AP Bio Chapter 6 Practice Quiz

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Questions and Answers

Which of these options is correct regarding enzymes?

Enzymes speed up the rate of the reaction without changing the ΔG for the reaction. (correct)

All of the listed responses are correct.

Enzymes are consumed during the reaction.

Enzymes decrease the reaction rate.

What is the most reasonable explanation for the low velocity of an enzyme at 10°C?

There is too little activation energy available. (correct)

The substrate becomes a competitive inhibitor at lower temperature.

The enzyme was denatured.

The hydrogen bonds that define the structure of the enzyme's active site are unstable.

The cofactors required by the enzyme system lack the thermal energy required to activate the enzyme.

Which of the following statements about enzymes is incorrect?

An enzyme is consumed during the reaction it catalyzes. (correct)

An enzyme is very specific in terms of which substrate it binds to.

Enzymes can be used to accelerate both anabolic and catabolic reactions.

An enzyme lowers the activation energy of a chemical reaction.

Most enzymes are proteins.

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. Signup and view all the answers

What does the term 'induced fit' of an enzyme mean?

The enzyme changes its shape slightly as the substrate binds to it. Signup and view all the answers

Which statements correctly describe the roles of heat in biological reactions?

The first and second choices are correct. Signup and view all the answers

Above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. What would lead to a faster conversion of substrate into product under these conditions?

The first and second listed responses are correct. Signup and view all the answers

Which of the following environments or actions would not affect the rate of an enzyme reaction?

None of the listed responses is correct. Signup and view all the answers

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. Signup and view all the answers

Which of these statements about enzyme inhibitors is true?

The action of competitive inhibitors may be reversible or irreversible. Signup and view all the answers

What best explains the observation that succinylcholine decreases the rate of acetylcholine hydrolysis?

Succinylcholine must be a competitive inhibitor with acetylcholine. Signup and view all the answers

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 Signup and view all the answers

Which of the following statements about allosteric proteins is/are true?

All of the first three listed responses are correct. Signup and view all the answers

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. What best explains why this decrease occurs?

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site. Signup and view all the answers

Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling, which of the following statements is most likely to be true?

High levels of ADP act as an allosteric activator of catabolic pathways. Signup and view all the answers

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _ is to _.

Exergonic; endergonic Signup and view all the answers

Most cells cannot harness heat to perform work because:

Temperature is usually uniform throughout a cell. Signup and view all the answers

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 Signup and view all the answers

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to:

Add more of the enzyme. Signup and view all the answers

Some bacteria are metabolically active in hot springs because:

Their enzymes have high optimal temperatures. Signup and view all the answers

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?

Nothing; the reaction will stay at equilibrium. Signup and view all the answers

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. Signup and view all the answers

Which of the following situations does not represent an energy transformation?

The coupling of ATP hydrolysis to the production of a proton gradient across a membrane by a proton pump Signup and view all the answers

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?

Organisms acquire energy from, and lose energy to, their surroundings. Signup and view all the answers

Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics?

To obey the first law, the crops must represent an open system. Signup and view all the answers

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. Signup and view all the answers

Which is the most abundant form of energy in a cell?

Chemical energy Signup and view all the answers

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. Signup and view all the answers

According to the second law of thermodynamics, which of the following is true?

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists. Signup and view all the answers

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. Signup and view all the answers

Which of the following has the most free energy per molecule?

A starch molecule Signup and view all the answers

The electronic arrangement in which of the following molecules means that this (these) molecule(s) has/have greater free energy than the others?

Methane Signup and view all the answers

Which part of the equation ΔG = ΔH - TΔS tells you if a process is spontaneous?

ΔG Signup and view all the answers

If, during a process, the system becomes more ordered, then _____.

ΔS is negative Signup and view all the answers

When one molecule is broken down into six component molecules, which of the following will always be true?

ΔS is positive. Signup and view all the answers

From the equation ΔG = ΔH - TΔS it is clear that _____.

The first three choices are correct. Signup and view all the answers

An exergonic (spontaneous) reaction is a chemical reaction that _____.

Releases energy when proceeding in the forward direction Signup and view all the answers

Which of the following reactions would be endergonic?

Glucose + fructose → sucrose Signup and view all the answers

Molecules A and B contain 110 kcal/mol of free energy and molecules B and C contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded?

The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants. Signup and view all the answers

Which of the following determines the sign of ΔG for a reaction?

The free energy of the reactants and the free energy of the products Signup and view all the answers

Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium?

The first and second listed responses are correct. Signup and view all the answers

Which of the following is an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP, involved in the production of electrochemical gradients?

Proton movement against a gradient of protons Signup and view all the answers

In general, the hydrolysis of ATP drives cellular work by _____.

Releasing free energy that can be coupled to other reactions Signup and view all the answers

Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell against the ion's concentration gradient?

This is an example of energy coupling. Signup and view all the answers

Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because _____.

The negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP Signup and view all the answers

When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations?

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions. Signup and view all the answers

What best characterizes the role of ATP in cellular metabolism?

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate. Signup and view all the answers

The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?

The hydrolysis of ATP Signup and view all the answers

A chemical reaction is designated as exergonic rather than endergonic when _____.

The potential energy of the products is less than the potential energy of the reactants Signup and view all the answers

Which of the following is changed by the presence of an enzyme in a reaction?

The activation energy Signup and view all the answers

What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction?

Neither the sign nor the magnitude of ΔG have anything to do with the speed of a reaction. Signup and view all the answers

How do enzymes lower activation energy?

The first two responses above are correct. Signup and view all the answers

All enzymes increase the rate of a reaction by raising the activation energy for reactions.

False Signup and view all the answers

In biological systems, processes that involve a decrease in entropy are often accompanied by an increase in _____ in the surroundings.

entropy Signup and view all the answers

What characterizes the relationship between exergonic and endergonic reactions?

Exergonic reactions release energy while endergonic reactions consume energy. Signup and view all the answers

Study Notes

Catabolism vs. Anabolism

Catabolism involves breaking down molecules and releasing energy, while anabolism involves building complex molecules and requires energy input.
Exergonic reactions release energy, while endergonic reactions absorb energy.

Enzymatic Activity

Enzymes increase reaction rates without altering ΔG (Gibbs free energy) values.
Reaction rate can be increased by adding more enzyme when substrate saturation occurs.
Enzymes are specific and create an enzyme-substrate complex, facilitating chemical reactions.

Metabolic Processes

Cellular respiration (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is exergonic and does not require external energy input.
The first and second laws of thermodynamics dictate energy flow and metabolism in organisms.
Organisms are thermodynamically open systems, exchanging energy with their surroundings.

Thermodynamics in Biology

ATP hydrolysis releases free energy, which can drive endergonic reactions through energy coupling.
The increase in organization (decrease in entropy) in living systems requires constant energy input.
Endergonic reactions, like forming glucose-6-phosphate from glucose, often couple with ATP hydrolysis.

Energy Transformations

Enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) are critical in understanding reaction spontaneity and metabolic pathways.
Exergonic reactions have a lower potential energy in products compared to reactants.
Energy derived from glucose breakdown releases energy as heat.

Active Sites and Enzyme Function

The active site of enzymes allows specific substrate binding and typically resembles a groove on the enzyme's surface.
Temperature affects enzyme activity; low temperatures may limit the activation energy necessary for reactions to occur.

Misconceptions about Enzymes

Enzymes are not consumed during the reactions they catalyze and can be reused.
Enzymatic reactions can be saturated, meaning an increase in substrate won't increase the rate further.

Overall Metabolism

ATP's instability in phosphate bonds makes it effective as an energy intermediary.
Metabolic pathways are usually far from equilibrium, maintained by regular substrate removal and external energy input.### Induced Fit of Enzymes
Enzymes change shape slightly when substrate binds, optimizing the fit between them and enhancing catalytic activity.

Role of Heat in Biological Reactions

Heat is necessary for substrates to overcome activation energy barriers.
Increased heat raises kinetic energy of substrates, which speeds up enzyme-catalyzed reactions.

Enzyme Saturation and Reaction Rate

Above a certain substrate concentration, reaction rates may drop due to enzyme saturation.
Increasing enzyme concentration or slightly raising temperature can enhance substrate conversion under saturation.

Factors Affecting Enzyme Activity

pH, temperature, and substrate concentration all significantly influence enzyme activity.
No environmental factor listed can be considered unaffected in their impact on enzyme reactions.

pH and Enzyme Activity

High or low pH can disrupt hydrogen bonding and ionic interactions, altering the shape of the enzyme's active site, thus affecting its function.

Enzyme Inhibitors

Competitive inhibitors may bind reversibly or irreversibly to the active site, decreasing enzyme activity.
Noncompetitive inhibitors affect enzyme function but do not hinder substrate binding.

Succinylcholine as a Competitive Inhibitor

Succinylcholine competes with acetylcholine at the active site, reducing acetylcholine hydrolysis rates until more acetylcholine is present.

Allosteric Regulation

Allosteric regulation stabilizes the active form of enzymes via molecule binding, either enhancing or inhibiting activity.

Characteristics of Allosteric Proteins

Allosteric proteins can be inhibited and are impacted by environmental changes, existing in both active and inactive forms.

Impact of Allosteric Inhibitors

Allosteric inhibitors induce structural changes in enzymes, preventing substrate binding at the active site and reducing product formation.

Energy Regulation in Metabolic Pathways

The balance of ATP and ADP levels regulates energy supply and demand in catabolic and anabolic pathways.
High ADP levels activate catabolic pathways, promoting energy production.

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Description

Test your knowledge on key concepts from Chapter 6 of AP Biology. This quiz includes questions related to catabolism, anabolism, and energy transformation in cells. Engage with flashcards designed to reinforce your understanding of biochemical processes.