Rate of an enzyme-catalyzed reaction as a function of varying reactant
concentration, with the concentration of enzyme constant.
In the figure, why does the reaction rate plateau at higher reactant concentrations?
A) Feedback inhibition by product occurs at high reactant concentrations.
B) Most enzyme molecules are occupied by substrate at high reactant concentrations.
C) The reaction nears equilibrium at high reactant concentrations.
D) The rate of the reverse reaction increases with reactant concentration.
Displays of nocturnal mammals are usually _____.
A) visual and auditory
B) tactile and visual
C) olfactory and auditory
D) visual and olfactory
Melatonin is secreted by the_____.
A) hypothalamus during the day
B) pineal gland during the night
C) autonomic nervous system during the winter
D) posterior pituitary gland during the day
Which of the following contradicts the one-gene, one-enzyme hypothesis?
A) A mutation in a single gene can result in a defective protein.
B) Alkaptonuria results when individuals lack a single enzyme involved in the catalysis
of homogentisic acid.
C) Sickle-cell anemia results in defective hemoglobin.
D) A single antibody gene can code for different related proteins, depending on the
splicing that takes place post-transcriptionally.
Use the following information to answer the question(s) below.
An elementary school science teacher decided to liven up the classroom with a
saltwater aquarium. Knowing that saltwater aquaria can be quite a hassle, the teacher
proceeded stepwise. First, the teacher conditioned the water. Next, the teacher decided
to stock the tank with various marine invertebrates, including a polychaete, a siliceous
sponge, several bivalves, a shrimp, several sea anemones of different types, a colonial
hydra, a few coral species, an ectoproct, a sea star, and several herbivorous gastropod
varieties. Lastly, she added some vertebratesa parrotfish and a clownfish. She arranged
for daily feedings of copepods and feeder fish.
The bivalves started to die one by one; only the undamaged shells remained. To keep
the remaining bivalves alive, the teacher would most likely need to remove the _____.
A) sea anemones
B) sea star
C) gastropods
D) ectoprocts
If an animal cell suddenly lost the ability to produce GTP, what might happen to its
signaling system?
A) It would not be able to activate and inactivate the G protein on the cytoplasmic side
of the plasma membrane.
B) It would be able to carry out reception and transduction but would not be able to
respond to a signal.
C) It would use ATP instead of GTP to activate and inactivate the G protein on the
cytoplasmic side of the plasma membrane.
D) It would employ a transduction pathway directly from an external messenger.
Use the following information to answer the question(s) below.
Giardia intestinalis is an intestinal parasite of humans and other mammals that causes
intestinal ailments in most people who ingest the cysts. Upon ingestion, each cyst
releases two motile cells, called trophozoites. These attach to the small intestine’s lining
via a ventral adhesive disk. The trophozoites anaerobically metabolize glucose from the
host’s intestinal contents to produce ATP. Reproduction is completely asexual, occurring
by longitudinal binary fission of trophozoites, with each daughter cell receiving two
haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large
intestine by secreting around itself a case that is resistant to cold, heat, and dehydration.
Infection usually occurs by drinking untreated water that contains cysts.
If the mitosomes of Giardia contain no DNA, yet are descendants of what were once
free-living organisms, then where are we likely to find the genes that encode their
structures, and what accounts for their current location there?
A) plasmids; conjugation
B) plasmids; transformation
C) nucleus; horizontal gene transfer
D) nucleus; S phase
Unequal crossing over during prophase I can result in one sister chromosome with a
deletion and another with a duplication. A mutated form of hemoglobin, so-called
hemoglobin Lepore, exists in the human population. Hemoglobin Lepore has a deleted
series of amino acids. If this mutated form was caused by unequal crossing over, what
would be an expected consequence?
A) There should also be persons whose hemoglobin contains two copies of the series of
amino acids that is deleted in hemoglobin Lepore.
B) Each of the genes in the hemoglobin gene family must show the same deletion.
C) The deleted gene must have undergone exon shuffling.
D) The deleted region must be located in a different area of the individual’s genome.
At which stage of a basidiomycete’s life cycle would reproduction be halted if an
enzyme that prevented the fusion of hyphae was introduced?
A) fertilization
B) karyogamy
C) plasmogamy
D) germination
Refer to the information and figure below to answer the following question(s).
A certain (hypothetical) organism is diploid, has either blue or orange wings as the
consequence of one of its genes on chromosome 12, and has either long or short
antennae as the result of a second gene on chromosome 19, as shown in the figure.
If a female of this species has one chromosome 12 with a blue gene and another
chromosome 12 with an orange gene, and has both number 19 chromosomes with short
genes, she will produce which of the following egg types?
A) only blue short gene eggs
B) only orange short gene eggs
C) one-half blue short and one-half orange short gene eggs
D) three-fourths blue short and one-fourth orange short gene eggs
Which of the following is an example of cooperativity?
A) the binding of an end product of a metabolic pathway to the first enzyme that acts in
the pathway
B) one enzyme in a metabolic pathway passing its product to act as a substrate for the
next enzyme in the pathway
C) a molecule binding at one unit of a tetramer, allowing faster binding at each of the
other three
D) binding of an ATP molecule along with one of the substrate molecules in an active
site
Use the following information to answer the question(s) below.
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, at which time she had merely experienced a mild sore throat and swollen lymph
nodes in her neck. This time, though infected, she does not get sick.
Which of the following should be the same in identical twins?
A) the set of antibodies produced
B) the set of major histocompatability (MHC) molecules produced
C) the set of T cell antigen receptors produced
D) the susceptibility to a particular virus
A fish species known for its success in the aphotic zone may have which of the
following characteristics?
I) symbioses with photosynthetic organisms
II) highly developed chemoreception
III) adaptations for burrowing
IV) adaptations for sit-and-wait predation
A) only I and III
B) only I, II, and IV
C) only II, III, and IV
D) only I, II, and III
Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart
when they are fertile. This kind of isolation is most similar to which of the following
reproductive isolating mechanisms?
A) temporal isolation
B) behavioral isolation
C) habitat isolation
D) gametic isolation
Shoot elongation in a growing bud is due primarily to _____.
A) cell division at the shoot apical meristem
B) cell elongation directly below the shoot apical meristem
C) cell elongation localized in each internode
D) cell division at the shoot apical meristem and cell elongation directly below the
shoot apical meristem
Plants do not have a circulatory system like that of some animals. If a water molecule in
a plant did “circulate” (that is, go from one point in a plant to another and back in the
same day), it would require the activity of _____.
A) only the xylem
B) only the phloem
C) only the endodermis
D) both the xylem and the phloem
Which of the following sex and generation combinations most directly produces the
integument of a pine seed?
A) male gametophyte
B) female gametophyte
C) male sporophyte
D) female sporophyte
In a series of mapping experiments, the recombination frequencies for four different
linked genes of Drosophila were determined as shown in the figure above. What is the
order of these genes on a chromosome map?
A) rb-cn-vg-b
B) cn-rb-b-vg
C) b-rb-cn-vg
D) vg-cn-b-rb
Jaws first occurred in which extant group of fishes?
A) lampreys
B) chondrichthyans
C) ray-finned fishes
D) placoderms
You are studying a large tropical reptile that has a high and relatively stable body
temperature. How would you determine whether this animal is an endotherm or an
ectotherm?
A) You know from its high and stable body temperature that it must be an endotherm.
B) You know that it is an ectotherm because it is not a bird or mammal.
C) You subject this reptile to various temperatures in the lab and find that its body
temperature and metabolic rate change with the ambient temperature. You conclude that
it is an ectotherm.
D) You note that its environment has a high and stable temperature. Because its body
temperature matches the environmental temperature, you conclude that it is an
ectotherm.
The alternative pathways of photosynthesis using the C4 or CAM systems are said to be
compromises. Why?
A) Each one minimizes both water loss and rate of photosynthesis.
B) C4 compromises on water loss and CAM compromises on photorespiration.
C) Both minimize photorespiration but expend more ATP during carbon fixation.
D) CAM plants allow more water loss, while C4 plants allow less CO2 into the plant.
How many electrons are involved in a single covalent bond?
A) one
B) two
C) three
D) four
Which of the following is characteristic of ciliates?
A) They use pseudopods as feeding structures.
B) They are often multinucleate.
C) They can exchange genetic material with other ciliates by the process of mitosis.
D) Most live as solitary autotrophs in fresh water.
Which kind of metabolic poison would most directly interfere with glycolysis?
A) an agent that reacts with oxygen and depletes its concentration in the cell
B) an agent that binds to pyruvate and inactivates it
C) an agent that closely mimics the structure of glucose but is not metabolized
D) an agent that reacts with NADH and oxidizes it to NAD+
Use the following information to answer the question(s) below.
The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of
South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of
high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season
ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest
floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of
nuts are harvested each year. Scientists have discovered that the pale yellow flowers of
Brazil nut trees cannot fertilize themselves and admit only female orchid bees as
pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with
teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of
the seeds, buries others, and leaves still others inside the fruit, which moisture can now
enter. The uneaten seeds may subsequently germinate.
The agouti is most directly involved with the Brazil nut tree’s dispersal of _____.
A) female gametophytes
B) sporophyte embryos
C) sporophyte megaspores
D) female gametes
It became apparent to Watson and Crick after completion of their model that the DNA
molecule could carry a vast amount of hereditary information in which of the
following?
A) sequence of bases
B) phosphate-sugar backbones
C) complementary pairing of bases
D) side groups of nitrogenous bases
Which factor is most important for explaining why there are equal numbers of snapping
shrimp species on either side of the isthmus?
A) the relative shortness of time they have been separated
B) the depth of the ocean
C) the number of actual depth habitats between the surface and the sea floor
D) the elevation of the isthmus above sea level
You observe the gametes of a fungal species under the microscope and realize that they
resemble animal sperm. To which of the following group does the fungus belong?
A) Chytrids
B) Zygomycetes
C) Basidiomycota
D) Ascomycota
Folic acid supplements have become especially important for pregnant women because
_____.
A) folic acid supplies vitamins that only pregnant women can use
B) the fetus makes high levels of folic acid
C) folic acid deprivation is associated with neural tube abnormalities in a fetus
D) folic acid deprivation is a cause of heart abnormalities in a newborn
Mycorrhizae are to the roots of vascular plants as endophytes are to vascular plants’
_____.
A) leaf mesophyll
B) stem apical meristems
C) root apical meristems
D) xylem
What is a major difference between mitosis and meiosis I in a diploid organism?
A) Sister chromatids separate in mitosis, while homologous pairs of chromosomes
separate in meiosis I.
B) Sister chromatids separate in mitosis, while homologous pairs of chromosomes
separate in meiosis II.
C) DNA replication takes place prior to mitosis, but not before meiosis I.
D) Only meiosis I results in daughter cells that contain identical genetic information.
Which of the following statements is true?
A) A band of ribosomes determines where a cell plate will form in a dividing plant cell.
B) The way in which a plant cell differentiates is determined by the position of the
nucleus in the developing plant cell.
C) Homeotic genes often control morphogenesis.
D) Plant cells differentiate because the cytoskeleton determines which genes will be
turned “on” and “off.”
A ribozyme is _____.
A) a catalyst that uses RNA as a substrate
B) an RNA with catalytic activity
C) an enzyme that catalyzes the association between the large and small ribosomal
subunits
D) an enzyme that synthesizes RNA as part of the transcription process
Ions diffuse across membranes through specific ion channels down _____.
A) their chemical gradients
B) their concentration gradients
C) the electrical gradients
D) their electrochemical gradients