Deck 6: Energy Flow in the Life of a Cell

Question 1

During photosynthesis, plants convert light energy to chemical energy. This is an example of

A) increasing entropy.
B) a spontaneous reaction.
C) the second law of thermodynamics.
D) chemical equilibrium.
E) the first law of thermodynamics.

Answer 1

E

Question 2

When, if ever, do molecules stop moving?

A) At absolute zero (- 273.15°C)
B) At the freezing point (0°C)
C) At the boiling point (100°C)
D) Never

Answer 2

A

Question 3

Activation energy is necessary for all reactions.

A) endergonic
B) coupled
C) chemical
D) exergonic

Answer 3

C

Question 4

Energy that is not converted to useful energy is usually given off as

A) radioactivity.
B) light.
C) electricity.
D) heat.
E) entropy.

Question 5

Each of the following requires 12 carbon atoms. Which of the arrangements of carbon atoms has the greatest entropy?

A) 12 molecules of carbon dioxide, CO₂
B) 2 molecules of the monosaccharide glucose, C6H12O6
C) 4 molecules of the monosaccharide pyruvate, C3H₄O₃
D) 1 molecule of the disaccharide maltose, C12H₂2O11

Question 6

How is your body able to work against the effects of entropy?

A) Regular exercise
B) Eating a balanced diet and proper nourishment
C) Regular work
D) Sunbathing

Question 7

A(n) chemical reaction releases energy, whereas a(n) reaction requires an input of energy.

A) exergonic; endergonic
B) endergonic; exergonic
C) equilibrium; exergonic
D) enzymatic; endergonic
E) endergonic; enzymatic

Question 8

In an isolated system, all of the following are true of the second law of thermodynamics EXCEPT

A) the amount of useful energy decreases.
B) reactions cause energy to be converted from more useful to less useful forms.
C) there is a natural tendency toward greater disorder in the organization of matter (increase in entropy).
D) all chemical reactions release more energy than they consume.

Question 9

Which of the following is part of the first law of thermodynamics?

A) Energy cannot be transferred or transformed.
B) Potential energy equals kinetic energy in a reaction.
C) Energy cannot be created or destroyed.
D) Kinetic energy is stored energy.
E) Exergonic reactions are coupled with endergonic reactions.

Question 10

Entropy is a measure of an increase in

A) high- level energy.
B) kinetic energy.
C) potential energy.
D) organization.
E) randomness.

Question 11

Similar to a car, a human body is about efficient in converting chemical energy to movement.

A) 95%
B) 75%
C) 25%
D) 1%

Question 12

What is the ultimate source of energy for almost all forms of life on Earth?

A) Nuclear energy
B) Solar energy
C) Heat energy
D) Chemical energy
E) Thermal energy

Question 13

When solid sodium hydroxide is added to water, the solution gets hot. This is an example of a(n)

A) endergonic process.
B) conversion of kinetic energy to potential energy.
C) exergonic process.
D) enzyme- catalyzed process.
E) release of activation energy.

Question 14

Why is photosynthesis considered an endergonic reaction?

A) Photosynthesis does not comply with the physical laws of the universe.
B) Low- energy reactants are converted to high- energy products.
C) Activation energy is not required.
D) Sugar has less energy than does the sun.
E) Protein catalysts are not needed.

Question 15

How is it possible for living organisms to comply with the second law of thermodynamics?

A) Sunlight functions as an ultimate source of energy for most forms of life on Earth.
B) Chemical reactions inside cells mostly cause an increase in high- level energy.
C) Organisms are able to function efficiently on heat energy alone.
D) Living organisms are unique in that they do not require energy for survival.
E) Living organisms are totally isolated systems that are not subject to the laws of physics.

Question 16

In exergonic chemical reactions,

A) energy is stored by the reactions.
B) the reactants have less energy than do the products.
C) the reactants and products have equal amounts of energy.
D) the reactants have more energy than do the products.

Question 17

All of the following statements are true of the first law of thermodynamics EXCEPT

A) one form of energy may be converted to a different form of energy.
B) the total amount of energy within a closed system remains the same.
C) the amount of useful energy decreases when energy is converted from one form to another.
D) the first law of thermodynamics is often called the law of the conservation of energy.

Question 18

Which of the following does NOT have much potential energy?

A) A diver on a springboard
B) A glucose molecule
C) A ball that has rolled downhill and stopped
D) A 9- volt battery
E) A water droplet at the top of a waterfall

Question 19

In the liver, the polysaccharide glycogen is broken down into glucose monomers. The glucose molecules are then released into the blood when blood sugar levels need to be raised. This process is an example of a(n) reaction.

A) kinetic
B) potential
C) exergonic
D) endergonic

Question 20

Which of the following has the greatest amount of kinetic energy?

A) The cool air surrounding the car engine
B) A moving car
C) A tank of gasoline
D) A hot car engine
E) An unlit firecracker

Question 21

Which of the following lowers the activation energy of a biochemical reaction?

A) Presence of a catalyst
B) Low concentration of reactants
C) High temperature
D) Altering pH to 7
E) High concentration of products

Question 22

Why is photosynthesis a coupled reaction?

A) Photosynthesis requires two reactants: carbon dioxide and water.
B) Sunlight energy enters a plant and is ultimately lost as heat.
C) The exergonic reaction occurs in the plant, and the endergonic reaction occurs in the sunlight.
D) The exergonic reaction occurs in the plant, and the endergonic reaction occurs in the soil.
E) An exergonic reaction occurs in the sunlight, and an endergonic reaction occurs in the plant.

Question 23

Most reactions in the body occur too slowly to sustain life. This is because

A) there is not enough ATP in body cells.
B) many reactions require large inputs of activation energy.
C) no catalysts are present in body cells.
D) all reactions in the body are endergonic.
E) most biological catalysts are not active at body temperature (37°C).

Question 24

Which of the following is NOT a commonly used energy carrier in the cell?

A) ATP
B) NAD
C) H₂O
D) FAD

Question 25

All of the following statements about catalysts are true EXCEPT

A) catalysts increase the reaction rate.
B) catalysts are not permanently altered during reaction.
C) catalysts increase activation energy requirements.
D) biological catalysts are specific enzymes.
E) catalysts can be used repeatedly.

Question 26

When a muscle cell demands energy to perform its work of contraction, ATP

A) manufactures more ATP.
B) catalyzes the reaction.
C) is broken down and liberates energy.
D) enters a metabolic pathway.
E) is phosphorylated.

Question 27

Place these steps of enzyme catalysis in the correct order: 1. The substrate and enzyme change shape.
2) The substrate enters the active site.
3) The enzyme reverts to its original configuration.
4) The product is expelled.

A) 2, 1, 4, 3
B) 1, 3, 4, 2
C) 2, 3, 1, 4
D) 1, 2, 3, 4
E) 2, 1, 3, 4

Question 28

Which molecule stores energy for just a short period of time?

A) Protein
B) Phospholipids
C) Glycogen
D) Steroids
E) ATP

Question 29

When a high- energy bond in ATP is broken, what primarily happens to the released energy?

A) It converts inorganic phosphates to energy- carrier molecules.
B) It is lost as light energy.
C) It provides the energy needed to drive endergonic reactions in the cell.
D) It polarizes the cell.
E) It functions as a second messenger.

Question 30

Enzymes are important because they

A) allow reactions to occur at body temperature.
B) increase the body temperature of organisms.
C) can enable organisms to evade the laws of thermodynamics.
D) are structural proteins that make up bodily tissues.
E) bind irreversibly to substrates.

Question 31

The most common energy carrier molecule in living organisms is

A) glucose.
B) NADPH.
C) ATP.
D) ADP.
E) DNA.

Question 32

A "high- energy" bond in an ATP molecule is located between

A) adenine and the first phosphate group.
B) ribose and the first phosphate group.
C) two phosphate groups.
D) adenine and ribose.

Question 33

Which of the following functions as a biological catalyst?

A) Energy- carrier molecule
B) Substrate
C) Enzyme
D) Amino acid
E) Steroid

Question 34

ATP is an energy carrier. Where is the energy actually located?

A) Between the sugar and the phosphate
B) Attached to the nucleotide
C) In the bonds between phosphate groups
D) Attached to the phosphate group
E) Inside the phosphate

Question 35

Which of the following statements regarding enzymes is FALSE?

A) Enzymes are proteins that function as biological catalysts.
B) Enzymes are highly specific for the molecules to which they attach.
C) The activity of enzymes can be regulated by factors in their environment.
D) Enzymes provide energy for the reactions they catalyze.
E) An enzyme may be used many times for the same specific reaction.

Question 36

Which of the following is the best description of a coupled reaction?

A) Two reactions, where the product of the first reaction is the reactant of the second reaction
B) Two reactions that occur in the same organelle
C) Reactions that occur during sexual reproduction
D) Two reactions that occur simultaneously
E) A reaction that occurs right after another reaction

Question 37

Imagine that you are conducting an experiment on a yeast enzyme known as sucrase. This enzyme is used by yeast cells to break down the disaccharide sucrose into the monosaccharides glucose and fructose. What type of reaction is this?

A) Metergonic
B) Endergonic
C) Exergonic
D) Spontaneous

Question 38

The reactant in an enzyme- catalyzed reaction is the

A) product.
B) allosteric inhibitor.
C) activation energy.
D) active site.
E) substrate.

Question 39

FADH₂ is an example of a(n)

A) protein.
B) enzyme- substrate complex.
C) active site.
D) enzyme.
E) electron carrier molecule.

Question 40

Which statement best describes the relationship between an enzyme and a reactant?

A) The relationship is temporary.
B) The enzyme and the reactant molecule are both permanently changed.
C) The resultant product and the enzyme are permanently bonded together.
D) Covalent chemical bonds stabilize the relationship.
E) One enzyme typically has many reactants with which it will associate.

Question 41

Sulfa antibiotics damage bacteria by affecting a certain bacterial enzyme. The sulfa antibiotic looks similar to a substrate normally required by the bacterial cells to live. The sulfa antibiotic occupies the active site of the required enzyme and blocks entry of its normal substrate. This prevents the bacteria from making nucleotides that are required for their reproduction and survival. Based on this information, the action of sulfa antibiotics is an example of

A) activation energy.
B) denaturing of proteins.
C) electron carriers.
D) competitive inhibition.

Question 42

Animals have enzymes that break apart starch molecules but not cellulose, despite the fact that both are made up of glucose subunits. Which enzyme characteristic best explains this?

A) Enzymes are not permanently changed by the reactions they promote.
B) All enzymes are proteins.
C) Enzymes are highly specific.
D) Enzyme activity is regulated.
E) Enzymes usually speed up chemical reactions.

Question 43

Kinetic energy is like sitting at the top of a hill, and potential energy is like coasting down that hill on your bike.

Question 44

Which of the following will bind to the active site of an enzyme?

A) Competitive inhibitor only
B) Noncompetitive inhibitor only
C) Allosteric inhibitor only
D) Substrate only
E) Both substrate and competitive inhibitor

Question 45

To say that an enzyme has been denatured means that

A) the enzyme is working at an optimal temperature.
B) an inhibitor has bound the enzyme at the active site.
C) the enzyme is working at its maximal rate.
D) its three- dimensional structure has changed and the enzyme can no longer function properly.

Question 46

The end product of a biosynthetic pathway often acts to block the initial step in that pathway. This phenomenon is called

A) substrate activation.
B) feedback inhibition.
C) allosteric activation.
D) denaturation.
E) irreversible inhibition.

Question 47

The addition of a competitive inhibitor slows down a particular reaction. What could be done to increase the rate of the reaction, even in the presence of the inhibitor?

A) Add more inhibitor.
B) Lower the temperature of the reaction.
C) Add a coenzyme.
D) Add more substrate.
E) Allow the reaction to reach equilibrium.

Question 48

Preservatives such as citric acid are added to foods to interfere with bacterial growth. This creates an acidic pH in the food. Why does this affect the bacteria that are present?

A) An acidic environment causes bacterial enzymes to fail or work less efficiently.
B) An acidic environment increases the activation energy more quickly in bacteria.
C) An acidic environment encourages endergonic reactions in the bacterial cells.
D) An acidic environment causes the bacteria to grow more rapidly.

Question 49

The burning of sugar is an example of an endergonic reaction, and photosynthesis is an example of an exergonic reaction.

Question 50

The hydrolysis of sucrose to glucose and fructose is a spontaneous reaction inside our bodies. However, if you dissolve sucrose in water and keep the solution overnight at room temperature, there is no detectable conversion to glucose and fructose. Why not?

A) The activation energy of the reaction decreases.
B) The energy of the products is higher than that of the energy of the reactants.
C) The reaction is endergonic.
D) The reaction requires a catalyst.
E) The reaction is at equilibrium.

Question 51

The optimum reaction rate of a particular enzyme occurs at pH 7.3 at 37°C. This reaction would probably proceed faster by

A) increasing the temperature to 38°C and keeping the pH at 7.3.
B) increasing the pH and maintaining the temperature at 37°C.
C) decreasing the pH and increasing the temperature.
D) increasing both temperature and pH.

Question 52

The law of conservation of energy states that although the form of energy used remains the same, the total amount of energy changes.

Question 53

The photosynthetic reaction is considered an endergonic reaction.

Question 54

In cells, endergonic reactions are often coupled with exergonic reactions that store energy.

Question 55

All of the following are examples of noncompetitive inhibitors EXCEPT

A) lead.
B) nerve gas.
C) arsenic.
D) mercury.

Question 56

Energy is defined as the capacity to do work.

Question 57

Competitive and noncompetitive enzyme inhibitors differ with respect to

A) the precise location on the enzyme to which they bind.
B) the temperature at which they work best.
C) their pH.
D) their energies of activation.

Question 58

For many enzymes, the rate of product formation increases as the concentration of the substrate increases. Eventually the rate of the reaction reaches a maximum at which further increases in the concentration of the substrate have no effect. Why?

A) At high concentrations of substrate, the activation energy of the reaction decreases.
B) The enzyme is no longer specific for the substrate.
C) At high concentrations of substrate, the reaction is endergonic.
D) At high concentrations of substrate, all of the enzyme active sites are being occupied by substrate molecules.
E) At high concentrations of substrate, the activation energy of the reaction increases.

Question 59

Triclosan is a broad- spectrum antibacterial agent used in many household products. It is structurally similar to polychlorobiphenylol, a substrate that binds to the active site of the enzyme sulfotransferase. Based on these facts, you can conclude that triclosan most likely

A) acts as a noncompetitive inhibitor.
B) functions as an enzyme when sulfotransferase is absent.
C) is a competitive inhibitor.
D) lowers the activation energy of chemical reactions.

Question 60

All of the following are ways in which enzymes are regulated by the cell EXCEPT

A) a heavy metal (such as lead) may block the enzymes non- active site.
B) by first synthesizing the enzyme in an inactive form.
C) by feedback inhibition.
D) a gene coding for the enzyme may be turned off.

Question 61

Sitting at the top of a slide, a child has energy; sliding down, she is using energy.

Question 62

The molecule is the major energy carrier in cells.

Question 63

In chemical reactions, the are converted into products.

Question 64

What is a simple definition of energy, from a biological perspective? Give some examples of how energy is used in a cell.

Question 65

The metabolism of a cell is the sum of all of its chemical reactions.

Question 66

Activation energy can be provided by the kinetic energy of moving molecules.

Question 67

Special molecules such as NADH and FADH₂ transport in cells, which can then be used as energy in the cell.

Question 68

The enzyme phosphoglucoisomerase catalyzes the conversion of glucose- 6- phosphate to
fructose- 6- phosphate. The region on phosphoglucoisomerase where glucose- 6- phosphate binds is called the
.

Question 69

AMP stores energy in its chemical bonds and is able to use that energy for work in the cell.

Question 70

Briefly describe the difference between kinetic energy and potential energy, and give an example of each.

Question 71

Briefly describe how ATP acts as an energy carrier in cells.

Question 72

ATP is considered a short- term form of energy for the cell, whereas or represent more stable, long- term energy stores.

Question 73

In chemical reactions, reactions release energy and reactions require an input of energy.

Question 74

The energy of movement is referred to as energy, and stored energy is referred to as _ energy.

Question 75

Briefly explain the two laws of thermodynamics.

Question 76

Energy transformations are not 100% efficient. Often, energy is released in the form of , which is in agreement with the second law of thermodynamics.

Question 77

Compare endergonic and exergonic chemical reactions using an analogy from everyday life.

Question 78

are biological catalysts.

Question 79

The second law of thermodynamics states that the , or disorder, of the universe is constantly increasing.

Question 80

The burning of sugars as fuels for runners is an example of a(n) _ _ chemical reaction, whereas the production of sugars during photosynthesis is an example of a(n) chemical reaction.