Chapter 6 Life's Mainspring: An Introduction to Energy
Biology: A Guide to the Natural World, 5e (Krogh)
1) Plants provide animals with which of the following?
A) food
B) oxygen
C) carbon dioxide
D) food and oxygen
E) food and carbon dioxide
Answer: D
Topic: Section 6.1
Skill: Knowledge/Comprehension
2) Which law of thermodynamics explains the fact that we must eat to gain the energy to perform the functions of life, such as breathing?
A) second law
B) fourth law
C) fifth law
D) first law
E) third law
Answer: D
Topic: Section 6.2
Skill: Application/Analysis
3) Living things are highly ordered. So why does life not violate the second law of thermodynamics?
A) Life can only violate the first law of thermodynamics.
B) Life only needs to follow the first law of thermodynamics.
C) Life takes in energy to maintain order and, in doing so, decreases order elsewhere.
D) Life gives off energy to maintain order and, in doing so, decreases order elsewhere.
Answer: C
Topic: Section 6.2
Skill: Application/Analysis
4) Which of the following has the most entropy?
A) steam
B) snow
C) an ice cube
D) hot water
E) liquid water
Answer: A
Topic: Section 6.2
Skill: Application/Analysis
5) When we metabolize our food, we produce heat that helps to keep us warm. Which of the following best describes why?
A) Chewing is exothermic; therefore, energy is released in the form of heat when we eat food.
B) When we break down food, all energy in the food is directly released in the form of heat.
C) Producing ATP from ADP is exothermic; therefore, energy is released in the form of heat.
D) When we break down our food, the reactions are not 100 percent efficient; therefore, energy is lost as heat.
Answer: D
Topic: Section 6.2
Skill: Knowledge/Comprehension
6) Entropy is the measure of ________ in a system.
A) energy
B) disorder
C) work
D) order
E) heat
Answer: B
Topic: Section 6.2
Skill: Knowledge/Comprehension
7) When you digest the starch in plants into glucose, some energy is lost as heat. This increases the ________ of the universe.
A) energy
B) order
C) entropy
D) potential
E) equilibrium
Answer: C
Topic: Section 6.2
Skill: Knowledge/Comprehension
8) Glucose can be broken down to provide energy for the beating of cilia. Therefore, the glucose must contain:
A) potential energy.
B) kinetic energy.
C) heat energy.
D) entropy.
Answer: A
Topic: Section 6.2
Skill: Knowledge/Comprehension
9) Kinetic energy is ________ and potential energy is ________.
A) stored energy; energy that is being used
B) stored energy; energy that can't be used
C) energy that can't be used; stored energy
D) energy that is being used; stored energy
Answer: D
Topic: Section 6.2
Skill: Knowledge/Comprehension
10) You work hard to pedal your bicycle up a steep hill. You rest when you get to the top, then you let your bicycle roll quickly down the other side of the hill. You converted ________ energy into ________ energy, then you converted it back into ________ energy.
A) potential; kinetic; potential
B) kinetic; potential; kinetic
C) heat; kinetic; heat
D) heat; potential; heat
Answer: B
Topic: Section 6.2
Skill: Knowledge/Comprehension
11) Which of the following accurately describes energy?
A) something that can cause movement
B) something that produces heat
C) something that has the capacity to do work
D) something that must be eaten
E) something that provides sunlight
Answer: C
Topic: Section 6.2
Skill: Knowledge/Comprehension
12) The first law of thermodynamics states that:
A) energy is required to bring molecules into a cell against a concentration gradient.
B) in energy-yielding reactions, matter goes from a more-ordered to a less-ordered state.
C) energy can be neither created nor destroyed.
D) all living organisms must eat to derive energy.
Answer: C
Topic: Section 6.2
Skill: Knowledge/Comprehension
13) The second law of thermodynamics states that:
A) energy is required to bring molecules into a cell against a concentration gradient.
B) energy can be neither created nor destroyed.
C) all living organisms must eat to derive energy.
D) in energy-yielding reactions, matter goes from a more-ordered to a less-ordered state.
Answer: D
Topic: Section 6.2
Skill: Knowledge/Comprehension
14) What percentage of the energy stored in glucose do humans recover by cellular respiration?
A) 100 percent
B) 48 percent
C) 52 percent
D) 37 percent
E) 15 percent
Answer: D
Topic: Section 6.2
Skill: Knowledge/Comprehension
15) During photosynthesis, plants use light energy to synthesize glucose from carbon dioxide. However, plants do not use up energy during photosynthesis; they merely convert it from light energy to chemical energy. This is an illustration of:
A) spontaneous reaction.
B) chemical equilibrium.
C) the second law of thermodynamics.
D) the first law of thermodynamics.
E) increasing entropy.
Answer: D
Topic: Section 6.2
Skill: Knowledge/Comprehension
16) Energy present in a system that is not usable to do work relates to the system's:
A) thermodynamics.
B) equilibrium.
C) work.
D) entropy.
E) temperature.
Answer: D
Topic: Section 6.2
Skill: Knowledge/Comprehension
17) Which of the following is true of energy?
A) It can be stored in chemical bonds.
B) It can be released by forming chemical bonds.
C) It can be transferred from one form to another with 100 percent efficiency.
D) It can be created from nothing.
Answer: A
Topic: Section 6.2
Skill: Knowledge/Comprehension
18) Which of the following is endergonic?
A) cells breaking down glucose into CO2
B) the burning of wood
C) the digestion of proteins in the stomach
D) breaking bonds in starch to produce glucose
E) the synthesis of glucose from carbon dioxide and water
Answer: E
Topic: Section 6.3
Skill: Application/Analysis
19) Which of the following is exergonic?
A) bringing glucose molecules together to form glycogen
B) plants producing glucose from CO2
C) bringing amino acids together to form proteins
D) cells breaking down glucose into CO2
Answer: D
Topic: Section 6.3
Skill: Application/Analysis
20) In the reaction glucose + oxygen → carbon dioxide + heat, the:
A) products have more potential energy than the reactants.
B) products have less potential energy than the reactants.
C) products have the same amount of potential energy as the reactants.
D) entropy has decreased.
Answer: B
Topic: Section 6.3
Skill: Application/Analysis
21) Coupled reactions are:
A) reactions in which endergonic reactions obtain the energy to go forward from exergonic reactions.
B) reactions in which exergonic reactions obtain the energy to go forward from endergonic reactions.
C) any reactions that are accelerated by an enzyme.
D) reactions that lower the activation energy of another reaction.
Answer: A
Topic: Section 6.3
Skill: Knowledge/Comprehension
22) The energy released during ________ reactions can be used to drive ________ reactions, and this is called ________ reactions.
A) endergonic; exergonic; coupled
B) exergonic; endergonic; coupled
C) endergonic; exergonic; mutually dependent
D) exergonic; endergonic; mutually dependent
Answer: B
Topic: Section 6.3
Skill: Knowledge/Comprehension
23) What is the energy currency of cells?
A) ATP
B) glucose
C) enzymes
D) ADP
E) vitamins
Answer: A
Topic: Section 6.4
Skill: Knowledge/Comprehension
24) In the ATP/ADP cycle:
A) food provides the energy needed to link phosphate to ADP to make ATP.
B) food provides the energy needed to break down ATP into ADP.
C) converting ADP into ATP is an energy-yielding reaction, whereas converting ATP into ADP is an energy-requiring reaction.
D) after powering a reaction, ADP becomes ATP.
Answer: A
Topic: Section 6.4
Skill: Knowledge/Comprehension
25) The structure of ATP includes each of the following except:
A) the nitrogenous base adenosine.
B) the sugar ribose.
C) the nitrogenous base adenine.
D) phosphate groups.
Answer: A
Topic: Section 6.4
Skill: Knowledge/Comprehension
26) In the following reaction, which of the following is an example of a substrate?
Lactase
Lactose → Glucose + Galactose
A) galactose
B) glucose
C) lactose
D) lactase
Answer: C
Topic: Section 6.5
Skill: Knowledge/Comprehension
27) The substance that is worked on by an enzyme is called:
A) product.
B) coenzyme.
C) inhibitor.
D) substrate.
Answer: D
Topic: Section 6.5
Skill: Knowledge/Comprehension
28) You have a friend who tells you she is lactose intolerant. She asks you to explain what this means. You say to her:
A) "You cannot digest milk because you cannot absorb it in your intestines."
B) "You are allergic to milk."
C) "You cannot digest milk because you do not have the enzyme to break down the sugar in the milk."
D) "You cannot digest the milk because you do not have the enzyme to break down the protein in the milk."
E) "You cannot digest the milk because you do not have the enzyme to break down the lipid in the milk."
Answer: C
Topic: Section 6.5
Skill: Knowledge/Comprehension
29) The diversity of chemical reactions occurring in a cell depends mostly on certain molecules present in the cells, which are called:
A) enzymes.
B) proteins.
C) cofactors.
D) coenzymes.
E) ribozymes.
Answer: A
Topic: Section 6.5
Skill: Knowledge/Comprehension
30) In a ________, multiple enzymes are working together in a multistep process.
A) feedback loop
B) coupled reaction
C) allosteric pathway
D) metabolic pathway
Answer: D
Topic: Section 6.5
Skill: Knowledge/Comprehension
31) Metabolism is the sum of all the:
A) ATP a cell contains.
B) energy a cell uses.
C) chemical reactions that a cell carries out.
D) vitamins a cell contains.
E) enzymes a cell contains.
Answer: C
Topic: Section 6.5
Skill: Knowledge/Comprehension
32) Enzymes work to speed up a chemical reaction by:
A) supplying the energy needed for the reaction.
B) increasing the activation energy of the reaction.
C) lowering the activation energy of the reaction.
D) attaching coenzymes to the substrate.
E) heating up the substrate.
Answer: C
Topic: Section 6.6
Skill: Knowledge/Comprehension
33) Some enzymes contain molecules in the active site that help facilitate chemical transformations. These molecules are called:
A) coenzymes.
B) products.
C) substrates.
D) co-substrates.
Answer: A
Topic: Section 6.6
Skill: Knowledge/Comprehension
34) Gasoline will not burn in your car's engine unless it is ignited with a spark from a sparkplug. In this situation, the spark is providing:
A) activation energy.
B) hydrolytic energy.
C) coenzyme energy.
D) enzymatic energy.
E) entropy.
Answer: A
Topic: Section 6.6
Skill: Application/Analysis
35) What makes an enzyme a catalyst?
A) its ability to change shape to fit the substrate
B) it speeds up a chemical reaction but can only be used once
C) it speeds up a chemical reaction but becomes changed by the reaction
D) it speeds up a chemical reaction but is not changed by the reaction
E) its amino acids
Answer: D
Topic: Section 6.6
Skill: Knowledge/Comprehension
36) Most enzymes are:
A) proteins.
B) nucleic acids.
C) lipids.
D) vitamins.
E) carbohydrates.
Answer: A
Topic: Section 6.6
Skill: Knowledge/Comprehension
37) Which of the following statements concerning enzymes is false?
A) They function as catalysts.
B) The active site of an enzyme has a shape that is specific for its given substrate.
C) They increase the activation energy required for chemical reactions to proceed.
D) Many enzymes utilize coenzymes, such as vitamins.
Answer: C
Topic: Section 6.6
Skill: Knowledge/Comprehension
38) Which would be an example of a catalyst in action?
A) a glycoprotein binding to a cell
B) a protein converting glucose and fructose into sucrose without being changed itself
C) glucose and galactose binding to form lactose
D) a phosphate group attached to a protein changing its shape
Answer: B
Topic: Section 6.6
Skill: Application/Analysis
39) Coenzymes:
A) serve as catalysts.
B) make proteins.
C) help enzymes to function.
D) break down sugars.
Answer: C
Topic: Section 6.6
Skill: Knowledge/Comprehension
40) Which of the following statements concerning enzymes is false?
A) They accelerate the rate of chemical reactions.
B) Many activities in living organisms require multiple enzymes.
C) One enzyme will work on many different substrate molecules to produce many different products.
D) They can carry out hundreds of chemical transformations per second.
Answer: C
Topic: Section 6.6
Skill: Knowledge/Comprehension
41) Where do substrates bind to enzymes?
A) in the active site
B) anywhere
C) in the substrate groove
D) in the effector site
Answer: A
Topic: Section 6.6
Skill: Knowledge/Comprehension
42) Which of the following is true of vitamins?
A) They serve as a major energy source for cells.
B) They are the main component of enzymes.
C) They can serve as enzymes.
D) They can serve as coenzymes.
Answer: D
Topic: Section 6.6
Skill: Knowledge/Comprehension
43) The function of chymotrypsin is to:
A) break down proteins into amino acids.
B) synthesize glycogen.
C) synthesize proteins.
D) break down glycogen into glucose.
Answer: A
Topic: Section 6.6
Skill: Knowledge/Comprehension
44) Which of the following describes a transition state molecule?
A) the distorted shape the product takes while being released from the enzyme
B) the distorted shape the substrate takes when being converted by an enzyme into product
C) the distorted shape the enzyme takes when converting substrate into product
D) the distorted shape a coenzyme takes while it is bound to an enzyme
Answer: B
Topic: Section 6.6
Skill: Knowledge/Comprehension
45) Methyl alcohol, also known as wood alcohol, is a common solvent and paint remover. It is poisonous if accidentally swallowed. The enzyme alcohol dehydrogenase in the liver converts methyl alcohol into formaldehyde, which then gets converted into a toxic product. Grain alcohol, ethyl alcohol, is also acted upon by alcohol dehydrogenase. One antidote for methyl alcohol poisoning is to make a person drink a lot of ethyl alcohol. This blocks the active site of the enzyme so that it can't bind to and break down the methyl alcohol. In this capacity, the ethyl alcohol is acting as a/an:
A) allosteric regulator.
B) coenzyme.
C) competitive inhibtor.
D) precursor.
Answer: C
Topic: Section 6.7
Skill: Application/Analysis
46) People with high cholesterol levels often take drugs in an attempt to lower their cholesterol levels. One such drug is Lipitor. How does this drug work?
A) It enhances the activity of enzymes that help break down cholesterol in the body.
B) It prevents cholesterol from the diet from being absorbed in the small intestine.
C) It acts as a competitive inhibitor by binding to the active site of enzymes that normally produce cholesterol.
D) It increases the activation energy of enzymes needed to produce cholesterol.
Answer: C
Topic: Section 6.7
Skill: Knowledge/Comprehension
47) What mechanism is used to finely tune enzyme activity according to the needs of the cell?
A) competitive inhibition
B) coupled reactions
C) enzyme specificity
D) allosteric regulation
Answer: D
Topic: Section 6.7
Skill: Application/Analysis
48) Which of the following is true of allosteric enzymes?
A) Their activity can be reduced when the product binds the enzyme.
B) Their activity can be reduced when the substrate binds the enzyme.
C) Their coenzyme is removed when the product binds the enzyme.
D) Their activity can be increased by competitive inhibitors.
Answer: A
Topic: Section 6.7
Skill: Knowledge/Comprehension
49) Why is allosteric regulation important to a cell?
A) It allows the cell to control how much of a metabolic product is produced.
B) It allows the cell to switch to other sources of energy besides ATP.
C) It reduces the cell's need for coenzymes.
D) It allows the cell to control how much activation energy is required for enzymatic reactions.
Answer: A
Topic: Section 6.7
Skill: Application/Analysis
50) In allosteric enzyme regulation, which of the following is false about the molecules that can inhibit enzyme activity?
A) They can cause the active site to have a poor shape for binding substrate.
B) They can increase substrate binding.
C) They cause a change in the enzyme's shape.
D) They can bind to a site other than the active site.
Answer: B
Topic: Section 6.7
Skill: Knowledge/Comprehension
51) When a product binds to an allosteric enzyme to slow its reaction, it does which of the following?
A) binds to the active site, blocking the binding of substrate
B) binds to a site other than the active site, changing the shape of the active site and decreasing the binding of substrate
C) binds to the substrate, blocking its binding of the active site
D) binds to the product production site, stopping the production of product
Answer: B
Topic: Section 6.7
Skill: Knowledge/Comprehension
52) It is possible for a cell to harvest 100 percent of the energy from a chemical reaction to produce movement.
Answer: FALSE
Topic: Section 6.2
Skill: Knowledge/Comprehension
53) Endergonic reactions release energy.
Answer: FALSE
Topic: Section 6.3
Skill: Knowledge/Comprehension
54) Cells can harvest the energy released during exergonic reactions to drive endergonic reactions.
Answer: TRUE
Topic: Section 6.3
Skill: Knowledge/Comprehension
55) Only eukaryotic cells depend on ATP.
Answer: FALSE
Topic: Section 6.4
Skill: Knowledge/Comprehension
56) Given enough time, sucrose can spontaneously break down into fructose and glucose in a glass of water.
Answer: TRUE
Topic: Section 6.5
Skill: Application/Analysis
57) Enzymes themselves are altered in the process of catalyzing chemical transformations.
Answer: FALSE
Topic: Section 6.6
Skill: Knowledge/Comprehension
58) Enzymes increase the activation energy needed for a particular reaction.
Answer: FALSE
Topic: Section 6.6
Skill: Knowledge/Comprehension
59) Allosteric regulation depends on inhibitors binding to the active site of enzymes.
Answer: FALSE
Topic: Section 6.7
Skill: Knowledge/Comprehension
Match the following.
A) thermodynamics
B) coupled reaction
C) endergonic reaction
D) exergonic reaction
E) bioenergetics
F) activation energy
G) ATP
60) Links the study of energy to life
Topic: Section 6.2
Skill: Knowledge/Comprehension
61) The study of energy
Topic: Section 6.2
Skill: Knowledge/Comprehension
62) The breakdown of large molecules into smaller ones, with the release of energy
Topic: Section 6.3
Skill: Knowledge/Comprehension
63) The building of larger molecules, requiring energy
Topic: Section 6.3
Skill: Knowledge/Comprehension
64) Using the energy from the breakdown of molecules to fuel the construction of new molecules
Topic: Section 6.3
Skill: Knowledge/Comprehension
65) A source of chemical energy for metabolic processes
Topic: Section 6.4
Skill: Knowledge/Comprehension
66) The energy required to initiate a chemical reaction
Topic: Section 6.6
Skill: Knowledge/Comprehension
Answers: 60) E 61) A 62) D 63) C 64) B 65) G 66) F
67) The study of the thermodynamics of biology is known as ________.
Answer: bioenergetics
Topic: Section 6.2
Skill: Knowledge/Comprehension
68) A reaction that requires the input of energy to move forward is ________.
Answer: endergonic
Topic: Section 6.3
Skill: Knowledge/Comprehension
69) A ________ is a set of enzymatically controlled steps that results in the completion of a product or process in an organism.
Answer: metabolic pathway
Topic: Section 6.5
Skill: Knowledge/Comprehension
70) Molecules that facilitate the work of enzymes by binding with them are ________.
Answer: coenzymes
Topic: Section 6.6
Skill: Knowledge/Comprehension
71) The regulation of an enzyme's activity by means of a molecule binding to a site on the enzyme other than its active site is called ________.
Answer: allosteric regulation
Topic: Section 6.7
Skill: Knowledge/Comprehension
72) It has been hypothesized that, if the sun disappeared, all life would end. Other than the obvious drop in temperature, why would humans probably die if the sun suddenly stopped shining?
Answer: Plants provide us with both the oxygen we need for breathing and the energy we need to survive. Plants harvest the energy of the sun and produce sugars that we can eat in order to gain energy.
Topic: Section 6.1
Skill: Application/Analysis
73) You have been asked to explain to a high school class the first law of thermodynamics and how this law affects the students' lives. Using your own words, describe the first law of thermodynamics, and give an example (other than the examples described in the chapter).
Answer: The first law of thermodynamics explains that energy cannot be created but that it can change forms. There are many valid examples a student might give. Examples could include ones in which something must be converting one type of energy into another, such as the need of chemical energy for life processes, converting the energy in wind to generate electricity, etc.
Topic: Section 6.2
Skill: Application/Analysis
74) You have been asked to explain to a high school class the second law of thermodynamics and how this law affects the students' lives. Using your own words, describe the second law of thermodynamics, and give an example (other than the examples described in the chapter).
Answer: The second law of thermodynamics explains that all spontaneous reactions tend toward more disorder and that increasing order requires an input of energy. There are many valid examples a student might give. An example could be that heat will flow from a hot object to a cold object but not from cold to hot, because that would mean creating more disorder without adding more energy.
Topic: Section 6.2
Skill: Application/Analysis
75) A ripped piece of paper will never spontaneously repair itself. Explain the law of thermodynamics that explains why this is so.
Answer: According to the second law of thermodynamics, an intact piece of paper has more order than a ripped piece; therefore, fixing the ripped paper would require an input of energy.
Topic: Section 6.2
Skill: Application/Analysis
76) Explain why it takes energy to create starch from glucose, but it does not take energy to create glucose from starch. In your explanation, describe the law of thermodynamics that explains this, and describe how.
Answer: Creating starch requires energy because it involves adding more order to the system, thereby decreasing entropy. By the second law of thermodynamics, to decrease entropy requires energy.
Topic: Section 6.2
Skill: Application/Analysis
77) Would ATP be the energy currency of the cell if the phosphate groups the cell contains were not charged? Why or why not?
Answer: No, the negative charges on the phosphate groups repel each other, making these bonds unstable; therefore, these bonds will easily break and will release a lot of energy when they do.
Topic: Section 6.4
Skill: Knowledge/Comprehension
78) Explain why enzymes are involved in exergonic reactions, such as lactose breaking down into glucose and galactose, and whether these reactions can occur spontaneously.
Answer: Although these reactions are exergonic and therefore could occur spontaneously, they would take a very long time to occur. Enzymes accelerate the rates of these reactions.
Topic: Section 6.6
Skill: Knowledge/Comprehension
79) Individuals with the genetic disease phenylketonuria (PKU) lack a single enzyme called phenylalanine hydroxylase, which converts the amino acid phenylalanine to the amino acid tyrosine. If this conversion does not happen, phenylalanine builds up and becomes toxic to the central nervous system, causing serious problems for the individual. The management of this disease is to avoid phenylalanine by severely limiting the amount of protein in the diet. How would this help?
Answer: Because phenylalanine is an amino acid, avoiding protein will limit the amount of phenylalanine the body takes in. If phenylalanine does not build up, the phenylalanine hydroxylase enzyme is not needed.
Topic: Section 6.5
Skill: Application/Analysis
80) Explain how vitamins play a role in cellular metabolism.
Answer: Vitamins are important coenzymes that help enzymes carry out many cellular functions.
Topic: Section 6.6
Skill: Knowledge/Comprehension
81) Phosphofructokinase is an enzyme involved in glycolysis, which is a metabolic pathway involved in ATP production. It can be allosterically regulated by both ATP and ADP. Why is regulating the activity of this enzyme important? Predict what will happen to the rate of reaction when ATP levels in the cell are high, and predict what will happen when the levels of ADP in the cell are high.
Answer: When ATP levels in the cell are high, the cell no longer needs to make more ATP, so ATP binds to and shuts down the enzyme. If there is a lot of ADP around, that means energy levels in the cell are low, and the binding of ADP increases enzyme activity, so more ATP is made.