Free Practice Quiz Question List

4 Energy and Thermodynamics in Biology Online Quiz Questions

Use this free practice quiz with 50 questions to review 4 Energy and Thermodynamics in Biology, test your knowledge, and prepare for your next test or exam.

50 questions

Choose one

1 point

A person climbs the same flight of stairs twice, once slowly and once quickly. Assuming the mechanical work is roughly the same on both climbs, which comparison is correct?

A
The faster climb requires more mechanical work and has the same average power.
B
The climbs involve roughly the same work, but the faster climb has greater average power.
C
The slower climb requires more mechanical work and has greater average power.
D
The climbs involve the same work and the same average power.

Choose all

1 point

Select all statements that support classifying an organism as an open system.

A
An organism takes in oxygen and releases carbon dioxide.
B
An organism is a closed system because it retains all matter while exchanging heat.
C
An organism takes in nutrients and water.
D
An organism releases waste and heat to its surroundings.

Choose one

1 point

A closed system absorbs $180\,\mathrm{J}$ of heat and does $65\,\mathrm{J}$ of work on its surroundings. Using the convention that heat added is positive and work done by the system is positive, what is the system's change in internal energy?

A
$\Delta U = -245\,\mathrm{J}$
B
$\Delta U = 65\,\mathrm{J}$
C
$\Delta U = 115\,\mathrm{J}$
D
$\Delta U = 245\,\mathrm{J}$

Choose one

1 point

A biochemical reaction has $\Delta G < 0$ under specified conditions. Which conclusion is justified by this information alone?

A
The reaction must occur quickly because its products have lower free energy.
B
The forward direction is thermodynamically favorable under the specified conditions, but the rate is not determined by this information alone.
C
The reaction cannot occur unless ATP is added.
D
The reaction must release heat, regardless of the values of enthalpy and entropy.

Choose one

1 point

A person holds a weight stationary at arm's length. Which statement best distinguishes the muscles' energy use from external mechanical work on the weight?

A
The muscles can use chemical energy to maintain posture even though little external mechanical work is done.
B
Maintaining posture must involve substantial external work because the muscles consume energy.
C
No energy is used by muscles unless an external object is visibly displaced.
D
Heat released by the muscles counts as external mechanical work.

Choose one

1 point

For a reaction at constant temperature and pressure, $\Delta H = -40\,\mathrm{kJ/mol}$ and $T\Delta S = +15\,\mathrm{kJ/mol}$ . Using $\Delta G = \Delta H - T\Delta S$ , what is $\Delta G$ ?

A
$+55\,\mathrm{kJ/mol}$
B
$-25\,\mathrm{kJ/mol}$
C
$+25\,\mathrm{kJ/mol}$
D
$-55\,\mathrm{kJ/mol}$

Choose all

1 point

Select all statements that correctly describe heat transfer in the listed biological or clinical situations.

A
A warming blanket in contact with a patient transfers heat by conduction.
B
Sweat evaporating from skin transfers energy away from the body.
C
A patient can transfer heat to cooler surroundings by radiation.
D
Convection requires direct contact between the patient and a solid object.
E
Heat is a substance stored inside a patient whenever body temperature rises.

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1 point

Select all statements that accurately describe ATP's role in cellular energy transfer.

A
ATP hydrolysis can release free energy that cells use to drive coupled tasks.
B
ATP supplies energy independently of food or other energy inputs.
C
Cells can couple a reaction that releases free energy to one that requires energy.
D
ATP transfers usable free energy between metabolic reactions and cellular tasks.
E
ATP allows cells to create energy without changing other forms of energy.

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1 point

A person increases their rate of exercise. Select all statements consistent with the body's energy use and temperature regulation.

A
Increased muscle activity can raise the body's chemical-energy use.
B
All chemical energy used during exercise becomes external mechanical work.
C
Heat production can rise as muscles increase their activity.
D
Core temperature regulation involves balancing heat production with heat loss.
E
If mechanical work increases, heat production must fall by the same amount.

Choose all

1 point

Select all statements that correctly describe what indirect calorimetry measures and estimates.

A
It measures oxygen consumption.
B
It measures carbon dioxide production.
C
It directly measures all heat leaving the body and therefore requires no estimate.
D
It uses gas-exchange measurements to estimate metabolic energy use.
E
It measures external mechanical work and treats that as total metabolic energy use.

Open ended

1 point

A motorized assist applies a constant force of $60\,\mathrm{N}$ along a load's direction of motion for a displacement of $2.5\,\mathrm{m}$ . The displacement takes $5.0\,\mathrm{s}$ . Calculate the mechanical work transferred to the load and the average power during the displacement. Show the formulas and include units.

Open ended

1 point

An organism maintains organized internal structures while exchanging matter and energy with its surroundings. Explain why this does not contradict the second law of thermodynamics, and identify the isolated system boundary relevant to applying the law.

Open ended

1 point

Before anesthesia induction, a patient's measured temperature is $35.8\,^{\circ}\mathrm{C}$ , and there is no urgent clinical circumstance. State the temperature threshold relevant to the guidance, explain what the reading implies for that recommendation, and describe how monitoring or warming measures relate to heat loss.

Open ended

1 point

A clinician wants to estimate a patient's metabolic energy expenditure without measuring the patient's external mechanical work. Explain what indirect calorimetry measures and how those measurements are used to obtain the estimate.

Choose one

1 point

After a person exercises, sweat evaporates from their skin and cools them. Which explanation correctly distinguishes heat from temperature in this example?

A
The skin’s temperature is the heat stored in the sweat.
B
Evaporation transfers energy away from the skin as sweat changes from liquid to vapor; temperature describes thermal state.
C
Sweat evaporation creates energy that cools the body.
D
Heat is a measure of how warm the skin is, while temperature is energy moving into the air.

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1 point

Which examples demonstrate matter or energy crossing a person's system boundary and thus show that a person is an open system? Select all correct choices.

A
A person takes in oxygen from the surroundings.
B
A person releases heat to the surroundings.
C
A person releases carbon dioxide to the surroundings.
D
A person is a closed system because their body maintains internal conditions.

Choose one

1 point

Two people each lift a weight with a constant upward force of $120\,\mathrm{N}$ through $2\,\mathrm{m}$ . The first takes $4\,\mathrm{s}$ , and the second takes $6\,\mathrm{s}$ . Which comparison of their work and average power is correct?

A
The first person does more work and has greater average power.
B
Both do $240\,\mathrm{J}$ of work; the first person’s average power is $60\,\mathrm{W}$ , compared with $40\,\mathrm{W}$ for the second.
C
Both do $240\,\mathrm{J}$ of work and have the same average power.
D
The second person does more work because the lift takes longer.

Choose one

1 point

A closed system receives $500\,\mathrm{J}$ of heat and does $180\,\mathrm{J}$ of work on its surroundings. Using the convention $\Delta U=Q-W$ , what is the change in its internal energy?

A
$-680\,\mathrm{J}$
B
$-320\,\mathrm{J}$
C
$320\,\mathrm{J}$
D
$680\,\mathrm{J}$

Choose one

1 point

At constant temperature and pressure, a biochemical reaction has $\Delta H=-12\,\mathrm{kJ/mol}$ and $T\Delta S=+5\,\mathrm{kJ/mol}$ . Which conclusion follows from $\Delta G=\Delta H-T\Delta S$ ?

A
$-7\,\mathrm{kJ/mol}$ , so the reaction must occur rapidly.
B
$-17\,\mathrm{kJ/mol}$ , so the reaction must occur rapidly.
C
$17\,\mathrm{kJ/mol}$ , so the reaction is thermodynamically favorable.
D
$-17\,\mathrm{kJ/mol}$ , indicating a favorable direction but not determining how quickly the reaction occurs.

Choose one

1 point

A clinician wants to estimate a patient’s metabolic energy use without measuring only visible mechanical work. Which description best characterizes indirect calorimetry?

A
It measures oxygen consumption and carbon dioxide production to estimate metabolic energy use.
B
It directly measures all heat released by the body and requires no gas measurements.
C
It measures only body temperature to determine the energy in food.
D
It measures external muscle work and treats that value as total metabolic energy use.

Choose all

1 point

Which statements correctly identify routes of heat transfer in patient care? Select all correct choices.

A
A warming blanket in contact with a patient can transfer heat by conduction.
B
Moving air can carry heat away from skin by convection.
C
Sweat cooling the skin is an example of heat transfer by radiation.
D
A patient can exchange heat by radiation without direct contact with another object.

Choose all

1 point

A cell couples ATP hydrolysis to a process that requires energy. Which statements correctly describe the role of ATP and the energy accounting? Select all correct choices.

A
ATP hydrolysis can be coupled to a reaction that requires energy.
B
ATP is an energy source independent of food and other inputs.
C
ATP can transfer usable free energy from energy-releasing reactions to cellular tasks.
D
ATP use does not violate energy conservation; metabolism transforms energy rather than creating it.

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1 point

A researcher is setting up an energy balance for an organism over a day. Which statements should guide the accounting? Select all correct choices.

A
An organism’s overall accounting must include energy entering and leaving with matter.
B
Chemical energy from nutrients can be transformed into cellular work, stored chemical energy, and heat.
C
Because an organism maintains internal conditions, its total energy balance can omit energy carried by incoming and outgoing matter.
D
Energy used by metabolism is transformed rather than created.

Choose all

1 point

A person climbs the same flight of stairs first slowly and then quickly during separate trials. Which statements best interpret the energy changes? Select all correct choices.

A
If the same stairs are climbed in less time, average power is greater even if the work is roughly the same.
B
Greater power means that more total work must have been done, regardless of the time taken.
C
Increased chemical-energy use during exercise can support muscle work and increase heat production.
D
Not all chemical energy used by muscles becomes external mechanical work.

Open ended

1 point

A closed system receives $500\,\mathrm{J}$ of heat. During the same process, it pushes an object $3\,\mathrm{m}$ in the direction of a constant $100\,\mathrm{N}$ force exerted by the system. Using $\Delta U=Q-W$ , calculate the system’s net work and change in internal energy. Show how the sign convention affects your result.

Open ended

1 point

A student argues that the growth of an organized tissue contradicts the second law because organization has increased. Explain why this conclusion is not justified. In your answer, relate the organism’s exchange with its surroundings to the entropy of the larger system.

Open ended

1 point

Before anesthesia, a patient’s temperature is $35.7^\circ\mathrm{C}$ . A team is also using indirect calorimetry to estimate the patient’s metabolic energy use. Explain what the calorimetry measurements can establish, how the temperature compares with the stated pre-induction recommendation, and why temperature monitoring or warming is relevant.

Choose one

1 point

A person holds a weight motionless at arm’s length. Which statement best distinguishes the external mechanical work on the weight from the energy used by the person’s muscles?

A
The muscles do external mechanical work because they exert a force, even though the weight does not move.
B
The muscles use energy to maintain posture, but do no external mechanical work on the stationary weight.
C
The muscles do no work of any kind because the weight does not move.
D
The muscles transfer heat to the weight, which counts as mechanical work.

Choose one

1 point

A person performs $600\,\mathrm{J}$ of work climbing a flight of stairs in $10\,\mathrm{s}$ , then performs the same work climbing the same stairs in $15\,\mathrm{s}$ . Which conclusion follows?

A
The first climb uses more total work because its average power is greater.
B
Both climbs have the same average power because they involve the same stairs.
C
The first climb has greater average power, while the total work is the same.
D
The second climb has greater average power because it takes longer.

Choose one

1 point

A warming blanket is warmer than a patient and transfers energy to the patient. Which statement correctly describes this process?

A
The blanket transfers heat to the patient because of a temperature difference; the patient’s temperature describes thermal state.
B
The blanket transfers temperature to the patient, while heat is the patient’s stored thermal state.
C
The blanket transfers heat only if it changes the patient’s temperature by a measurable amount.
D
The blanket and patient exchange energy, but the transfer cannot be called heat unless matter also moves.

Choose one

1 point

A researcher defines the entire organism as the thermodynamic system and tracks food, oxygen, wastes, carbon dioxide, and heat crossing its boundary. How should the organism be classified?

A
A closed system, because food energy is converted internally once the organism consumes it.
B
An isolated system, because the body maintains internal conditions despite environmental changes.
C
A closed system, because only heat, not matter, crosses the organism’s boundary.
D
An open system, because both matter and energy cross the organism’s boundary.

Choose one

1 point

A closed system absorbs $420\,\mathrm{J}$ of heat and does $160\,\mathrm{J}$ of work on its surroundings. Using $\Delta U=Q-W$ , with heat added and work done by the system positive, what is its change in internal energy?

A
$-260\,\mathrm{J}$
B
$260\,\mathrm{J}$
C
$580\,\mathrm{J}$
D
$-580\,\mathrm{J}$

Choose one

1 point

A complete energy balance is being constructed for an organism over a period in which it consumes nutrients, performs cellular work, stores some chemical energy, and releases heat and waste. Which accounting approach is consistent with the first law?

A
Include chemical energy entering with nutrients and energy leaving with matter, alongside transformations into work, stored chemical energy, and heat.
B
Count only heat and mechanical work, because chemical energy in nutrients is already part of the organism once food is eaten.
C
Count nutrients as matter but exclude their chemical energy, since energy conservation applies only to closed systems.
D
Treat metabolic energy as newly created inside the body, then subtract the heat released to find the balance.

Choose one

1 point

An organism becomes more internally organized while taking in usable energy and releasing heat and waste to its surroundings. Which interpretation is consistent with the second law?

A
The observation violates the second law, because entropy cannot decrease anywhere.
B
The observation is possible only if the organism is an isolated system.
C
The observation is compatible with the second law if the entropy increase in the surroundings offsets the local decrease.
D
The observation proves that the organism creates energy to maintain its internal organization.

Choose one

1 point

At constant temperature and pressure, a biochemical reaction has $\Delta H=-30\,\mathrm{kJ/mol}$ , $T=300\,\mathrm{K}$ , and $\Delta S=-0.05\,\mathrm{kJ/(mol\cdot K)}$ . Using $\Delta G=\Delta H-T\Delta S$ , which conclusion is justified?

A
The reaction has $\Delta G=-15\,\mathrm{kJ/mol}$ , so its stated direction is thermodynamically favorable, but its rate is not determined by this result.
B
The reaction has $\Delta G=-45\,\mathrm{kJ/mol}$ , so it must proceed rapidly.
C
The reaction has $\Delta G=+15\,\mathrm{kJ/mol}$ , so its stated direction is thermodynamically favorable.
D
The reaction has $\Delta G=-15\,\mathrm{kJ/mol}$ , which proves that it proceeds rapidly under these conditions.

Choose one

1 point

A cell couples an energy-requiring reaction to ATP hydrolysis. Which interpretation best describes ATP’s role in this process?

A
ATP makes the coupled reaction favorable by creating energy inside the cell, independently of nutrient inputs.
B
ATP hydrolysis can drive the reaction only by transferring heat to it.
C
ATP stores energy without involving free-energy changes, so it cannot couple reactions.
D
ATP hydrolysis can release free energy that is coupled to the energy-requiring reaction; ATP is not an independent energy source.

Choose one

1 point

During exercise, a person’s muscles perform more external mechanical work, and the body’s heat production also rises. Which explanation best accounts for both observations?

A
The rise in mechanical work means all additional chemical energy is converted into external work, leaving heat production unchanged.
B
Chemical-energy use and heat production can both rise as muscles perform more mechanical work; not all chemical energy becomes external work.
C
Heat production rises only if the body stops doing mechanical work, because work and heat cannot both result from metabolism.
D
The body must store all chemical energy not converted into mechanical work, so exercise cannot increase heat loss.

Choose one

1 point

A clinician wants to estimate a patient’s metabolic energy expenditure using indirect calorimetry. Which measurement-and-inference approach matches this method?

A
It directly measures heat loss and converts that measurement into a direct measurement of mechanical work.
B
It measures nutrient intake and waste mass, then calculates energy use without gas measurements.
C
It measures oxygen consumption and carbon dioxide production and uses these measurements to estimate metabolic energy use.
D
It measures core temperature and uses the temperature change alone to determine the energy used by metabolism.

Choose one

1 point

Before anesthesia induction, a patient’s temperature is measured at $35.8\,^{\circ}\mathrm{C}$ . Which action best reflects the stated temperature guidance while preserving its qualification?

A
Induction should always be delayed until temperature is at least $36.0\,^{\circ}\mathrm{C}$ , with no exception.
B
Check that temperature is at least $36.0\,^{\circ}\mathrm{C}$ before induction unless urgent clinical circumstances require otherwise.
C
A temperature below $36.0\,^{\circ}\mathrm{C}$ is acceptable before induction if warming measures are planned afterward.
D
Temperature should be checked only after induction, because pre-induction temperature does not inform heat-loss prevention.

Choose one

1 point

A constant force of $75\,\mathrm{N}$ acts along the direction of motion and moves an object $4\,\mathrm{m}$ . How much mechanical work is transferred?

A
19 J
B
300 J
C
75 J
D
1,200 J

Choose one

1 point

A person climbs the same staircase once quickly and once slowly. Assuming the person’s overall change in position is the same, which comparison is best supported?

A
The faster climb requires more work because it takes less time.
B
The slower climb has greater power because it lasts longer.
C
The faster climb has greater average power, while the work is roughly the same.
D
Both climbs have greater power than work because power is energy.

Choose one

1 point

Which statement correctly distinguishes heat from temperature in thermodynamics?

A
Temperature describes thermal state; heat is energy transferred because of a temperature difference.
B
Temperature is energy in transit; heat is the energy stored in an object.
C
Heat and temperature are interchangeable names for the same quantity.
D
Heat is a system’s thermal state; temperature is energy transferred between systems.

Choose one

1 point

A biological organism takes in food, water, and oxygen and releases waste, carbon dioxide, and heat. How should the organism be classified as a thermodynamic system?

A
It exchanges energy but no matter.
B
It exchanges matter but no energy.
C
It exchanges neither matter nor energy.
D
It exchanges both matter and energy.

Choose one

1 point

A closed system absorbs $520\,\mathrm{J}$ of heat and does $190\,\mathrm{J}$ of work on its surroundings. Using $\Delta U=Q-W$ , with heat added and work done by the system positive, what is its change in internal energy?

A
$-330\,\mathrm{J}$
B
$330\,\mathrm{J}$
C
$710\,\mathrm{J}$
D
$-710\,\mathrm{J}$

Choose one

1 point

Which approach gives the most complete first-law account of an organism’s energy over a period of time?

A
Count only external mechanical work, because heat and stored chemical energy are not energy transfers.
B
Count only the heat leaving the body, because food and oxygen carry matter rather than energy.
C
Account for energy entering and leaving with matter and for transformations into work, stored chemical energy, and heat.
D
Treat metabolism as a new energy input that is independent of nutrients.

Choose one

1 point

A cell builds and maintains highly organized structures. Which explanation best reconciles this with the second law of thermodynamics?

A
The organism is open and can maintain local organization while increasing the entropy of its surroundings.
B
The organism is isolated, so its own entropy must decrease as it becomes more organized.
C
The second law applies only to nonliving systems, not to organisms.
D
The organism creates energy to offset any decrease in its own entropy.

Choose one

1 point

At constant temperature and pressure, a reaction has $\Delta H=25\,\mathrm{kJ/mol}$ , $T=300\,\mathrm{K}$ , and $\Delta S=60\,\mathrm{J/(mol\,K)}$ . What is $\Delta G$ , and what does its sign indicate about the forward direction under these conditions?

A
$-43\,\mathrm{kJ/mol}$ ; favorable in the forward direction
B
$-7\,\mathrm{kJ/mol}$ ; favorable in the forward direction
C
$7\,\mathrm{kJ/mol}$ ; favorable in the forward direction
D
$7\,\mathrm{kJ/mol}$ ; not favorable in the forward direction

Choose one

1 point

Which description best explains ATP’s role in cellular energy use?

A
ATP creates free energy independently of food or other inputs.
B
ATP can transfer usable free energy from energy-releasing reactions to cellular tasks.
C
ATP makes every reaction thermodynamically favorable without coupling.
D
ATP stores only heat and cannot support cellular work.

Choose one

1 point

During exercise, muscle chemical-energy use and the rate of mechanical work both increase. Which conclusion about body heat is best supported?

A
All additional chemical energy becomes external mechanical work, so heat production stays unchanged.
B
Heat production rises only if the body stops losing heat.
C
Increased chemical-energy use supports greater muscle activity and also increases heat production.
D
Increased heat production proves that no energy was used for mechanical work.

Choose one

1 point

Which method estimates metabolic energy expenditure from measurements of oxygen consumption and carbon dioxide production?

A
Indirect calorimetry measures oxygen consumption and carbon dioxide production to estimate metabolic energy use.
B
Temperature monitoring measures only body temperature to calculate energy stored in tissue.
C
Mechanical work measurement uses external force and displacement to estimate cellular metabolism.
D
Direct measurement of body heat measures all metabolic energy use without other measurements.