Biochem Module 1 - KM

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

Enzyme-catalyzed sequential reactions that make up a metabolic pathway are normally separated in the cell for equal access to reactants

False

Glyceraldehyde has a chiral carbon so has two stereoisomers, which are called diastereomers

False

Glycine cannot serve as a buffer because it has two ionizable groups.

False

Glycosaminoglycans are polysaccharides composed of repeating disaccharide units in which one of the sugars is always N-acetylgalactosamine

False

Liver pyruvate kinase is activated by dephosphorylation in response to glucagon

False

Most proteins have blocked amino and carboxyl terminals

False

Non-catalyzed biochemical reactions always occur at physiological useful timescales

False

Oxidation-reduction reactions, which are the basis of many biochemical reactions and pathways, cannot take place in the absence of oxygen.

False

Phosphorylases and phosphatases catalyze the same reaction, the removal of a phosphate group

False

Protein folding is a random process, whereby a vast number of possible conformations are tested to find the desired most stable state

False

Proteins cannot self-assemble into a functional conformation after they have been denatured

False

Substrate-level phosphorylation is a term given to the loss of free energy when ATP is hydrolyzed.

False

________ between amide protons and carbonyl oxygens is necessary to stabilize a regular folding of protein secondary structure

Hydrogen bonding

Synthesis of sugar polymers is enzyme catalyzed and requires activated monomers like ________ in lactose biosynthesis

UDP-galactose

Bovine spongiform encephalopathy is an infectious disease caused by a prion protein, which undergoes a ________ change to become pathogenic

conformational

Several homologous proteins can be aligned to provide a ________ sequence

consensus

The chemical ________ can cleave amide bonds on the C-terminal side of methionine residues

cyanogen bromide

Acetyl CoA is a feed forward activator of the enzyme ________ ensuring sufficient oxaloacetate for the citric acid cycle to continue

pyruvate carboxylase

Pyruvate carboxylase and phosphoenolpyruvate carboxykinase catalyze reactions of gluconeogenesis that bypass the reaction of glycolysis that is catalyzed by ________.

pyruvate kinase

The functional organization of proteins where specific complexes of two or more polypeptides are formed is called ________ structure

quaternary

The equilibrium constant for a first-order ________ reaction is equivalent to the ratio of the rate constant for the forward and reverse reactions

reversible

A ribonucleic acid that can act as a biological catalyst is called a ________.

ribozyme

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

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

A reaction at equilibrium can be driven in one direction or the other by changing the ________ of reactants or products

concentration

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

Protein kinases add a phosphoryl group to the —OH group of a ________, ________, or ________ residue of the target protein

serine, tyrosine, threonine

The storage polysaccharides are ________ in plants and ________ in animals

starch, glycogen

Catalysts affect the thermodynamic f of a chemical reaction

False

Coenzymes or cofactors are irreversibly changed during catalysis

False

Conservative amino acid changes never affect stability or function of a protein

False

Electrostatic catalysis proceeds via covalent bonding interactions

False

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

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 ATP is -1300 kJ/mol glucose. Calculate the △G for the synthesis of ATP from ADP

+50kJmol^-1

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 of the glycolytic pathway

+79.9kJ/mol

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

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

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

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 △E∘ and △G∘

-25kJ/mol

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

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 (µmolL-1 sec-1)-1. Calculate the rate constant k

2 sec^-1

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 weak acid that is 0.2% ionized in a 0.2 M solution

3.39

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%

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/mol

36%

Calculate the pH of a 0.2 M acetate buffer (pKa = 4.77) that contains twice as much acid as conjugate base

4.47

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

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 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 under standard conditions is 30.6 kJmol-1. Assume also that the dietary energy is channeled through ATP with an energy transfer efficiency of ~50%.

66kg

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

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

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 α-ketoglutarate dehydrogenase by succinyl CoA E) Ca2+ activation of isocitrate dehydrogenase

A) Substrate availability

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) have no effect on the interactions between oppositely charged macroions. D) tend to cluster around macroions of the same charge. E) have large effects on pH.

A) encourage strong electrostatic interactions between oppositely charged macroions at low ionic strengths.

Almost all irreversible enzyme inhibitors bind noncovalently to the enzyme

False

The main energy-coupling compound in biochemical reactions that allows thermodynamically unfavorable processes to become favorable is ________.

ATP

Which of the following is considered to be the smallest carbohydrate? A) Glucose B) Dihydroxyacetone C) Ribose D) Xylose E) Formaldehyde

B) Dihydroxyacetone

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 the active site. D) A competitive inhibitor binds irreversibly to the enzyme at the active site. E) Reversible inhibitors bind to either free enzyme or the enzyme-substrate complex but not both

B) A competitive inhibitor does not affect Vmax.

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 to the outside of the inner mitochondrial membrane. C) Oxygen is reduced to water at complex IV of the mitochondrial respiratory chain. D) The citric acid cycle is linked directly to the mitochondrial respiratory chain at the site of complex II. E) During electron transport protons are pumped across the inner mitochondrial membrane from the matrix to the intermembrane space

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 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 active site in a sequential manner. C) It takes place in the mitochondrion. D) It is an oxidative decarboxylation. E) The product is acetyl CoenzymeA

B) Each intermediate in the five step reaction is able to diffuse to the next active site in a sequential manner.

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, oxygen and potassium.

B) Hydrogen, carbon, nutrogen, and oxygen

Which of the following is CORRECT when considering the tertiary structure of globular proteins? A) β sheets are usually twisted or wrapped into barrel structures. B) Hydrophobic residues are normally on the inside and hydrophilic residues are on the outside. C) The amino acid proline never occurs in a region where the polypeptide chain bends or turns. D) All parts of the proteins can be classified as helix, β sheet or turns. E) None of the above

B) Hydrophobic residues are normally on the inside and hydrophilic residues are on the outside.

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 velocity for an enzyme-catalyzed reaction. C) It is a measure of the rate of a catalytic process. D) It is a measure of enzyme efficiency. E) It has units of concentration

B) It is numerically equal to the substrate concentration required to reach half maximal velocity for an enzyme-catalyzed reaction.

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 stimulation of respiration by addition of ADP is stoichiometric. D) The rate of respiration is controlled by the balance between the △G's for phosphorylation of ADP, electron transport and proton pumping. E) Maintenance of respiratory control depends on the structural integrity of the mitochondrial inner membrane

B) Oxidative phosphorylation is regulated by allosteric mechanisms.

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

Which of the following modified amino acids is incorporated during translation rather than being modified post-translationally? A) Phosphoserine B) Selenocysteine C) γ-carboxyglutamate D) N-ε-acetyllysine E) 4-hydroxyproline

B) Selenocysteine

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 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.

The protein that makes up about a third of the total protein mass in animals is: A) β-keratin. B) collagen. C) hemoglobin. D) myoglobin. E) α-keratin

B) collagen.

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 occurs in multistep processes

B) is characterized by two molecules coming together to form a product.

Amylose and amylopectin are the principle storage polysaccharides of: A) bacteria. B) plants. C) animals. D) mollusks. E) insects

B) plants.

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.

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 DNA is electrostatically attracted to negatively charged regions on proteins. D) proteins and DNA interact using mainly hydrophobic interactions. E) both proteins and DNA are at their isoelectric points at physiological pH and tend to aggregate.

B) the negatively charged DNA is electrostatically attracted to positively charged regions on proteins.

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 ATP. E) the reoxidation of NAD+ from NADH

B) two reactions or pathways that share substrates and products, and result in no net gain of ATP.

Amino acids and simple organic compounds like carbon dioxide and hydrogen cyanide cannot be produced without the use of enzymes.

False

The water content in the human body is approximately: A) 90%. B) 80%. C) 70%. D) 60%. E) 50%.

C) 70%

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

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 systems expend energy to overcome entropy. E) The entropy of a biological system can decrease

C) Biological systems are highly ordered so entropy changes are not relevant.

Which of the following is NOT classed as a lipid? A) Cholesterol B) Palmitic acid C) Glycerol D) Phosphatidyl serine E) Triacylglycerol

C) Glycerol

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 they can create energy from their environments. D) Energy can be transferred between a system and the surroundings. E) In biochemical processes, energy can neither be created or destroyed.

C) Organisms are open systems as they can create energy from their environments.

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

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.

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 molecule. C) of the large negative enthalpy change associated with many noncovalent interactions. D) no intermediate stage disulphide bonds form during the folding process. E) all of the above

C) of the large negative enthalpy change associated with many noncovalent interactions.

One substrate level phosphorylation occurs in the citric acid cycle in the reaction catalyzed by: A) α-ketoglutarate dehydrogenase. B) succinate dehydrogenase. C) succinyl —CoA synthetase. D) isocitrate dehydrogenase. E) citrate synthase

C) succinyl —CoA synthetase

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 of phosphofructokinase

C) three strongly exergonic, nonequilibrium reactions

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.

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

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+, 2FADH2 and 4 ATP

D) 6C02, 10 NADH/H+, 2FADH2 and 4 ATP.

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 electrochemical gradient but electron transport continues without ATP production. C) Inhibitors disrupt electron flow as well as ATP synthesis. D) A proton gradient alone without a corresponding energy input is not sufficient to drive the synthesis of ATP. E) ATP synthesis occurs via simultaneous conformational changes in protein subunits containing catalytic sites

D) A proton gradient alone without a corresponding energy input is not sufficient to drive the synthesis of ATP.

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 transition state can increase a reaction rate. D) At a given temperature and time all molecules in a solution or a sample will have the same energy. E) An enzyme can increase a reaction rate by lowering the activation energy

D) At a given temperature and time all molecules in a solution or a sample will have the same energy.

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 phosphorylated at only one site. E) Glycogen synthase is activated by dephosphorylation

D) Glycogen synthase is phosphorylated at only one site

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 is sufficient for regulation of most enzyme-catalyzed reactions. E) Sometimes products can be competitive or uncompetitive

D) It is sufficient for regulation of most enzyme-catalyzed reactions.

Which of the following cannot be used as a precursor for gluconeogenesis? A) Glycerol B) Pyruvate C) Lactate D) Leucine E) Alanine

D) Leucine

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

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

In considering protein secondary structure which of the following is INCORRECT? A) An α helix repeats after 18 residues and has 3.6 residues per turn. B) A network of main-chain hydrogen bonds connect β strands in a β sheet. C) The most common structures are the α helix and the β sheet. D) The 310 helix is right-handed and often contains proline residues. E) The β strands can be in either parallel or antiparallel configuration

D) The 310 helix is right-handed and often contains proline residues

Amphipathic molecules are not able to interact via van der Waals forces

False

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 site aspartate and C1 of the substrate. C) A water molecule is deprotonated, which then attacks C1 of the substrate. D) The active site aspartic acid changes between being protonated and deprotonated. E) The active site glutamic acid changes between being protonated and deprotonated

D) The active site aspartic acid changes between being protonated and deprotonated.

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 off after membrane transport. D) The disulphide bonds form after the final proteolytic cleavage to yield mature insulin. E) It is stored in the pancreas in an inactive form

D) The disulphide bonds form after the final proteolytic cleavage to yield mature insulin.

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 is thermodynamically favorable under defined non-standard conditions. E) can predict whether a reaction will be thermodynamically favorable under standard conditions

D) can be used to calculate whether a reaction is thermodynamically favorable under defined non-standard conditions.

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 are changed. D) is related to the change in free energy of the reaction. E) cannot be used to determine whether a reaction will proceed in the direction as written under non-standard conditions

D) is related to the change in free energy of the reaction.

The primary gluconeogenic organ in animals is: A) skeletal muscle. B) kidney medulla. C) kidney cortex. D) liver. E) heart muscle

D) liver.

Nearly all proteins contain: A) cobalt. B) phosphorus. C) selenium. D) sulfur. E) none of the above.

D) sulfur.

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. E) none of the above

D) the molecular mass of denatured protein subunits.

At pH=0, the net charge on a polypeptide will be negative

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-reductases. E) A and D

E) A and D

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

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-phosphate

E) ATP decreases the apparent Km for fructose-6-phosphate

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

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 the surrounding water molecules. E) All of the above

E) All of the above

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 a range of different effectors for a single enzyme. E) All of the above

E) All of the above

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

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

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 cases. D) Apart from methionine, the only other amino acid with a single codon is tryptophan. E) Each of the three stop codons can also encode rare modified amino acids

E) Each of the three stop codons can also encode rare modified amino acids

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 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) Histidine, aspartate, lysine, and serine E) Histidine, aspartate, glutamate, arginine, and lysine

E) Histidine, aspartate, glutamate, arginine, and lysine

Which of the following statements about α-keratins is FALSE? A) They include a major class of protein that comprises hair, fingernails and animal skin. B) Individual molecules are α-helical. C) There is a strip of contiguous hydrophobic surface making a shallow spiral around the helix. D) They include a small globular regions covalently linked to the surface. E) Pairs of α-helices twist about each other in a coiled-coil structure held together entirely by hydrophobic interactions

E) Pairs of α-helices twist about each other in a coiled-coil structure held together entirely by hydrophobic interactions

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 receptors. E) Proteins are the only biological polymer that can catalyze biochemical reactions.

E) Proteins are the only biological polymer that can catalyze biochemical reactions.

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) α-ketoglutarate dehydrogenase D) Isocitrate dehydrogenase E) Succinyl —CoA synthetase

E) Succinyl —CoA synthetase

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 interact by van der Waals forces do not interpenetrate. D) The total interaction energy is the sum of the attractive and repulsive forces. E) They are not important in determining the stability of three-dimensional structures of proteins

E) They are not important in determining the stability of three-dimensional structures of proteins

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

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

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 phosphate groups. E) cleavage of either of its two phosphoanhydride bonds proceeds with a large negative △Go' of hydrolysis

E) cleavage of either of its two phosphoanhydride bonds proceeds with a large negative △Go' of hydrolysis

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 stopped-flow apparatus is used to measure rates of pre-steady state slow enzymatic reactions

False

A thermodynamically unfavorable reaction can become favorable when coupled to a highly endergonic reaction

False

All of the cytochromes in the mitochondrial respiratory chain contain the same heme moiety as found in hemoglobin

False

All of the reactions of both glycolysis and gluconeogenesis occur in the cytosol

False

The Pasteur effect describes the observation that yeast-metabolizing glucose anaerobically will dramatically increase their rate of glucose utilization when provided with air

False

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

The citric acid cycle is classed as a reductive pathway as it produces reduced electron carriers

False

The flux rate through the gluconeogenic pathway is directly proportional to the amount of carbohydrate in the diet.

False

The interactions that stabilize multisubunit complexes are different to those that stabilize tertiary structure

False

The pKa of each amino acid residue in a protein will not be influenced by the adjacent residue.

False

The principle component of a biological membrane is a triglyceride.

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

Tropocollagen is a double helix of two left-handed polypeptide chains

False

When referring to the amino acid sequences of proteins, sequence homology is the same as sequence similarity

False

Oligomycin is an inhibitor of ADP phosphorylation because it blocks the flow of protons through the ________.

Fo proton channel

________ chromatography is used to separate proteins based on their surface charge

Ion exchange

________ 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 pentose phosphate pathway provides ________ for reductive biosynthesis and ________ for nucleic acid biosynthesis

NADPH, ribose-5-phosphate

________ spectroscopy can be used to study dynamic processes in solution

Nuclear magnetic resonance

The chemical element ________ has a role in both transfer of energy as well as in the structure of nucleic acids.

Phosphorous

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 —Cα and Cα-Ccarbonyl bonds

Ramachandran

________, which are potentially damaging, are generated because the interactions between one electron and two electron carriers are not 100% efficient

Reactive oxygen species

Name the type of reaction that involves reversible electron transfer from a donor to an acceptor

Redox, oxidation-reduction

Water is both a hydrogen bond donor and acceptor

True

A Lineweaver-Burk plot can be used to determine KM using initial-rate data for an enzyme-catalyzed reaction

True

A reaction with a large negative free energy of hydrolysis can be coupled to the synthesis of ATP from ADP and Pi

True

All of the enzymes of the citric acid cycle are located in the mitochondrion

True

Anaerobic glycolysis can produce ATP at a much faster rate than aerobic oxidative phosphorylation

True

Both glycolysis and gluconeogenesis are controlled by fructose 2,6-bisphosphate in response to hormones

True

Catabolic processes involve degradation of complex molecules into simpler molecules with the net release of chemical energy

True

CoQ carries electrons from NADH-Coenzyme Q reductase and succinate dehydrogenase as well as other flavoproteins to CoQ:Cytochrome c oxidoreductase

True

Covalent modification can either activate or inhibit enzymes

True

D-ribose can form a ring structure with either four or five carbons in the ring

True

Feedback regulation of a metabolic pathway can either be activation or inhibition

True

Fibroin is a β-sheet protein, with a high proportion of glycine

True

Flux through the pentose phosphate pathway is controlled mainly by the NADP+/NADPH ratio in the cell

True

Glycogen is a major energy source for skeletal muscle contraction

True

Hydrogen bonds share features of both covalent and noncovalent bonds.

True

In a general redox reaction, the reductant becomes oxidized and the oxidant becomes reduced

True

In an enzyme-catalyzed reaction, the lifetime of the transition state is similar to the vibrational frequencies of covalent bonds

True

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

In size exclusion chromatography, the smallest proteins are eluted last

True

Life is an irreversible process, such that it never comes to equilibrium.

True

Many biochemical reactions that form biopolymers from monomeric units involve the removal of water.

True

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

Much of the regulation of gluconeogenesis is a result of the inhibition of glycolysis

True

NAD+, coenzyme A, thiamine pyrophosphate, lipoic acid and FAD are all cofactors used in the reaction catalyzed by pyruvate dehydrogenase

True

Pentoses and hexoses can form stable ring structures by internal hemiacetal formation

True

Protein biosynthesis uses only L-amino acids

True

Proteins are marked for secretion from the cell by the post translational addition of oligosaccharides

True

Proteins have an asymmetrical tertiary structure, while multisubunit proteins can exhibit several types of symmetry

True

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

Pyruvate carboxylase is an example of the ligase class of enzymes

True

Serine proteases make use of covalent catalysis as well as electrostatic stability of the transition state to achieve rate enhancement

True

The amino acid side chain residues in an α helix point outwards away from the center of the helix

True

The anabolic and catabolic processes of cellular metabolism can be coupled by ATP

True

The average charge on an amino acid below its pI will be positive

True

The folded conformation of proteins can be stabilized by the binding of a metal ion or cofactor

True

The cavity in the GroEL-GroES complex from E. coli provides a favorable environment that prevents ________ and mis-folding

aggregation

Fructose-1,6-bisphosphate is a feedforward ________ activator of liver pyruvate kinase

allosteric

Hexokinase, phosphofructokinase and pyruvate kinase are each subject to ________ control

allosteric

Heparin is a highly sulphated glycosaminoglycan that act as an ________.

anticoagulant

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

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

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

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

Electron transport through NADH-Coenzyme Q reductase (Complex I) is accompanied by transfer of ________ protons from the matrix to the intermembrane space

four

Genomics is concerned with the entire ________, while ________ is focused on identifying all of the proteins of a cell.

genome, proteomics

Maltose has a (1→4) α linkage between glucose and ________.

glucose

The major product from the action of glycogen phosphorylase and the debranching enzyme glucantransferase is ________.

glucose-1-phosphate

All amino acids have a chiral α-carbon EXCEPT ________.

glycine

Oxaloacetate is replenished via the ________ in plants and bacteria

glyoxylate pathway

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

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

The side chain of ________ has a pKa in the physiological pH range and is therefore often involved in proton transfer during enzymatic catalysis

histidine

The most important noncovalent interaction in biochemistry is the ________ bond.

hydrogen

An amphipathic molecule provides the foundation for biological membranes because they have both ________ and ________ functional groups.

hydrophilic, hydrophobic

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

Scurvy results in weakness in collagen fibres because the enzymes that catalyze ________ of proline and lysine residues in collagen require Vitamin C

hydroxylation

A graph of initial velocity vs substrate concentration will be ________ for an enzyme that obeys Michaelis-Menton kinetics

hyperbolic

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

Proteolytic cleavage is an example of an ________ post-translational modification

irreversible

A thermodynamically unfavorable reaction can become favorable if the mass action ratio is ________ than the equilibrium mass action ratio

less

In a favorable reaction the free energy of the products is ________ than the free energy of the reactants

less

List the four major classes of biological macromolecules.

lipids, carbohydrates, proteins, nucleic acids

The standard reduction potential is a measure of the ability of a reductant to ________ an electron

lose

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

The equilibrium state of a biochemical reaction is approached ________ in the presence of a catalyst

more rapidly

Random substrate binding, ordered substrate binding and the ping-pong mechanism are all features of ________ enzyme-catalyzed reactions

multisubstrate

If hydroxide is added to an amino acid it will become increasingly ________ charged.

negatively

Polysaccharide digestion and glycogen breakdown involve sequential cleavage from ________ ends of glucose polymers

non-reducing

The formation of an enzyme-substrate complex tends to be thermodynamically favorable due to ________ interactions between the substrate and enzyme

noncovalent

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

An amide bond between the α-carboxylic acid group of one amino acid and the α-amino group on another is called a ________.

peptide bond

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

Arsenic poisoning acts by inhibiting the citric acid cycle at the point of both pyruvate dehydrogenase and α-ketoglutarate dehydrogenase because it makes a stable adduct with the ________ groups of the dihydrolipoamide intermediate

sulphydryl

O-linked glycans are attached to proteins through the hydroxyl group of serine or ________ and sometimes ________.

threonine, tyrosine

Transamination reactions can be used to provide intermediates for the citric acid cycle

true

The net charge on an amino acid at its isoelectric point (pI) is ________.

zero

Catalytically inactive enzyme precursors are called ________.

zymogens