Biology Chapter 8 Flashcards

Questions and Answers

What best characterizes the role of ATP in cellular metabolism?

The charge on the phosphate group of ATP tends to make the molecule very water-soluble.

The release of free energy during the hydrolysis of ATP heats the surrounding environment.

The ΔG associated with its hydrolysis is positive.

It is catabolized to carbon dioxide and water.

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate. (correct)

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

the conversion of glucose + fructose to make sucrose

the active transport of a phosphate ion into the cell

the formation of ATP from ADP + Pi

the contraction of a muscle cell

the hydrolysis of ATP (correct)

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

it absorbs more energy

the products are less complex than the reactants

activation energy exceeds net energy release

activation energy is required

the potential energy of the products is less than the potential energy of the reactants (correct)

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?

by locally concentrating the reactants Signup and view all the answers

Enzymes speed up the rate of the reaction without changing the (change in) G for the reaction.

True Signup and view all the answers

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. Signup and view all the answers

A plot of reaction rate against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that _____.

there is too little activation energy available Signup and view all the answers

An enzyme is consumed during the reaction it catalyzes.

False Signup and view all the answers

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 is meant by the 'induced fit' of an enzyme?

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

Which of the following statements correctly describe(s) the role(s) of heat in biological reactions?

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

Which of the following would lead to a faster conversion of substrate into product under saturated 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

Which of the following correctly explains why the addition of 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. Why does this decrease occur?

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. 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 would occur?

Nothing; the reaction would 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 represent(s) a transformation of one type of energy to another?

All of the above 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 and lose energy from their surroundings. 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 of the following is an example of the second law of thermodynamics as it applies to biological reactions?

The first, second, and third choices are correct. 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 an increase in entropy in the environment that life occurs in. 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 one of the following has the most free energy per molecule?

A starch molecule 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 one 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

What must be true if the reaction AB + CD → AC + BD occurs spontaneously?

The difference between ΔH and TΔS must be negative. Signup and view all the answers

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

A decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change 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

Which of the following processes tend to keep metabolic pathways away from equilibrium?

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

Which of the following is an example of the cellular work 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 cells, ATP is hydrolyzed to ADP and Pi, but in the test tube it is hydrolyzed to carbon dioxide and water. Signup and view all the answers

Study Notes

Exergonic and Endergonic Reactions

Catabolism is an exergonic process, releasing energy; anabolism is endergonic, requiring energy.
Example: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O represents a reaction that occurs without additional energy input.

Enzymatic Activity

When an enzyme is saturated with substrate, adding more enzyme speeds up reaction rates.
Optimal temperatures for some bacteria allow their enzymes to function effectively in extreme heat, such as hot springs.

Thermodynamics in Organisms

Organisms are thermodynamically open systems, exchanging energy with their surroundings.
The second law of thermodynamics states that the entropy decrease in living organisms is balanced by increased entropy in their environment.

ATP and Energy

ATP hydrolysis releases energy that is coupled to drive endergonic reactions.
The free energy from ATP hydrolysis can be used for cellular work, such as transporting protons against their gradient.
Stability of ATP's phosphate bonds is due to repulsive forces between negatively charged groups.

Free Energy Changes (ΔG)

ΔG indicates whether reactions are spontaneous. A negative ΔG means a spontaneous reaction.
Reactions that lead to increased molecular organization (decrease in entropy) are typically endergonic.

Energy Coupling and Metabolic Pathways

Continuous removal of metabolic products and external energy input keeps pathways away from equilibrium.
The hydrolysis of ATP is crucial in coupling exergonic reactions to more energy-demanding processes.

Chemical Reaction Designations

Exergonic reactions release energy; they occur spontaneously when the potential energy of products is less than that of the reactants.
Enzymes lower the activation energy needed for reactions but do not change ΔG.

Additional Facts

The transformation of energy types (e.g., chemical to mechanical) occurs in various processes, such as photosynthesis and combustion.
An example of endergonic reaction is the synthesis of sucrose from glucose and fructose.

Summary of Thermodynamic Principles

Energy input is necessary to maintain low entropy in living systems.
The first law of thermodynamics states that energy can transform forms but total energy remains constant.
Understanding energy dynamics is critical for analyzing cellular metabolic functions and reactions.### Gibbs Free Energy (ΔG)
ΔG indicates the spontaneity of a reaction; its sign determines if a reaction is spontaneous.
The magnitude of ΔG does not correlate with the reaction speed.
Enzymes do not change the ΔG but can influence the rate of reactions by lowering activation energy.

Enzyme Function

Enzymes lower activation energy by locally concentrating reactants.
They produce an enzyme-substrate complex but are not consumed during the catalytic process.
Enzymes are crucial in both anabolic and catabolic reactions and exhibit specificity towards substrates.

Activation Energy

Lower temperatures (e.g., 10°C) result in less enzymatic activity due to insufficient activation energy.
The shape of enzyme active sites is flexible, allowing slight changes when substrates bind (induced fit).

Temperature and Enzyme Activity

Enzyme activity generally increases with temperature until a peak is reached, after which it may diminish.
Certain conditions (e.g., excessive heat or cold) can denature enzymes, affecting their function.

pH Impact

Enzyme activity is sensitive to pH; extreme pH conditions can disrupt hydrogen bonds, altering the active site's shape.
Enzymes have optimal pH ranges for activity, outside of which activity declines.

Inhibition Mechanisms

Competitive inhibitors resemble substrates and bind to the active site, competing for binding; their effects can be reversed by increasing substrate concentration.
Noncompetitive inhibitors bind to alternative sites, influencing enzyme activity without competing with the substrate.
Allosteric regulation involves inhibitors or activators affecting enzyme shape and function through binding at sites distinct from the active site.

Allosteric Regulation

Allosteric proteins exist in active/inactive forms and respond to environmental changes and inhibitor action.
High levels of ADP can stimulate catabolic pathways, driving energy production aligned with anabolic demands.

Summary of Key Points

Enzymes are essential biological catalysts that accelerate reactions without being consumed.
Their activity depends on environmental conditions such as temperature and pH, which can alter enzyme structure and functionality.
The mechanisms of inhibition (competitive and noncompetitive) play significant roles in regulating metabolic pathways.

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Test your understanding of crucial concepts in Biology Chapter 8 with these flashcards. Focus on key terms like exergonic and endergonic as you explore the relationship between catabolism and anabolism. Perfect for reinforcing your knowledge in cellular processes.