Biology Ch. 8
How does ATP drive transport work inside a cell?
By phosphorylating a transport protein
Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?
Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site.
Which of the following states the relevance of the first law of thermodynamics to biology?
Energy can be freely transformed among different forms as long as the total energy is conserved.
The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which of the following statements accurately defines energy coupling?
Exergonic reactions drive endergonic reactions.
Which of the following reactions would be endergonic?
Glucose + fructose → sucrose
Which of these statements about enzyme inhibitors is true?
The action of inhibitors may be reversible or irreversible.
How does the phosphorylation of glutamic acid (Glu) provide energy for the rest of the reaction to occur?
The addition of a phosphate to Glu forms a phosphorylated intermediate with more free energy than Glu. The ammonia can thus displace the phosphate in an exergonic reaction.
Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?
The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.
Which of the following statements about ATP (adenosine triphosphate) is correct?
The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways.
At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What statement best explains the difference in how pH affects the function of this enzyme?
The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.
Which of the following statements about feedback inhibition of a metabolic pathway is correct?
The final product of a metabolic pathway is usually the compound that regulates the pathway.
What best characterizes the role of ATP in cellular metabolism?
The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
At which pH did trypsin function the best?
Trypsin functioned best at pH 7
Which of the following statements is true regarding potential energy and kinetic energy?
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.
Which of these is exhibiting kinetic energy?
a space station orbiting Earth
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
cellular respiration
A change in an enzyme's structure that results in it not being able to perform its function is called
denaturation
A cell can only carry out an _______________ reaction by pairing it with an ______________ reaction, such as ATP hydrolysis.
endergonic; exergonic
A reaction that occurs spontaneously - without an input of energy - is ______________.
exergonic
The following reactionA --> B + C + heatis a(n) _____ reaction.
exergonic
The reaction ADP + P --> ATP is a(n) _____ reaction.
exergonic
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?
gamma γ-phosphate (the terminal phosphate)
In this reaction _____.
heat has been released to the environment
Which of these are by-products of cellular respiration?
heat, carbon dioxide, and water
Enzyme activity is affected by pH because __________.
high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
hydrolysis
Exergonic reactions result in products that have less free energy than the reactants, thus free energy is released and ΔG is _________________.
negative
Chemical energy is a form of _____ energy.
potential
In general, enzymes are what kinds of molecules?
proteins
Enzymes work by _____.
reducing activation energy (EA)
An exergonic (spontaneous) reaction is a chemical reaction that __________.
releases energy when proceeding in the forward direction
What is the ideal temperature for amylase function?
Amylase functioned best at 37 degrees C.
What is happening at the molecular level that explains why enzymes function differently at different temperatures? Select all that apply.
At a temperature that is too low, the enzymes and substrate molecules won't collide as often since they are moving more slowly. At a temperature that is too high, the enzymes will become denatured and lose the ability to react with their substrates. At the ideal temperature, the enzymes and substrate molecules will interact, generating product molecules as quickly as possible.
Which of the following is the strongest evidence that protein structure and function are correlated?
Denatured (unfolded) proteins do not function normally
If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
Energy input into the organism must be occurring to drive the decrease in entropy.
Now you will run the simulation to find out how the concentration of glucose changes over time when the lactase enzyme is added to a solution of lactose. Remember that glucose is one of the products of the breakdown of lactose by the lactase enzyme. The amount of glucose produced represents the dependent variable.Reset the simulation to its default settings.Run the simulation. Which graph best represents the results?
Glucose is produced when the lactase enzyme metabolizes lactose into glucose and galactose. The rate of the enzyme acting on lactose will slow down as less lactose is available for the enzyme to catalyze the chemical reaction. The slowing rate is observed as the line flattens.
Which of the following is changed by the presence of an enzyme in a reaction?
The activation energy
Which of the following is a chemical reaction?
The formation of a covalent bond between two amino acids.
Because an enzyme speeds up a chemical reaction, it is called a
catalyst
Enzymes are described as catalysts, which means that they __________.
increase the rate of a reaction without being consumed by the reaction
Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy?
potential energy with the covalent bonds of a sugar molecule
What is energy coupling?
the use of energy released from an exergonic reaction to drive an endergonic reaction
The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of __________.
a catabolic pathway
A(n) _____ reaction occurs spontaneously.
exergonic
What name is given to the reactants in an enzymatically catalyzed reaction?
substrae
The molecule that an enzyme reacts with is called the
substrate
Environmental conditions such as___ and ___ can affect enzyme function.
temperature and PH
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 is a competitive inhibitor
A chemical reaction occurs between the amino acids alanine (Ala) and glycine (Gly), forming the compound alanylglycine. The simple conversion reaction of alanine and glycine into this compound is endergonic, with a ΔG of 6.9 kcal/mol. Therefore, it requires ATP hydrolysis to drive the nonspontaneous reaction. Calculate the free energy change for the whole process, applying what you know about ATP hydrolysis.
ΔG = -0.4 kcal/mol
Which of the following statements about enzyme function is correct?
Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.
Which of the following statements about enzymes is true?
Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.
At which pH did pepsin function the best? In other words, at which pH were the most amino acids produced after 20 minutes?
Pepsin functioned best at pH 2.
Based on the observations that pepsin's optimal pH is 2 and trypsin's optimal pH is 7, what can you conclude about the environments in which these two enzymes function in the body?
Pepsin's environment in the stomach is very acidic, and trypsin's environment in the small intestine has a neutral pH
What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components?
Positive
Which of these is ATP?
3 Phosphate groups attached to a Ribose attached to Adenine
What is the optimal temperature for the fastest rate of reaction for the lactase enzyme?
37 degrees Celsius
What is the ideal temperature for Taq polymerase function?
7aq polymerase functioned best at 75 degrees C.
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 endergonic reaction.
Which of the following statements is correct regarding kinetic and potential energy?
Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure.
A reaction that occurs nonspontaneously - it requires an input of energy - is ______________.
endergonic
This graph illustrates a(n) _____ reaction.
endergonic
Which of these reactions requires a net input of energy from its surroundings?
endergonic
An enzyme _____.
is an organic catalyst
What is the optimal pH for the rate of reaction for the lactase enzyme in this simulation?
pH 7
Endergonic reactions result in products that have more free energy than the reactants, thus free energy is absorbed and ΔΔG is _________________.
positive
Which of the following statements about equilibrium of chemical reactions is correct?
A reaction that is at equilibrium is not capable of doing any work.
In cells, what is usually the immediate source of energy for an endergonic reaction?
ATP
As ATP begins to build up in a cell, metabolism slows down. How does this happen?
ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.
Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?
ATP can be regenerated by the addition of a phosphate group to ADP.
Select the highest energy form of adenosine from the following images.
Adenosine triphosphate (ATP) is the high-energy form of adenosine because it contains the most phosphate groups (three). This molecule fuels many different endergonic (energy-requiring) enzymatic processes in biological organisms. ATP molecules diffuse or are transported to the place where the energy is needed and deliver chemical energy from the breaking of their phosphate bonds.
Which of the following correctly states the relationship between anabolic and catabolic pathways?
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
At low temperatures, a particular enzyme catalyzes a reaction, but at a slow rate. At high temperatures, the enzyme is completely inactive. What statement best explains the difference in how temperature affects the function of this enzyme?
At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional.
Which of the following statements correctly describes cofactors and coenzymes?
Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.
How does ATP drive mechanical work inside a cell?
By binding to motor proteins
Which of the following is true regarding metabolic pathways?
Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.
Which of the following statements about the active site of an enzyme is correct?
The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.
What happened to the amount of product (disaccharides) produced as you increased the initial amount of starch and why?
The amount of product increased as the initial starch increased. The enzyme continued to break down the starch.
Which of the following statements is correct regarding ATP?
The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.
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 entropy of the products is greater than the entropy of the reactants.
An enzyme's substrate fits into the ___ on the enzyme.
active site
The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of __________.
allosteric regulation
"Conservation of energy" refers to the fact that _____.
energy cannot be created or destroyed but can be converted from one form to another
What is the correct label for "A"?
energy of activation The energy of activation must be overcome in order for a reaction to proceed.
Select the INCORRECT association.
exergonic ... uphill
ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called __________.
feedback inhibition
As a result of its involvement in a reaction, an enzyme _____.
is unchanged
When is the rate of reaction the fastest during this simulation run?
minutes 0-4
An exergonic reaction __________ free energy, and an endergonic reaction __________ free energy.
releases; absorbs
In general, the hydrolysis of ATP drives cellular work by __________.
releasing free energy that can be coupled to other reactions
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes?
the enzyme has an allosteric regulatory site
Chemical equilibrium is reached when
the forward and reverse reactions occur at the same rate so that the concentrations of reactants and products remain the same
In this reaction _____.
the products have less potential energy than the reactants
