biology
37) During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a △G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the △G for the new reaction?
-20 kcal/mol
35) Starting with one molecule of isocitrate and ending with fumarate, what is the maximum number of ATP molecules that could be made through substrate-level phosphorylation?
1
37) How many molecules of carbon dioxide (CO2) would be produced by five turns of the citric acid cycle
10
20) Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed during glycolysis?
100%
41) For each molecule of glucose that is metabolized by glycolysis and the citric acid cycle, what is the total number of NADH + FADH2 molecules produced?
12
34) How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?
2
in glycolysis, for each molecule of glucose oxidized to pyruvate
2 molecules of ATP are used and 4 molecules of ATP are produced
60) Assume a mitochondrion contains 58 NADH and 19 FADH2. If each of the 77 dinucleotides were used, approximately how many ATP molecules could be generated as a result of oxidative phosphorylation (chemiosmosis)?
212
62) Recall that the complete oxidation of a mole of glucose releases 686 kcal of energy (Δ G = -686 kcal/mol). The phosphorylation of ADP to form ATP stores approximately 7.3 kcal per mole of ATP. What is the approximate efficiency of cellular respiration for a ʺmutantʺ organism that produces only 29 moles of ATP for every mole of glucose oxidized, rather than the usual 36-38 moles of ATP?
30%
71) What happens at the end of the chain?
4 electrons combine with oxygen
61) Approximately what percentage of the energy of glucose (C6H12O6) is transferred to storage in ATP as a result of the complete oxidation of glucose to CO2 and water in cellular respiration
40%
57) Each time a molecule of glucose (C6H12O6) is completely oxidized via aerobic respiration, how many oxygen molecules (O2) are required?
6
59) Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in cellular respiration?
76
18) Which step involves an endergonic reaction?
A
19) Which step consists of a phosphorylation reaction in which ATP is the phosphate source?
A
3) When electrons move closer to a more electronegative atom, what happens?
A and C are correct.
65) Which of the following statements describes enzyme cooperativity?
A substrate molecule bound to an active site affects the active site of several subunits.
51) Which of the following bests describes the reaction?
A) negative △G, spontaneous
14) The mathematical expression for the change in free energy of a system is △G =△H-T△S. Which of the following is (are) correct?
AG is the change in free temperature
66) Which of the following is the most correct interpretation of the figure?
ATP is a molecule that acts as an intermediary to store energy for cellular work.
66) After the second agitation of the membrane vesicles, what must be lost from the membrane?
ATP synthase, in whole or in part
53) Which of the following represents the activation energy required for the enzyme-catalyzed reaction?
B
4) For living organisms, which of the following is an important consequence of the first law of thermodynamics?
B) The organism ultimately must obtain all of the necessary energy for life from its environment
26) Which of the following statements is true concerning catabolic pathways?
B) They are usually coupled with anabolic pathways to which they supply energy in the form of ATP.
61) How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
B) by changing the shape of a reactant
16) In which step is an inorganic phosphate added to the reactant?
C
17) In which reaction does an intermediate pathway become oxidized?
C
54) Which of the following represents the activation energy required for a noncatalyzed reaction?
C
29) A number of systems for pumping across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they donʹt often hydrolyze ATP unless they are simultaneously transporting ions. Small increases in calcium ions in the cytosol trigger a number of different intracellular reactions, so the cells must keep the calcium concentration quite low. Muscle cells also transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a muscle cell cytosol has a free calcium ion concentration of 10-7 in a resting cell, while the concentration in the SR can be 10-2, then how is the ATPase acting?
C) ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
64) In liver cells, the inner mitochondrial membranes are about 5 X the area of the outer mitochondrial membranes, and about 17 X that of the cellʹs plasma membrane. What purpose must this serve?
C) It increases the surface for oxidative phosphoryation.
46) Based on this information, which of the following is correct?
C) Succinate is the substrate, and fumarate is the product.
33) Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in
C) breaking the bond between glucose and fructose and forming new bonds from the atoms of water.
35) A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because
C) the activation energy barrier for this reaction cannot be surmounted.
50) Which of the following would be the same in an enzyme-catalyzed or noncatalyzed reaction?
D
52) Which of the following represents the difference between the free-energy content of the reaction and the free-energy content of the products?
D
5) Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
D) As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth
8) Which of the following statements is representative of the second law of thermodynamics?
D) Cells require a constant input of energy to maintain their high level of organization.
7) Which of the following statements is a logical consequence of the second law of thermodynamics?
D) Every chemical reaction must increase the total entropy of the universe.
55) Which best describes the reaction?
D) The amount of free energy released as a result of the catalyzed reaction is indicated by D
56) Assume that the reaction has a △G of -5.6 kcal/mol. Which of the following would be true?
D) The reaction would result in an increase in entropy (S) and a decrease in the total energy content of the system
17) Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?
D) a chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive
23) When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation?
E) Reactant and product concentrations are not the same
67) In coupled reactions, in which direction would the endergonic reaction be driven relative to the clockwise direction of the ATP reaction above and shown in the figure?
E) it would be shown in a clockwise direction at the top of the figure
69) Which of the following most accurately describes what is happening along this chain
Each electron carrier alternates between being reduced and being oxidized
4) Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy
Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).
44) Which of the following is true of enzymes?
Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
47) During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?
FADH2
82) Glycolysis is thought to be one of the most ancient of metabolic processes. Which statement supports this idea?
Glycolysis is the most widespread metabolic pathway
42) A young animal has never had much energy. He is brought to a veterinarian for help and is sent to the animal hospital for some tests. There they discover his mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of his condition?
His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
28) When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?
It can be added to other molecules in order to activate them.
22) Why is ATP an important molecule in metabolism?
It provides energy coupling between exergonic and endergonic reactions.
28) Why is glycolysis described as having an investment phase and a payoff phase?
It uses stored ATP and then forms a net increase in ATP.
23) The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mole and the free energy for the reduction of NAD+ to NADH is +53 kcal/mole. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?
Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.
8) Which of the following statements describes NAD+?
NAD is reduced to NADH during both glycolysis and the citric acid cycle.
5) If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur?
Nothing; reaction would stay at equilibrium
57) In order to attach a particular amino acid to the tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase, is required, along with ATP. Initially, the enzyme has an active site for ATP and another for the amino acid, but it is not able to attach the tRNA. What must occur in order for the final attachment to occur?
The binding of the first two molecules must cause a 3-dimensional change that opens anothwr active site on the enzyme
39) According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?
The binding of the substrate changes the shape of the enzymeʹs active site.
31) Which of the following statements is (are) true about enzyme-catalyzed reactions?
The reaction is faster than the same reaction in the absence of the enzyme.
14) Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen.
11) Which of the following is an example of potential rather than kinetic energy?
a food molecule made up of energy rich macromolecules
69) Which of the following is an example of cooperativity?
a molecule binding at one unit of a tetramer allowing faster binding at each of the other three
36) Carbon skeletons for amino acid biosynthesis are supplied by intermediates of the citric acid cycle. Which intermediate would supply the carbon skeleton for synthesis of a five-carbon amino acid?
a-ketoglutarate
11) The oxygen consumed during cellular respiration is involved directly in which process or event?
accepting electrons at the end of the electron transport chain
32) Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?
acetyl CoA
93) Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?
acetyl CoA
48) The primary role of oxygen in cellular respiration is to
act as an acceptor for electrons and hydrogen, forming water
34) Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reactionʹs
activation energy
31) How does pyruvate enter the mitochondrion?
active transport
32) How can one increase the rate of a chemical reaction?
add a catalyst
4) If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to
add more of the enzyme
65) After the first disruption, when electron transfer and ATP synthesize still occur, what must be present?
all of the electron transport proteins as well as atp synthase
88) Phosphofructokinase is an important control enzyme in the regulation of cellular respiration. Which of the following statements describes a function of phosphofructokinase?
allosteric enzyme
63) Substance A functions as
allosteric inhibitor
27) Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
68) Some enzymatic regulation is allosteric. In such cases, which of the following would usually be found?
an enzyme with more than one subunit
59) Which of the following is likely to lead to an increase in the concentration of ATP in a cell?
an increase in a cellʹs catabolic activity
12) Which of the following is considered an open system?
an organism
24) Which of the following is most similar in structure to ATP?
an rna nucleotide
72) Which of the following couples chemiosmosis to energy storage?
atp synthase
78) In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
atp, carbon dioxide, ethyanol
15) Which step shows a split of one molecule into two smaller molecules?
b
92) What is the purpose of beta oxidation in respiration?
breakdown of fatty acids
1) What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
catabolic pathways
1) Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
catabolism
60) When you have a severe fever, what may be a grave consequence if this is not controlled?
change in the folding of enzymes
43) Cellular respiration harvests the most chemical energy from which of the following?
chemiosmotic phosphorylation
45) Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)
cofactor necessary for enzyme activity.
71) Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?
compartmentalization of enzymes into defined organelles
43) Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
competitive inhibition
47) What is the purpose of using malonic acid in this experiment?
competitive inhibitor.
85) When muscle cells are oxygen deprived, the heart still pumps. What must the heart cells be able to do?
continue aerobic metabolism when skeletal muscle cannot
54) When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the
creation of a proton gradient.
9) Where does glycolysis takes place?
cytosol
49) Which of the following represents the △G of the reaction?
d
9) Which of the following types of reactions would decrease the entropy within a cell?
dehydration reactions
20) A chemical reaction that has a positive △G is correctly described as
endergonic
3) Which of the following is a statement of the first law of thermodynamics?
energy cannot be created or destroyed
25) What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?
energy coupling
51) In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + Pi to ATP?
energy released from movement of protons through ATP synthase
6) Whenever energy is transformed, there is always an increase in the
entropy of the universe
36) Which of the following statements regarding enzymes is true?
enzymes increase the rate of a reaction
48) Which of the following terms best describes the reaction?
exergonic
1) Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as __________ is to __________.
exergonic; endergonic
81) An organism is discovered that consumes a considerable amount of sugar, yet does not gain much weight when denied air. Curiously, the consumption of sugar increases as air is removed from the organismʹs environment, but the organism seems to thrive even in the absence of air. When returned to normal air, the organism does fine. Which of the following best describes the organism?
facultative anaerobe.
64) The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as
feedback inhibition
83) Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
found in cytosol, does not involve oxygen, present in most organisms.
12) Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent
glycolysis
74) Which of the following normally occurs whether or not oxygen (O2) is present?
glycolysis
76) Which metabolic pathway is common to both cellular respiration and fermentation?
glycolysis
75) Which of the following occurs in the cytosol of a eukaryoticcell
glycolysis and fermentation
26) A molecule that is phosphorylated
has an increased chemical reactivity; it is primed to do cellular work.
90) Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?
in photosynthesizing cells in dark periods and in other tissues all the time
86) When muscle cells undergo anaerobic respiration, they become fatigued and painful. This is now known to be caused by
increase in potassium ions
89) Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount ATP in a cell would be expected to
inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
55) Where is ATP synthase located in the mitochondrion?
inner membrane
67) It should be possible to reconstitute the abilities of the vesicles if which of the following is added?
intact ATP synthase
10) The organization of organisms has become increasingly complex with time. This statement
is consistent with the second law of thermodynamics
38) The active site of an enzyme is the region that
is involved in the catalytic reaction of an enzyme
27) When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
it is lost to the environment
2) The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction
loses electrons loses energy
13) Which of the following is true of metabolism in its entirety?
metabolism is a property of organismal life
45) Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
52) Energy released by the electron transport chain is used to pump H + ions into which location?
mitochondrial intermembrane space
33) During cellular respiration, acetyl CoA accumulates in which location? A) cytosol
mitochondrial matrix
50) During oxidative phosphorylation, H2O is formed. Where does the oxygen for the synthesis of the water come from?
molecular oxygen
70) The parts of the figure labeled with Roman numerals symbolize what concept?
multimeric groups of proteins in 4 complexes
) What is the reducing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD
nadh
68) The accompanying figure shows the electron transport chain. Which of the following is the combination of substances that is initially added to the chain?
nadh , fadh2 , electrons
15) What is the change in free energy of a system at chemical equilibrium?
no net change
40) Carbon dioxide (CO2) is released during which of the following stages of cellular reactants
oxidation of pyruvate to acetyl CoA and the citric acid cycle
56) It is possible to prepare vesicles from portions of the inner membrane of the mitochondrial components. Which one of the following processes could still be carried on by this isolated inner membrane?
oxidative phosphorylation
58) Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
80) One function of both alcohol fermentation and lactic acid fermentation is to
oxidize nadh to nad
6) When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes
oxidized
7) When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a hydrogen ion) the molecule becomes
reduced
79) In alcohol fermentation, NAD+ is regenerated from NADH during which of the following?
reduction of acetaldehyde to ethanol
87) You have a friend who lost 7 kg (about 15 pounds) of fat on a ʺlow carbʺ diet. How did the fat leave her body?
released as carbon dioxide and water
21) During glycolysis, when glucose is catabolized to pyruvate, most of the energy of glucose is
retained in the pyruvate.
13) An electron loses potential energy when it
shifts to a more electronegative atom
73) Which of the following describes ubiquinone?
small hydrophobic coenzyme
62) What is substance X?
substrate
77) The ATP made during fermentation is generated by which of the following?
substrate-level phosphorylation
10) The ATP made during glycolysis is generated by
substrate-level phosphorylation.
84) Muscle cells, when an individual is exercising heavily and when the muscle becomes oxygen deprived, convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells?
taken to the liver and converted back to pyruvate
2) Most cells cannot harness heat to perform work because
temperature is usually uniform throughout a cell.
2) The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is
the H concentration gradient across the inner mitochondrial membrane
58) Competitive inhibitors block the entry of substrate into the active site of an enzyme. On which of the following properties of an active site does this primarily depend?
the ability of an enzyme to form a template for holding and joining molecules
70) Among enzymes, kinases catalyze phosphorylation, while phosphatases catalyze removal of phosphate(s). A cellʹs use of these enzymes can therefore function as an on-off switch for various processes. Which of the following is probably involved?
the change in a proteinʹs charge leading to a conformational change
53) The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation is
the difference in H+ concentrations on opposite sides of the inner mitochondrial membrane.
21) Which of the following best describes enthalpy (H)?
the heat content of a chemical system
16) Which of the following is true for all exergonic reactions?
the reaction proceeds with a net release of free energy
63) What is proton-motive force?
the transmembrane proton concentration gradient
6) Some bacteria are metabolically active in hot springs because
their enzymes have high optimal temperatures
30) What must be the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in DNA and RNA?
there is no difference
2) Which of the following is (are) true for anabolic pathways?
they consume energy to build up polymers from monomers
30) Why is coenzyme A, a sulfur containing molecule derived from a B vitamin, added?
to provide a relatively unstable molecule whose acetyl portion can readily bind to oxaloacetate
91) In vertebrate animals, brown fat tissueʹs color is due to abundant mitochondria. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few mitochondria. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue?
to regulate temperature by converting energy from NADH oxidation to heat
72) An important group of peripheral membrane proteins are enzymes, such as the phospholipases that attack the head groups of phospholipids leading to the degradation of damaged membranes. What properties must these enzymes exhibit?
water solubility
