Chapter 8: An Introduction to Metabolism Flashcards
1
Q
The totality of an organism’s chemical reactions is called
A
Metabolism
2
Q
Begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product.
A
Metabolic Pathway
3
Q
Each step of the pathway is catalyzed by a specific enzyme
A
FREEBEE
4
Q
Metabolic pathways that release energy by breaking down complex molecules to simpler compounds
A
Catabolic Pathways
5
Q
Metabolic pathways that consume energy to build complicated molecules from simpler ones
A
Anabolic Pathways
6
Q
Another name for an Anabolic Pathway is…?
A
Biosynthetic Pathway
7
Q
What kind of metabolic pathway is cellular respiration? Why?
A
Catabolic because you are breaking down glucose and other organic fuels in the presence of O2 to form Co2 and H20.
8
Q
What kind of metabolic pathway is the synthesis of proteins? Why?
A
Anabolic, because you are building a more complicated molecule (protein) amino acids.
9
Q
The study of how energy flows through living organisms is termed..?
A
Bioenergetics
10
Q
Energy
A
The capacity to cause change
11
Q
Energy associated with the relative motion of objects
A
Kinetic Energy
12
Q
Kinetic energy associated with the random movement of atoms or molecules
A
Thermal energy
13
Q
Thermal energy in transfer from one object to another is called
A
Heat
14
Q
Light is also a type of energy that can be harnessed to perform work, such as powering photosynthesis in green plants
A
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15
Q
Energy that is not kinetic that matter possesses because of its location or structure
A
Potential energy
16
Q
Potential energy available for release in a chemical reaction
A
Chemical energy
17
Q
Biochemical pathways, carried out in the context of cellular structures, enables cells to release chemical energy from food molecules and use the energy to power life processes.
A
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18
Q
Way to remember potential and kinetic energy that Mrs. P taught:
A
Imagine a snowboarder at the top of a slope:
- The snowboarder has more potential energy at the top of the mountain than going down the slope.
- Snowboarding converts potential energy into kinetic energy.
- The snowboarder has less potential energy on the slope than at the top of the mountain.
- The ski lift up converts kinetic energy back into potential energy to once again be used while going down the slope.
19
Q
The study of the energy transformations that occur in a collection of matter is called
A
Thermodynamics
20
Q
Denotes the matter under study
A
“system”
21
Q
Everything outside the system, rest of the universe
A
“surroundings”
22
Q
A system that is unable to exchange either energy or matter with its surroundings is..?
A
“isolated system”
23
Q
A system where energy and matter can be transferred between the system and its surroundings.
A
“open system”
24
Q
Which time of system do organisms use? Why?
A
An open system, because they absorb energy and release heat and metabolic waste products (CO2) to the surroundings.
25
Give an example of an isolated system and why.
Liquid in a thermos bottle. Because it is unable to exchange either energy or matter with its surroundings outside the thermos.
26
There are 4 laws of thermodynamics total. How many of them govern energy transformations in organisms and all collections of matter? Which ones?
2, The first and second laws.
27
"energy can be transferred and transformed, but it cannot be created or destroyed" is which law of thermodynamics?
The first law.
28
The first law is also known as..?
The principle of conservation of energy.
29
T/F The energy of the universe varies
False, it is constant.
30
If energy cannot be destroyed, why can't organisms simply recycle their energy over and over again?
During every energy transfer or transformation, some energy becomes unavailable to do work.
31
Measure of disorder or randomness in the universe..
Entropy
32
The more randomly arranged a collection of matter is, the ______ the entropy.
Greater
33
"every energy transfer or transformation increases the entropy of the universe" is which law of thermodynamics?
The second law.
34
A process that, by itself, leads to an increase in entropy and can proceed without requiring an input of energy is called..?
A spontaneous process.
35
Think of "energetically favorable" instead of spontaneous when talking about "spontaneous processes" because they do not happen quickly. Some can but not all of them do.
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36
Some examples of spontaneous processes are...
- an explosion
- rusting of an old car over time (furthering the point that spontaneous processes are not always immediate)
37
A process that, considered on its own, leads to a decrease in entropy is said to be...?
A nonspontaneous process.
38
Nonspontaneous processes will only occur if...
Energy is supplied.
39
Certain events occur spontaneously while others do not. For example, the flow of water downhill occurs spontaneously while the flow of water uphill only occurs with the input of energy.
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40
When energy is lost as heat, does it increase or decrease the entropy of its surroundings?
Increase.
41
Is the evolution of biological order consistent with the laws of thermodynamics?
Yes.
42
How does the second law of thermodynamics help explain the diffusion of a substance across a membrane?
The second law is the trend toward randomization, or increasing entropy.
When the concentrations of a substance on both sides of a membrane are equal, the distribution is more random than when they are unequal.
Diffusion of a substance to a region where it is initially less concentrated increases entropy, making it a spontaneous (energy favorable) process as described by the second law.
\*If confused, refer to Figure 7.10 on page 131.
43
Describe the forms of energy found in an apple as it grows on a tree, then falls, then is digested by someone who eats it.
The apple has potential energy in its position hanging on the tree, and the sugars and other nutrients it contains have chemical energy.
The apple has kinetic energy as it falls from the tree to the ground.
When the apple is digested and its molecules are broken down, some of the chemical energy is used to do work, and the rest is lost as thermal energy.
44
If you were to place a teaspoon of sugar in the bottom of a glass of water, it would dissolve completely over time. Left longer, eventually the water would disappear and the sugar crystals would reappear. Explain these observations in terms of entropy.
The sugar crystals become less ordered (entropy increases) as they dissolve and become randomly spread out in the water. Over time, the water evaporates, and the crystals form again because the water volume is insufficient to keep them in solution. While the reappearance of sugar crystals may represent a "spontaneous" increase in order (decrease in entropy) it is balanced by the decrease in order (increase in entropy) of the water molecules, which changed from a relatively compact arrangement as liquid water to a much more dispersed and disordered form of water vapor.
45
The surroundings + the system =
The universe.
46
In relation to energy, the G represents..?
The Gibbs free energy of a system. Simply, free energy.
47
The portion of a system's energy that can perform work when temperature and pressure are uniform through the system, as in a living cell.
Free energy
48
What is the chemical equation for free energy?
ΔG= ΔH-TΔS
49
In the equation for free energy, what does ΔH symbolize?
The change in the system's enthalpy. (in biological systems, equivalent to total energy)
50
In the equation for free energy, what does ΔS symbolize?
The change in the system's entropy.
51
In the equation for free energy, what does T stand for?
The absolute temperature in Kelvin (K) units.
(K=°C+273)
52
If the value for ΔG is negative, then ΔH must be\_\_\_\_\_\_\_\_ or TΔS must be ________ or\_\_\_\_.
Negative (the system gives up enthalpy and H decreases)
Positive (the system gives up order and H decreases)
Both.
53
If the value of ΔG for a process is negative, it is ALWAYS a ______ reaction.
Spontaneous
54
If the value of ΔG is positive or equal to zero, it is a _______ reaction.
Nonspontaneous
55
Another equation to think of ΔG as is:
ΔG=G (final state) - G (initial state)
This means that ΔG can ONLY be negative when the process involves a loss of free energy during the change from initial state to final state. Because it has less free energy, the system in its final state is less likely to change and is therefore more stable than it was previously.
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56
Free energy can also be used as a measure of a systems instability.
The higher the G the ___ stable.
The lower the G the ___ stable.
less
more
57
The state of maximum stability is termed
Equilibrium
58
As a reaction proceeds toward equilibrium, the free energy of the mixture of reactants and products \_\_\_\_\_\_\_.
Decreases.
59
As a reaction somehow gets pushed away from equilibrium, free energy \_\_\_\_\_\_\_.
Increases.
60
T/F Systems can move spontaneously away from equilibrium.
False.
61
Think of equilibrium as a free-energy valley. Any change from the equilibrium position will have a positive ΔG and will not be spontaneous.
A process is spontaneous and can perform work only when it is moving toward equilibrium.
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62
"energy outward"
exergonic
63
"energy inward"
Endergonic
64
A reaction that proceeds with a net release of free energy.
Exergonic reaction
65
A reaction that absorbs free energy from its surroundings.
Endergonic reaction
66
State whether or not the following reaction is:
spontaneous or nonspontaneous
and
If energy is released or required
**Exergonic Reactions**
Spontaneous
Energy released
67
State whether or not the following reaction is:
spontaneous or nonspontaneous
and
If energy is released or required
**Endergonic Reactions**
Nonspontaneous
Energy required
68
In endergonic reactions, ΔG is \_\_\_\_\_\_.
Positive.
69
T/F a cell that reaches metabolic equilibrium is dead.
True
70
T/F a living cell is in equilibrium
FALSE.
71
What prevents the cell from reaching equilibrium?
The constant flow of materials into and out of the cell.
72
Cellular respiration uses glucose and oxygen. which have high levels of free energy and water, which have low levels of free energy.
Is cellular respiration spontaneous or not?
Is it exergonic or endergonic?
What happens to the energy released from glucose?
Cellular respiration is a spontaneous and exergonic process. The energy released from glucose is used to do work in the cell or is lost as heat.
73
Some nighttime partygoers wear glow in the dark necklaces. The necklaces start glowing once they are "activated" by snapping the necklace in a way that allows two chemicals to react and emit light in the form of chemiluminescence.
Is the chemical reaction exergonic or endergonic?
Explain your answer.
The reaction would be exergonic because it releases energy. (in this case energy is released in the form of light)
74
What does ATP stand for?
Adenosine triphosphate
75
What are the 3 main kinds of work a cell does?
- Chemical work
- Transport work
- Mechanical work
76
The synthesis of polymers from monomers is an example of what type of work?
Chemical
77
The pumping of substances across membranes against the direction of spontaneous movement is an example of what type of work?
Transport work
78
The beating of cilia, contraction of muscle cells and the movement of chromosomes during cellular respiration is an example of what kind of work?
Mechanical work
79
What is energy coupling?
The use of an exergonic process to drive an endergonic one
80
What is the immediate source of energy that powers cellular work and is responsible for mediating energy coupling in cells?
ATP
81
Where in ATP are the bonds broken during hydrolysis?
Between the phosphate groups
82
What is hydrolysis?
Breaking apart of ATP by adding water
83
What is the formula for hydrolysis?
ATP+H2O = ADP+P
84
What does ADP stand for?
Adenosine diphosphate
85
The recipent molecule with the phosphate group covalently bonded to it is then called a _____ \_\_\_\_\_\_.
Phosphorylated intermediate
86
The key to coupling exergonic and endergonic reactions is the formation of the phosphorylated intermediate. This is because its is more reactive (unstable) than the original phosphorylated molecule.
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87
Glutamine synthesis from glutamic acid by itself is ________ (ΔG is positive) so it is not spontaneous.
Endergonic
\*\*\*Refer to figure 8.10a on page 150
88
What are the two steps of glutamine synthesis? (coupled by a phosphorylated intermediate)
1. ATP phosphorylates glutamic acid, making it less stable.
2. Ammonia displaces the phosphate group, forming glutamine.
\*\*\*Refer to figure 8.10b on page 150
89
Based on the following information, what is the free-energy change for the overall reaction?
ΔG for the glutamic acid conversion to glutamine is (+3.4 kcal/mol)
+
ΔG for ATP hydrolysis (-7.3 kcal/mol)
-3.9 kcal/mol
Because net ΔG is negative, this makes this process exergonic, so it occurs spontaneously.
90
Why does hydrolysis of ATP power transport and mechanical work in the cell?
Because ATP hydrolysis leads to a change in a protein's shape and often its abiliity to bind another molecule.
91
What are the two ways hydrolysis leads to a change in the shapes and binding affinities of proteins?
Directly and indirectly
92
How does hydrolysis **directly** lead to a change in the shape and binding affinity of a protein?
By phosphorylation
93
How does hydrolysis **indirectly** lead to a change in the shape and binding affinity of a protein?
Throught the noncovalent binding of ATP and its hydrolytic products.
94
ATP synthesis from ADP+P _____ energy.
Requires
95
ATP hydrolysis to ADP+P ______ energy.
Yields
96
Energy from catabolism is
exergonic or endergonic?
energy-consuming or energy-releasing?
- Exergonic
- Energy-releasing
97
Energy for cellular work is
exergonic or endergonic?
energy-consuming or energy-releasing?
- endergonic
- energy consuming
98
Energy release by breakdown reaction (catabolism) in the cell is used to ________ ADP, regenerating ATP.
Phosphorylate
99
\_\_\_\_\_ ______ \_\_\_\_ stored in ATP drives most cellular work.
Chemical Potential energy
100
energy-yielding
exergonic
101
energy-processing
endergonic
102
T/F plants use light energy to produce ATP
True
103
Why can a working muscle cell recycle its entire pool of ATP in less than a minute?
Because ATP can be regenerated by phosphorylation of ADP.
104
How does ATP typically transfer energy from exergonic to endergonic reactions in the cell?
ATP usually transfers energy to endergonic processes by phosphorylating (adding phosphate groups to) other molecules. (exergonic processes phosphorylate ADP to regenerate ATP)
105
Which of the following has more free energy:
acid + ammonia + ATP
OR
Glutamine + ADP + P
???
A set of couples reactions can transform the first combination into the second. Since this is an exergonic process overall, ΔG is negative and the first combination must have more free energy.
106
A macromolecule that acts as a catalyst is termed..?
Enzyme
107
What is a catalyst?
A chemical agent that speeds up a chemical reaction without being consumed by the reaction.
108
Why do we need enzymes?
Because some spontaneous reactions take a really long time to complete. If we didn't have enzymes, chemical traffic through the pathways of metabolism would become terribly congested because of the slow reactions.
109
The energy required to contort the reactant molecules so the bonds can break is known as the..?
Free energy of activation
110
Free energy of activation is otherwise known as..?
activation energy
111
We can think of activation energy as the energy required to push the reactants to the top of an energy barrier or uphill so that the downhill part of a reaction can begin.
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112
Unstable condition that results from the molecules absorbing enough energy for the bonds to break:
Transition state
113
After bonds have been broke, new bonds form, releasing energy to the surroundings. This forms the \_\_\_\_.
Products
114
Heat can increase the rate of reaction by allowing reactions to attain the ____ state more often.
Transition
115
Why does heat not work well in biological systems to speed up reactions?
1. Heat denatures proteins and kills cells
2. Heat would speed up ALL reactions, not just those that are needed.
116
Instead of heat, what do organisms to speed up reactions?
Enzyme
117
T/F an enzyme can make an endergonic reaction exergonic.
Haha, no.
118
How does an enzyme speed up a reaction?
By lowering its activation energy.
119
The reactant an enzyme acts on is reffered to as the enzyme's..?
Substrate
120
What is formed when the enzyme binds to its substrate?
an enzyme-substrate complex
121
A restricted region of the enzyme molecule that actually binds to the substrate:
Active site
122
Induced fit
The binding of a subtrate and enzyme becoming tighter after initial contact
123
What is the purpose of "induced fit"?
To bring chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction.
124
T/F most metabolic actions are reversible
True
125
The point in a reaction where all of the enzyme molecules have their active sites engaged is termed..?
Saturated
126
When an enzyme population is said to be saturated, the only way to increase the rate of product formation is to \_\_\_\_\_\_\_.
Add more enzyme
127
T/F cells can increase the rate of reaction by producing enzyme molecules.
True
128
What are optimal conditions?
Conditions where enzymes work better than other conditions
129
Up to a point, the rate of an enzymatic reaction increases with heat, but after a certain point it will drop sharply, why does this occur?
Because the thermal agitation of the enzyme molecule disrupts the hydrogen bonds, ionic bonds, and other weak interactions that stabilize the active shape of the enzyme, and the protein molecule eventually denatures.
130
Each enzyme has an ________ temperature at which its reaction rate is greatest.
optimal
131
Most human enzymes have an optimal temperature that lies from __ to __ degrees in C.
35, 40
132
Thermophilic bacteria that live in hot springs contain enzymes with optimal temperatures of __ degrees C or higher.
70
133
Just like enzymes have an optimal temperature, they also have an optimal pH.
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134
The optimal pH for most enzymes fall in the range of pH \_\_\_\_.
6-8
135
Although most enzymes in the body fall between 6-8, pepsin works best at a pH of\_\_\_.
2
136
Another enzyme in the body that breaks the rule is more alkaline, trypsin for example has an optimal pH of ___ and would be denatured in the stomach.
8
137
What are cofactors?
nonprotein helpers for catalytic activity
138
zinc, iron, and copper are all examples of..?
inorganic cofactors
139
Are cofactors inorganic or organic?
inorganic
140
If the cofactor is organic, it is more correctly referred to as a \_\_\_\_\_\_\_\_.
Coenzyme
141
Why are most vitamins important in nutrition?
Because they act as coenzymes or raw materials from which coenzymes are made.
142
Certain chemicals selectively inhibit the action of specific enzymes. These are called..?
Enzyme inhibitors
143
If an enzyme inhibitor attaches to the enzyme by covalent bonds, the inhibition is usually \_\_\_\_\_\_\_.
Irreversible
144
If an enzyme inhibitor is attached to an enzyme by weak interactions, it is usually \_\_\_\_\_\_\_.
Reversible
145
An inhibitor that mimics the substrate and competes for the active site.
Competitive inhibitor
146
An inhibitor that binds to the enzyme away from the active site, altering the shape of the enzyme so that even if the substrate can bind, the active site functions less effectively, if at all.
Noncompetitive inhibitor
147
Many antibiotics are inhibitors of specific enzymes in bacteria, for example, penicillin blocks the active site of an enzyme that many bacteria use to make their cell walls.
FREEBEE
148
T/F most enzymes are proteins
TRUE
149
a permanent change in a gene is known as a
mutation
150
Can enzymes evolve?
Yes, in some cases.
151
Many spontaneous reactions occur very slowly. Why don't all spontaneous reactions occur instantly?
A spontaneous reaction is a reaction that is exergonic. However, if it has a high activation energy that is rarely attained, the rate of reaction may be low.
152
Why do enzymes only act on specific substrates?
Only the specific substrate(s) will fit properly into the active site of an enzyme, the part of the enzyme that carries out catalysis.
153
Malonate is an inhibitor of the enzyme succinate dehydrogenase. How would you determine whether malonate is a competitive or noncompetitive inhibitor?
In the presence of malonate, increase the concentration of the normal substrate (succinate) and see whether the rate of reaction increases. If it does, malonate is a competitive inhibitor.
154
Term used to describe any case in which a protein's function at one site is affected by the binding of a regulatory molecule to a separate site.
Allosteric regulation
155
What 2 things can allosteric regulation result in?
1. Inhibition of an enzyme
2. Stimulation of enzyme
156
The binding of an ______ to a regulatory site stabilizes the shape that has functional active sites.
Activator
157
The binding of an _________ stabilizes the inactive form of an enzyme.
Inhibitor
158
The subunits of an allosteric enzyme fit together in such a way that a shape change in one subunit is transmitted to all others. Through this interaction of subunits, a single activator or inhibitor molecule that binds to one regulatory site will affect the active sites of all subunits.
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159
Would ATP function as an inhibitor or an activator? Why?
An inhibitor. Because it binds to several catabolic enzymes allosterically, lowering their affinity for substrate and thus inhibiting their activity.
160
Would ADP function as an inhibitor or an activator? Why?
An activator. Because catabolism functions in regenerating ATP.
161
If ATP production lags behind its use, ___ accumulates and activates the enzymes that speed up catabolism, producing more ATP.
ADP
162
If the supply of ATP exceeds demand, what will happen to catabolism?
It will slow down as ATP molecules accumulate and bind to the same enzymes, inhibiting them.
163
What is the term for when a substrate molecule binds to one active site in a multisubunit enzyme and triggers a shape in all the subunits, thereby increasing catalytic activity at other active sites?
Cooperativity
164
What is the result of cooperativity?
This mechanism amplifies the response of enzymes to substrates.
For example: One substrate molecule primes an enzyme to act on additional substrate molecules more readily.
165
T/F Cooperativity is considered "allosteric" regulation because binding of the substrate to one active sites affects catalysis in another active site.
True
166
Although hemoglobin is not an enzyme, (it carries O2), classic studies on hemoglobin have elucidated the principle of cooperativity. Why is this?
This is because hemoglobin is made up of four subunits, each with an oxygen-binding site.
The binding of an oxygen molecule to one binding site increases the affinity for oxygen of the remaining binding sites. Thus, where oxygen is at high levels, (lungs or gills), hemoglobins affinity for oxygen increases ans more binding sites are filled.
In oxgen deprived tissues, the release of each oxygen molecule decreases the oxygen affinity of the other binding sites, resulting in the release of oxygen where it is most needed.
This is how cooperativity works in multisubunit enzymes.
167
When ATP allosterically inhibits an enzyme in an ATP-generating pathway, the result is ______ \_\_\_\_\_\_\_\_, a common mode of metabolic control.
Feedback inhibition
168
What happens in feeback inhibition?
A metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway.
169
Why is feedback inhibition used in cells?
So that it prevents the cell from making more of the end product than is necessary and wasting chemical resources.
170
T/F the cell is a bag of chemicals with thousands of different kinds of enzymes and substrates in a random mix.
False, the cell is compartmentalized, and cellular structures help bring order to metabolic pathways.
171
Some enzymes and enzyme complexes have fixed locations within the cell and act as structural components of particular membranes. Others are in a solution within particular membrane-closed eukaryotic organelles, each with its own internal chemical environment.
For example: In eukaryotic cells, the enzymes for cellular respiration reside in specific locations within the mitochondria.
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172
How do an activator and an inhibitor have different effects on an allosterically regulated enzyme?
The activator binds in such a way that it stablizes the active form of an enzyme, whereas the inhibitor stabilizes the inactive form.
173
Regulations of isoleucine sythesis is an example of feedback inhibition of an anabolic pathway. With that in mind, explain how ATP might be involved in feedback inhibition of a catabolic pathway.
A catabolic pathway breaks down organic molecules, generating energy that is stored in ATP molecules. In feedback inhibition of such a pathway, ATP (one product) would act as an allosteric inhibitor of an enzyme catalyzing an early step in the catabolic process. When ATP is plentiful, the pathway would be turned off and no more would be made.
174
# Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ______ is to \_\_\_\_\_\_\_.
a. exergonic; spontaneous
b. exergonic; endergonic
c. free energy; entropy
d. work; energy
b.exergonic; endergonic
175
Most cells cannot harness heat to perform work because
a. heat does not involve a transfer of energy
b. cells do not have much thermal energy; they are relatively cool
c. temperature is usually uniform throughout a cell
d. heat can never be used to do work
c. temperature is usually uniform throughout a cell
176
Which of the following metabolic processes can occur without a net influx of energy from some other process?
a. ADP + P → ATP + H2O
b. C6H12O6 + 6 O2 → 6 O2 + 6 H2O
c. 6 CO2 + 6 H2O → C6H12O6 + 6 O2
d. Amino acids → Protein
b. C6H12O6 + 6 O2 → 6 O2 + 6 H2O
177
If an enzyme in a solution is saturated with substrate, the most effective way to obtain a faster yield fo products is to
a. add more of the enzyme
b. heat the solution to 90 degrees C
c. add more substrate
d. add a noncompetitive inhibitor
a. add more of the enzyme
178
Some bacteria are metabolically active in hot springs because
a. they are able to maintain a lower internal temperature
b. high temperatures make catalysis unnecessary
c. their enzymes have high optimal temperatures
d. their enzymes are completely insensitive to temperature
c. their enzymes have high optimal temperatures
179
If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?
a. additional substrate will be formed
b. the reaction will change from endergonic to exergonic
c. the free energy of the system will change
d. nothing; the reaction will stay at equilibrium
d. nothing; the reaction will stay at equilibrium
