C? and C?-Ccarbonyl bonds
Ramachandran
Which of the following statements about ?-keratins is FALSE?
A) They include a major class of protein that comprises hair, fingernails and animal skin.
B) Individual molecules are ?-helical.
C) There is a strip of contiguous hydrophobic surface making a s
E) Pairs of ?-helices twist about each other in a coiled-coil structure held together entirely by hydrophobic interactions
The protein that makes up about a third of the total protein mass in animals is:
A) ?-keratin.
B) collagen.
C) hemoglobin.
D) myoglobin.
E) ?-keratin
B) collagen.
Fibroin is a ?-sheet protein, with a high proportion of glycine
True
Tropocollagen is a double helix of two left-handed polypeptide chains
False
Scurvy results in weakness in collagen fibres because the enzymes that catalyze ________ of proline and lysine residues in collagen require Vitamin C
hydroxylation
Which of the following is CORRECT when considering the tertiary structure of globular proteins?
A) ? sheets are usually twisted or wrapped into barrel structures.
B) Hydrophobic residues are normally on the inside and hydrophilic residues are on the outsi
B) Hydrophobic residues are normally on the inside and hydrophilic residues are on the outside.
Proteins cannot self-assemble into a functional conformation after they have been denatured
False
Protein folding is a random process, whereby a vast number of possible conformations are tested to find the desired most stable state
False
The folded conformation of proteins can be stabilized by the binding of a metal ion or cofactor
True
The interactions that stabilize multisubunit complexes are different to those that stabilize tertiary structure
False
Protein folding is a thermodynamically favorable process under physiological conditions because:
A) there is an increase in entropy associated with protein folding.
B) there is a decrease in entropy of the solvent by burying hydrophobic groups within the
C) of the large negative enthalpy change associated with many noncovalent interactions.
The cavity in the GroEL-GroES complex from E. coli provides a favorable environment that prevents ________ and mis-folding
aggregation
Bovine spongiform encephalopathy is an infectious disease caused by a prion protein, which undergoes a ________ change to become pathogenic
conformational
Proteins have an asymmetrical tertiary structure, while multisubunit proteins can exhibit several types of symmetry
True
The functional organization of proteins where specific complexes of two or more polypeptides are formed is called ________ structure
quaternary
Which technique is able to investigate secondary structural features of proteins?
A) Infrared spectroscopy
B) Ultraviolet spectroscopy
C) Fluorescence spectroscopy
D) Circular dichroism
E) All of the above
E) All of the above
________ spectroscopy can be used to study dynamic processes in solution
Nuclear magnetic resonance
SDS gel electrophoresis can be used to determine:
A) whether subunits in a protein complex are identical or not.
B) the molecular mass of a native protein complex.
C) the overall charge on a polypeptide.
D) the molecular mass of denatured protein subunits
D) the molecular mass of denatured protein subunits.
Which of the following statement is FALSE?
A) The free energy barrier in a chemical reaction must be overcome in order for products to form.
B) An increase in temperature can result in an increased reaction rate.
C) Lowering the free energy of the transit
D) At a given temperature and time all molecules in a solution or a sample will have the same energy.
In a favorable reaction the free energy of the products is ________ than the free energy of the reactants
less
Catalysts affect the thermodynamic f of a chemical reaction
False
Pyruvate carboxylase is an example of the ligase class of enzymes
True
In an enzyme-catalyzed reaction, the lifetime of the transition state is similar to the vibrational frequencies of covalent bonds
True
Non-catalyzed biochemical reactions always occur at physiological useful timescales
False
Electrostatic catalysis proceeds via covalent bonding interactions
False
A second-order reaction:
A) occurs when one substrate is converted into one product.
B) is characterized by two molecules coming together to form a product.
C) is the rate-limiting step of a reaction.
D) has a rate constant with units of (time)-1.
E) only
B) is characterized by two molecules coming together to form a product.
The equilibrium constant for a first-order ________ reaction is equivalent to the ratio of the rate constant for the forward and reverse reactions
reversible
Enzymes can accelerate reactions by:
A) binding a substrate or substrates.
B) promoting the removal or addition of protons.
C) correctly positioning a metal ion for catalysis.
D) lowering the energy for activation.
E) all of the above
E) all of the above
The equilibrium state of a biochemical reaction is approached ________ in the presence of a catalyst
more rapidly
The lock and key model of substrate binding and enzymatic catalysis explains:
A) the release of product.
B) substrate specificity.
C) formation of a transition state.
D) the catalytic mechanism.
E) structural changes that occur on substrate binding
B) substrate specificity.
Which of the following amino acid residues are often involved in proton transfers in enzyme-catalyzed reactions?
A) Histidine, aspartate, serine, and cysteine
B) Serine, tyrosine, arginine, and cysteine
C) Glutamine, asparagine, lysine, and tyrosine
D) Hi
E) Histidine, aspartate, glutamate, arginine, and lysine
The ________ hypothesis suggests that an enzyme can induce distortion of the substrate or the substrate can induce conformational changes in the enzyme that stabilize the transition state
induced fit
The formation of an enzyme-substrate complex tends to be thermodynamically favorable due to ________ interactions between the substrate and enzyme
noncovalent
Which of the following statements about the proposed mechanisms of action for hen egg white lysozyme does NOT support either model?
A) Glycosidic bond cleavage occurs by general acid/base catalysis.
B) A covalent intermediate is formed between an active s
D) The active site aspartic acid changes between being protonated and deprotonated.
A Lineweaver-Burk plot for a first order enzyme-catalyzed reaction gives values of 1/KM = 2.5 � 104 (M)^-1 and 1/Vmax of 1.25 � 10^-2 (�molL-1 sec-1)-1. Calculate the rate constant k
2 sec^-1
Serine proteases make use of covalent catalysis as well as electrostatic stability of the transition state to achieve rate enhancement
True
A common feature of serine proteases is the catalytic triad consisting of a nucleophile, a general base and an acid. In chymotrypsin these amino acid residues are ________, ________, and ________ respectively
serine, histidine, aspartic acid
The cofactor NAD+ is:
A) a reductant.
B) an oxidant.
C) oxidized to NADH/H+ in dehydrogenase reactions.
D) able to accept 2 electrons and 2 protons.
E) covalently linked to enzymes in whose catalytic activity it assists
B) an oxidant.
Coenzymes or cofactors are irreversibly changed during catalysis
False
Which of the following statements applies to metalloenzymes?
A) Some metal ions assist in ATP binding.
B) Amino acid residues in the enzyme are never covalently linked to the metal ion.
C) The metal does not bind at the catalytic site.
D) Many are oxido-r
E) A and D
Metal ions are often required for catalytic efficiency but they may not remain permanently bound to the protein or take part in the catalytic process
True
Which of the following statements BEST describes the Michaelis-Menton constant KM?
A) It is numerically equal to the affinity between the enzyme and its substrate.
B) It is numerically equal to the substrate concentration required to reach half maximal ve
B) It is numerically equal to the substrate concentration required to reach half maximal velocity for an enzyme-catalyzed reaction.
A mutation causing an amino acid change in an enzyme that affects the turnover number kcat will always affect the KM as well
False
A Lineweaver-Burk plot can be used to determine KM using initial-rate data for an enzyme-catalyzed reaction
True
A graph of initial velocity vs substrate concentration will be ________ for an enzyme that obeys Michaelis-Menton kinetics
hyperbolic
Random substrate binding, ordered substrate binding and the ping-pong mechanism are all features of ________ enzyme-catalyzed reactions
multisubstrate
Which of the following statements about inhibitors of enzyme-catalyzed reactions is TRUE?
A) An uncompetitive inhibitor typically affects KM but not kcat.
B) A competitive inhibitor does not affect Vmax.
C) An uncompetitive inhibitor will always bind at t
B) A competitive inhibitor does not affect Vmax.
A reversible ________ inhibitor is one that binds to the active site of an enzyme but cannot undergo the chemical conversion step of the reaction
competitive
Which of the following is NOT a feature of substrate-level enzyme regulation?
A) A high substrate concentration will speed up the rate of reaction.
B) A high product concentration will slow the rate of reaction.
C) The product can be a competitor.
D) It i
D) It is sufficient for regulation of most enzyme-catalyzed reactions.
Almost all irreversible enzyme inhibitors bind noncovalently to the enzyme
False
Feedback regulation of a metabolic pathway can either be activation or inhibition
True
Which of the following is a feature of allosteric regulation of enzyme activity?
A) Ligand binding causes a conformation change in the enzyme.
B) Allosteric enzymes often have multiple active sites.
C) Cooperativity in substrate binding.
D) There is often
E) All of the above
Covalent modification can either activate or inhibit enzymes
True
Protein kinases add a phosphoryl group to the �OH group of a ________, ________, or ________ residue of the target protein
serine, tyrosine, threonine
Proteolytic cleavage is an example of an ________ post-translational modification
irreversible
Catalytically inactive enzyme precursors are called ________.
zymogens
A ribonucleic acid that can act as a biological catalyst is called a ________.
ribozyme
A stopped-flow apparatus is used to measure rates of pre-steady state slow enzymatic reactions
False
Carbohydrates are components of the following:
A) the membrane of red blood cells.
B) nucleic acids.
C) the hormone erythropoietin.
D) the bacterial cell wall.
E) all of the above
E) all of the above
Which of the following is an example of a monosaccharide?
A) Galactose
B) Lactose
C) Amylose
D) Maltose
E) None of the above
A) Galactose
Glyceraldehyde has a chiral carbon so has two stereoisomers, which are called diastereomers
False
Pentoses and hexoses can form stable ring structures by internal hemiacetal formation
True
Which of the following is considered to be the smallest carbohydrate?
A) Glucose
B) Dihydroxyacetone
C) Ribose
D) Xylose
E) Formaldehyde
B) Dihydroxyacetone
D-ribose can form a ring structure with either four or five carbons in the ring
True
Maltose has a (1?4) ? linkage between glucose and ________.
glucose
Synthesis of sugar polymers is enzyme catalyzed and requires activated monomers like ________ in lactose biosynthesis
UDP-galactose
Amylose and amylopectin are the principle storage polysaccharides of:
A) bacteria.
B) plants.
C) animals.
D) mollusks.
E) insects
B) plants.
The storage polysaccharides are ________ in plants and ________ in animals
starch, glycogen
N-linked glycans are attached to proteins through N-acetylglucosamine or N-acetyl galactosamine to the amide side chain of:
A) glutamine.
B) histidine.
C) asparagine.
D) arginine.
E) lysine
C) asparagine.
Glycosaminoglycans are polysaccharides composed of repeating disaccharide units in which one of the sugars is always N-acetylgalactosamine
False
Proteins are marked for secretion from the cell by the post translational addition of oligosaccharides
True
Heparin is a highly sulphated glycosaminoglycan that act as an ________.
anticoagulant
O-linked glycans are attached to proteins through the hydroxyl group of serine or ________ and sometimes ________.
threonine, tyrosine
Calculate the amount of ATP in kg that is turned over by a resting human every 24 hours. Assume that a typical human contains ~50g of ATP (Mr 505) and consumes ~8000 kJ of energy in food each day. The energy stored in the terminal anhydride bond of ATP un
66kg
The anabolic and catabolic processes of cellular metabolism can be coupled by ATP
True
Catabolic processes involve degradation of complex molecules into simpler molecules with the net release of chemical energy
True
Name the type of reaction that involves reversible electron transfer from a donor to an acceptor
Redox, oxidation-reduction
Which of the following produces the largest number of reducing equivalents when oxidized?
A) Glucose
B) NADPH
C) NADH
D) Palmitic acid
E) A hydrogen atom
D) Palmitic acid
ATP has a high phosphoryl group transfer potential because:
A) it is chemically unstable.
B) it has a high rate of spontaneous hydrolysis at physiological pH and temperature.
C) it exhibits resonance stabilization prior to hydrolysis.
D) it has three phos
E) cleavage of either of its two phosphoanhydride bonds proceeds with a large negative ?Go' of hydrolysis
Substrate-level phosphorylation is a term given to the loss of free energy when ATP is hydrolyzed.
False
The main energy-coupling compound in biochemical reactions that allows thermodynamically unfavorable processes to become favorable is ________.
ATP
Under physiological conditions the complete oxidation of glucose to carbon dioxide and water in the presence of oxygen has a ?G of -2900 kJ/mol glucose. This process can be coupled to the synthesis of ~32 mol ATP. The ?G of the coupled reactions to make A
+50kJmol^-1
Which of the following can be used as a metabolic control mechanism?
A) Enzyme compartmentation
B) Action of hormones
C) Covalent modification of an enzyme
D) Regulation of enzyme degradation
E) All of the above
E) All of the above
A futile cycle is:
A) the citric acid cycle.
B) two reactions or pathways that share substrates and products, and result in no net gain of ATP.
C) two opposing cellular reactions that are independently controlled.
D) an endergonic reaction that uses up AT
B) two reactions or pathways that share substrates and products, and result in no net gain of ATP.
Enzyme-catalyzed sequential reactions that make up a metabolic pathway are normally separated in the cell for equal access to reactants
False
Reactions in metabolic pathways that are subject to regulation are those that are displaced far from ________.
equilibrium
An enzyme that catalyzes a committed step in a metabolic pathway has a high ________.
flux control coefficient
The standard free energy change in physiological conditions (?G?') for the reaction catalyzed by malate dehydrogenase in the citric acid cycle
malate + NAD+ oxaloacetate + NADH + H+
is ~+29 kJmol^-1
Calculate the actual ?G' at 37?C if Keq' is 1.02 � 10^-5
-0.62 kJmol^-1
Anaerobic glycolysis can produce ATP at a much faster rate than aerobic oxidative phosphorylation
True
Which of the following types of reaction does NOT occur in glycolysis?
A) Isomerization
B) Nucleophilic attack
C) Aldol condensation
D) Oxidation
E) Dehydration
C) Aldol condensation
The standard free energy change of the glycolytic pathway to pyruvate is -79.9 kJ/mol, while the standard free energy change associated with gluconeogenesis from pyruvate is -42.7 kJ/mol. What would the standard free energy change be for a direct reversal
+79.9kJ/mol
Glycolysis is regulated primarily by:
A) the availability of glucose-6-phosphate.
B) three strongly endergonic, nonequilibrium reactions.
C) three strongly exergonic, nonequilibrium reactions.
D) allosteric effectors of pyruvate kinase.
E) phosphorylation
C) three strongly exergonic, nonequilibrium reactions
Which of the following statements about regulation of phosphofructokinase is FALSE?
A) AMP is an activator.
B) ADP is an activator.
C) Citrate is an inhibitor.
D) Fructose 2,6-bisphosphate is an activator.
E) ATP decreases the apparent Km for fructose-6-p
E) ATP decreases the apparent Km for fructose-6-phosphate
Liver pyruvate kinase is activated by dephosphorylation in response to glucagon
False
Hexokinase, phosphofructokinase and pyruvate kinase are each subject to ________ control
allosteric
Fructose-1,6-bisphosphate is a feedforward ________ activator of liver pyruvate kinase
allosteric
The oxidation of glucose to lactate has a standard free energy change of approximately -196 kJ/mol. Calculate the efficiency of energy conversion if the standard free energy change for the production of ATP from ADP and inorganic phosphate is +32.2 kJ/mol
33.8%
All of the reactions of both glycolysis and gluconeogenesis occur in the cytosol
False
The flux rate through the gluconeogenic pathway is directly proportional to the amount of carbohydrate in the diet.
False
Much of the regulation of gluconeogenesis is a result of the inhibition of glycolysis
True
Which of the following cannot be used as a precursor for gluconeogenesis?
A) Glycerol
B) Pyruvate
C) Lactate
D) Leucine
E) Alanine
D) Leucine
Flux through the pentose phosphate pathway is controlled mainly by the NADP+/NADPH ratio in the cell
True
The primary gluconeogenic organ in animals is:
A) skeletal muscle.
B) kidney medulla.
C) kidney cortex.
D) liver.
E) heart muscle
D) liver.
________ from muscle working anaerobically is released to blood and can be taken up by liver where it is converted to pyruvate by the enzyme lactate dehydrogenase
Lactate
The Pasteur effect describes the observation that yeast-metabolizing glucose anaerobically will dramatically increase their rate of glucose utilization when provided with air
False
Both glycolysis and gluconeogenesis are controlled by fructose 2,6-bisphosphate in response to hormones
True
Pyruvate carboxylase and phosphoenolpyruvate carboxykinase catalyze reactions of gluconeogenesis that bypass the reaction of glycolysis that is catalyzed by ________.
pyruvate kinase
Glycogen is a major energy source for skeletal muscle contraction
True
Polysaccharide digestion and glycogen breakdown involve sequential cleavage from ________ ends of glucose polymers
non-reducing
The major product from the action of glycogen phosphorylase and the debranching enzyme glucantransferase is ________.
glucose-1-phosphate
Which of the following is NOT involved in glycogen synthesis?
A) UDP-glucose
B) Glycogenin
C) Amylo-(1,4 to 1,6)-transglycosylase
D) Glycogen synthase
E) Glycogen phosphorylase
E) Glycogen phosphorylase
Which statement about control of glycogen metabolism is INCORRECT?
A) Epinephrine signals glycogen breakdown in muscle.
B) Glucagon signals glycogen breakdown in liver.
C) Glycogen phosphorylase is activated by phosphorylation.
D) Glycogen synthase is pho
D) Glycogen synthase is phosphorylated at only one site
Phosphorylases and phosphatases catalyze the same reaction, the removal of a phosphate group
False
The pentose phosphate pathway provides ________ for reductive biosynthesis and ________ for nucleic acid biosynthesis
NADPH, ribose-5-phosphate
Which of the following techniques can be used to quantify protein-protein interactions?
A) Co-immunoprecipitation
B) Affinity chromatography
C) Chemical cross-linking
D) Surface plasmon resonance
E) The two-hybrid system
D) Surface plasmon resonance
Oxaloacetate is replenished via the ________ in plants and bacteria
glyoxylate pathway
The glyoxylate cycle in plants and bacteria can be used for net carbohydrate synthesis from fat because isocitrate lyase yields glyoxylate and ________ without the loss of two carbons as occurs in the citric acid cycle
succinate
All of the enzymes of the citric acid cycle are located in the mitochondrion
True
Which of the following does NOT apply to the reaction catalyzed by the pyruvate dehydrogenase complex?
A) The process is highly exergonic and essentially irreversible in vivo.
B) Each intermediate in the five step reaction is able to diffuse to the next a
B) Each intermediate in the five step reaction is able to diffuse to the next active site in a sequential manner.
NAD+, coenzyme A, thiamine pyrophosphate, lipoic acid and FAD are all cofactors used in the reaction catalyzed by pyruvate dehydrogenase
True
The citric acid cycle is classed as a reductive pathway as it produces reduced electron carriers
False
The two carbon atoms that are lost as CO2 in the third and fourth steps of the citric acid cycle are the same as the two carbon atoms of acetyl CoA because of the stereochemistry of the isocitrate dehydrogenase reaction
False
Which of the following enzymes catalyzes a reaction of the citric acid cycle that does NOT produce reduced electron carriers?
A) Malate dehydrogenase
B) Succinate dehydrogenase
C) ?-ketoglutarate dehydrogenase
D) Isocitrate dehydrogenase
E) Succinyl �CoA
E) Succinyl �CoA synthetase
Arsenic poisoning acts by inhibiting the citric acid cycle at the point of both pyruvate dehydrogenase and ?-ketoglutarate dehydrogenase because it makes a stable adduct with the ________ groups of the dihydrolipoamide intermediate
sulphydryl
One substrate level phosphorylation occurs in the citric acid cycle in the reaction catalyzed by:
A) ?-ketoglutarate dehydrogenase.
B) succinate dehydrogenase.
C) succinyl �CoA synthetase.
D) isocitrate dehydrogenase.
E) citrate synthase
C) succinyl �CoA synthetase
Taking one mole of glucose through glycolysis and the citric acid cycle generates:
A) 6C02, 8 NADH/H+, 1FADH2 and 1 ATP.
B) 6C02, 8 NADH/H+, 1FADH2 and 2 ATP.
C) 6C02, 10 NADH/H+, 2FADH2 and 2 ATP.
D) 6C02, 10 NADH/H+, 2FADH2 and 4 ATP.
E) 6C02, 8 NADH/H+
D) 6C02, 10 NADH/H+, 2FADH2 and 4 ATP.
Which of the following does NOT regulate flux through the citric acid cycle?
A) Substrate availability
B) The ratio of [NAD+]/[NADH]
C) Allosteric inhibition of isocitrate dehydrogenase by ADP
D) Inhibition of ?-ketoglutarate dehydrogenase by succinyl CoA
A) Substrate availability
The malate dehydrogenase reaction has a strongly positive standard free energy change but it proceeds in the direction of oxaloacetate because the concentration of ________ is maintained at exceedingly low levels
oxaloacetate
Transamination reactions can be used to provide intermediates for the citric acid cycle
true
The citric acid cycle can be considered both a ________ and anabolic pathway as it is used to oxidise acetyl CoA to carbon dioxide as well as to provide precursors for other ________ pathways
catabolic, biosynthetic
Acetyl CoA is a feed forward activator of the enzyme ________ ensuring sufficient oxaloacetate for the citric acid cycle to continue
pyruvate carboxylase
Electrons are transferred through the respiratory chain from reduced NADH or FADH2 to oxygen in small steps with each step in the pathway associated with a slightly more ________ reduction potential
positive
Calculate the standard free energy change for the reactionFADH2 + 1/2O2 ? FAD + H2O given that the standard reduction potential for the reduction of oxygen to water is +0.82 V and for the reduction of FAD to FADH2 is +0.03 V
-152kJ/mol
Which of the following statements is FALSE?
A) All of the protein complexes of the mitochondrial respiratory chain are bound in the inner mitochondrial membrane.
B) Cytochrome c and coenzyme Q are both soluble electron carriers that are loosely attached t
B) Cytochrome c and coenzyme Q are both soluble electron carriers that are loosely attached to the outside of the inner mitochondrial membrane.
Which of the following is NOT an electron acceptor in the mitochondrial respiratory chain?
A) FMN
B) FAD
C) Fe3+
D) Cu2+
E) CoQH2
E) CoQH2
All of the cytochromes in the mitochondrial respiratory chain contain the same heme moiety as found in hemoglobin
False
CoQ carries electrons from NADH-Coenzyme Q reductase and succinate dehydrogenase as well as other flavoproteins to CoQ:Cytochrome c oxidoreductase
True
Which of the following statements about oxidative phosphorylation by ATP synthase is FALSE?
A) The electrochemical gradient across the inner mitochondrial membrane generated by electron flow is used to synthesize ATP.
B) Uncouplers dissipate the electroch
D) A proton gradient alone without a corresponding energy input is not sufficient to drive the synthesis of ATP.
Electron transport through NADH-Coenzyme Q reductase (Complex I) is accompanied by transfer of ________ protons from the matrix to the intermembrane space
four
The Q cycle is responsible for transferring electrons from a two-electron donor ________ to a one-electron acceptor ________ at the point of complex III of the mitochondrial respiratory chain
CoQH2, cytochrome c
Calculate the free energy change associated with transporting one proton from the matrix to the intermembrane space at 37?C where the electrical potential across the membrane is ~ = 170 mV and the ?pH is +0.75
+20.85kJ/mol
Proton-driven rotation of the c-ring of the F0 unit of the F1F0 ATP synthase is required for complete passage of protons from the intermembrane space to the matrix
True
Oligomycin is an inhibitor of ADP phosphorylation because it blocks the flow of protons through the ________.
Fo proton channel
Which of the following is NOT true of respiratory control?
A) Oxidative phosphorylation is absolutely dependent on the continued flow of electrons from substrates to oxygen.
B) Oxidative phosphorylation is regulated by allosteric mechanisms.
C) The stimul
B) Oxidative phosphorylation is regulated by allosteric mechanisms.
Energy derived from oxidation of acetyl-CoA in the citric acid cycle is used for the production of ________ in brown adipose tissue because the mitochondria are rich in UCP1
heat
In animal cells the mitochondrial electron transport chain is responsible for reoxidizing most of the NADH produced by oxidative pathways regardless of the cellular compartment in which it was produced
True
The ATP yield from NADH transported across the mitochondrial inner membrane by the glycerol phosphate shuttle is the same as if the malate/aspartate shuttle were used
False
Calculate the efficiency of energy conversion from glucose under aerobic conditions assuming that 32 moles of ATP are produced for each mole of glucose and given that ?G0' for glucose oxidation is -2870kJ/mol and the ?G0' for ATP hydrolysis is -32.2 kJ/mo
36%
Which of the following is NOT involved in the enzymatic inactivation of reactive oxygen species?
A) Superoxide dismutase
B) Catalase
C) Vitamin C
D) Peroxiredoxin
E) Peroxidase
C) Vitamin C
________, which are potentially damaging, are generated because the interactions between one electron and two electron carriers are not 100% efficient
Reactive oxygen species