Download BIOLOGY COMPETITION REVIEW QUESTIONS PRACTICE EXAM

BIOLOGY COMPETITION REVIEW QUESTIONS
30. Which statement about ATP synthesis is FALSE?
a. ATP is synthesized only in chloroplasts and mitochondria.
b. ATP synthesis in the chloroplast occurs in the thylakoid region of this organelle.
c. Proton motive force (proton gradient) drives the formation of ATP in mitochondria.
d. ATP synthases are protein complexes that allow protons to cross membranes.
e. Substrate level phosphorylation of ADP does not require ATP synthase to catalyse
the reaction.
2. In the evolution of life on Earth the early primitive cells that were present must
have obtained their energy by:
a. glycolysis and fermentation.
b. aerobic respiration.
c. cyclic phosphorylation.
d. noncyclic phosphorylation.
e. oxidative phosphorylation.
47. How does a noncompetitive inhibitor inhibit binding of a substrate to an enzyme?
a. It binds to the substrate.
b. It binds to the active site.
c. It lowers the activation energy.
d. It increases the change in free energy ( G) of the reaction.
e. It changes the shape of the active site.
47. Which statement about enzymes is FALSE?
a. They function best at a particular pH.
b. All enzymes are catalysts.
c. They function best at specific temperatures but break down at high temperatures.
d. They undergo a major chemical change after reacting with their specific substrate.
e. They are essential to the metabolism of cells for the conversion of energy.
41. A scientist grew some plant cells in a liquid culture medium in the light. When he
looked at the culture, it appeared green. He then added some sugar to the medium
and turned off the lights. After a few days, the culture appeared white, but when he
examined a few drops of the culture under the light microscope using the 10x
objective, he counted twice as many cells per millilitre than had been present before
he turned the lights off. Which is the best explanation of these results?
a. The plant cells died, and the cells seen under the microscope were bacteria that
had used the sugar for food.
b. Because plant cells contain mitochondria, they used the energy from respiration to
continue growing in the dark.
c. In the absence of light, chloroplasts turn into mitochondria and can use sugar for
respiration.
d. In the dark, energy can be produced by chloroplasts as long as they have a source
of sugar.
e. In the light, photosynthesis results in proteins being stored in the chloroplasts,
and this protein can be broken down in the dark to release energy for cell growth.
44. Which statement about glycolysis is FALSE?
a. During glycolysis, glucose is metabolized to pyruvate with the formation of ATP
and NADH+H+.
b. The initial step in glycolysis requires the phosphorylation of glucose by the
enzyme phosphoglucomutase.
c. The conversion of phosphoenolpyruvate to pyruvate is catalysed by the enzyme
pyruvate kinase and results in the formation of ATP.
d. The end product of glycolysis, pyruvate, can be used by yeast to produce ethanol
during fermentation.
e. Glycolysis occurs outside the mitochondria.
33. The sequence of steps in cellular respiration is:
a. Pyruvate oxidation --> electron transport chain citric --> acid (Krebs) cycle
b. Pyruvate oxidation --> citric acid (Krebs) cycle --> electron transport chain
c. Citric acid (Krebs) --> cycle pyruvate oxidation --> electron transport chain
d. Citric acid (Krebs) --> cycle electron transport chain --> pyruvate oxidation
e. Electron transport chain --> pyruvate oxidation --> citric acid (Krebs) cycle
5. In the absence of oxygen, cells capable of fermentation:
a. accumulate glucose.
b. no longer produce ATP.
c. accumulate pyruvate.
d. oxidize FAD.
e. oxidize NADH to produce NAD+.
24. Which of the following use their own metabolic energy to maintain a near
constant body temperature?
i. Fish iv. Amphibians
ii. Birds v. Mammals
iii. Reptiles
a. i, ii, iii, iv and v
b. ii, iii, iv and v
c. ii, iii and v
d. ii and v
e. v only
18. When an organism is temporarily deprived of oxygen it obtains its energy from:
a. the citric acid (Krebs) cycle.
b. the respiratory electron-transport chain.
c. the oxidation of pyruvic-acid to acetyl-CoA.
d. glycolysis and fermentation.
e. none of the above.
19. Which statement about photosynthesis is FALSE?
a. In green plants, both photosystems I and II are required for the synthesis of
NADPH+H+.
b. The first stable product of photosynthesis in the majority of green plants (C3-type
plants) is 3-phosphoglycerate.
c. In normal aerobic environments and saturating levels of light, an increase in CO 2
concentration from 0.03% to 0.06% (300 ppm to 600 ppm) will result in an increase
in the rate of CO2 fixation by most green plants (C3-type plants).
d. Photosynthesis is a redox process: H2O is oxidized, CO2 is reduced.
e. The enzymes required for CO2 fixation in plants are located only in the grana of
the chloroplast.
43. In what respects are the photosynthetic adaptations of C 4 plants and CAM plants
similar?
a. In both cases, the stomata normally close during the day.
b. Both types of plants make their sugar without the Calvin-Benson cycle.
c. In both cases, an enzyme other than rubisco carries out the first step in carbon
fixation.
d. Both types of plants make most of their sugar in the dark.
e. Neither C4 plants nor CAM plants have grana in their chloroplasts.
37. Which statement about the two pathways of photosynthesis is FALSE?
a. The first pathway (the light reactions) captures light energy and produces ATP and
NADPH + H+.
b. The second pathway (the Calvin-Benson cycle) uses the products of the first
pathway and CO2 to produce sugars.
c. The second pathway is also known as the dark reactions because none of its
reactions uses light directly.
d. The light reactions occur within chloroplasts; the Calvin-Benson cycle takes place
in the cytosol.
e. Both pathways stop in the dark.
44. Which of the following conditions would yield the highest rate of photosynthesis
(as measured by the release of O2)?
Answer: a
22. Which statement about the light reactions of photosynthesis is FALSE?
a. Chlorophyll a is the only pigment that can absorb photons.
b. Electrons from chlorophyll a are boosted to a higher energy level.
c. As electrons are lost from chlorophyll a through the electron transport chain, they
are replaced through the photolysis of water.
d. The photolysis of water releases protons into the interior of chloroplast membrane
sacs (thylakoids), thus generating a proton gradient that can drive ATP synthesis.
e. Photophosphorylation results in the reduction of NADP+ to NADPH.
30. Coupled biochemical reactions are important in determining thermodynamic
order within cells. The figure below shows two hypothetical reactions, I and II. Which
statement about these reactions is FALSE?
a. The splitting of ATP to ADP + Pi releases about 7.3 kcal/mole.
b. The reaction of compound A to produce compound B requires an input of about 4
kcal/mole, which is provided by reaction II.
c. Reaction I is exergonic, yielding 4 kcal/mole.
d. The two coupled reactions release about 3.3 kcal/mole.
e. To drive reaction I, the splitting of ATP to ADP + Pi is always required.
34. If ÎG of a chemical reaction is negative and the change in entropy is positive,
what can one conclude about the reaction?
a. It is endergonic.
b. It is exergonic.
c. It requires energy.
d. It is anabolic.
e. It will not reach equilibrium.
32. Which statement is FALSE?
a. Catabolism refers to the metabolic breakdown of complex molecules into more
simple molecules.
b. An exothermic reaction is one in which energy is released.
c. The term "activation energy" is used to describe the total amount of energy
released by a reaction.
d. Enzymes are able to catalyse certain reactions by lowering the activation energy.
e. The synthesis of carbohydrates from CO2 and H2O by photosynthesis is an
example of an endothermic reaction.
16. The second law of thermodynamics states that as entropy increases, free
(usable) energy:
a. is released as heat energy.
b. varies inversely with the absolute temperature.
c. increases.
d. decreases.
e. remains constant.
22. What two characteristics make water different from most other compounds?
a. Its solid state is less dense than its liquid state, and it takes up large amounts of
heat to change to its gaseous state.
b. Its solid state is less dense than its liquid state, and it takes up only small
amounts of heat to change to its gaseous state.
c. Its solid state is more dense than its liquid state, and it takes up large amounts of
heat to change to its gaseous state.
d. Its solid state is more dense than its liquid state, and it takes up only small
amounts of heat to change to its gaseous state.
e. Its solid state is just as dense as its liquid state, and it takes up no heat to change
to its gaseous state.
5. Which statement about the properties of water and its role in biological systems is
FALSE?
a. In a water molecule, hydrogen atoms are linked to the oxygen atom by polar
covalent bonds.
b. The combination of hydrophobic and hydrophilic interactions of a protein with
water can influence the shape of the protein.
c. The solubility of NaCl in water is a product of the interactions between the water
molecules and the ions in the salt.
d. Water is a liquid at room temperature because of the hydrogen bonds that occur
between individual water molecules.
e. Water boils at 100 C as a result of the breakage of the bonds between the
hydrogen and oxygen atoms.
6. The graph below shows the percent content of proteins, lipids, and carbohydrates
in the storage tissues ofseeds from five different species. (Other seed components
such as minerals are not shown.) Which storage tissue has the greatest lipid
content?
a. Species A
b. Species B
c. Species C
d. Species D
e. Species E
12. Which statement about proteins is CORRECT?
a. The primary structure of a protein is composed of many branched chains.
b. Proteins always contain an amino group at one end and the amino acid methionine
at the other end.
c. The formation of disulfide bridges between cysteine amino acids can modify a
protein's primary structure.
d. Charged amino acids are frequently found in the hydrophobic interior of a folded
protein.
e. The quaternary structure of proteins is the result of the interactions of two or
more independent polypeptide chains.
13. One aspect of genetic engineering involves the modification of proteins to
improve their function. Which statement would NOT be a logical goal for researchers
in this field?
a. Increase the hydrophobicity of a protein so that it will function in the aqueous
environment of the cell cytoplasm.
b. Improve the binding of a specific substrate to an enzyme.
c. Modification of an enzyme active site to increase the rate of catalysis.
d. Increase the stability of a protein so that it may function at a higher temperature.
e. Change the amino acid content of the protein to improve its value as a more
nutritious food for animals or humans.
36. Which statement is FALSE?
a. Carbohydrates always contain carbon, hydrogen, and oxygen.
b. Carbohydrates are assembled from units of fatty acids.
c. Carbohydrates can be used as an energy source for plant and animal cells.
d. Cellulose and starch are carbohydrates.
e. Sucrose is made from joining glucose with fructose.
27. Which chemical bonds are considered the strongest, requiring the most energy to
break?
a. Ionic bonds
b. Hydrogen bonds
c. Van der Waals forces
d. Covalent bonds
e. Polar bonds
3. What occurs when fat is synthesized?
a. One fatty acid and one glycerol molecule are hydrolysed.
b. Three fatty acid molecules combine with a molecule of glycerol to produce a
molecule of fat plus three molecules of water.
c. Three fatty acid molecules are hydrolysed by three molecules of water and one
molecule of glycerol to produce a fat molecule.
d. One fatty acid and one glycerol molecule are condensed.
e. All bonds between the carbon atoms in the hydrocarbon chain become single
bonds.
12. A scientist was studying the production of a protein that was released by an
animal cell into a culture medium. She found that the protein only appeared in the
culture medium after she added a few drops of a hormone to the cell. Before adding
the hormone, she labelled the protein inside the cell with a fluorescent dye and
looked at the cell under the light microscope: the dye was seen in flattened sheets
and tube-like structures throughout the cell, and in stacks of flattened sac-like
structures. After adding the hormone, the dye was also seen as small dots clustered
against the cell membrane. Which statement most likely explains these
observations?
a. The hormone stimulates protein synthesis in the cell vacuole; the protein is then
passed to the Golgi apparatus, and eventually passes through the cell membrane by
passive diffusion.
b. The hormone triggers the synthesis of the protein in the endoplasmic reticulum
and it is then secreted outside of the cell via channel proteins in the cell membrane.
c. The protein is made on parts of the cytoskeleton, is passed to the Golgi apparatus,
and is secreted through hormone-stimulated exocytosis.
d. The protein is made in the endoplasmic reticulum, is passed to the Golgi
apparatus, and is secreted through hormone-stimulated exocytosis.
e. The protein is made in the Golgi apparatus, is passed to the endoplasmic
reticulum, and is secreted through hormone-stimulated pinocytosis.
29. NaCl is harmful to most crop plants. A scientist at the University of Toronto
genetically modified a plant so that it could be grown in dry parts of the world where
the available water has a high level of NaCl. This genetically modified plant copes
with the high levels of NaCl by transporting salt into its vacuoles where it
accumulates to abnormally high levels. Which feature would be observed in the
genetically modified plant when compared to a non-modified plant?
a. The leaves in the modified plant are more yellow in colour.
b. The modified plant has salt crystals on the surface of its leaves.
c. The cytosol (the material between the plasma membrane and the vacuole
membrane, excluding the organelles) in the modified plant has a lower osmotic
pressure.
d. The cytosol in the modified plant has a higher osmotic pressure.
e. The osmotic pressure is the same in both plants.
16. Some single-celled, non-photosynthetic organisms have a water expulsion
vacuole that collects water from the cytoplasm and expels it from the cell. If you
were trying to grow one of these organisms in the laboratory, which growth medium
would be closest to its natural habitat? A dilute, aqueous, nutrient solution:
a. supplemented with 1M NaCl.
b. supplemented with 1M sucrose.
c. supplemented with 1M glucose.
d. supplemented with 1M KCl.
e. with no supplements.
14. A scientist isolated pieces of plasma membrane from an animal cell and put them
in an apparatus so that the membrane separated two reservoirs of distilled water.
When she added a dilute solution of acetic acid to one side (side A) of the
membrane, the pH of the solution on the other side (side B) did not change. She
then ground up a culture of animal cells, filtered out the organelles and bits of
membrane, and added this cell extract to side A. The pH of the solution in side B
then dropped. What is the most reasonable explanation for the drop in pH in side B?
a. The cell extract contained lipids that dissolved in the membrane.
b. The cell extract caused the acetic acid to dissociate.
c. Protons moved across the membrane by diffusion.
d. Protons moved across the membrane by passive transport.
e. Protons moved across the membrane by active transport.
31. The content of a large vacuole in a eukaryotic cell has the same osmotic pressure
as the surrounding cytoplasm, to prevent it from shrinking or bursting. If this
eukaryotic cell is placed in a 3 M sucrose solution:
a. the cell would burst.
b. the vacuole would expand and burst.
c. the cell and the vacuole would both shrink.
d. the cell would shrink but the vacuole would remain the same size.
e. nothing would happen, because a 3 M sucrose solution has the same osmotic
pressure as the cell cytoplasm.
1. When a cell that was deprived of nutrients was given glucose, the pH within its
vacuoles dropped. The best reason for this observation is that:
a. a starved cell pumps protons across the plasma membrane to the cell exterior.
b. the dissociation of glucose in the vacuoles releases hydrogen ions.
c. protons leave the vacuole by passive transport.
d. protons enter the vacuole by passive transport.
e. protons enter the vacuole by active transport.
12. Which of the following signal transduction molecules is NOT bound to the plasma
membrane?
a. Cyclic AMP (cAMP)
b. Peptide hormone receptors
c. G proteins
d. Adenylyl cyclase
e. Phospholipase C
31. An electron microscope can visualize structures smaller than 100 nanometres
(nm). Which structures could you only see with the aid of an electron microscope?
i. A frog egg
ii. A plant chloroplast
iii. A virus particle
iv. A protein molecule
v. Most bacteria
a. i, ii, and v
b. ii and iii
c. iii and iv
d. iii and v
e. iv only
15. Which of the following organelles from a living specimen can NOT be observed
under the light microscope (using a x100 objective)?
a. The nucleus of a plant cell.
b. Ribosomes in an animal cell.
c. Chloroplasts in a plant cell.
d. The nucleolus of an animal cell.
e. Mitochondria in a plant cell.
44. A scientist discovered that a protein associated with the plasma membrane of a
cultured animal cell disappeared from the membrane soon after a hormone was
added to the cell. After adding the hormone, if she disrupted the cell and centrifuged
it, the protein did not stay in solution but went to the bottom of the centrifuge tube.
After adding the hormone, if she disrupted the cell and dissolved all membranes with
a detergent before centrifuging, the protein remained in solution. Which statement
best explains her results?
a. The protein was a peripheral membrane protein that came off the membrane after
hormone treatment.
b. The hormone caused the cell to make endocytotic vesicles that specifically formed
at sites in the plasma membrane that contained the protein.
c. The hormone destroyed the protein.
d. The hormone bound to the protein to make the protein heavier.
e. The hormone caused the plasma membrane to break into fragments, causing the
cell to make new plasma membrane without the protein.
32. Which statement is CORRECT?
a. Membranes of living organisms are in a fluid state, rather than in a gel state.
b. Membranes are semipermeable: large molecules such as proteins can easily move
across them.
c. Hydrophilic organic molecules easily diffuse across membranes in eukaryotic cells.
d. In plants, the plasma membrane is known as the cell wall.
e. Rough endoplasmic reticulum is the name given to clusters of ribosomes attached
to the cytoskeleton.
28. DNA fingerprinting has become a familiar forensic tool and has been cited in
recent criminal trials. It is possible to do DNA fingerprinting with even a very minute
sample of DNA because:
a. DNA contains only four different types of nitrogenous bases.
b. there are large quantities of DNA in each cell of the body.|
c. DNA determines a very specific polypeptide chain.
d. one can use the polymerase chain reaction.
e. gel electrophoresis is very effective.
2. You are given a nucleic acid that you think is single-stranded DNA, but you are not
sure. You analyse the
nucleotide composition of the sample. Which of the following compositions would
confirm your thinking?
a. Adenine 38% – Cytosine 12% – Guanine 12% – Uracil 38%
b. Adenine 22% – Cytosine 32% – Guanine 17% – Uracil 29%
c. Adenine 22% – Cytosine 32% – Guanine 17% – Thymine 29%
d. Adenine 38% – Cytosine 12% – Guanine 12% – Thymine 38%
e. None of the above, as this methodology will not resolve the matter.
29. The ratio of __________ in DNA is 1:1.
a. guanine to adenine
b. adenine to thymine
c. cytosine to adenine
d. uracil to cytosine
e. uracil to thymine
23. What DNA sequence information is NOT present in a sequence of complementary
DNA (cDNA)?
i. Introns
ii. Exons
iii. 3' untranslated region
iv. Promoter
a. i and ii
b. i and iv
c. ii and iv
d. iii only
e. iv only
5. Which statement best describes why DNA replication is referred to as “semiconservative”?
a. At each replication, each DNA molecule retains one strand intact and synthesizes
the other strand from new material.
b. After one round of replication, half of the DNA contains the original material and
half is made up of new material.
c. After two rounds of replication, all of the DNA contains a mixture of original and
new material.
d. Within each strand, the number of purines equals the number of pyrimidines.
e. During replication, one strand acts as “leading” and the other as “lagging.”
35. Arrange the following steps involved in synthesis of a protein in the correct
order.
i. A complementary RNA copy of DNA is made.
ii. The DNA double helix unwinds.
iii. mRNA binds to ribosomes.
iv. The amino acids of two adjacent tRNAs form a peptide bond.
v. mRNA leaves the nucleus.
vi. An anticodon of tRNA recognizes an mRNA codon.
a. i, ii, iii, v, vi, iv
b. ii, i, iii, v, iv, vi
c. ii, i, iii, iv, vi, v
d. iv, v, ii, i, vi, iii
e. ii, i, v, iii, vi, iv
29. Scientists estimate that there are approximately 30,000 to 50,000 genes in
humans and an even greater number of proteins produced. This is because:
a. the relationship between genes and proteins is not known.
b. primary RNA transcripts can be alternatively spliced to make different mRNAs.
c. DNA replication occurs throughout life, so that more genes are produced as a
person gets older.
d. both the coding and the template strand of a single gene is transcribed.
e. the mRNA code is translated by the ribosome in the forward and reverse direction.
24. If a molecule of mRNA, prior to splicing or polyadenylation, has 15% A, 20% G,
30% U, and 35% C, what is the composition of the double-stranded DNA that it was
transcribed from?
a. 15% T, 20% C, 30% A, 35% G
b. 15% G, 20% A, 30% C, 35% T
c. 22.5% T, 22.5% A, 27.5% G, 27.5% C
d. 17.5% G, 17.5% A, 32.5% T, 32.5% C
e. 25% A, 25% C, 25% G, 25% T
15. If a polypeptide was encoded by the following mRNA sequence how long (number
of amino acids) would it be? (A table of the genetic code is provided.)
5'-CGAUGUUCCAAGUGAUGCAUAAAGAGUAGC-3'
a. 5
b. 7
c. 8
d. 9
e. 10
49. Which characteristic is shared by ammonia, urea, and uric acid?
a. They are all nitrogenous wastes.
b. They all need large amounts of water for excretion.
c. They all require about the same amount of energy to produce.
d. They are all equally toxic.
e. They are all produced in the kidney.
42. Which of the following is NOT a function of the mammalian kidney?
a. Water retention
b. Regulation of sodium in the blood
c. Excretion of toxins
d. Synthesis of urea
e. Water excretion
28. In a comparison of amounts of urea in human urine, the largest amount of urea
would be found with a diet very rich in:
a. animal fat.
b. simple carbohydrates (e.g., sucrose).
c. complex carbohydrates (e.g, starches).
d. protein.
e. fruits and vegetables.
39. With respect to the blood, the mammalian kidney does NOT have an important
role in maintaining which of the following?
a. Water content
b. Osmotic concentration
c. Blood pressure
d. Salt levels
e. Glucose levels
32. Cells have a resting membrane potential of approximately !60 mV. If a cell
received a stimulus that opened Na+ channels in the plasma membrane:
a. K+ ions would enter the cell against their chemical/concentration gradient.
b. Na+ ions would enter the cell down their electrochemical gradient.
c. the membrane potential would change to !80 mV.
d. Na+ ions would leave the cell down their chemical/concentration gradient.
e. K+ ions would leave the cell down their electrical gradient.
12. If the vagus nerves (main nerves of the parasympathetic nervous system) were
cut, which of the following would be true?
a. The heart would stop beating.
b. The diaphragm would be paralysed.
c. Adrenaline secretion by the adrenal gland would cease.
d. None of a, b and c.
e. All of a, b and c.
28. Which of the following would NOT be associated with a decrease in the
conduction velocity of nerve impulses in a neuron?
a. Increasing the length of the axon.
b. Removing the myelin sheath.
c. Cooling the axon.
d. Reducing extracellular Na+ concentration.
e. Decreasing the diameter of the axon.
47. You are a doctor examining a patient who has some difficulty walking, and who
complains about a weakness in the left leg. You find an absence of some reflex
responses to stimuli applied to the left foot; the right foot is normal. Direct electrical
stimulation to leg nerves causes normal muscle twitches in the left foot. Which is
most likely to be the cause of the patient’s condition?
a. Degeneration of myelin sheaths of the motor neurons of the leg.
b. A back injury causing damage to the nerves entering the spinal cord.
c. Low production of the neurotransmitter acetylcholine.
d. A neck injury causing spinal cord damage.
e. Disease of the autonomic nervous system.
31. In a hormonal control system, hormone X inhibits the secretion of substance Y. If
this system works by positive feedback, which of the following would be CORRECT?
a. Substance Y stimulates the production of hormone X.
b. Secretion of substance Y should stop completely.
c. Levels of hormone X should not be affected by levels of substance Y.
d. Levels of substance Y will stabilize at a moderate level.
e. Both (a) and (d) are correct.
36. "Homeostasis" implies maintaining a constant condition in the body. Yet
organisms have to change; for example, when they grow and develop, and when
they respond to internal needs such as hunger and reproduction. Which one of the
following would allow a controlled change in a system regulated by negative
feedback?
a. An increased gain in the feedback loop; that is, a larger response to any "error"
(departure from the set-point).
b. A reversal of sign in the feedback loop to make it positive.
c. A change in the set-point of the feedback loop toward a new value.
d. An "opening" of the loop; for example, by blocking signals conveying error
information.
e. A decrease in the rate with which the loop responds to errors.
7. Which bodily process involves a positive feedback loop?
a. Kidney function
b. Insulin secretion
c. Sweating
d. Muscle contraction
e. Childbirth