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Student Solution Manual
Chapter 1
1 Figure 1.6 1: C; 2: F; 3: A; 4: B; 5: D; 6: E. The original hypothesis is incorrect, as the coffeemaker works when
plugged into the outlet. Alternative hypotheses include that the toaster might be broken or that the toaster wasn't turned
on. 3 Figure 1.16 Communities exist within populations which exist within ecosystems. 4 B 6 D 8 C 10 C 12 B 14
D 16 Answers will vary, but should apply the steps of the scientific method. One possibility could be a car which
doesn’t start. The hypothesis could be that the car doesn’t start because the battery is dead. The experiment would be
to change the battery or to charge the battery and then check whether the car starts or not. If it starts, the problem was
due to the battery, and the hypothesis is accepted. 18 Answers will vary. Topics that fall inside the area of biological
study include how diseases affect human bodies, how pollution impacts a species’ habitat, and how plants respond
to their environments. Topics that fall outside of biology (the “study of life”) include how metamorphic rock is formed
and how planetary orbits function. 20 Answers will vary. Layers of sedimentary rock have order but are not alive.
Technology is capable of regulation but is not, of itself, alive. 22 During your walk, you may begin to perspire, which
cools your body and helps your body to maintain a constant internal temperature. You might also become thirsty and
pause long enough for a cool drink, which will help to restore the water lost during perspiration.
Chapter 2
1 Figure 2.3 Carbon-12 has six neutrons. Carbon-13 has seven neutrons. 3 Figure 2.24 C 4 A 6 C 8 D 10
C 12 D 14 Ionic bonds are created between ions. The electrons are not shared between the atoms, but rather are
associated more with one ion than the other. Ionic bonds are strong bonds, but are weaker than covalent bonds,
meaning it takes less energy to break an ionic bond compared with a covalent one. 16 Buffers absorb the free
hydrogen ions and hydroxide ions that result from chemical reactions. Because they can bond these ions, they
prevent increases or decreases in pH. An example of a buffer system is the bicarbonate system in the human body.
This system is able to absorb hydrogen and hydroxide ions to prevent changes in pH and keep cells functioning
properly. 18 Carbon is unique and found in all living things because it can form up to four covalent bonds between
atoms or molecules. These can be nonpolar or polar covalent bonds, and they allow for the formation of long chains of
carbon molecules that combine to form proteins and DNA.
Chapter 3
1 Figure 3.5 Glucose and galactose are aldoses. Fructose is a ketose. 3 Figure 3.33 Adenine is larger than cytosine
and will not be able to base pair properly with the guanine on the opposing strand. This will cause the DNA to bulge.
DNA repair enzymes may recognize the bulge and replace the incorrect nucleotide. 4 C 6 A 8 D 10 B 12 D 14
C 16 B 18 C 20 C 21 Biological macromolecules are organic because they contain carbon. 23 Amino acids can
be linked into long chains through condensation reactions. One of the hydrogen atoms bonded to the nitrogen atom
of an amino acid reacts with the –OH group attached to the terminal carbon on another amino acid. Since both ends
of the molecule can participate in condensation reactions, peptide bonds can be made in both directions to create
a long amino acid chain. 25 The β 1-4 glycosidic linkage in cellulose cannot be broken down by human digestive
enzymes. Herbivores such as cows, koalas, and buffalos are able to digest grass that is rich in cellulose and use it as
a food source because bacteria and protists in their digestive systems, especially in the rumen, secrete the enzyme
cellulase. Cellulases can break down cellulose into glucose monomers that can be used as an energy source by
the animal. 27 Fat serves as a valuable way for animals to store energy. It can also provide insulation. Waxes can
protect plant leaves and mammalian fur from getting wet. Phospholipids and steroids are important components of
animal cell membranes, as well as plant, fungal, and bacterial membranes. 29 Fats have a higher energy density
than carbohydrates (averaging 9kcal/gram versus 4.3kcal/gram respectively). Thus, on a per gram basis, more energy
can be stored in fats than can be stored in carbohydrates. Additionally, fats are packaged into spherical globules
to minimize interactions with the water-based plasma membrane, while glycogen is a large branched carbohydrate
that cannot be compacted for storage. 31 A change in gene sequence can lead to a different amino acid being
added to a polypeptide chain instead of the normal one. This causes a change in protein structure and function.
For example, in sickle cell anemia, the hemoglobin β chain has a single amino acid substitution—the amino acid
glutamic acid in position six is substituted by valine. Because of this change, hemoglobin molecules form aggregates,
and the disc-shaped red blood cells assume a crescent shape, which results in serious health problems. 33 The
protein must form a channel in the plasma membrane that allows water into the cell since water cannot cross the
plasma membrane by itself. Since aquaporins are embedded in the plasma membrane and connect with both the
intracellular and extracellular spaces, it must be amphipathic like the plasma membrane. The top and bottom of the
protein must contain charged or polar amino acids (hydrophilic) to interact with the aqueous environments. The exterior
transmembrane region must contain non-polar amino acids (hydrophobic) that can interact with the phospholipid tails.
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However, the inside of this channel must contain hydrophilic amino acids since they will interact with the traveling water
molecules. 35 The four types of RNA are messenger RNA, ribosomal RNA, transfer RNA, and microRNA. Messenger
RNA carries the information from the DNA that controls all cellular activities. The mRNA binds to the ribosomes that are
constructed of proteins and rRNA, and tRNA transfers the correct amino acid to the site of protein synthesis. microRNA
regulates the availability of mRNA for translation.
Chapter 4
1 Figure 4.7 Substances can diffuse more quickly through small cells. Small cells have no need for organelles and
therefore do not need to expend energy getting substances across organelle membranes. Large cells have organelles
that can separate cellular processes, enabling them to build molecules that are more complex. 3 Figure 4.18 It would
end up on the outside. After the vesicle passes through the Golgi apparatus and fuses with the plasma membrane, it
turns inside out. 4 C 6 D 8 D 10 B 12 D 14 A 16 C 18 D 20 D 22 C 24 D 25 A light microscope would be ideal
when viewing a small living organism, especially when the cell has been stained to reveal details. 27 A transmission
electron microscope would be ideal for viewing the cell’s internal structures, because many of the internal structures
have membranes that are not visible by the light microscope. 29 The cell theory states: All living things are
made of cells.;Cells are the most basic unit of life.;New cells arise from existing cells. All humans are multicellular
organisms whose smallest building blocks are cells. Adult humans begin with the fusion of a male gamete cell with
a female gamete cell to form a fertilized egg (single cell). That cell then divides into two cells, which each divides
into two more cells, and so forth until all the cells of a human embryo are made. As the embryo passes through all
the developmental stages to make an adult human, the cells that are added arise from division of existing cells. 31
Some microbes are beneficial. For instance, E. coli bacteria populate the human gut and help break down fiber in
the diet. Some foods such as yogurt are formed by bacteria. 33 Both are similar in that they are enveloped in a
double membrane, both have an intermembrane space, and both make ATP. Both mitochondria and chloroplasts have
DNA, and mitochondria have inner folds called cristae and a matrix, while chloroplasts have chlorophyll and accessory
pigments in the thylakoids that form stacks (grana) and a stroma. 35 “Form follows function” refers to the idea that the
function of a body part dictates the form of that body part. As an example, compare your arm to a bat’s wing. While
the bones of the two correspond, the parts serve different functions in each organism and their forms have adapted
to follow that function. 37 Centrioles and flagella are alike in that they are made up of microtubules. In centrioles, two
rings of nine microtubule “triplets” are arranged at right angles to one another. This arrangement does not occur in
flagella. 39 A macrophage engulfs a pathogen by rearranging its actin microfilaments to bend the plasma membrane
around the pathogen. Once the pathogen is sealed in an endosome inside the macrophage, the vesicle is walked
along microtubules until it combines with a lysosome to digest the pathogen. 41 They differ because plant cell walls
are rigid. Plasmodesmata, which a plant cell needs for transportation and communication, are able to allow movement
of really large molecules. Gap junctions are necessary in animal cells for transportation and communication. 43 E. coli
infections generally cause food poisoning, meaning that the invading bacteria cross from the lumen of the gut into the
rest of the body. Tight junctions hold the epithelial layer that lines the digestive tract together so that the material that
crosses into the body is tightly regulated. One way E. coli can avoid this regulation is to destroy the tight junctions so
that it can enter the body between the epithelial cells, rather than having to go through the cells.
Chapter 5
1 Figure 5.12 No, it must have been hypotonic as a hypotonic solution would cause water to enter the cells, thereby
making them burst. 3 Figure 5.19 A decrease in pH means an increase in positively charged H+ ions, and an increase
in the electrical gradient across the membrane. The transport of amino acids into the cell will increase. 4 A 6 A 8
C 10 A 12 D 14 D 16 B 18 C 20 B 21 The fluid characteristic of the cell membrane allows greater flexibility to
the cell than it would if the membrane were rigid. It also allows the motion of membrane components, required for
some types of membrane transport. 23 Peripheral proteins can bind to other molecules in the extracellular space.
However, they cannot directly transmit a signal to the inside of the cell since they do not have a transmembrane domain
(region that goes through the plasma membrane to the inside of the cell). They must associate with integral membrane
proteins in order to pass the signal to the inside of the cell. 25 Water moves through a membrane in osmosis because
there is a concentration gradient across the membrane of solute and solvent. The solute cannot effectively move to
balance the concentration on both sides of the membrane, so water moves to achieve this balance. 27 Decreasing
temperature will decrease the kinetic energy in the system. A lower temperature means less energy in the molecules,
so they will move at a slower speed. Lowering temperature also decreases the kinetic energy of the molecules in
the plasma membrane, compressing them together. This increases the density of the plasma membrane, which slows
diffusion into the cell. 29 The cell harvests energy from ATP produced by its own metabolism to power active transport
processes, such as the activity of pumps. 31 Intestinal epithelial cells use active transport to fulfill their specific role as
the cells that transfer glucose from the digested food to the bloodstream. Intestinal cells are exposed to an environment
with fluctuating glucose levels. Immediately after eating, glucose in the gut lumen will be high, and could accumulate
in intestinal cells by diffusion. However, when the gut lumen is empty, glucose levels are higher in the intestinal cells. If
glucose moved by facilitated diffusion, this would cause glucose to flow back out of the intestinal cells and into the gut.
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Active transport proteins ensure that glucose moves into the intestinal cells, and cannot move back into the gut. It also
ensures that glucose transport continues to occur even if high levels of glucose are already present in the intestinal
cells. This maximizes the amount of energy the body can harvest from food. 33 The proteins allow a cell to select
what compound will be transported, meeting the needs of the cell and not bringing in anything else.
Chapter 6
1 Figure 6.8 A compost pile decomposing is an exergonic process; enthalpy increases (energy is released) and
entropy increases (large molecules are broken down into smaller ones). A baby developing from a fertilized egg is
an endergonic process; enthalpy decreases (energy is absorbed) and entropy decreases. Sand art being destroyed
is an exergonic process; there is no change in enthalpy, but entropy increases. A ball rolling downhill is an exergonic
process; enthalpy decreases (energy is released), but there is no change in entropy. 3 Figure 6.14 Three sodium ions
could be moved by the hydrolysis of one ATP molecule. The ∆G of the coupled reaction must be negative. Movement
of three sodium ions across the membrane will take 6.3 kcal of energy (2.1 kcal × 3 Na+ ions = 6.3 kcal). Hydrolysis of
ATP provides 7.3 kcal of energy, more than enough to power this reaction. Movement of four sodium ions across the
membrane, however, would require 8.4 kcal of energy, more than one ATP molecule can provide. 4 C 6 C 8 B 10
A 12 A 14 C 16 Physical exercise involves both anabolic and catabolic processes. Body cells break down sugars
to provide ATP to do the work necessary for exercise, such as muscle contractions. This is catabolism. Muscle cells
also must repair muscle tissue damaged by exercise by building new muscle. This is anabolism. 18 A spontaneous
reaction is one that has a negative ∆G and thus releases energy. However, a spontaneous reaction need not occur
quickly or suddenly like an instantaneous reaction. It may occur over long periods due to a large energy of activation,
which prevents the reaction from occurring quickly. 20 The ant farm had lower entropy before the earthquake because
it was a highly ordered system. After the earthquake, the system became much more disordered and had higher
entropy. 22 The activation energy for hydrolysis is very low. Not only is ATP hydrolysis an exergonic process with a
large −∆G, but ATP is also a very unstable molecule that rapidly breaks down into ADP + Pi if not utilized quickly. This
suggests a very low EA since it hydrolyzes so quickly. 24 Feedback inhibition allows cells to control the amounts of
metabolic products produced. If there is too much of a particular product relative to the cell’s needs, feedback inhibition
effectively causes the cell to decrease production of that particular product. In general, this reduces the production of
superfluous products and conserves energy, maximizing energy efficiency.
Chapter 7
1 Figure 7.11 After DNP poisoning, the electron transport chain can no longer form a proton gradient, and ATP
synthase can no longer make ATP. DNP is an effective diet drug because it uncouples ATP synthesis; in other words,
after taking it, a person obtains less energy out of the food he or she eats. Interestingly, one of the worst side effects of
this drug is hyperthermia, or overheating of the body. Since ATP cannot be formed, the energy from electron transport
is lost as heat. 3 Figure 7.14 The illness is caused by lactate accumulation. Lactate levels rise after exercise, making
the symptoms worse. Milk sickness is rare today but was common in the midwestern United States in the early
1800s. 4 A 6 C 8 B 10 C 12 C 14 A 16 A 18 ATP provides the cell with a way to handle energy in an efficient
manner. The molecule can be charged, stored, and used as needed. Moreover, the energy from hydrolyzing ATP
is delivered as a consistent amount. Harvesting energy from the bonds of several different compounds would result
in energy deliveries of different quantities. 20 All cells must consume energy to carry out basic functions, such as
pumping ions across membranes. A red blood cell would lose its membrane potential if glycolysis were blocked, and
it would eventually die. 22 Q and cytochrome c are transport molecules. Their function does not result directly in ATP
synthesis in that they are not pumps. Moreover, Q is the only component of the electron transport chain that is not
a protein. Ubiquinone and cytochrome c are small, mobile electron carriers, whereas the other components of the
electron transport chain are large complexes anchored in the inner mitochondrial membrane. 24 Fermentation uses
glycolysis only. Anaerobic respiration uses all three parts of cellular respiration, including the parts in the mitochondria
like the citric acid cycle and electron transport; it also uses a different final electron acceptor instead of oxygen gas. 26
Citrate can inhibit phosphofructokinase by feedback regulation.
Chapter 8
1 Figure 8.6 Levels of carbon dioxide (a necessary photosynthetic substrate) will immediately fall. As a result, the rate
of photosynthesis will be inhibited. 3 Figure 8.18 D 4 A 6 B 8 B 10 A 12 C 14 A 16 D 18 C 20 C 21 The
outcome of light reactions in photosynthesis is the conversion of solar energy into chemical energy that the chloroplasts
can use to do work (mostly anabolic production of carbohydrates from carbon dioxide). 23 The energy carriers that
move from the light-dependent reaction to the light-independent one are “full” because they bring energy. After the
energy is released, the “empty” energy carriers return to the light-dependent reaction to obtain more energy. There
is not much actual movement involved. Both ATP and NADPH are produced in the stroma where they are also used
and reconverted into ADP, Pi, and NADP+. 25 The stomata regulate the exchange of gases and water vapor between
a leaf and its surrounding environment. When the stomata are closed, the water molecules cannot escape the leaf,
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Student Solution Manual
Chapter 1
1 Figure 1.6 1: C; 2: F; 3: A; 4: B; 5: D; 6: E. The original hypothesis is incorrect, as the coffeemaker works when
plugged into the outlet. Alternative hypotheses include that the toaster might be broken or that the toaster wasn't turned
on. 3 Figure 1.16 Communities exist within populations which exist within ecosystems. 4 B 6 D 8 C 10 C 12 B 14
D 16 Answers will vary, but should apply the steps of the scientific method. One possibility could be a car which
doesn’t start. The hypothesis could be that the car doesn’t start because the battery is dead. The experiment would be
to change the battery or to charge the battery and then check whether the car starts or not. If it starts, the problem was
due to the battery, and the hypothesis is accepted. 18 Answers will vary. Topics that fall inside the area of biological
study include how diseases affect human bodies, how pollution impacts a species’ habitat, and how plants respond
to their environments. Topics that fall outside of biology (the “study of life”) include how metamorphic rock is formed
and how planetary orbits function. 20 Answers will vary. Layers of sedimentary rock have order but are not alive.
Technology is capable of regulation but is not, of itself, alive. 22 During your walk, you may begin to perspire, which
cools your body and helps your body to maintain a constant internal temperature. You might also become thirsty and
pause long enough for a cool drink, which will help to restore the water lost during perspiration.
Chapter 2
1 Figure 2.3 Carbon-12 has six neutrons. Carbon-13 has seven neutrons. 3 Figure 2.24 C 4 A 6 C 8 D 10
C 12 D 14 Ionic bonds are created between ions. The electrons are not shared between the atoms, but rather are
associated more with one ion than the other. Ionic bonds are strong bonds, but are weaker than covalent bonds,
meaning it takes less energy to break an ionic bond compared with a covalent one. 16 Buffers absorb the free
hydrogen ions and hydroxide ions that result from chemical reactions. Because they can bond these ions, they
prevent increases or decreases in pH. An example of a buffer system is the bicarbonate system in the human body.
This system is able to absorb hydrogen and hydroxide ions to prevent changes in pH and keep cells functioning
properly. 18 Carbon is unique and found in all living things because it can form up to four covalent bonds between
atoms or molecules. These can be nonpolar or polar covalent bonds, and they allow for the formation of long chains of
carbon molecules that combine to form proteins and DNA.
Chapter 3
1 Figure 3.5 Glucose and galactose are aldoses. Fructose is a ketose. 3 Figure 3.33 Adenine is larger than cytosine
and will not be able to base pair properly with the guanine on the opposing strand. This will cause the DNA to bulge.
DNA repair enzymes may recognize the bulge and replace the incorrect nucleotide. 4 C 6 A 8 D 10 B 12 D 14
C 16 B 18 C 20 C 21 Biological macromolecules are organic because they contain carbon. 23 Amino acids can
be linked into long chains through condensation reactions. One of the hydrogen atoms bonded to the nitrogen atom
of an amino acid reacts with the –OH group attached to the terminal carbon on another amino acid. Since both ends
of the molecule can participate in condensation reactions, peptide bonds can be made in both directions to create
a long amino acid chain. 25 The β 1-4 glycosidic linkage in cellulose cannot be broken down by human digestive
enzymes. Herbivores such as cows, koalas, and buffalos are able to digest grass that is rich in cellulose and use it as
a food source because bacteria and protists in their digestive systems, especially in the rumen, secrete the enzyme
cellulase. Cellulases can break down cellulose into glucose monomers that can be used as an energy source by
the animal. 27 Fat serves as a valuable way for animals to store energy. It can also provide insulation. Waxes can
protect plant leaves and mammalian fur from getting wet. Phospholipids and steroids are important components of
animal cell membranes, as well as plant, fungal, and bacterial membranes. 29 Fats have a higher energy density
than carbohydrates (averaging 9kcal/gram versus 4.3kcal/gram respectively). Thus, on a per gram basis, more energy
can be stored in fats than can be stored in carbohydrates. Additionally, fats are packaged into spherical globules
to minimize interactions with the water-based plasma membrane, while glycogen is a large branched carbohydrate
that cannot be compacted for storage. 31 A change in gene sequence can lead to a different amino acid being
added to a polypeptide chain instead of the normal one. This causes a change in protein structure and function.
For example, in sickle cell anemia, the hemoglobin β chain has a single amino acid substitution—the amino acid
glutamic acid in position six is substituted by valine. Because of this change, hemoglobin molecules form aggregates,
and the disc-shaped red blood cells assume a crescent shape, which results in serious health problems. 33 The
protein must form a channel in the plasma membrane that allows water into the cell since water cannot cross the
plasma membrane by itself. Since aquaporins are embedded in the plasma membrane and connect with both the
intracellular and extracellular spaces, it must be amphipathic like the plasma membrane. The top and bottom of the
protein must contain charged or polar amino acids (hydrophilic) to interact with the aqueous environments. The exterior
transmembrane region must contain non-polar amino acids (hydrophobic) that can interact with the phospholipid tails.
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However, the inside of this channel must contain hydrophilic amino acids since they will interact with the traveling water
molecules. 35 The four types of RNA are messenger RNA, ribosomal RNA, transfer RNA, and microRNA. Messenger
RNA carries the information from the DNA that controls all cellular activities. The mRNA binds to the ribosomes that are
constructed of proteins and rRNA, and tRNA transfers the correct amino acid to the site of protein synthesis. microRNA
regulates the availability of mRNA for translation.
Chapter 4
1 Figure 4.7 Substances can diffuse more quickly through small cells. Small cells have no need for organelles and
therefore do not need to expend energy getting substances across organelle membranes. Large cells have organelles
that can separate cellular processes, enabling them to build molecules that are more complex. 3 Figure 4.18 It would
end up on the outside. After the vesicle passes through the Golgi apparatus and fuses with the plasma membrane, it
turns inside out. 4 C 6 D 8 D 10 B 12 D 14 A 16 C 18 D 20 D 22 C 24 D 25 A light microscope would be ideal
when viewing a small living organism, especially when the cell has been stained to reveal details. 27 A transmission
electron microscope would be ideal for viewing the cell’s internal structures, because many of the internal structures
have membranes that are not visible by the light microscope. 29 The cell theory states: All living things are
made of cells.;Cells are the most basic unit of life.;New cells arise from existing cells. All humans are multicellular
organisms whose smallest building blocks are cells. Adult humans begin with the fusion of a male gamete cell with
a female gamete cell to form a fertilized egg (single cell). That cell then divides into two cells, which each divides
into two more cells, and so forth until all the cells of a human embryo are made. As the embryo passes through all
the developmental stages to make an adult human, the cells that are added arise from division of existing cells. 31
Some microbes are beneficial. For instance, E. coli bacteria populate the human gut and help break down fiber in
the diet. Some foods such as yogurt are formed by bacteria. 33 Both are similar in that they are enveloped in a
double membrane, both have an intermembrane space, and both make ATP. Both mitochondria and chloroplasts have
DNA, and mitochondria have inner folds called cristae and a matrix, while chloroplasts have chlorophyll and accessory
pigments in the thylakoids that form stacks (grana) and a stroma. 35 “Form follows function” refers to the idea that the
function of a body part dictates the form of that body part. As an example, compare your arm to a bat’s wing. While
the bones of the two correspond, the parts serve different functions in each organism and their forms have adapted
to follow that function. 37 Centrioles and flagella are alike in that they are made up of microtubules. In centrioles, two
rings of nine microtubule “triplets” are arranged at right angles to one another. This arrangement does not occur in
flagella. 39 A macrophage engulfs a pathogen by rearranging its actin microfilaments to bend the plasma membrane
around the pathogen. Once the pathogen is sealed in an endosome inside the macrophage, the vesicle is walked
along microtubules until it combines with a lysosome to digest the pathogen. 41 They differ because plant cell walls
are rigid. Plasmodesmata, which a plant cell needs for transportation and communication, are able to allow movement
of really large molecules. Gap junctions are necessary in animal cells for transportation and communication. 43 E. coli
infections generally cause food poisoning, meaning that the invading bacteria cross from the lumen of the gut into the
rest of the body. Tight junctions hold the epithelial layer that lines the digestive tract together so that the material that
crosses into the body is tightly regulated. One way E. coli can avoid this regulation is to destroy the tight junctions so
that it can enter the body between the epithelial cells, rather than having to go through the cells.
Chapter 5
1 Figure 5.12 No, it must have been hypotonic as a hypotonic solution would cause water to enter the cells, thereby
making them burst. 3 Figure 5.19 A decrease in pH means an increase in positively charged H+ ions, and an increase
in the electrical gradient across the membrane. The transport of amino acids into the cell will increase. 4 A 6 A 8
C 10 A 12 D 14 D 16 B 18 C 20 B 21 The fluid characteristic of the cell membrane allows greater flexibility to
the cell than it would if the membrane were rigid. It also allows the motion of membrane components, required for
some types of membrane transport. 23 Peripheral proteins can bind to other molecules in the extracellular space.
However, they cannot directly transmit a signal to the inside of the cell since they do not have a transmembrane domain
(region that goes through the plasma membrane to the inside of the cell). They must associate with integral membrane
proteins in order to pass the signal to the inside of the cell. 25 Water moves through a membrane in osmosis because
there is a concentration gradient across the membrane of solute and solvent. The solute cannot effectively move to
balance the concentration on both sides of the membrane, so water moves to achieve this balance. 27 Decreasing
temperature will decrease the kinetic energy in the system. A lower temperature means less energy in the molecules,
so they will move at a slower speed. Lowering temperature also decreases the kinetic energy of the molecules in
the plasma membrane, compressing them together. This increases the density of the plasma membrane, which slows
diffusion into the cell. 29 The cell harvests energy from ATP produced by its own metabolism to power active transport
processes, such as the activity of pumps. 31 Intestinal epithelial cells use active transport to fulfill their specific role as
the cells that transfer glucose from the digested food to the bloodstream. Intestinal cells are exposed to an environment
with fluctuating glucose levels. Immediately after eating, glucose in the gut lumen will be high, and could accumulate
in intestinal cells by diffusion. However, when the gut lumen is empty, glucose levels are higher in the intestinal cells. If
glucose moved by facilitated diffusion, this would cause glucose to flow back out of the intestinal cells and into the gut.
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Active transport proteins ensure that glucose moves into the intestinal cells, and cannot move back into the gut. It also
ensures that glucose transport continues to occur even if high levels of glucose are already present in the intestinal
cells. This maximizes the amount of energy the body can harvest from food. 33 The proteins allow a cell to select
what compound will be transported, meeting the needs of the cell and not bringing in anything else.
Chapter 6
1 Figure 6.8 A compost pile decomposing is an exergonic process; enthalpy increases (energy is released) and
entropy increases (large molecules are broken down into smaller ones). A baby developing from a fertilized egg is
an endergonic process; enthalpy decreases (energy is absorbed) and entropy decreases. Sand art being destroyed
is an exergonic process; there is no change in enthalpy, but entropy increases. A ball rolling downhill is an exergonic
process; enthalpy decreases (energy is released), but there is no change in entropy. 3 Figure 6.14 Three sodium ions
could be moved by the hydrolysis of one ATP molecule. The ∆G of the coupled reaction must be negative. Movement
of three sodium ions across the membrane will take 6.3 kcal of energy (2.1 kcal × 3 Na+ ions = 6.3 kcal). Hydrolysis of
ATP provides 7.3 kcal of energy, more than enough to power this reaction. Movement of four sodium ions across the
membrane, however, would require 8.4 kcal of energy, more than one ATP molecule can provide. 4 C 6 C 8 B 10
A 12 A 14 C 16 Physical exercise involves both anabolic and catabolic processes. Body cells break down sugars
to provide ATP to do the work necessary for exercise, such as muscle contractions. This is catabolism. Muscle cells
also must repair muscle tissue damaged by exercise by building new muscle. This is anabolism. 18 A spontaneous
reaction is one that has a negative ∆G and thus releases energy. However, a spontaneous reaction need not occur
quickly or suddenly like an instantaneous reaction. It may occur over long periods due to a large energy of activation,
which prevents the reaction from occurring quickly. 20 The ant farm had lower entropy before the earthquake because
it was a highly ordered system. After the earthquake, the system became much more disordered and had higher
entropy. 22 The activation energy for hydrolysis is very low. Not only is ATP hydrolysis an exergonic process with a
large −∆G, but ATP is also a very unstable molecule that rapidly breaks down into ADP + Pi if not utilized quickly. This
suggests a very low EA since it hydrolyzes so quickly. 24 Feedback inhibition allows cells to control the amounts of
metabolic products produced. If there is too much of a particular product relative to the cell’s needs, feedback inhibition
effectively causes the cell to decrease production of that particular product. In general, this reduces the production of
superfluous products and conserves energy, maximizing energy efficiency.
Chapter 7
1 Figure 7.11 After DNP poisoning, the electron transport chain can no longer form a proton gradient, and ATP
synthase can no longer make ATP. DNP is an effective diet drug because it uncouples ATP synthesis; in other words,
after taking it, a person obtains less energy out of the food he or she eats. Interestingly, one of the worst side effects of
this drug is hyperthermia, or overheating of the body. Since ATP cannot be formed, the energy from electron transport
is lost as heat. 3 Figure 7.14 The illness is caused by lactate accumulation. Lactate levels rise after exercise, making
the symptoms worse. Milk sickness is rare today but was common in the midwestern United States in the early
1800s. 4 A 6 C 8 B 10 C 12 C 14 A 16 A 18 ATP provides the cell with a way to handle energy in an efficient
manner. The molecule can be charged, stored, and used as needed. Moreover, the energy from hydrolyzing ATP
is delivered as a consistent amount. Harvesting energy from the bonds of several different compounds would result
in energy deliveries of different quantities. 20 All cells must consume energy to carry out basic functions, such as
pumping ions across membranes. A red blood cell would lose its membrane potential if glycolysis were blocked, and
it would eventually die. 22 Q and cytochrome c are transport molecules. Their function does not result directly in ATP
synthesis in that they are not pumps. Moreover, Q is the only component of the electron transport chain that is not
a protein. Ubiquinone and cytochrome c are small, mobile electron carriers, whereas the other components of the
electron transport chain are large complexes anchored in the inner mitochondrial membrane. 24 Fermentation uses
glycolysis only. Anaerobic respiration uses all three parts of cellular respiration, including the parts in the mitochondria
like the citric acid cycle and electron transport; it also uses a different final electron acceptor instead of oxygen gas. 26
Citrate can inhibit phosphofructokinase by feedback regulation.
Chapter 8
1 Figure 8.6 Levels of carbon dioxide (a necessary photosynthetic substrate) will immediately fall. As a result, the rate
of photosynthesis will be inhibited. 3 Figure 8.18 D 4 A 6 B 8 B 10 A 12 C 14 A 16 D 18 C 20 C 21 The
outcome of light reactions in photosynthesis is the conversion of solar energy into chemical energy that the chloroplasts
can use to do work (mostly anabolic production of carbohydrates from carbon dioxide). 23 The energy carriers that
move from the light-dependent reaction to the light-independent one are “full” because they bring energy. After the
energy is released, the “empty” energy carriers return to the light-dependent reaction to obtain more energy. There
is not much actual movement involved. Both ATP and NADPH are produced in the stroma where they are also used
and reconverted into ADP, Pi, and NADP+. 25 The stomata regulate the exchange of gases and water vapor between
a leaf and its surrounding environment. When the stomata are closed, the water molecules cannot escape the leaf,
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