Some bacteria are metabolically active in hot springs because

A) they are able to maintain a lower internal temperature

B) high temperature make catalysis unnecessary

C) their enzymes have high optimal temperatures

D) their enzymes are completely insensitive to temperature

C

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

A) addition 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

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
A) catalysis
B) metabolism
C) anabolism
D) dehydration
E) catabolism

E

Which of the following is (are) true for anabolic pathways?
A) They do not depend on enzymes.
B) They are usually highly spontaneous chemical reactions.
C) They consume energy to build up polymers from monomers.
D) They release energy as they degrade polymers to monomers.
E) They consume energy to decrease the entropy of the organism and its environment.

C

Which of the following types of reactions would decrease the entropy within a cell?
A) anabolic reactions
B) hydrolysis
C) respiration
D) digestion
E) catabolic reactions

A

Which of the following statements is true concerning catabolic pathways?
A) They combine molecules into more energy-rich molecules.
B) They supply energy, primarily in the form of ATP, for the cell's work.
C) They are endergonic.
D) They are spontaneous and do not need enzyme catalysis.
E) They build up complex molecules such as protein from simpler compounds.

B

Which of the following is the most correct interpretation of the figure?
A) Inorganic phosphate is created from organic phosphate.
B) Energy from catabolism can be used directly for performing cellular work.
C) ADP + Pi are a set of molecules that store energy for catabolism.
D) ATP is a molecule that acts as an intermediary to store energy for cellular work.
E) Pi acts as a shuttle molecule to move energy from ATP to ADP.

D

How do cells use the ATP cycle shown in the figure?
A) Cells use the cycle to recycle ADP and phosphate.
B) Cells use the cycle to recycle energy released by ATP hydrolysis.
C) Cells use the cycle to recycle ADP, phosphate, and the energy released by ATP hydrolysis.
D) Cells use the cycle to generate or consume water molecules as needed.
E) Cells use the cycle primarily to generate heat.

A

Which of the following is a statement of the first law of thermodynamics?
A) Energy cannot be created or destroyed.
B) The entropy of the universe is decreasing.
C) The entropy of the universe is constant.
D) Kinetic energy is stored energy that results from the specific arrangement of matter.
E) Energy cannot be transferred or transformed.

A

For living organisms, which of the following is an important consequence of the first law of thermodynamics?
A) The energy content of an organism is constant.
B) The organism ultimately must obtain all of the necessary energy for life from its environment.
C) The entropy of an organism decreases with time as the organism grows in complexity.
D) Organisms grow by converting energy into organic matter.
E) Life does not obey the first law of thermodynamics.

B

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
A) Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.
B) Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe.
C) Living organisms do not follow the laws of thermodynamics.
D) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
E) Living organisms are able to transform energy into entropy.

D

Which of the following statements is a logical consequence of the second law of thermodynamics?
A) If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe.
B) If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe.
C) Every energy transfer requires activation energy from the environment.
D) Every chemical reaction must increase the total entropy of the universe.
E) Energy can be transferred or transformed, but it cannot be created or destroyed.

D

Which of the following statements is representative of the second law of thermodynamics?
A) Conversion of energy from one form to another is always accompanied by some gain of free energy.
B) Heat represents a form of energy that can be used by most organisms to do work.
C) Without an input of energy, organisms would tend toward decreasing entropy.
D) Cells require a constant input of energy to maintain their high level of organization.
E) Every energy transformation by a cell decreases the entropy of the universe.

D

Biological evolution of life on Earth, from simple prokaryote-like cells to large, multicellar eukaryotic organisms,
A) has occurred in accordance with the laws of thermodynamics.
B) has caused an increase in the entropy of the planet.
C) has been made possible by expending Earth's energy resources.
D) has occurred in accordance with the laws of thermodynamics, by expending Earth's energy resources and causing an increase in the entropy of the planet.
E) violates the laws of thermodynamics because Earth is a closed system.

A

Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein?
A) +ΔH, +ΔS, +ΔG
B) +ΔH, -ΔS, -ΔG
C) +ΔH, -ΔS, +ΔG
D) -ΔH, -ΔS, +ΔG
E) -ΔH, +ΔS, +ΔG

C

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's
A) entropy.
B) activation energy.
C) endothermic level.
D) equilibrium point.
E) free-energy content.

B

Whenever energy is transformed, there is always an increase in the
A) free energy of the system.
B) free energy of the universe.
C) entropy of the system.
D) entropy of the universe.
E) enthalpy of the universe.

D

The mathematical expression for the change in free energy of a system is ΔG =ΔH - TΔS. Which of the following is (are) correct?
A) ΔS is the change in enthalpy, a measure of randomness.
B) ΔH is the change in entropy, the energy available to do work.
C) ΔG is the change in free energy.
D) T is the temperature in degrees Celsius.

C

Which of the following is true for all exergonic reactions?
A) The products have more total energy than the reactants.
B) The reaction proceeds with a net release of free energy.
C) The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants.
D) A net input of energy from the surroundings is required for the reactions to proceed.
E) The reactions are rapid.

B

Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?
A) a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium
B) a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings
C) an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment
D) a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway
E) no possibility of having chemical equilibrium in any living cell

D

For the hydrolysis of ATP to ADP + Pi, the free energy change is -7.3 kcal/mol under standard conditions (1 M concentration of both reactants and products). In the cellular environment, however, the free energy change is about -13 kcal/mol. What can we conclude about the free energy change for the formation of ATP from ADP and Pi under cellular conditions?
A) It is +7.3 kcal/mol.
B) It is less than +7.3 kcal/mol.
C) It is about +13 kcal/mol.
D) It is greater than +13 kcal/mol.
E) The information given is insufficient to deduce the free energy change.

C

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
A) by binding at the active site of the enzyme
B) by changing the shape of the enzyme's active site
C) by changing the free energy change of the reaction
D) by acting as a coenzyme for the reaction
E) by decreasing the activation energy of the reaction

B

Which of the following is an example of potential rather than kinetic energy?
A) the muscle contractions of a person mowing grass
B) water rushing over Niagara Falls
C) light flashes emitted by a firefly
D) a molecule of glucose
E) the flight of an insect foraging for food

D

A system at chemical equilibrium
A) consumes energy at a steady rate.
B) releases energy at a steady rate.
C) consumes or releases energy, depending on whether it is exergonic or endergonic.
D) has zero kinetic energy.
E) can do no work.

E

Which of the following best describes enthalpy (H)?
A) the total kinetic energy of a system
B) the heat content of a chemical system
C) the system's entropy
D) the cell's energy equilibrium
E) the condition of a cell that is not able to react

B

Which of the following is the smallest closed system?
A) a cell
B) an organism
C) an ecosystem
D) Earth
E) the universe

E

The light reactions of photosynthesis supply the Calvin Cycle with

A) light energy

B) CO₂ and ATP

C) H₂O and NADPH

D) ATP and NADPH

D

Which of the following sequences correctly represents the flow of electrons during photosynthesis?

A) NADPH --> O₂ --> CO₂

B) H₂O --> NADPH --> Calvin Cycle

C) H₂O --> photosystem I --> photosystem II

D) NADPH --> electron transport chain --> O₂

B

How is photosynthesis similar to C₄ plants and CAM plants?

A) In both cases, only photosynthesis I is used

B) Both types of plants make sugar without the Calvin Cycle

C) In both cases, rubisco is not used to fix carbon initially

D) Both types of plants make most of their sugar in the dark

C

Which of the following statements is a correct distinction between autotrophs and heterotrophs?

A) Autotrophs, but not necessarily heterotrophs, can nourish themselves beginning with CO₂ and other nutrients that are inorganic

B) Only heterotrophs require chemical compounds from the environment

C) Cellular respiration is unique to heterotrophs

D) Only heterotrophs have mitochondria

A

Which of the following does not occur during the Calvin cycle?

A) carbon fixation

B) oxidation of NADPH

C) release of oxygen

D) regeneration of the CO₂ acceptor

C

In mechanism, photophosphorylation is most similar to

A) substrate-level phosphorylation in glycolysis

B) oxidative phosphorylation in cellular respiration

C) carbon fixation

D) reduction of NADP⁺

B

Which process is most directly driven by light energy?

A) creation of pH gradient by pumping protons across the thylakoid membrane

B) reduction of NADP⁺ molecules

C) removal of electrons from chlorophyll molecules

D) ATP synthesis

C

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
A) CO₂ and glucose
B) H₂O and O₂
C) ADP, Pi, and NADP⁺
D) electrons and H⁺
E) ATP and NADPH

E

Photosynthesis is not responsible for
A) oxygen in the atmosphere.
B) the ozone layer.
C) most of the organic carbon on Earth's surface.
D) atmospheric CO₂.
E) fossil fuels.

E

Where does the Calvin cycle take place?
A) stroma of the chloroplast
B) thylakoid membrane
C) cytoplasm surrounding the chloroplast
D) interior of the thylakoid (thylakoid space)
E) outer membrane of the chloroplast

A

Which of the events listed below occurs in the light reactions of photosynthesis?
A) NADP is produced.
B) NADPH is reduced to NADP⁺.
C) Carbon dioxide is incorporated into PGA.
D) ATP is phosphorylated to yield ADP.
E) Light is absorbed and funneled to reaction-center chlorophyll a.

E

In a cyanobacterium, the reactions that produce NADPH occur in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but is not part of photosynthesis.

A

The reactions that produce molecular oxygen (O₂) take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but are not part of photosynthesis.

A

In C₃ photosynthesis, the reactions that require ATP take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but is not part of photosynthesis.

B

In a plant leaf, the reactions that produce NADH occur in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but is not part of photosynthesis.

D

Reactions that require CO₂ take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but is not part of photosynthesis.

B

The NADPH required for the Calvin cycle comes from
A) reactions initiated in photosystem I.
B) reactions initiated in photosystem II.
C) the citric acid cycle.
D) glycolysis.
E) oxidative phosphorylation.

A

What is the primary function of the Calvin cycle?
A) use ATP to release carbon dioxide
B) use NADPH to release carbon dioxide
C) split water and release oxygen
D) transport RuBP out of the chloroplast
E) synthesize simple sugars from carbon dioxide

E

As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find 30,000 molecules of ATP consumed, but only 20,000 molecules of NADPH. Where did the extra ATP molecules come from?
A) photosystem II
B) photosystem I
C) cyclic electron flow
D) linear electron flow
E) chlorophyll

C

Some photosynthetic bacteria (e.g., purple sulfur bacteria) have only photosystem I, whereas others (e.g., cyanobacteria) have both photosystem I and photosystem II. Which of the following might this observation imply?
A) Photosystem II was selected against in some species.
B) Photosynthesis with only photosystem I is more ancestral.
C) Photosystem II may have evolved to be more photoprotective.
D) Linear electron flow is more primitive than cyclic flow of electrons.
E) Cyclic flow is more necessary than linear electron flow.

B

In thylakoids, protons travel through ATP synthase from the thylakoid space to the stroma. Therefore, the catalytic "knobs" of ATP synthase would be located
A) on the side facing the thylakoid space.
B) on the ATP molecules themselves.
C) on the pigment molecules of photosystem I and photosystem II.
D) on the stromal side of the membrane.
E) built into the center of the thylakoid stack (granum).

D

Which statement describes the functioning of photosystem II?
A) Light energy excites electrons in the thylakoid membrane electron transport chain.
B) Photons are passed along to a reaction-center chlorophyll.
C) The P680 chlorophyll donates a pair of protons to NADP⁺, which is thus converted to NADPH.
D) The electron vacancies in P680⁺ are filled by electrons derived from water.
E) The splitting of water yields molecular carbon dioxide as a by-product.

D

Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be
A) to determine if they have thylakoids in the chloroplasts.
B) to test for liberation of O₂ in the light.
C) to test for CO₂ fixation in the dark.
D) to do experiments to generate an action spectrum.
E) to test for production of either sucrose or starch.

B

In autotrophic bacteria, where are the enzymes located that can carry on carbon fixation (reduction of carbon dioxide to carbohydrate)?
A) in chloroplast membranes
B) in chloroplast stroma
C) in the cytosol
D) in the nucleoid
E) in the infolded plasma membrane

C

Phosphofructokinase is an important control enzyme in the regulation of cellular respiration. Which of the following statements correctly describes phosphofructokinase activity?
A) It is inhibited by AMP.
B) It is activated by ATP.
C) It is activated by citrate, an intermediate of the citric acid cycle.
D) It catalyzes the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate, an early step of glycolysis.
E) It is an allosteric enzyme.

E

Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount of ATP in a cell would be expected to
A) inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
B) activate the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
C) inhibit the enzyme and thus increase the rates of glycolysis and the citric acid cycle.
D) activate the enzyme and increase the rates of glycolysis and the citric acid cycle.
E) inhibit the enzyme and thus increase the rate of glycolysis and the concentration of citrate.

A

High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of
A) competitive inhibition.
B) allosteric regulation.
C) the specificity of enzymes for their substrates.
D) an enzyme requiring a cofactor.
E) positive feedback regulation.

B

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
A) It allows for an increased rate of glycolysis.
B) It allows for an increased rate of the citric acid cycle.
C) It increases the surface for oxidative phosphorylation.
D) It increases the surface for substrate-level phosphorylation.
E) It allows the liver cell to have fewer mitochondria.

C

The ATP made during glycolysis is generated by
A) substrate-level phosphorylation.
B) electron transport.
C) photophosphorylation.
D) chemiosmosis.
E) oxidation of NADH to NAD⁺.

A

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
A) 0%
B) 2%
C) 10%
D) 38%
E) 100%

E

In addition to ATP, what are the end products of glycolysis?
A) CO₂ and H₂O
B) CO₂ and pyruvate
C) NADH and pyruvate
D) CO₂ and NADH
E) H₂O, FADH₂, and citrate

C

Starting with one molecule of glucose, the energy-containing products of glycolysis are
A) 2 NAD⁺, 2 pyruvate, and 2 ATP.
B) 2 NADH, 2 pyruvate, and 2 ATP.
C) 2 FADH₂, 2 pyruvate, and 4 ATP.
D) 6 CO₂, 2 ATP, and 2 pyruvate.
E) 6 CO₂, 30 ATP, and 2 pyruvate.

B

n glycolysis, for each molecule of glucose oxidized to pyruvate
A) two molecules of ATP are used and two molecules of ATP are produced.
B) two molecules of ATP are used and four molecules of ATP are produced.
C) four molecules of ATP are used and two molecules of ATP are produced.
D) two molecules of ATP are used and six molecules of ATP are produced.
E) six molecules of ATP are used and six molecules of ATP are produced.

B

Why is glycolysis described as having an investment phase and a payoff phase?
A) It both splits molecules and assembles molecules.
B) It attaches and detaches phosphate groups.
C) It uses glucose and generates pyruvate.
D) It shifts molecules from cytosol to mitochondrion.
E) It uses stored ATP and then forms a net increase in ATP.

E

During aerobic respiration, electrons travel downhill in which sequence?
A) food → citric acid cycle → ATP → NAD⁺
B) food → NADH → electron transport chain → oxygen
C) glucose → pyruvate → ATP → oxygen
D) glucose → ATP → electron transport chain → NADH
E) food → glycolysis → citric acid cycle → NADH → ATP

B

What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions?
A) glucose
B) ethanol
C) pyruvate
D) lactic acid
E) either ethanol or lactic acid

A

The body tissue that consists largely of material located outside of cells is

A) epithelial tissue

B) connective tissue

C) muscle tissue

D) nervous tissue

B

Which of the following would increase the rate of heat exchange between an animal and its environment?

A) feathers of fur

B) vasoconstriction

C) wind blowing across the body surface

D) countercurrent heat exchanger

C

Consider the energy budgets for a human, an elephant, a penguin, a mouse, and a snake. The ______ would have the highest total annual energy expenditure, and the ______ would have the highest expenditure per unit mass.

A) elephant; mouse

B) elephant; human

C) mouse; snake

D) penguin; mouse

A

Compared with a smaller cell, a larger cell of the same shape has

A) less surface area

B) less surface area per unit of volume

C) the same surface area-to-volume ratio

D) a smaller cytoplasm-to-nucleus ratio

B

An animal's inputs of energy and materials would exceed its outputs

A) if the animal is an endotherm, which must always take in more energy because of its high metabolic rate

B) if it is actively forging for food

C) if it is growing and increasing its mass

D) never; homeostasis makes these energy and material budgets always balance

C

You are studying a large tropical reptile that has a high and relatively stable body temperature. How would you determine whether this animal is an endotherm or an ectotherm?

A) You know form its high and stable body temperature that it must be an endotherm

B) You subject this reptile to various temperatures in the lab to find that its body temperature and metabolic rate change with the ambient temperature. You conclude that it is an ectotherm

C) You note that tis environment has a high and stable temperature. Because its body temperature matches the environmental temperature, you can conclude that it is an ectotherm.

D) You measure the metabolic rate of the reptile, and because it is higher than that of a related species that lives in temperate forests, you conclude that this reptile is an endotherm and its relative is an ectotherm

B

Which of the following animals uses the largest percentage of its energy budget for homeostatic regulation?

A) a marine jelly (an invertebrate)

B) a snake in a temperate forest

C) a desert insect

D) a desert bird

D

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the

A) oxidation of glucose and other organic compounds

B) flow of electrons down the electron transport chain

C) H⁺ concentration gradient across the membran holding ATP synthase

D) transfer of phosphate to ADP

C

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

A) the citric acid cycle

B) the electron transport chain

C) glycolysis

D) reduction of pyruvate to lactate

C

The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is

A) oxygen

B) water

C) NAD⁺

D) pyruvate

A

In mitochondria, exergonic redox reactions

A) are the source of energy driving prokaryotic ATP synthesis

B) provide the energy that establishes the proton gradient

C) reduce carbon atoms to carbon dioxide

D) are coupled via phosphorylated intermediates to endergonic processes

B

What is the oxidizing agent in the following reaction?

Pyruvate + NADH + H⁺ --> Lactate + NAD⁺

A) oxygen

B) NADH

C) lactate

D) pyruvate

D

Most CO₂ from catabolism is released during

A) glycolysis

B) the citric acid cycle

C) lactate fermentation

D) electron transport

B

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

A) the pH of the matrix increases

B) ATP synthase pumps protons by active transport

C) the electrons gain free energy

D) NAD⁺ is oxidized

A

Brown fat cells produce a protein called thermogenin in their mitochondrial inner membrane. Thermogenin is a channel for facilitated transport of protons across the membrane. What will occur in the brown fat cells when they produce thermogenin?
A) ATP synthesis and heat generation will both increase.
B) ATP synthesis will increase, and heat generation will decrease.
C) ATP synthesis will decrease, and heat generation will increase.
D) ATP synthesis and heat generation will both decrease.
E) ATP synthesis and heat generation will stay the same.

C

1) When the temperature of the outside air exceeds their internal body temperature, jackrabbits living in hot, arid lands will
A) dilate the blood vessels in their large ears to transfer more body heat to the environment.
B) constrict the blood vessels in their large ears to reduce transfer of external heat to the blood in their ears.
C) increase motor movements to find a sunny area to maximize heat transfer into their bodies.
D) increase pigmentation in their ears, darkening them to maximize their capacity to take up heat.
E) begin involuntary shivering of their skeletal muscles in order to generate more metabolic heat.

B

Humans can lose, but cannot gain, heat through the process of
A) conduction.
B) convection.
C) radiation.
D) evaporation.
E) metabolism.

D

An overheated and sick dog in a hot environment will have an impaired thermoregulatory response when its
A) evaporative heat loss increases.
B) metabolic heat production decreases.
C) body temperature increases to match the environmental temperature.
D) blood vessels near its skin increase vasoconstriction.
E) behavioral response takes it to a cooler location.

C