Darwinʹs mechanism of natural selection required long time spans in order to modify species. From whom did
Darwin get the concept of Earthʹs ancient age?
Charles Darwin was the first person to propose
that evolution occurs.
a mechanism for how evolution occurs.
that the Earth is older than a few thousand years.
a mechanism for evolution that was supported by evidence.
a way to use artificial selection as a means of domesticating plants and animals.
Which of these conditions should completely prevent the occurrence of natural selection in a population over
All variation between individuals is due only to environmental factors.
The environment is changing at a relatively slow rate.
The population size is large.
The population lives in a habitat where there are no competing species present.
Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus?
All species are fixed in the form in which they are created.
Populations tend to increase at a faster rate than their food supply normally allows.
Earth changed over the years through a series of catastrophic upheavals.
The environment is responsible for natural selection.
Earth is more than 10,000 years old.
Given a population that contains genetic variation, what is the correct sequence of the following events, under
the influence of natural selection?
1. Well-adapted individuals leave more offspring than do poorly adapted individuals.
2. A change occurs in the environment.
3. Genetic frequencies within the population change.
4. Poorly adapted individuals have decreased survivorship.
2 → 4 → 1 → 3
4 → 2 → 1 → 3
4 → 1 → 2 → 3
4 → 2 → 3 → 1
2 → 4 → 3 → 1
To observe natural selectionʹs effects on a population, which of these must be true?
One must observe more than one generation of the population.
The population must contain genetic variation.
Members of the population must increase or decrease the use of some portion of their anatomy.
A and C only
A and B only
During drought years on the Galapagos, small, easily eaten seeds become rare, leaving mostly large,
hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, what should
one expect to result from natural selection?
Small birds gaining larger beaks by exercising their mouth parts.
Small birds mutating their beak genes with the result that later-generation offspring have larger beaks.
Small birds anticipating the long drought and eating more to gain weight and, consequently, growing
More small-beaked birds dying than larger-beaked birds. The offspring produced in subsequent
generations have a higher percentage of birds with large beaks.
Larger birds eating less so smaller birds can survive
Which of the following must exist in a population before natural selection can act upon that population?
Genetic variation among individuals
Variation among individuals caused by environmental factors
B and C only
A, B, and C
How many separate species, both extant and extinct, are depicted in this tree?
Which statement best describes the evolution of pesticide resistance in a population of insects?
Individual members of the population slowly adapt to the presence of the chemical by striving to meet
the new challenge.
All insects exposed to the insecticide begin to use a formerly silent gene to make a new enzyme that
breaks down the insecticide molecules.
Insects observe the behavior of other insects that survive pesticide application, and adjust their own
behaviors to copy those of the survivors.
Offspring of insects that are genetically resistant to the pesticide become more abundant as the
susceptible insects die off.
Some members of a photosynthetic plant species are genetically resistant to an herbicide, while other members
of the same species are not resistant to the herbicide. Which combination of events should cause the most
effective replacement of the non-herbicide-resistant strain of plants by the resistant strain?
1. The presence of the herbicide in the environment
2. The absence of the herbicide from the environment
3. The maintenance of the proper conditions for one generation
4. The maintenance of the proper conditions for many generations
1 and 3
1 and 4
2 and 3
2 and 4
Of the following anatomical structures, which is homologous to the wing of a bird?
Dorsal fin of a shark
Hindlimb of a kangaroo
Wing of a butterfly
Tail fin of a flying fish
Flipper of a cetacean
Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, these
bones having developed from very similar embryonic tissues. How do biologists interpret these similarities?
By identifying the bones as being homologous
By the principle of convergent evolution
By proposing that humans, bats, and dolphins share a common ancestor
A and C only
A, B, and C
Which of the following pieces of evidence most strongly supports the common origin of all life on Earth?
All organisms require energy.
All organisms use essentially the same genetic code.
All organisms reproduce.
All organisms show heritable variation.
All organisms have undergone evolution.
Which of the following statements most detracts from the claim that the human appendix is a completely
The appendix can be surgically removed with no immediate ill effects.
The appendix might have been larger in fossil hominids.
The appendix has a substantial amount of defensive lymphatic tissue
Individuals with a larger-than-average appendix leave fewer offspring than those with a
In a million years, the human species might completely lack an appendix.
Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as do fish, even
though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal
fins and tails of ichthyosaurs and fish are
examples of convergent evolution.
adaptations to a common environment.
A and C only
B and C only
Monkeys of South and Central America have prehensile tails, meaning that their tails can be used to grasp
objects. The tails of African and Asian monkeys are not prehensile. Which discipline is most likely to provide
an evolutionary explanation for how this difference in tails came about?
Heterozygote advantage should be most closely linked to which of the following?
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by
nonpolar covalent bonds.
polar covalent bonds.
van der Waals interactions.
An example of a hydrogen bond is the bond between
C and H in methane (CH4).
the H of one water molecule and the O of another water molecule.
Na+and Cl- in salt.
the two hydrogen atoms in a molecule of hydrogen gas (H2).
Mg+and Cl- in MgCl2.
What gives rise to the cohesiveness of water molecules?
nonpolar covalent bonds
both A and C
Which of the following takes place as an ice cube cools a drink?
Molecular collisions in the drink increase.
Kinetic energy in the drink decreases.
A calorie of heat energy is transferred from the ice to the water of the drink.
The specific heat of the water in the drink decreases.
Evaporation of the water in the drink increases.
The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one
were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature
of 20 kg of water how many degrees Celsius?
Which type of bond must be broken for water to vaporize?
nonpolar covalent bonds
polar covalent bonds
Hydrophobic substances such as vegetable oil are
nonpolar substances that repel water molecules.
nonpolar substances that have an attraction for water molecules.
polar substances that repel water molecules.
polar substances that have an affinity for water.
charged molecules that hydrogen-bond with water molecules.
One mole (mol) of a substance is
6.02 × 10^23 molecules of the substance.
1 g of the substance dissolved in 1 L of solution.
the largest amount of the substance that can be dissolved in 1 L of solution.
the molecular mass of the substance expressed in grams.
A and D only
When an ionic compound such as sodium chloride (NaCl) is placed in water the component atoms of the NaCl
crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently
bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous
solution. Which of the following solutions would be expected to contain the greatest number of particles
(molecules or ions)?
1 L of 0.5 M NaCl
1 L of 0.5 M glucose
1 L of 1.0 M NaCl
1 L of 1.0 M glucose
C and D will contain equal numbers of particles.
The molecular mass of glucose (C6H12O6) is 180 g. Which of the following procedures should you carry out to
make a 0.5 M solution of glucose?
Dissolve 0.5 g of glucose in a small volume of water, and then add more water until the total volume of
solution is 1 L.
Dissolve 90 g of glucose in a small volume of water, and then add more water until the total volume of
the solution is 1 L.
Dissolve 180 g of glucose in a small volume of water, and then add more water until the total volume of
the solution is 1 L.
Dissolve 0.5 g of glucose in 1 L of water.
Dissolve 180 g of glucose in 1 L of water.
You have a freshly-prepared 0.1M solution of glucose in water. Each liter of this solution contains how many
6.02 × 10^23
3.01 × 10^23
6.02 × 10^24
12.04 × 10^23
6.02 × 10^22
You have a freshly-prepared 1M solution of glucose in water. You carefully pour out a 100 mL sample of that
solution. How many glucose molecules are included in that 100 mL sample?
6.02 × 10^23
3.01 × 10^23
6.02 × 10^24
12.04 × 10^23
6.02 × 10^22
Which of the following ionizes completely in solution and is considered to be a strong base (alkali)?
What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M?
Organic chemistry is a science based on the study of
vital forces interacting with matter.
water and its interaction with other kinds of molecules.
The experimental approach taken in current biological investigations presumes that
simple organic compounds can be synthesized in the laboratory from inorganic precursors, but complex organic compounds like carbohydrates and proteins can only be synthesized by living organisms.
a life force ultimately controls the activities of living organisms and this life force cannot be studied by physical or chemical methods.
although a life force, or vitalism, exists in living organisms, this life force cannot be studied by physical or chemical methods.
living organisms are composed of the same elements present in nonliving things, plus a few special trace elements found only in living organisms or their products.
living organisms can be understood in terms of the same physical and chemical laws that can be used to explain all natural phenomena.
Which of the following people used this apparatus to study the formation of organic compounds?
Which of the following statements best describes the carbon atoms present in all organic molecules?
They were incorporated into organic molecules by plants.
They were processed into sugars through photosynthesis.
They are ultimately derived from carbon dioxide
Only A and C are correct.
A, B, and C are correct.
All of the following are part of a prokaryotic cell except:
a cell wall
a plasma membrane.
an endoplasmic reticulum.
Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?
smooth endoplasmic reticulum
The fact that the outer membrane of the nuclear envelope has bound ribosomes allows one to most reliably conclude that
at least some of the proteins that function in the nuclear envelope are made by the ribosomes on the nuclear envelope
the nuclear envelope is not part of the endomembrane system
the nuclear envelope is physically separated from the endoplasmic reticulum.
small vesicles from the Golgi fuse with the nuclear envelope
nuclear pore complexes contain proteins
Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large and complex lipids. Which cellular organelle must be involved in this condition?
the endoplasmic reticulum
the Golgi apparatus
Which of the following produces and modifies polysaccharides that will be secreted?
Which of the following contains hydrolytic enzymes?
Which organelle often takes up much of the volume of a plant cell?
Which plant cell organelle contains its own DNA and ribosomes?
Which animal cell organelle contains enzymes that transfer hydrogen from various substrates to oxygen?
The chemical reactions involved in respiration are virtually identical between prokaryotic and eukaryotic cells. In eukaryotic cells, ATP is synthesized primarily on the inner membrane of the mitochondria. In light of the endosymbiont theory for the evolutionary origin of mitochondria, where is most ATP synthesis likely to occur in prokaryotic cells?
in the cytoplasm
on the inner mitochondrial membrane
on the endoplasmic reticulum
on the inner plasma membrane
on the inner nuclear envelope
Which of the following are capable of converting light energy to chemical energy?
A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and
mitochondria. It could be a cell from
an animal, but not a plant.
a plant, but not an animal.
a plant or an animal.
any kind of organism.
According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
They can move laterally along the plane of the membrane.
They frequently flip-flop from one side of the membrane to the other.
They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
They are free to depart from the membrane and dissolve in the surrounding solution.
They have hydrophilic tails in the interior of the membrane
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
an amino acid
Which of the following statements is correct about diffusion?
It is very rapid over long distances.
It requires an expenditure of energy by the cell.
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
It requires integral proteins in the cell membrane.
If a membrane protein in an animal cell is involved inthe cotransport of glucose and sodiumions into the cell, which of the following is most likely true?
The sodium ions are moving down their electrochemical gradient while glucose is moving up.
Glucose is entering the cell along its concentration gradient.
Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
Potassium ions move across the same gradient as sodium ions.
A substance that blocked sodium ions from binding to the cotransport protein would also block the transport of glucose.
Which of the following statements about xylem is incorrect?
It conducts material upward.
It conducts materials within dead cells.
It transports mainly sugars and amino acids.
It has a lower water potential than soil does.
No energy input from the plant is required for xylem transport.
Root hairs are most important to a plant because they
anchor a plant in the soil
increase the surface area for absorption.
provide a habitat for nitrogen-fixing bacteria.
contain xylem tissue.
What is the role of proton pumps in root hair cells?
establish ATP gradients
acquire minerals from the soil
pressurize xylem transport
eliminate excess electrons
A and D only
A water molecule could move all the way through a plant from soil to root to leaf to air and pass through a living cell only once. This living cell would be a part of which structure?
the Casparian strip
a guard cell
the root epidermis
the root cortex
What is the main force by which most of the water within xylem vessels moves toward the top of a tree?
active transport of ions into the stele
atmospheric pressure on roots
evaporation of water through stoma
the force of root pressure
osmosis in the root
Which of the following are defenses that some plants use against herbivory?
production of the unusual amino acid canavanine
release of volatile compounds that attract parasitoid wasps
association of plant tissues with mycorrhizae
A and B only
A, B, and C
Plants are affected by an array of pathogens. Which of the following is not a plant defense against disease?
cells near the point of infection destroying themselves to prevent the spread of the infection
production of chemicals that kill pathogens
acquiring gene-for-gene recognition that allows specific proteins to interact so that the plant can produce defenses against the pathogen
a waxy cuticle that pathogens have trouble penetrating
All of the above are plant defenses against disease.
The transduction pathway that activates systemic acquired resistance in plants is initially signaled by
red, but not far-red, light.
A short-day plant exposed to nights longer than the minimum for flowering but interrupted by short flashes of light will flower.
A long-day plant will flower only when the night is longer than a critical value.
An example of a properly functioning homeostatic control system is seen when
the level of glucose in the blood is abnormally high whether or not a meal has been eaten.
a blood cell shrinks when placed in a solution of salt and water.
the core body temperature of a runner rises gradually from 37°C to 45°C.
the kidneys excrete salt into the urine when dietary salt levels rise.
the blood pressure increases in response to an increase in blood volume.
Positive feedback has occurred when
an increase in blood sugar increases the secretion of a hormone that stimulates the movement of sugar out of the blood.
a decrease in blood sugar increases the secretion of a hormone that increases the conversion of glycogen to glucose.
uterine contractions needed for the birthing process are expedited by the pressure of a moving baby in its mother's uterus.
an increase in calcium concentration increases the secretion of a hormone that promotes the storage of calcium in bone.
a decrease in blood calcium increases the amount of the hormone that causes the release of calcium from bone.
In a survivably cold environment, an ectotherm is more likely to survive an extended period of food deprivation than would an equally sized endotherm because the ectotherm
invests little energy in temperature regulation.
has greater insulation on its body surface.
maintains a higher basal metabolic rate.
metabolizes its stored energy more readily than can the endotherm.
expends more energy per kg of body mass than does the endotherm.
Humans can lose, but cannot gain, heat through the process of
An example of an ectothermic organism that has few or no behavioral options when it comes to its ability to adjust its body temperature is a
sea star, a marine invertebrate.
bluefin tuna, a predatory fish.
honeybee in a hive.
is only seen in mammals
is a term equivalent to "cold-blooded."
involves the production of heat through metabolism
is only seen in insects
is a characteristic of most animals
An example of an organism that has only behavioral controls over its body temperature is the
The temperature-regulating center of vertebrate animals is located in the
subcutaneous layer of the skin.
Ingested foods inside the digestive tract of snakes are typically digested by
What does the difference in temperature between arteries and veins in the goose's legs indicate?
Which of the following differentiates T cells and B cells?
T cells but not B cells are stimulated to increase the rate of their cell cycles.
Only B cells are produced from stem cells of the bone marrow.
T cells but not B cells can directly attack and destroy invading pathogens.
T cells but not B cells have surface markers.
Only B cells take part in cell-mediated immunity.
The MHC is important in a T cell's ability to
recognize specific parasitic pathogens.
distinguish self from nonself.
identify specific bacterial pathogens.
identify specific viruses.
recognize differences among types of cancer.
The following events occur when a mammalian immune system first encounters a
pathogen. Which shows the correct sequence in which they occur?
I. Pathogen is destroyed.
II. Lymphocytes secrete antibodies.
III. Antigenic determinants from pathogen bind to antigen receptors on lymphocytes.
IV. Lymphocytes specific to antigenic determinants from pathogen become numerous.
V. Only memory cells remain.
I → III → II → IV → V
III → II → I → V → IV
II → I → IV → III → V
IV → II → III → I → V
III → IV → II → I → V
Which cell type interacts with both the humoral and cell-mediated immune
helper T cells
natural killer cells
cytotoxic T cells
Which of the following is accounted for by immunological memory?
the human body's ability to distinguish self from nonself
the observation that some strains of the pathogen that causes dengue fever cause worse
disease than others
the ability of a helper T cell to signal B cells via cytokines
the ancient observation that someone who had recovered from the plague could safely care
for those newly diseased
the ability of the immune system to present antigen fragments in association with MHC
An otherwise healthy student in your class is infected with EBV, the virus that causes infectious
mononucleosis. The same student had already been infected when she was a child, and she had
merely experienced a mild sore throat and swollen lymph nodes in her neck. This time, though
infected, she does not get sick. The EBV antigen fragments will be presented by the virus-infected cells along with which of
class I MHC molecules
class II MHC molecules
A nonfunctional CD4 protein on a helper T cell would result in the helper T cell being unable
respond to T-independent antigens.
lyse tumor cells.
stimulate a cytotoxic T cell.
interact with a class I MHC-antigen complex
interact with a class II MHC-antigen complex.
Naturally acquired passive immunity would involve the
injection of vaccine.
ingestion of interferon.
placental transfer of antibodies.
absorption of pathogens through mucous membranes.
injection of antibodies.
What accounts for antibody switching (i.e., the switch of one B cell from producing one class
of antibody to another antibody class that is responsive to the same antigen)?
mutation in the genes of that B cell, induced by exposure to the antigen
the rearrangement of V region genes in that clone of responsive B cells
a switch in the kind of antigen-presenting cell that is involved in the immune response
a patient's reaction to the first kind of antibody made by the plasma cells
the shuffling of exons for one C region type to another attached to the V-J transcript
In which of the cases could the mother exhibit an anti-Rh-factor reaction to the
When an individual is subject to short-term starvation, most available food is used to provide energy(metabolism) rather than building blocks (growth and repair). Which hormone would be particularly active intimes of food shortage?
Based on their effects, which pair below could be considered antagonistic?
prostaglandin F and nitric oxide
growth hormone and ecdysone
endocrine and exocrine glands
hormones and target cells
neurosecretory cells and neurotransmitters
For this pair of items, choose the option that best describes their relationship.
(A) The number of purines in the DNA strand 5ʹ-AAGAGGAGAAA-3ʹ
(B) The number of pyrimidines in the DNA strand 5ʹ-AAGAGGAGAAA-3ʹ
Item (A) is greater than item (B).
Item (A) is less than item (B).
Item (A) is exactly or very approximately equal to item (B).
Item (A) may stand in more than one of the above relations to item (B).
Which of the following is not a polymer?
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a
molecule made by linking three glucose molecules together by dehydration reactions?
Which of the following descriptors is true of the molecule shown in Figure 5.1?
The reaction could be coupled to power an endergonic reaction with a ΔG of +6.2 kcal/mol.
The reaction could be coupled to power an exergonic reaction with a ΔG of +8.8 kcal/mol.
The reaction would result in a decrease in entropy (S) and an increase in the total energy content (H) of the system.
The reaction would result in an increase in entropy (S) and a decrease in the total energy content (H) of the system.
The reaction would result in products (C + D) with a greater free-energy content than in the initial reactants (A + B).
involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.
requiresnerve cells to release a neurotransmitter into the synapse
occurs only in paracrine yeast cells.
has been found in plants but not animals.
involves mating factors attaching to target cells and causing production of new paracrine cells.
What would be true for the signaling system in an animal cell that lacks the ability to produce GTP?
It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
It could activate only the epinephrine system.
It would be able to carry out reception and transduction, but would not be able to respond to a signal.
Only A and C are true.
A, B, and C are true.
Up to 60% of all medicines used today exert their effects by influencing what structures in the cell membrane?
ligand-gated ion channel receptors
Which of the following are chemical messengers that pass through the plasma membrane of cells & have receptor molecules in the cytoplasm?
A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.
Where would you expect to find the carboxyl end?
at the exterior surface
at the cytosol surface
connected with the loop at H5 and H6
between the membrane layers
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?
G protein-coupled receptors
ligand-gated ion channels
receptor tyrosine kinases
Sutherland discovered that epinephrine signals
a decrease in levels of cAMP as a result of bypassing the plasma membrane.
lower blood glucose by binding to liver cells.
interactions with insulin inside muscle cells.
interactions directly with glycogen phosphorylase.
elevation of cytosolic concentrations of cyclic AMP.
Which of the following describes cell communication systems?
Cell signaling evolved more recently than systems such as the immune system of vertebrates.
Communicating cells are usually close together.
Most signal receptors are bound to the outer membrane of the nuclear envelope.
Lipid phosphorylation is a major mechanism of signal transduction.
In response to a signal, the cell may alter activities by changes in cytosol activity or intranscription of RNA.
Which of the following most likely would be an immediate result of growth factor binding to its receptor?
protein kinase activity
adenylyl cyclase activity
protein phosphatase activity
Adenylyl cyclase has the opposite effect of which of the following?
If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, oneapproach might be to
design a compound that blocks epinephrine receptor activation.
design a compound that inhibits cAMP production in liver cells.
design a compound that inhibits phosphorylase activity.
design a compound to block G-protein activity in liver cells.
All of the above are possible approaches.
Which of the following statements is true?
When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate anumber of nearby molecules
In response to some G-protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium.
In most cases, signal molecules interact with the cell at the plasma membrane and then enter the cell and eventually the nucleus.
Toxins such as those that cause botulism and cholera interfere with the ability of activated G proteins to hydrolyze GTP to GDP, resulting in phosphodiesterase activity in the absence of an appropriate signal molecule.
Protein kinase A activation is one possible result of signal molecules binding to G protein-linked receptors.
One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vesselsand increase of blood in the penis, facilitating erection. cGMP is inhibited, therefore the signal isprolonged. The original signal that is now inhibited would have
hydrolyzed cGMP to GMP.
hydrolyzed GTP to GDP
removed GMP from the cell.
The nucleus and most of the organelles in a neuron are located in the
For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in
the depolarization of the neuron
the hyperpolarization of the neuron
the replacement of potassium ions with sodium ions.
the replacement of potassium ions with calcium ions
the neuron switching on its sodium-potassium pump to restore the initial conditions
Although the membrane of a "resting" neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also
fully permeable to sodium ions.
slightly permeable to sodium ions
fully permeable to calcium ions.
impermeable to sodium ions
highly permeable to chloride ions.
The operation of the sodium-potassium "pump" moves
sodium and potassium ions into the cell.
sodium and potassium ions out of the ce
sodium ions into the cell and potassium ions out of the cell.
sodium ions out of the cell and potassium ions into the cell.
sodium and potassium ions into the mitochondria.
A "resting" motor neuron is expected to
release lots of acetylcholine.
have high permeability to sodium ions.
be equally permeable to sodium and potassium ions.
exhibit a resting potential that is more negative than the "threshold" potential.
have a higher concentration of sodium ions on the inside of the cell than on the outside
The "threshold" potential of a membrane
is the point of separation from a living to a dead neuron.
is the lowest frequency of action potentials a neuron can produce.
is the minimum hyperpolarization needed to prevent the occurrence of action potentials.
is the minimum depolarization needed to operate the voltage-gated sodium and potassium channels.
is the peak amount of depolarization seen in an action potential.
A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to
prevent the hyperpolarization phase of the action potential.
prevent the depolarization phase of the action potential.
prevent graded potentials
increase the release of neurotransmitter molecules.
have most of its effects on the dendritic region of a neuron.
After the depolarization phase of an action potential, the resting potential is restored by
the opening of sodium activation gates.
the opening of voltage-gated potassium channels and the closing of sodium channels.
a decrease in the membrane's permeability to potassium and chloride ions.
a brief inhibition of the sodium-potassium pump
the opening of more voltage-gated sodium channels.
The membrane potential is closest to the equilibrium potential for potassium at label
In the sequence of permeability changes for a complete action potential, the first of these events that occurs is
the activation of the sodium-potassium "pump."
the inhibition of the sodium-potassium "pump."
the opening of voltage-gated sodium channels.
the closing of voltage-gated potassium channels.
the opening of voltage-gated potassium channels.
Neurotransmitters are released from axon terminals via
The observation that the acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it is an example of
a voltage-gated sodium channel.
a voltage-gated potassium channel.
a ligand-gated sodium channel.
a second-messenger-gated sodium channel.
a chemical that inhibits action potentials.
An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to
all neurotransmitter molecules.
The activity of acetylcholine in a synapse is terminated by
its active transport across the presynaptic membrane.
its diffusion across the presynaptic membrane.
its active transport across the postsynaptic membrane
its diffusion across the postsynaptic membrane.
its degradation by a hydrolytic enzyme on the postsynaptic membrane
When several EPSPs arrive at the axon hillock from different dendritic locations, depolarizing the postsynaptic cell to threshold for an action potential, this is an example of
the refractory state.
an action potential with an abnormally high peak of depolarization.
Functionally, which cellular location is the neuron's "decision-making site" as to whether or not an action potential will be initiated?
Which of the following types of reactions would decrease the entropy within a cell?
Which of the following is an example of potential rather than kinetic energy?
the muscle contractions of a person mowing grass
water rushing over Niagara Falls
light flashes emitted by a firefly
a molecule of glucose
the flight of an insect foraging for food
Which of the following is true of metabolism in its entirety in all organisms?
Metabolism depends on a constant supply of energy from food.
Metabolism depends on an organism's adequate hydration.
Metabolism uses all of an organism's resources.
Metabolism is a property of organismal life.
Metabolism manages the increase of entropy in an organism.
What is the change in free energy of a system at chemical equilibrium?
no net change
Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?
a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium
a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings
an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment
a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway
no possibility of having chemical equilibrium in any living cell
When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are as follows:
+ΔG, +ΔH, +ΔS.
+ΔG, +ΔH, -ΔS.
+ΔG, -ΔH, -ΔS.
-ΔG, +ΔH, +ΔS.
-ΔG, -ΔH, -ΔS
Which of the following best describes enthalpy (H)?
the total kinetic energy of a system
the heat content of a chemical system
the system's entropy
the cell's energy equilibrium
the condition of a cell that is not able to react
When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation?
Cells are open systems, but a test tube is a closed system.
Cells are less efficient at heat production than nonliving systems.
The hydrolysis of ATP in a cell produces different chemical products than does the reaction in a test tube.
The reaction in cells must be catalyzed by enzymes, but the reaction in a test tube does not need enzymes.
Reactant and product concentrations in the test tube are different from those in the cell.
What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
It is used to power yet more cellular work.
It is used to store energy as more ATP.
It is used to generate ADP from nucleotide precursors.
It is lost to the environment.
It is transported to specific organs such as the brain.
A number of systems for pumping across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they don't often hydrolyze ATP unless they are simultaneously transporting ions. Small increases in calcium ions in the cytosol trigger a number of different intracellular reactions, so the cells must keep the calcium concentration quite low. Muscle cells also transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a muscle cell cytosol has a free calcium ion concentration of 10-7 in a resting cell, while the concentration in the SR can be 10-2, then how is the ATPase acting?
The ATP must be powering an inflow of calcium from the outside of the cell into the SR
ATP must be transferring Pi to the SR to enable this to occur.
ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
The calcium ions must be diffusing back into the SR along the concentration gradient.
The route of calcium ions must be from SR to the cytosol, to the cell's environment.
What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
Which of the following statements describes the results of this reaction?
C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy
C₆H₁₂O₆ is oxidized and O₂ is reduced.
O₂ is oxidized and H₂O is reduced.
CO₂ is reduced and O₂ is oxidized
C₆H₁₂O₆ is reduced and CO₂ is oxidized.
O₂ is reduced and CO₂ is oxidized
Where does glycolysis take place in eukaryotic cells?
mitochondrial outer membrane
mitochondrial inner membrane
mitochondrial intermembrane space
Which step in Figure 9.1 shows a split of one molecule into two smaller molecules?
Starting with one molecule of glucose, the "net" products of glycolysis are
2 NAD⁺, 2 pyruvate, and 2 ATP
2 NADH, 2 pyruvate, and 2 ATP
2 FADH₂, 2 pyruvate, and 4 ATP
6 CO₂, 2 ATP, and 2 pyruvate.
6 CO₂, 30 ATP, and 2 pyruvate
Why is glycolysis described as having an investment phase and a payoff phase?
It both splits molecules and assembles molecules
It attaches and detaches phosphate groups.
It uses glucose and generates pyruvate.
It shifts molecules from cytosol to mitochondrion.
It uses stored ATP and then forms a net increase in ATP
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.
These three steps result in the formation of
acetyl CoA, O₂, and ATP.
acetyl CoA, FADH₂, and CO₂
acetyl CoA, FAD, H₂, and CO₂.
acetyl CoA, NADH, H⁺, and CO₂.
acetyl CoA, NAD⁺, ATP, and CO₂
How many molecules of carbon dioxide (CO2) would be produced by five turns of the citric acid cycle?
Which of the following describes the sequence of electron carriers in the electron transport chain, starting with the least electronegative?
ubiquinone (Q), cytochromes (Cyt), FMN, Fe•S
cytochromes (Cyt), FMN, ubiquinone, Fe∙S
Fe•S, FMN, cytochromes (Cyt), ubiquinone
FMN, Fe•S, ubiquinone, cytochromes (Cyt)
cytochromes (Cyt), Fe•S, ubiquinone, FMN
Where does the Calvin cycle take place?
stroma of the chloroplast
cytoplasm surrounding the chloroplast
interior of the thylakoid (thylakoid space)
outer membrane of the chloroplast
When oxygen is released as a result of photosynthesis, it is a direct by-product of
splitting water molecules.
the electron transfer system of photosystem I
the electron transfer system of photosystem II.
Figure 10.1 shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?