Energy is conserved. This means that in any system,
1) high-quality energy input equals high-quality energy output
2) total energy input equals total energy output
3) energy is constantly recycled
4) light energy is released to replace the original input of solar energy
2) total energy input equals total energy output.
Kinetic energy is energy in motion. Potential energy is ___ energy.
stored
Which of the following is highest in chemical energy?
1) one molecule of glucose
2) one molecule of ATP
3) one molecule of H2
4) one molecule of CO2
#1: one molecule of glucose
In cellular respiration, most energy is released and transferred to ATP when ____.
high-energy electrons “fall” to lower energy levels
Which of these is exhibiting kinetic energy?
1) a rock on a mountain ledge
2) a space station orbiting Earth
3) a person sitting on a couch while watching TV
4) the high-energy phosphate bonds of a molecule of ATP
5) an archer with a flexed bow
#2: a space station orbiting Earth
“Conservation of energy” refers to the fact that ___.
1) the entropy of the universe is always increasing
2) no chemical reaction is 100% efficient
3) energy cannot be created or destroyed but can be converted from one form to another
4) if you conserve energy you will not be as tired
5) the net amount of disorder is always increasing
#3: energy cannot be created or destroyed but can be converted from one form to another
Chemical energy is a form of ____ energy.
1) potential
2) kinetic
3) motion
4) entropic
5) heat
#1: potential
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
1) potentiation
2) redox
3) digestion
4) anabolism
5) cellular respiration
#5: cellular respiration
Which of these are by-products of cellular respiration?
1) water
2) glucose and water
3) ATP
4) heat and water
5) ATP and water
#4: heat and water
Kinetic energy differs from chemical energy in that
1) kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules
2) kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat
3) chemical energy is a particular form of kinetic energy
4) kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement
#1: kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules
Light is ____ energy, which is converted by plants into molecules, which possess ____ energy.
1) chemical … kinetic
2) kinetic … chemical
3) chemical … potential
4) potential … kinetic
#2: kinetic … chemical

Light is kinetic energy, and molecules possess chemical energy. Chemical energy refers to the potential energy that can be released during chemical reactions.

A steer must eat at least 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates…
1) the first law of thermodynamics
2) that some energy is destroyed in every energy conversion
3) that energy transformations are typically 100% efficient
4) the second law of thermodynamics
#4: the second law of thermodynamics
What is the basic difference between exergonic and endergonic reactions?
1) Exergonic reactions release energy; endergonic reactions absorb it.
2) Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds.
3) In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true.
4) Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds.
#1: Exergonic reactions release energy; endergonic reactions absorb it.
When a cell uses chemical energy to perform work, it uses the energy released from a(n) ____ reaction to drive a(n) ____ reaction.
1) exergonic … spontaneous
2) spontaneous … exergonic
3) endergonic … exergonic
4) exergonic … endergonic
#4: exergonic … endergonic
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
1) entropic
2) anabolism
3) dehydration decomposition
4) dehydration synthesis
5) hydrolysis
#5: hydrolysis

Hydrolysis involves breaking bonds with the addition of water.

The transfer of a phosphate group to a molecule or compound is called
1) ionization
2) phosphorylation
3) carboxylation
4) hydrogenation
2) phosphorylation
The reaction A –> B + C + heat is released in a(n) ___ reaction.
1) exchange
2) anabolic
3) endergonic
4) exergonic
5) dehydration synthesis
#4: Exergonic

Energy has been released.

A(n) ____ reaction occurs spontaneously.
1) endergonic
2) kinetic
3) exergonic
4) anabolic
5) chemical
#3: exergonic

In exergonic reactions the products have less potential energy than the reactants.

Which of these reactions requires a net input of energy from its surroundings?
1) catabolic
2) endergonic
3) exergonic
4) ATP –> ADP + P
5) hydrolysis
#2: endergonic

The products of endergonic reactions have more potential energy than the reactants.

In cells, what is usually the immediate source of energy for an endergonic reaction?
1) ADP
2) as spontaneous reactions, endergonic reactions do not need an addition of energy
3) ATP
4) glucose
5) sugar
#3: ATP

The hydrolysis of ATP provides the energy needed for an endergonic reaction.

The reaction ADP + P –> ATP is a(n) ___ reaction.
1) exergonic
2) hydrolysis
3) endergonic
4) spontaneous
5) chemical
#3: endergonic

Energy has been acquired from the surroundings.

The energy for an endergonic reaction comes from a(n) ___ reaction.
1) ADP + P –> ATP
2) anabolic
3) synthesis
4) exergonic
5) glucose + glucose –> maltose
#4: exergonic

The energy released by an exergonic reaction can be used to drive an endergonic reaction.

What is the fate of the phosphate group that is removed when ATP is converted to ADP?
1) It is used to convert an ATP into an AQP.
2) It is acquired by a reactant in an endergonic reaction.
3) It is broken down into one phosphorus and four oxygen atoms.
4) It is acquired by a reactant in an spontaneous reaction.
5) It is acquired by a reactant in an exergonic reaction.
#2: It is acquired by a reactant in an endergonic reaction.

By acquiring the phosphate group the reactant acquires energy.

Select the INCORRECT association.
1) potential energy … positional energy
2) exergonic … uphill
3) kinetic energy … motion
4) exergonic … spontaneous
5) enzyme … protein
#2: exergonic … uphill

Exergonic reactions release energy.

What is energy coupling?
1) the use of an enzyme to reduce EA
2) relationships between the reactants and products in an exergonic reaction
3) the hydrolysis of ATP to ADP + P
4) The use of energy released from an exergonic reaction to drive an endergonic reaction
5) a barrier to the initiation of a reaction
#4: the use of energy released from an exergonic reaction to drive an endergonic reaction

This is energy coupling.

How do cells use ATP to raise the energy level of reaction substrates?
1) ATP is hydrolyzed to release its energy
2) the ADP part of ATP is bound to the substrate
3) the terminal phosphate of ATP is bound to the substrate
4) all of the above
#3: The terminal phosphate of ATP is bound to the substrate.

The bond between Pi and the substrate preserves much of the energy that was in ATP.

Why is ATP a good source of energy for biological reactions?
1) links between adenine and sugar are unstable
2) the answer is still unknown
3) peroxide links are highly reactive
4) links between sugar and phosphate are unstable
5) triphosphate chains are unstable
#5: Triphosphate chains are unstable.

The instability is associated with high energy, favoring reactions that break the triphosphate chain.

A reaction is said to be unfavorable if…
1) a: it will be very slow without a catalyst
2) b: the free energy change for the reaction is positive
3) c: equilibrium favors the reactants, not the products
4) both a and c
5) both b and c
#5: Both b and c.

If the free energy change for the reaction is positive, equilibrium favors the reactants and say the reaction is unfavorable.

The reaction A –> B is unfavorable by itself, but through energy-coupling, cells can use ATP to convert A into B. How is this done?
1) a: hydrolysis of ATP releases heat that is used by the unfavorable reaction
2) b: ATP acts as a catalyst to speed the unfavorable reaction
3) c: the unfavorable reaction is replaced by two favorable reactions
4) both a and b
5) both b and c
#3: C: The unfavorable reaction is replaced by two favorable reactions.

The first reaction transfers part of ATP to A, making a high-energy product. That product is then converted to B. Both reactions release energy, so both are favorable.

How do cells replace the energy-rich ATP that is destroyed in energy-coupled reactions?
1) a: chloroplast sue light energy to synthesize ATP
2) b: mitochondria synthesize ATP using energy that’s released by oxidizing sugars and fats
3) c: ribosomes use catalytic RNA to couple ADP with Pi
4) both a and b
5) both a, b and c
#4: both a and b

Plants have both chloroplasts and mitochondria. Animals lack chloroplasts; they get sugars and fats from other organisms to fuel their mitochondria.

Which statement is true of enzymes?
1) a: enzymes can be either proteins or RNA molecules
2) b: when a cell makes an enzyme, it makes many copies
3) c: their substrate specificity involves matching of shapes
4) both a and b
5) a, b, and c
#5: a, b, and c

There are many copies of each enzyme; they’re usually proteins but sometimes they are RNA; and they only attack substrates that fit the shape and charge of the active site.

What’s false?
1) Enzymes may change shape when they bind substrates;
2) Enzymes provide no energy for the reaction, except collision energy;
3) Enzymes may release substrates.
None of the statements are false.

Enzymes do all these things.

How can “induced fit” influence the specificity of an enzyme?
1) a: it cannot influence the specificity of an enzyme
2) b: it moves the reactive portion of the enzyme closer to the substrate
3) c: the enzyme’s active site changes shape to fit the correct substrate but not other molecules
4) both b and c
5) none of the above
#4: both b and c

The active site of the enzyme will change shape to make a better fit with only the appropriate substrate, which can bring the reactive portion of the enzyme closer to the substrate.

Enzymes speed reactions mainly by…
1) protecting the catalysts
2) providing activation energy
3) lowering EA
4) raising the kinetic energy of the reactants
5) none of the above
#3: lowering EA

Enzymes always lower EA, though they may have other effects as well. With a lower EA, more collisions can produce the transition state.

Which fact is most important in explaining how enzymes speed reactions?
1) High-energy collisions are less common than low-energy collisions.
2) Every reaction step adds to the time required for the overall reaction.
3) Large molecules collide more energetically than small molecules.
4) It takes less energy to break a hydrogen bond than a covalent bond.
5) Very low potential energy tends to make molecules unstable.
#1: High-energy collisions are less common than low-energy collisions.

Enzymes provide reaction pathways that have low activation energy requirements. This allows low-energy collisions to cause reactions.

In an experiment with an enzyme, the 58th amino acid seems to form a covalent bond with a substrate molecule as part of the catalytic process. What would you say?
1) At some point the bond between the amino acid and the substrate must break.
2) This is probably a case where the enzyme changes the position of equilibrium.
3) There must be an error. Enzymes don’t make covalent bonds with substrates.
4) This is possible in theory, but it’s never been observed.
5) It couldn’t happen. Catalysis doesn’t alter the enzyme.
#1: At some point the bond between the amino acid and the substrate must break.

To work repeatedly, the enzyme must return to its original state at the end of each catalytic cycle. Some steps may form bonds or break bonds between the enzyme and substrate.

Substrates bind to an enzyme’s ____ site.
1) allosteric
2) active
3) inhibitory
4) phosphate
#2: active
Most enzymes are ____.
1) lipids
2) minerals
3) proteins
4) carbohydrates
5) nucleic acids
#3: proteins

Most enzymes are proteins.

Enzymes work by ____.
1) decreasing the potential energy difference between reactant and product
2) adding energy to a reaction
3) adding a phosphate group to a reactant
4) increasing the potential energy difference between reactant and product
5) reducing activation energy
#5: reducing activation energy

Enzymes work by reducing energy of activation.

An enzyme ____.
1) increases the activation energy of a reaction
2) is an organic catalyst
3) is a source of energy for endergonic reactions
4) is an inorganic catalyst
5) can bind to nearly any molecule
#2: is an organic catalyst

Enzymes are proteins that behave as catalysts.

What name is given to the reactants in an enzymatically catalyzed reaction?
1) substate
2) active sites
3) reactors
4) products
#1: substrate

This is the name given to the reactants in an enzymatically catalyzed reaction.

As a result of its involvement in a reaction, an enzyme ____.
1) loses a phosphate group
2) loses energy
3) permanently alters its shape
4) is uncharged
5) is used up
#4: is unchanged

Enzymes are not changed as a result of their participation in a reaction.

Heating inactivates enzymes by
1) changing the enzyme’s three-dimensional shape
2) causing enzyme molecules to stick together
3) breaking the covalent bonds that hold the molecule together
4) removing phosphate groups from the enzyme
#1: changing the enzyme’s three-dimensional shape
When an enzyme catalyzes a reaction,
1) it lowers the activation energy of the reaction
2) it raises the activation energy of the reaction
3) it acts as a reactant
4) it is used once and discarded
#1: it lowers the activation energy of the reaction
Which of the following statements regarding enzymes is true?
1) an enzyme’s function is unaffected by changes in pH
2) enzymes inorganic
3) all enzymes depend on protein cofactors to function
4) enzymes catalyze specific reactions
#4: Enzymes catalyze specific reactions.
How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a non-competitive inhibitor?
1) Competitive inhibitors interfere with the enzyme; non-competitive inhibitors interfere with the reactants.
2) Competitive inhibitors bind to the enzyme reversibly; non-competitive inhibitors bind to it irreversibly.
3) Competitive inhibitors change the enzyme’s tertiary structure; non-competitive inhibitors cause polypeptide sub-units to dissociate.
4) Competitive inhibitors bind to the active site of the enzyme; non-competitive inhibitors bind to a different site.
#4: Competitive inhibitors bind to the active site of the enzyme; non-competitive inhibitors bind to a different site.
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