BIO 121 EXAM 2 MASTERINGBIO
Select the highest energy form of adenosine from the following images.
1
Based on the graph, what is the optimal pH for pepsin activity? 2 3.5 8 10
2
Which of these is ATP?
3 Phosphate groups attached to a Ribose attached to Adenine
Based on the graph, what is the optimal pH for trypsin activity? 2 3.5 8 10
8
In cells, what is usually the immediate source of energy for an endergonic reaction? -ADP -sugar -glucose -ATP -as spontaneous reactions, endergonic reactions do not need an addition of energy
ATP
Which of the following statements about equilibrium of chemical reactions is correct? -The equilibrium point of a reaction represents the least stable configuration for that reaction. -A reaction that is at equilibrium is not capable of doing any work. -The equilibrium point is where the system has the highest free energy -Most reactions in a living cell are close to equilibrium. -Reactions can only go in the direction toward equilibrium.
A reaction that is at equilibrium is not capable of doing any work.
Which of the following is the most correct interpretation of the figure? -ADP + Pi are a set of molecules that store energy for catabolism. -Energy from catabolism can be used directly for performing cellular work. -Pi acts as a shuttle molecule to move energy from ATP to ADP. -ATP is a molecule that acts as an intermediary to store chemical energy for cellular work.
ATP is a molecule that acts as an intermediary to store chemical energy for cellular work.
You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down. What can you do to speed the reaction up again? -Add more inhibitor to speed up the reaction. -Add more substrate; it will outcompete the inhibitor and increase the reaction rate. -Increase the temperature. -Increase the pH.
Add more substrate; it will outcompete the inhibitor and increase the reaction rate.
Which of the following is a true statement? -Anabolic pathways break down molecules, require energy, and are endergonic. -Catabolic pathways break down molecules, require energy, and are exergonic. -Catabolic pathways build molecules, release energy, and are exergonic. -Anabolic pathways build molecules, require energy, and are endergonic.
Anabolic pathways build molecules, require energy, and are endergonic.
An enzyme is considered a _____________ because it speeds up chemical reactions without being used up.
catalyst
What will happen to the rates of the forward and reverse reactions when a catalyst is added? -Forward rate increases; reverse rate decreases. -Both forward and reverse rates increase. -Both forward and reverse rates decrease. -Forward rate decreases; reverse rate increases.
Both forward and reverse rates increase.
Which of the following metabolic processes can occur without a net influx of energy from some other process? -C6H12O6 + 6 O2 → 6 CO2 + 6 H2O -ADP + P i → ATP + H2O -amino acids → protein -glucose + fructose → sucrose -6 CO2 + 6 H2O → C6H12O6 + 6 O2
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
Which of the following is the strongest evidence that protein structure and function are correlated? -Denatured (unfolded) proteins do not function normally. -Enzymes tend to be globular in shape. -Proteins have four distinct levels of structure and many functions. -Proteins can readily form hydrogen bonds with water.
Denatured (unfolded) proteins do not function normally.
What happens along an electron transport chain? -Protons are pumped through ATP synthase, making ATP. -Electrons are passed from molecule to molecule, gaining potential energy at each step. -Electrons are passed from a reducing agent to an oxidizing agent, releasing free energy at each step. -Electrons store energy that can be used to break down sugar molecules.
Electrons are passed from a reducing agent to an oxidizing agent, releasing free energy at each step.
Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction? -Increase the pH. -Increase the temperature. -Increase the enzyme concentration. -Increase the substrate concentration.
Increase the enzyme concentration.
What is the fate of the phosphate group that is removed when ATP is converted to ADP? -It is acquired by a reactant in an exergonic reaction. -It is broken down into one phosphorus and four oxygen atoms. -It is acquired by a reactant in a spontaneous reaction. -It is used to convert an ATP into an AQP. -It is acquired by a reactant in an endergonic reaction.
It is acquired by a reactant in an endergonic reaction.
A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose? -It is stored in pyruvate. -It is stored in the ATP that was formed by glycolysis and the citric acid cycle. -It is stored in NADH and FADH2 -It was lost as heat. -It is stored in the carbon dioxide and water molecules released by these processes.
It is stored in NADH and FADH2
Select the correct statement about chemical energy, a term used by biologists to refer to potential energy available for release in a chemical reaction. -A photosynthetic cell within a plant leaf produces chemical energy, stored within glucose molecules. -Light energy is converted to chemical energy during photosynthesis. -When a glucose molecule is catabolized to CO2 and H2O, chemical energy is lost.
Light energy is converted to chemical energy during photosynthesis.
Using the figure to guide your response, select the best explanation for why natural selection might have resulted in the optimal pH for pepsin. -Natural selection favors enzymatic activity of pepsin at a pH of 2.0 because 2.0 is the pH inside the small intestine. -Natural selection favors enzymatic activity of pepsin at a pH of 2.0 because 2.0 is the pH inside the stomach. -Natural selection favors enzymatic activity of pepsin at a pH of 8.0 because 8.0 is the pH inside the small intestine. -There is no clear relationship between the enzymatic activity of pepsin, a stomach enzyme, and the pH inside the stomach.
Natural selection favors enzymatic activity of pepsin at a pH of 2.0 because 2.0 is the pH inside the stomach.
Which of the following statements is most likely to be true in the case of the feedback-regulated enzymatic pathway shown? -P0 binds E4 and activates it. -P2 binds E2 and activates it. -P4 binds E1 and deactivates it. -P3 binds E2 and activates it -P4 binds E3 and deactivates it.
P4 binds E1 and deactivates it.
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes? -The active site can provide heat from the environment that raises the energy content of the substrate. -The active site of the enzyme can provide a microenvironment with a different pH that facilitates the reaction. -Binding of the substrate to the active site can stretch bonds in the substrate that need to be broken. -The binding of two substrates in the active site provides the correct orientation for them to react to form a product. -The enzyme binds a cofactor that interacts with the substrate to facilitate the reaction.
The active site can provide heat from the environment that raises the energy content of the substrate.
Which of the following statements about the chemiosmotic synthesis of ATP is correct? -The energy for production of ATP from ADP comes directly from a gradient of electrons across the inner mitochondrial membrane. -Oxygen participates directly in the reaction that makes ATP from ADP and P. -The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane. -The chemiosmotic synthesis of ATP occurs only in eukaryotic cells, because it occurs in mitochondria. -Chemiosmotic ATP synthesis requires oxygen.
The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane.
The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation? -The compound forms a covalent bond with one of the amino acid residues needed for enzyme activity. -The compound is a competitive inhibitor. -The compound is a negative allosteric regulator. -The compound reduces disulfide bonds, causing the enzyme molecules to partially unfold. -The compound causes a cofactor to be lost from the enzyme.
The compound is a competitive inhibitor.
Which of the following statements about ATP (adenosine triphosphate) is correct? -The hydrolysis of ATP can supply energy needed for catabolic pathways. -Almost all of the free energy released on the hydrolysis of ATP is released as heat. -The hydrolysis of ATP is an endergonic process. The energy release on hydrolysis of ATP is the result of breaking a bond between the ribose and a phosphate group. -The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways.
The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways.
Which of the following statements is not true of most cellular redox reactions? -The electron acceptor is reduced, acting as an oxidizing agent. -The reactant that is oxidized loses electrons, acting as a reducing agent. -The reactant that is reduced gains electrons. -The electron acceptor is reduced, acting as a reducing agent.
The electron acceptor is reduced, acting as a reducing agent.
Which of the following statements about the role of ATP in cell metabolism is true? -The free energy released by ATP hydrolysis has a much more negative ΔG value than the hydrolysis of phosphate groups from other phosphorylated molecules. -The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule. -The phosphate bonds of ATP are unusually strong bonds.
The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule.
Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is correct? -The reverse reaction, making glucose from water and carbon dioxide, must be an exergonic reaction. -The entropy of the universe decreases as the result of this reaction. -The free energy lost in this combustion is less than the energy that appears as heat. -The entropy of the products is greater than the entropy of the reactants. -This is the process of cellular respiration, an anabolic pathway that releases free energy.
The entropy of the products is greater than the entropy of the reactants.
Which of the following would be unlikely to contribute to the substrate specificity of an enzyme? -The enzyme has an allosteric regulatory site. -A positive charge on the substrate is attracted to a negative charge in the active site of the enzyme. -A hydrophobic group on the substrate interacts with several hydrophobic amino acids on the enzyme. -The enzyme has the ability to change its configuration in response to the substrate binding. -A similar shape exists between a pocket on the surface of the enzyme and a functional group on the substrate.
The enzyme has an allosteric regulatory site.
You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely. What can you do to regain the activity of the enzyme? -Removing the irreversible inhibitor should get the reaction working again. -The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity. -Adding more substrate will increase the rate of reaction. -Adding more inhibitor should get the reaction up to speed again.
The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.
Which of the following statements about feedback regulation of a metabolic pathway is correct? -Accumulation of the product of the pathway increases further formation of that product. -The final product of a metabolic pathway is usually the compound that regulates the pathway. -The enzyme that is regulated by feedback inhibition is usually the last enzyme in the metabolic pathway. -The products of the pathway become the reactants for a different reaction, and thus products are unable to accumulate. -The compound that regulates the pathway acts as a competitive inhibitor or a positive allosteric regulator.
The final product of a metabolic pathway is usually the compound that regulates the pathway.
Which of the following is a chemical reaction? -The formation of a covalent bond between two amino acids. -The melting of ice. -Making a hydrogen bond between a water molecule and a sugar molecule. -Changing a carbon atom to a nitrogen atom by radioactive decay.
The formation of a covalent bond between two amino acids.
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP? -redox -potentiation -cellular respiration -digestion -anabolism
cellular respiration
Which of the following is true for all exergonic reactions? -A net input of energy from the surroundings is required for the reactions to proceed. -The reaction goes only in a forward direction: All reactants will be converted to products. -The reaction proceeds with a net release of free energy. -The products have more total energy than the reactants.
The reaction proceeds with a net release of free energy.
The Haber process is typically carried out at a temperature of approximately 500∘C. What would happen to the rate of the forward reaction if the temperature were lowered to 100∘C?
The reaction rate would decrease
What would happen to the rate of the forward reaction if the concentration of nitrogen were decreased?
The reaction rate would decrease
Plants are photoautotrophs. What does this mean? -They are attracted to light. -They are the primary consumers of the biosphere. -They synthesize their own food from inorganic materials. -They use light energy to drive the synthesis of organic molecules from inorganic materials. -They generate oxygen.
They use light energy to drive the synthesis of organic molecules from inorganic materials.
The graph presents three activation energy profiles for a chemical reaction (the hydrolysis of sucrose): an uncatalyzed reaction, and the same reaction catalyzed by two different enzymes. Rank these by reaction rate, as measured by the rate of product formation per unit time, from lowest reaction rate to highest reaction rate. reaction catalyzed by enzyme A reaction catalyzed by enzyme B Uncatalyzed reaction
Uncatalyzed reaction, reaction catalyzed by enzyme A, reaction catalyzed by enzyme B
Which of the following is true of the energy levels of electrons in shells? -Electrons must lose energy to move from the first to the second shell. -All the electrons in an atom have similar energy levels. -Valence electrons have a higher energy level than those in other filled shells. -Electrons do not have potential energy, just kinetic energy.
Valence electrons have a higher energy level than those in other filled shells.
Which of the following statements is true regarding potential energy and kinetic energy? -Water gains kinetic energy as it falls through a dam; water uses potential energy as it moves the blades of turbines in the dam to generate electricity. -Water at the top of a dam has kinetic energy; water falling through a dam has potential energy. The moving water performs work by moving the blades of turbines in the dam to generate electricity. -Water at the top of a dam has potential energy; water falling through a dam has kinetic energy. The moving water performs work by moving the blades of turbines in the dam to generate electricity. -Water gains potential energy as it falls through a dam; water uses kinetic energy as it moves the blades of turbines in the dam to generate electricity.
Water at the top of a dam has potential energy; water falling through a dam has kinetic energy. The moving water performs work by moving the blades of turbines in the dam to generate electricity.
The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of _____. -a catabolic pathway -an endergonic pathway -a pathway in which the entropy of the system decreases -a pathway that converts organic matter into energy -a pathway that occurs in animal cells but not plant cells
a catabolic pathway
Two molecules with the chemical formulas C6H12O6 and C6H12O2 are probably -a fat and a nucleotide -a monosaccharide and a fatty acid -a monosaccharide and a nucleotide -a nucleic acid and a fat
a monosaccharide and a fatty acid
Which of these is exhibiting kinetic energy? -a space station orbiting Earth -a rock on a mountain ledge -an archer with a flexed bow -the high-energy phosphate bonds of a molecule of ATP -a person sitting on a couch while watching TV
a space station orbiting Earth
trans-
across
A substrate binds to an enzyme at the ____________ , where the reaction occurs.
active site
The competitive inhibitor competes with the substrate for the ____________ on the enzyme. -active site -competitive -enzyme -Irreversible -noncompetitive -substrate
active site
If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to -add an allosteric inhibitor. -heat the solution to 90°C. -add a noncompetitive inhibitor. -add more substrate. -add more of the enzyme.
add more of the enzyme.
-trop-
change, turn, move
A ___________ , such as a vitamin, binds to an enzyme and plays a role in catalysis.
cofactor
A (n) ____________ inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate. -active site -competitive -enzyme -Irreversible -noncompetitive -substrate
competitive
When properly aligned, the enzyme and substrate form an enzyme-substrate (ES) ______________.
complex
Which of these are by-products of cellular respiration? -carbon dioxide and water -ATP, carbon dioxide, and water -ATP and carbon dioxide -heat, carbon dioxide, and water -glucose, carbon dioxide, and water
heat, carbon dioxide, and water
An enzyme is ____________ when it loses its native conformation and its biological activity.
denatured
Enzymes work by _____. -increasing the potential energy difference between reactant and product -decreasing the potential energy difference between reactant and product -adding energy to a reaction -reducing EA -adding a phosphate group to a reactant
reducing EA
The reaction ADP + P --> ATP is a(n) _____ reaction. -spontaneous -chemical -endergonic -exergonic -hydrolysis
endergonic
This graph illustrates a(n) _____ reaction. -hydrolysis -spontaneous -exergonic -catabolic -endergonic
endergonic
Which of these reactions requires a net input of energy from its surroundings? -hydrolysis -endergonic -ATP --> ADP + P -exergonic -catabolic
endergonic
"Conservation of energy" refers to the fact that _____. -no chemical reaction is 100 percent efficient -the entropy of the universe is always increasing -energy cannot be created or destroyed but can be converted from one form to another -if you conserve energy you will not be as tired -the net amount of disorder is always increasing
energy cannot be created or destroyed but can be converted from one form to another
What is the correct label for "A"? -ATP -enzyme energy -energy of activation -uphill -substrate energy
energy of activation
-ase
enzyme
When the noncompetitive inhibitor is bonded to the enzyme, the shape of the ____________ is distorted. -active site -competitive -enzyme -Irreversible -noncompetitive -substrate
enzyme
A(n) _____ reaction occurs spontaneously. -chemical -anabolic -exergonic -kinetic -endergonic
exergonic
The energy for an endergonic reaction comes from a(n) _____ reaction. -synthesis -exergonic -anabolic -glucose + glucose --> maltose -ADP + P --> ATP
exergonic
The following reaction A --> B + C + heat is a(n) _____ reaction. -anabolic -endergonic -exchange -dehydration synthesis -exergonic
exergonic
Select the INCORRECT association. -kinetic energy ... motion -exergonic ... spontaneous -enzyme ... protein -exergonic ... uphill -potential energy ... positional energy
exergonic ... uphill
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _______ is to _______. -entropy; enthalpy -exergonic; spontaneous -free energy; entropy -exergonic; endergonic -work; energy
exergonic; endergonic
therm-
heat
In this reaction _____. - entropy has decreased -the chemical energy of the products is greater than that of the reactants - heat has been released to the environment -the kinetic energy of the reactants is less than that of the products -disorder has decreased
heat has been released to the environment
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule? -anabolism -dehydration decomposition -dehydration synthesis -entropic -hydrolysis
hydrolysis
Enzymes are described as catalysts, which means that they _____. -increase the free energy of the reactants to make the reaction go faster -are proteins -increase the rate of a reaction without being consumed by the reaction -can alter the free energy change (ΔG) for a chemical reaction -provide activation energy for the reactions they facilitate
increase the rate of a reaction without being consumed by the reaction
Which of the following would increase the rate of the reverse reaction? -increasing the concentration of ammonia -decreasing the temperature -increasing the concentration of nitrogen
increasing the concentration of ammonia
Usually, a(n) _____________ inhibitor forms a covalent bond with an amino acid side group within the active site, which prevents the substrate from entering the active site or prevents catalytic activity. -active site -competitive -enzyme -Irreversible -noncompetitive -substrate
irreversible
An enzyme _____. -increases the EA of a reaction -is a source of energy for endergonic reactions -can bind to nearly any molecule -is an organic catalyst -is a inorganic catalyst
is an organic catalyst
As a result of its involvement in a reaction, an enzyme _____. -loses a phosphate group -permanently alters its shape. -loses energy -is unchanged -is used up
is unchanged
The overall function of the Calvin cycle is _____. -capturing sunlight -producing carbon dioxide -oxidizing glucose -making sugar -splitting water
making sugar
lac- (or lact-)
milk
kin- (or kinet-)
moving
A (n) ______________ inhibitor binds to a site on the enzyme that is not the active site. -active site -competitive -enzyme -Irreversible -noncompetitive -substrate
noncompetitive
A covalent bond is likely to be polar when -the two atoms sharing electrons are different elements. -one of the atoms sharing electrons is more electronegative than the other. -the two atoms sharing electrons are the same elements. -the two atoms sharing electrons have the same electronegativity.
one of the atoms sharing electrons is more electronegative than the other.
allo-
other
extra-
outside of
Which of the following is a product of the light reactions of photosynthesis? -glyceraldehyde-3-phosphate -water and CO2 -oxygen, ATP, and NADPH -high-energy photons -NADP+ and RuBP
oxygen, ATP, and NADPH
Chemical energy is a form of _____ energy. -heat -motion -entropic -kinetic -potential
potential
In general, enzymes are what kinds of molecules? -lipids -proteins -nucleic acids -carbohydrates -minerals
proteins
Look at the graph of reaction rate versus substrate concentration for an enzyme. In which region does the reaction rate remain constant? -region A -region B -region C
region C
Refer again to the graph. In which region is the enzyme saturated with substrate? -region A -region B -region C
region C
An enzyme is considered ___________ because of its ability to recognize the shape of a particular molecule.
specific
When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____. -fixing carbon -oxidizing glucose -breaking down ATP -splitting water -removing them from NADPH
splitting water
Enzyme inhibitors disrupt normal interactions between an enzyme and its ____________. -active site -competitive -enzyme -Irreversible -noncompetitive -substrate
substrate
In a catalyzed reaction a reactant is often called a _______________.
substrate
What name is given to the reactants in an enzymatically catalyzed reaction? -substrate -products -EA -active sites -reactors
substrate
glyc-
sweet
Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy? -the energy associated with a gradient of ions across a membrane: kinetic energy -the covalent bonds of a sugar molecule: potential energy -the motion of individual molecules: potential energy -the energy related to the height of a bird above the ground: kinetic energy -the heat released from a living organism: potential energy
the covalent bonds of a sugar molecule: potential energy
Chemical equilibrium is reached when -concentrations of reactants and products remain the same. -there are equal concentrations of reactants and products. -concentrations of products are higher than the concentrations of reactants. -the forward and reverse reactions occur at the same rate.
the forward and reverse reactions occur at the same rate.
In this reaction _____. -the products have less potential energy than the reactants -AC is a reactant -entropy has decreased -the products have been rearranged to form reactants -CD is a product
the products have less potential energy than the reactants
What is energy coupling? -a barrier to the initiation of a reaction -the hydrolysis of ATP to ADP + P -the use of energy released from an exergonic reaction to drive an endergonic reaction -a description of the energetic relationship between the reactants and products in an exergonic reaction -the use of an enzyme to reduce EA
the use of energy released from an exergonic reaction to drive an endergonic reaction
Some bacteria are metabolically active in hot springs because -their enzymes are completely insensitive to temperature. -they are able to maintain a lower internal temperature. -high temperatures make catalysis unnecessary. -they use molecules other than proteins or RNAs as their main catalysts. -their enzymes have high optimal temperatures.
their enzymes have high optimal temperatures.
Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration? -breaking down ATP, so that ADP and P can be reused -producing complex molecules from chemical building blocks -catabolism of sugars and related compounds -the breakdown of glucose to carbon dioxide and water -transforming the energy in glucose and related molecules into a chemical form that cells can use for work
transforming the energy in glucose and related molecules into a chemical form that cells can use for work
sub-
under, below
The electrons stripped from glucose in cellular respiration end up in which compound? -carbon dioxide -NADH -oxygen -water -ATP
water
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions? -α -phosphate (the phosphate closest to ribose) -β-phosphate (the middle phosphate) -γ-phosphate (the terminal phosphate) -adenine group -ribose sugar
γ-phosphate (the terminal phosphate)
