Exam 3

Question 1

The process of photosynthesis probably originated _____.

A) in plants

B) in prokaryotes

C) in fungi

D) three separate times during evolution

Answer 1

B) in prokaryotes

Question 2

In autotrophic bacteria, where is chlorophyll located?

A) in chloroplast membranes

B) in the ribosomes

C) in the nucleoid

D) in the infolded plasma membrane

Answer 2

D) in the infolded plasma membrane

Question 3

Plants photosynthesize _____.

A) only in the light but respire only in the dark

B) only in the dark but respire only in the light

C) only in the light but respire in light and dark

D) and respire only in the light

Answer 3

C) only in the light but respire in light and dark

Question 4

Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide. In fact, it comes from _____.

A) water

B) glucose

C) air

D) electrons from NADPH

Answer 4

A) water

Question 5

If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), later analysis will show that all of the following molecules produced by the algae contain 18O EXCEPT _____.

A) glyceraldehyde 3-phosphate (G3P)

B) glucose

C) ribulose bisphosphate (RuBP)

D) O2

Answer 5

D) O2

Question 6

Every ecosystem must have _____.

A) autotrophs and heterotrophs

B) producers and primary consumers

C) photosynthesizers

D) autotrophs

Answer 6

D) autotrophs

Question 7

When oxygen is released as a result of photosynthesis, it is a direct by-product of _____.

A) splitting water molecules

B) chemiosmosis

C) the electron transfer system of photosystem I

D) the electron transfer system of photosystem II

Answer 7

A) splitting water molecules

Question 8

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

A) Cellular respiration is unique to heterotrophs.

B) Only heterotrophs have mitochondria.

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

D) Only heterotrophs require oxygen.

Answer 8

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

Question 9

Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light.

What did Engelmann conclude about the congregation of bacteria in the red and blue areas?

A) Bacteria congregated in these areas due to an increase in the temperature of the red and blue light.

B) Bacteria congregated in these areas because these areas had the most oxygen being released.

C) Bacteria are attracted to red and blue light and thus these wavelengths are more reactive than other wavelengths.

D) Bacteria congregated in these areas due to an increase in the temperature caused by an increase in photosynthesis.

Answer 9

B) Bacteria congregated in these areas because these areas had the most oxygen being released.

Question 10

Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light.

An outcome of Engelmann’s experiment was to help determine the relationship between _____.

A) wavelengths of light and the rate of aerobic respiration

B) wavelengths of light and the amount of heat released

C) wavelengths of light and the rate of photosynthesis

D) the concentration of carbon dioxide and the rate of photosynthesis

Answer 10

C) wavelengths of light and the rate of photosynthesis

Question 11

A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be needed.

What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?

A) full-spectrum white light

B) green light

C) a mixture of blue and red light

D) UV light

Answer 11

C) a mixture of blue and red light

Question 12

A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be needed.

Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are absorbed by this pigment?

A) red and yellow

B) blue and violet

C) green and yellow

D) blue, green, and red

Answer 12

B) blue and violet

Question 13

Halobacterium has a photosynthetic membrane that appears purple. Its photosynthetic action spectrum is the inverse of the action spectrum for green plants. (That is, the Halobacterium action spectrum has a peak where the green plant action spectrum has a trough.) What wavelengths of light do the Halobacterium photosynthetic pigments absorb?

A) red and yellow

B) blue, green, and red

C) green and yellow

D) blue and red

Answer 13

C) green and yellow

Question 14

Why are there several structurally different pigments in the reaction centers of photosystems?

A) Excited electrons must pass through several pigments before they can be transferred to electron acceptors of the electron transport chain.

B) This arrangement enables the plant to absorb light energy of a variety of wavelengths.

C) They enable the plant to absorb more photons from light energy, all of which are at the same wavelength.

D) They enable the reaction center to excite electrons to a higher energy level.

Answer 14

B) This arrangement enables the plant to absorb light energy of a variety of wavelengths.

Question 15

If pigments from a particular species of plant are extracted and subjected to paper chromatography, which of the following is most likely?

A) Paper chromatography for the plant would isolate a single band of pigment that is characteristic of that particular plant.

B) Paper chromatography would separate the pigments from a particular plant into several bands.

C) The isolated pigments would be some shade of green.

D) Paper chromatography would isolate only the pigments that reflect green light.

Answer 15

B) Paper chromatography would separate the pigments from a particular plant into several bands.

Question 16

In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and _____.

A) carotenoids and other pigments are still present in the leaves

B) the degraded chlorophyll changes into many other colors

C) water supply to the leaves has been reduced

D) sugars are sent to most of the cells of the leaves

Answer 16

A) carotenoids and other pigments are still present in the leaves

Question 17

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?

A) ATP is synthesized from the energy absorbed.

B) A carboxylation reaction of the Calvin cycle occurs.

C) Electrons are stripped from NADPH.

D) An electron is excited.

Answer 17

D) An electron is excited.

Question 18

As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?

A) It excites electrons of the reaction center of photosystem I.

B) It is lost as heat.

C) It is used to establish and maintain a proton gradient.

D) It is used to phosphorylate NAD+ to NADPH, the molecule that accepts electrons from photosystem I.

Answer 18

C) It is used to establish and maintain a proton gradient.

Question 19

The final electron acceptor associated with photosystem I is _____.

A) oxygen

B) water

C) NADP

D) NADPH

Answer 19

C) NADP

Question 20

The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come?

A) the electron carrier, plastocyanin

B) photosystem I

C) water

D) oxygen

Answer 20

C) water

Question 21

In the thylakoid membranes, the pigment molecules in a light-harvesting complex _____.

A) split water and release oxygen from the reaction-center chlorophyll

B) absorb and transfer light energy to the reaction-center chlorophyll

C) synthesize ATP from ADP and i

D) transfer electrons to ferredoxin and then NADPH

Answer 21

B) absorb and transfer light energy to the reaction-center chlorophyll

Question 22

Which of the following are directly associated with photosystem I?

A) receiving electrons from the thylakoid membrane electron transport chain

B) generation of molecular oxygen

C) extraction of hydrogen electrons from the splitting of water

D) passing electrons to the cytochrome complex

Answer 22

A) receiving electrons from the thylakoid membrane electron transport chain

Question 23

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 to _____.

A) determine if they have thylakoids in the chloroplasts

B) test for liberation of O2 in the light

C) test for CO2 fixation in the dark

D) do experiments to generate an action spectrum

Answer 23

B) test for liberation of O2 in the light

Question 24

What are the products of linear electron flow?

A) heat and fluorescence

B) ATP and P700

C) ATP and NADPH

D) ADP and NADP+

Answer 24

C) ATP and NADPH

Question 25

As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find that 30,000 molecules of ATP were consumed, but only 20,000 molecules of NADPH were consumed. Where did the extra ATP molecules come from?

A) photosystem II

B) photosystem I

C) cyclic electron flow

D) linear electron flow

Answer 25

C) cyclic electron flow

Question 26

Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will most directly affect the _____.

A) splitting of water

B) flow of electrons from photosystem II to photosystem I

C) synthesis of ATP

D) reduction of NADP+

Answer 26

C) synthesis of ATP

Question 27

In a plant cell, where are the ATP synthase complexes located?

A) thylakoid membrane only

B) inner mitochondrial membrane only

C) thylakoid membrane and inner mitochondrial membrane

D) thylakoid membrane and plasma membrane

Answer 27

C) thylakoid membrane and inner mitochondrial membrane

Question 28

In mitochondria, chemiosmosis moves protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis moves protons from the _____.

A) matrix to the stroma

B) stroma to the thylakoid space

C) intermembrane space to the matrix

D) thylakoid space to the stroma

Answer 28

B) stroma to the thylakoid space

Question 29

Which of the following statements best describes the relationship between photosynthesis and respiration?

A) Respiration runs the biochemical pathways of photosynthesis in reverse.

B) Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules

C) Photosynthesis occurs only in plants; respiration occurs only in animals.

D) Photosynthesis is catabolic; respiration is anabolic.

Answer 29

B) Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules

Question 30

In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during _____.

A) photosynthesis only

B) respiration only

C) photosynthesis and respiration

D) neither photosynthesis nor respiration

Answer 30

C) photosynthesis and respiration

Question 31

Carbon dioxide is split to form oxygen gas and carbon compounds _____.

A) during photosynthesis

B) during respiration

C) during photosynthesis and respiration

D) in neither photosynthesis nor respiration

Answer 31

D) in neither photosynthesis nor respiration

Question 32

What is the relationship between the wavelength of light and the quantity of energy per photon?

A) They have a direct, linear relationship.

B) They are inversely related.

C) They are logarithmically related.

D) They are separate phenomena.

Answer 32

B) They are inversely related.

Question 33

P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary?

A) It is the receptor for the most excited electron in either photosystem of photosynthesis.

B) It is the molecule that transfers electrons to plastoquinone (Pq) of the electron transfer system.

C) It transfers its electrons to reduce NADP+ to NADPH.

D) It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.

Answer 33

D) It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.

Question 34

Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?

A) They serve as accessory pigments to increase light absorption.

B) They protect against oxidative damage from excessive light energy.

C) They shield the sensitive chromosomes of the plant from harmful ultraviolet radiation.

D) They reflect orange light and enhance red light absorption by chlorophyll.

Answer 34

B) They protect against oxidative damage from excessive light energy.

Question 35

In a plant, the reactions that produce molecular oxygen (O2) take place in _____.

A) the light reactions alone

B) the Calvin cycle alone

C) the light reactions and the Calvin cycle

D) neither the light reactions nor the Calvin cycle

Answer 35

A) the light reactions alone

Question 36

The accumulation of free oxygen in Earth’s atmosphere began with the origin of _____.

A) life and respiratory metabolism

B) cyanobacteria using photosystem II

C) chloroplasts in photosynthetic eukaryotic algae

D) land plants

Answer 36

B) cyanobacteria using photosystem II

Question 37

In its mechanism, photophosphorylation is most similar to _____.

A) substrate-level phosphorylation in glycolysis

B) oxidative phosphorylation in cellular respiration

C) the Calvin cycle

D) reduction of NADP+

Answer 37

B) oxidative phosphorylation in cellular respiration

Question 38

Which process is most directly driven by light energy?

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

B) carbon fixation in the stroma

C) reduction of NADP+ molecules

D) removal of electrons from chlorophyll molecules

Answer 38

D) removal of electrons from chlorophyll molecules

Question 39

A gardener is concerned that her greenhouse is getting too hot from too much light and seeks to shade her plants with colored translucent plastic sheets, the color of which allows passage of only that wavelength. What color should she use to reduce overall light energy but still maximize plant growth?

A) green

B) blue

C) orange

D) Any color will work equally well.

Answer 39

B) blue

Question 40

A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask. The dissolved oxygen in the flask with algae will _____.

A) always be higher

B) always be lower

C) be higher in the light, but the same in the dark

D) be higher in the light, but lower in the dark

Answer 40

D) be higher in the light, but lower in the dark

Question 41

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, i, and NADP+

D) ATP and NADPH

Answer 41

D) ATP and NADPH

Question 42

Where does the Calvin cycle take place?

A) stroma of the chloroplast

B) thylakoid membrane

C) interior of the thylakoid (thylakoid space)

D) outer membrane of the chloroplast

Answer 42

A) stroma of the chloroplast

Question 43

What is the primary function of the Calvin cycle?

A) use NADPH to release carbon dioxide

B) split water and release oxygen

C) transport RuBP out of the chloroplast

D) synthesize simple sugars from carbon dioxide

Answer 43

D) synthesize simple sugars from carbon dioxide

Question 44

In the process of carbon fixation, RuBP attaches a CO2 to produce a six-carbon molecule, which is then split to produce two molecules of 3-phosphoglycerate. After phosphorylation and reduction produces glyceraldehyde 3-phosphate (G3P), what more needs to happen to complete the Calvin cycle?

A) addition of a pair of electrons from NADPH

B) regeneration of ATP from ADP

C) regeneration of RuBP

D) regeneration of NADP+

Answer 44

C) regeneration of RuBP

Question 45

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

A) NADPH → O2 → C O2

B) H2O → NADPH → Calvin cycle

C) NADPH → chlorophyll → Calvin cycle

D) NADPH → electron transport chain → O2

Answer 45

B) H2O → NADPH → Calvin cycle

Question 46

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

A) oxidation of NADPH

B) release of oxygen

C) regeneration of the CO2 acceptor

D) consumption of ATP

Answer 46

B) release of oxygen

Question 47

What compound provides the reducing power for Calvin cycle reactions?

A) ATP

B) NADH

C) NADP+

D) NADPH

Answer 47

D) NADPH

Question 48

What would be the expected effect on plants if the atmospheric CO2 concentration was doubled?

A) All plants would experience increased rates of photosynthesis.

B) C3 plants would have faster growth; C4 plants would be minimally affected.

C) C4 plants would have faster growth; C3 plants would be minimally affected.

D) C3 plants would have faster growth; C4 plants would have slower growth.

Answer 48

B) C3 plants would have faster growth; C4 plants would be minimally affected.

Question 49

Why are C4 plants able to photosynthesize with no apparent photorespiration?

A) They do not participate in the Calvin cycle.

B) They use PEP carboxylase to initially fix CO2.

C) They conserve water more efficiently.

D) They exclude oxygen from their tissues.

Answer 49

B) They use PEP carboxylase to initially fix CO2

Question 50

CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they _____.

A) fix CO2 into organic acids during the night

B) fix CO2 into sugars in the bundle-sheath cells

C) fix CO2 into pyruvate in the mesophyll cells

D) use photosystem I and photosystem II at night

Answer 50

A) fix CO2 into organic acids during the night

Question 51

The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?

A) Each one minimizes both water loss and rate of photosynthesis.

B) C4 compromises on water loss and CAM compromises on photorespiration.

C) Both minimize photorespiration but expend more ATP during carbon fixation.

D) CAM plants allow more water loss, while C4 plants allow less CO2 into the plant.

Answer 51

C) Both minimize photorespiration but expend more ATP during carbon fixation.

Question 52

If plant gene alterations cause plants to be deficient in photorespiration, what would most probably occur?

A) Photosynthetic efficiency would be reduced at low light intensities.

B) Cells would carry on the Calvin cycle at a much slower rate.

C) There would be more light-induced damage to the cells.

D) Less oxygen would be produced.

Answer 52

C) There would be more light-induced damage to the cells.

Question 53

Compared to C3 plants, C4 plants _____.

A) can continue to fix CO2 even at lower CO2 concentrations and higher oxygen concentrations

B) have higher rates of photorespiration

C) do not use rubisco for carbon fixation

D) make a four-carbon compound, oxaloacetate, which is then delivered to the citric acid cycle in mitochondria

Answer 53

A) can continue to fix CO2 even at lower CO2 concentrations and higher oxygen concentrations

Question 54

Photorespiration _____.

A) generates carbon dioxide and consumes ATP and oxygen

B) generates ATP and sugars and consumes oxygen and carbon dioxide

C) generates oxygen and consumes ATP, carbon dioxide, and sugars

D) consumes carbon dioxide and generates ATP, sugars, and oxygen

Answer 54

A) generates carbon dioxide and consumes ATP and oxygen

Question 55

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes _____.

a. an oxidizing agent
b. hydrolyzed
c. reduced
d. oxidized

Answer 55

d. oxidized

Question 56

When electrons move closer to a more electronegative atom, what happens? The more electronegative atom is _____.

a. oxidized, and energy is consumed
b. reduced, and energy is consumed
c. reduced, and energy is released
d. oxidized, and energy is released

Answer 56

c. reduced, and energy is released

Question 57

The oxygen consumed during cellular respiration is involved directly in which process or event?

a. accepting electrons at the end of the electron transport chain
b. glycolysis
c. the citric acid cycle
d. the oxidation of pyruvate to acetyl CoA

Answer 57

a. accepting electrons at the end of the electron transport chain

Question 58

In the initial “energy investment” stage of glycolysis, which enzymes are responsible for using ATP to transfer a phosphate to glucose (or its derivatives)?

a. dehydrogenases
b. catecholases
c. kinases
d. isomerases

Answer 58

c. kinases

Question 59

Canine phosphofructokinase (PFK) deficiency afflicts Springer spaniels, affecting an estimated 10% of the breed. Given its critical role in glycolysis, one implication of the genetic defect resulting in PFK deficiency in dogs is _____.

a. elevated blood-glucose levels in the dog’s blood
b. early embryonic mortality
c. an intolerance for exercise
d. a reduced life span

Answer 59

c. an intolerance for exercise

Question 60

The first step of glycolysis expends energy through the addition of phosphate to glucose, resulting in glucose-6-phosphate. Which of these enzymes is most likely responsible for catalyzing this reaction?

a. hexokinase
b. phosphoglyceromutase
c. phosphoglucose isomerase
d. glyceraldehyde-3-phosphate dehydrogenase

Answer 60

a. hexokinase

Question 61

Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?

a. oxidation of pyruvate to acetyl CoA and the citric acid cycle
b. oxidative phosphorylation and fermentation
c. glycolysis and the oxidation of pyruvate to acetyl CoA
d. fermentation and glycolysis

Answer 61

a. oxidation of pyruvate to acetyl CoA and the citric acid cycle

Question 62

Which electron carrier(s) function in the citric acid cycle?

a. NAD+ only
b. NADH and FADH2
c. the electron transport chain
d. ADP and ATP

Answer 62

b. NADH and FADH2

Question 63

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A.

The three listed steps result in the formation of _____.

a. acetyl CoA, O2, and ATP
b. acetyl CoA, NADH, and CO2
c. acetyl CoA, NAD+, ATP, and CO2
d. acetyl CoA, FADH2, and CO2

Answer 63

b. acetyl CoA, NADH, and CO2

Question 64

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 substrate-level phosphorylation.
d. It increases the surface for oxidative phosphorylation.

Answer 64

d. It increases the surface for oxidative phosphorylation.

Question 65

In chemiosmosis, what is the most direct source of energy that is used to convert ADP + i to ATP?

a. energy released from substrate-level phosphorylation
b. energy released from movement of protons through ATP synthase, down their electrochemical gradient
c. energy released as electrons flow through the electron transport system
d. No external source of energy is required because the reaction is exergonic.

Answer 65

b. energy released from movement of protons through ATP synthase, down their electrochemical gradient

Question 66

Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of _____.

a. pyruvate
b. NADH
c. acetyl-CoA
d. glucose

Answer 66

b. NADH

Question 67

You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave his body?

a. It was converted to heat and then released.
b. It was released as CO2 and H2O.
c. It was converted to urine and eliminated from the body.
d. It was converted to ATP, which weighs much less than fat.

Answer 67

b. It was released as CO2 and H2O.

Question 68

How many acetyl CoA molecules would result from the complete beta-oxidation of a 14-carbon fatty acid?

a. 7
b. 1
c. 2

Answer 68

a. 7

Question 69

The oxidation of a molecule of glucose (a 6-carbon sugar) results in two molecules of pyruvate, or 2 molecules of acetyl CoA. During the oxidation of glucose, 2 carbons are lost and only 4 are able to enter the TCA cycle as acetyl CoA. By comparison, the beta oxidation of fatty acids breaks fatty acids into 2-carbon units, which are each used to generate acetyl CoA.

Based on this information, which of these starting molecules would produce the most ATP if completely oxidized by a eukaryotic cell and used to drive oxidative phosphorylation of ATP?

a. one molecule of a 12-carbon fatty acid
b. 3 molecules of glucose
c. 3 molecules of glucose and one molecule of a 12-carbon fatty acid have the same useable amount of carbons to make acetyl CoA, so they would be basically the same.
d. Neither can be used by eukaryotic cells

Answer 69

c. 3 molecules of glucose and one molecule of a 12-carbon fatty acid have the same useable amount of carbons to make acetyl CoA, so they would be basically the same.

Question 70

Which of the following occurs in the cytosol of a eukaryotic cell?

a. oxidation of pyruvate to acetyl CoA
b. citric acid cycle
c. glycolysis and fermentation
d. fermentation and chemiosmosis

Answer 70

c. glycolysis and fermentation

Question 71

During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?

a. carbon dioxide (CO2)
b. molecular oxygen (O2)
c. pyruvate (C3H3O3-)
d. glucose (C6H12O6)

Answer 71

b. molecular oxygen (O2)

Question 72

During aerobic respiration, electrons travel downhill in which sequence?

a. glucose → pyruvate → ATP → oxygen
b. glucose → ATP → electron transport chain → NADH
c. food → glycolysis → citric acid cycle → NADH → ATP
d. glucose → NADH → electron transport chain → oxygen

Answer 72

d. glucose → NADH → electron transport chain → oxygen

Question 73

The electron transport chain can use a single molecule of NADH to generate 3 ATPs and a single molecule of FADH2 to generate 2 ATPs. Imagine that you have a single glucose molecule. How many ATPs would be generated per molecule of acetyl CoA that enters the TCA cycle (following oxidation of one glucose molecule), if you only count ATP generated from NADH or FADH2 in the electron transport chain? For this question, use only NADH and FADH2 that is generated through the TCA cycle.

a. 22
b. 11
c. 36

Answer 73

a. 22

Question 74

f the electron transport chain can use a single molecule of NADH to generate 3 ATPs and a single molecule of FADH2 to generate 2 ATPs, how many ATPs would be generated per molecule of acetyl CoA that enters the TCA cycle, if you only count ATP generated from NADH or FADH2 in the electron transport chain?

a. 22
b. 36
c. 11
d. 18

Answer 74

c. 11

Question 75

Catabolic pathways _____.

a. are spontaneous and do not need enzyme catalysis
b. combine molecules into more energy-rich molecules
c. supply energy, primarily in the form of ATP, for the cell’s work
d. are endergonic

Answer 75

c. supply energy, primarily in the form of ATP, for the cell’s work

Question 76

Anabolic pathways _____.

a. release energy as they degrade polymers to monomers
b. consume energy to build up polymers from monomers
c. are usually highly spontaneous chemical reactions
d. consume energy to decrease the entropy of the organism and its environment

Answer 76

b. consume energy to build up polymers from monomers

Question 77

Biological evolution of life on Earth, from simple prokaryote-like cells to large, multicellular eukaryotic organisms, _____.

a. has caused an increase in the entropy of the planet
b. 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
c. has occurred in accordance with the laws of thermodynamics
d. has been made possible by expending Earth’s energy resources

Answer 77

c. has occurred in accordance with the laws of thermodynamics

Question 78

Which of the following types of reactions would decrease the entropy within a cell?

a. anabolic reactions
b. digestion
c. hydrolysis
d. catabolic reactions

Answer 78

a. anabolic reactions

Question 79

Biological systems use free energy based on empirical data that all organisms require a constant energy input. The first law of thermodynamics states that energy can be neither created nor destroyed. For living organisms, which of the following statements is an important consequence of this first law?

a. The energy content of an organism is constant except for when its cells are dividing.
b. The entropy of an organism decreases with time as the organism grows in complexity.
c. Organisms are unable to transform energy from the different states in which it can exist.
d. The organism must ultimately obtain all the necessary energy for life from its environment.

Answer 79

d. The organism must ultimately obtain all the necessary energy for life from its environment.

Question 80

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. As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
b. Living organisms are able to transform energy into entropy.
c. 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.
d. Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.

Answer 80

a. As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.

Question 81

Which of the following is true for all exergonic reactions?

a. A net input of energy from the surroundings is required for the reactions to proceed.
b. The products have more total energy than the reactants.
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. The reaction proceeds with a net release of free energy.

Answer 81

d. The reaction proceeds with a net release of free energy.

Question 82

The mathematical expression for the change in free energy of a system is ΔG =ΔH - TΔS. Which of the following is (are) correct?

a. ΔH is the change in entropy, the energy available to do work.
b. T is the temperature in degrees Celsius.
c. ΔS is the change in enthalpy, a measure of randomness.
d. ΔG is the change in free energy.

Answer 82

d. ΔG is the change in free energy.

Question 83

Chemical equilibrium is relatively rare in living cells. An example of a reaction at chemical equilibrium in a cell would be _____.

a. an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment
b. one in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium
c. a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell
d. one in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell’s surroundings

Answer 83

c. a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell

Question 84

A system at chemical equilibrium _____.

a. releases energy at a steady rate
b. has zero kinetic energy
c. can do no work
d. consumes energy at a steady rate

Answer 84

c. can do no work

Question 85

How do cells use the ATP cycle?

a. Cells use the cycle to recycle energy released by ATP hydrolysis.
b. Cells use the cycle to recycle ADP and phosphate.
c. Cells use the cycle to recycle ADP, phosphate, and the energy released by ATP hydrolysis.
d. Cells use the cycle primarily to generate heat

Answer 85

b. Cells use the cycle to recycle ADP and phosphate.

Question 86

A reaction that has ∆G of +1.9 kcal/mol would not occur spontaneously, but could occur spontaneously when coupled to they hydrolysis of ATP. If the hydrolysis of one molecule of ATP to ADP + Pi has ∆G of -7.3 kcal/mol, hydrolysis of how many molecules of ATP would need to be coupled to this reaction for it to occur spontaneously?

a. 3 molecules of ATP
b. 1 molecule of ATP
c. 2 molecules of ATP

Answer 86

b. 1 molecule of ATP

Question 87

Why is ATP an important molecule in metabolism?

a. It provides energy coupling between exergonic and endergonic reactions.
b. Its terminal phosphate bond has higher energy than the other two phosphate bonds.
c. Its terminal phosphate group contains a strong covalent bond that, when hydrolyzed, releases free energy.
d. Its hydrolysis provides an input of free energy for exergonic reactions.

Answer 87

a. It provides energy coupling between exergonic and endergonic reactions.

Question 88

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

a. insufficient cofactors
b. allosteric inhibition
c. the need for a coenzyme
d. competitive inhibition

Answer 88

d. competitive inhibition

Question 89

The active site of an enzyme is the region that _____.

a. is involved in the catalytic reaction of the enzyme
b. binds noncompetitive inhibitors of the enzyme
c. is inhibited by the presence of a coenzyme or a cofactor
d. binds allosteric regulators of the enzyme

Answer 89

a. is involved in the catalytic reaction of the enzyme

Question 90

The lock-and-key analogy for enzymes applies to the specificity of enzymes _____.

a. interacting with ions
b. interacting with water
c. binding to their substrate
d. as they form their tertiary and quaternary structure

Answer 90

c. binding to their substrate

Question 91

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction’s _____.

a. equilibrium point
b. entropy
c. activation energy
d. free-energy content

Answer 91

c. activation energy

Question 92

Which of the following is true of enzymes?

a. Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.
b. Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.
c. Enzyme function is increased if the 3- D structure or conformation of an enzyme is altered.
d. Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

Answer 92

d. Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

Question 93

Which of the following statements about quorum sensing is FALSE? Quorum sensing _____.

a. is particularly well studied because of its medical importance
b. may result in biofilm formation
c. is species specific
d. is cell-cell communication in eukaryotes

Answer 93

d. is cell-cell communication in eukaryotes

Question 94

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

a. Estrogen is kept away from the surface of any cells not able to bind it at the surface.
b. Estrogen is produced in very large concentration by nearly every tissue of the body.
c. Estrogen binds to specific receptors inside many kinds of cells, each with different responses.
d. Each cell responds in the same way when steroids bind to the cell surface.

Answer 94

c. Estrogen binds to specific receptors inside many kinds of cells, each with different responses.

Question 95

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

a. digestion of unwanted parasite populations
b. formation of mating complexes
c. aggregation of bacteria that can cause cavities
d. secretion of substances that inhibit foreign bacteria

Answer 95

c. aggregation of bacteria that can cause cavities

Question 96

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?

a. tyrosines
b. serine and threonine
c. glycine and glutamic acid
d. glycine and histidine

Answer 96

b. serine and threonine

Question 97

The toxin of Vibrio cholerae causes profuse diarrhea because it _____.

a. modifies calmodulin and activates a cascade of protein kinases
b. modifies a G protein involved in regulating salt and water secretion
c. binds with adenylyl cyclase and triggers the formation of cAMP
d. signals IP3 to act as a second messenger for the release of calcium

Answer 97

b. modifies a G protein involved in regulating salt and water secretion

Question 98

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound _____.

a. that increases cAMP production in liver cells
b. that activates epinephrine receptors
c. to block G protein activity in liver cells
d. that increases phosphorylase activity

Answer 98

c. to block G protein activity in liver cells

Question 99

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound _____.

a. that increases phosphodiesterase activity
b. that stimulates cAMP production in liver cells
c. that mimics epinephrine and can bind to the epinephrine receptor
d. to stimulate G protein activity in liver cells

Answer 99

a. that increases phosphodiesterase activity

Question 100

Which of the following is a correct association?

a. kinase activity and the addition of a tyrosine
b. phosphodiesterase activity and the removal of phosphate groups
c. GTPase activity and hydrolysis of GTP to GDP
d. adenylyl cyclase activity and the conversion of cAMP to AMP

Answer 100

c. GTPase activity and hydrolysis of GTP to GDP

Question 101

Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. HER2 is sometimes excessive in cancer cells. This information can now be utilized in breast cancer treatment if which of the following is true?

a. if HER2, administered by injection, causes cell division
b. if the patient has RTKs only in cancer cells
c. if the patient’s cancer cells have excessive levels of HER2
d. if the patient’s genome codes for the HER2 receptor

Answer 101

c. if the patient’s cancer cells have excessive levels of HER2

Question 102

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

a. receptor tyrosine kinases
b. ligand-gated ion channels
c. G protein-coupled receptors
d. steroid receptors

Answer 102

a. receptor tyrosine kinases

Question 103

A drug designed to inhibit the response of cells to testosterone would most likely result in _____.

a. lower cytoplasmic levels of cAMP
b. an increase in cytosolic calcium concentration
c. a decrease in G protein activity
d. a decrease in transcriptional activity of certain genes

Answer 103

d. a decrease in transcriptional activity of certain genes

Question 104

The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is not a problem for steroids because _____.

a. steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane
b. steroids do not directly affect cells but instead alter the chemistry of blood plasma
c. the receptors can be readily stimulated to exit and relocate on the membrane surface
d. steroids must first bond to a steroid activator, forming a complex that then binds to the cell

Answer 104

a. steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane

Question 105

Which of the following is true during a typical cAMP-type signal transduction event?

a. The second messenger is the last part of the system to be activated.
b. Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.
c. The hormone activates the second messenger by directly binding to it.
d. The second messenger amplifies the hormonal response by attracting more hormones to the cell being affected.

Answer 105

b. Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

Question 106

Which of the following is the best explanation for the inability of a specific animal cell to reduce the Ca2+ concentration in its cytosol compared with the extracellular fluid?

a. blockage of the synaptic signal
b. low levels of protein kinase in the cell
c. loss of transcription factors
d. insufficient ATP levels in the cytosol

Answer 106

d. insufficient ATP levels in the cytosol

Question 107

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they _____.

a. counter the harmful effects of phosphatases
b. always lead to the same cellular response
c. amplify the original signal many times
d. are species specific

Answer 107

c. amplify the original signal many times

Question 108

In signal transduction, phosphatases _____.

a. prevent a protein kinase from being reused when there is another extracellular signal
b. amplify the second messengers such as cAMP
c. inactivate protein kinases and turn off the signal transduction
d. move the phosphate group of the transduction pathway to the next molecule of a series

Answer 108

c. inactivate protein kinases and turn off the signal transduction

Question 109

Adenylyl cyclase has the opposite effect of which of the following?

a. phosphorylase
b. protein kinase
c. protein phosphatase
d. phosphodiesterase

Answer 109

d. phosphodiesterase

Question 110

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

a. It would be able to carry out reception and transduction but would not be able to respond to a signal.
b. It would employ a transduction pathway directly from an external messenger.
c. It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
d. It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

Answer 110

d. It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

Question 111

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result?

a. excess skin loss
b. activation of a developmental pathway found in the worm but not in humans
c. formation of molecular pores in the mitochondrial outer membrane
d. a form of cancer in which there is insufficient apoptosis

Answer 111

d. a form of cancer in which there is insufficient apoptosis

Question 112

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

a. Ced-9 remains inactive until it is signaled by ced-3 and other caspases.
b. Ced-9 prevents blebbing by its action on the cell membrane.
c. Ced-9 cleaves to produce ced-3 and ced-4.
d. It prevents the caspase activity of ced-3 and ced-4.

Answer 112

d. It prevents the caspase activity of ced-3 and ced-4.