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Midterm I
Biology 143 – October 5, 2007
Dr. Andrew Laursen
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the
question.
1. How does a scientific theory differ from a scientific hypothesis?
A) There is no difference-the terms are interchangeable.
B) A theory is an explanation for a very general phenomenon or observation; hypotheses treat
more specific observations.
C) Theories define scientific laws; hypotheses are used to set up experiments.
D) A hypothesis is an explanation for a very general phenomenon; theories treat more specific
issues.
2. At the pH found in cells (about 7.0), what happens to the carboxyl group on an amino acid?
A) It acts as a base and gains a proton, giving it a positive charge.
B) It acts as an acid and loses a proton, giving it a negative charge.
C) It remains neutral, like water, and does not have a charge.
D) It is reduced, and tends to act as an electron donor in redox reactions.
3. How does this affect the behaviour of the amino acid?
A) Allows the amino acid to form branched chains during polymerization
B) Makes the amino acid more hydrophobic
C) Makes the amino acid more hydrophilic
D) None of the above
4. Which of the following involves a decrease in free energy?
A) polymerization
B) condensation
C) hydrolysis
D) chemical evolution
5. Such a reaction could occur spontaneously
A) False
B) True
6. Imagine you are an anthropologist and you come upon an ancient garbage dump. You want to know
how old the site is, so you can learn more about the people who created it. You decide the best approach
would be carbon dating. You know that when new organic matter (such as food) forms, the total carbon
pool is 0.04% 14C (the rest is 12C and 13C). You also know that the half-life of 14C is ~ 5700 years. When
you analyze the garbage from the dump, you find that the carbon is 0.005% 14C. Approximately how old is
the dump?
A) 5,700 years
B) 11,400 years
C) 17,100 years
D) 22,800 years
7. Consider the following bonds: C-H & C-O. Which of the following statements is true?
A) The O-H bond has greater chemical energy, and an oxidation reaction converting C-H bond to
C-O bond will be endergonic
B) The O-H bond has greater chemical energy, and an oxidation reaction converting C-H bond to
C-O bond will be exergonic
C) The C-H bond has greater chemical energy, and a reduction reaction converting C-O bond to
C-H bond will be endergonic
D) The C-H bond has greater chemical energy, and a reduction reaction converting C-O bond to
C-H bond will be exergonic
Refer to the diagram of a molecule below when answering questions 8 - 13:
8. This molecule is a monomer, used to build a larger organic molecule (polymer). What type of monomer
is this?
A) Amino acid
B) Monosaccharide
C) Nucleotide
D) Fatty acid
9. Imagine that several of these monomers (identical to the one above) were connected to each other.
Which of the following would be true of the resulting polymer?
A) It would be hydrophilic
B) It would be hydrophobic
C) It would diffuse easily through a cell membrane
D) Not enough information to tell
10. The bonds formed when these monomers polymerize are referred to as:
A) Phosphodiester bonds
B) Glucosidic linkages
C) Hydrogen bonds
D) Peptide bonds
11. The polymer’s overall shape would be attributed to what types of interactions?
A) Van der Waals
B) Hydrogen bonds
C) Ionic bonds
D) A and B only
E) All of the above
12. Which would be the most likely function of this polymer in a cell?
A) Storage of hereditary information
B) Structural component of cell
C) Storage of energy
D) All of the above
13. Where would this polymer most likely be located?
A) In the nucleoplasm of the cell
B) In the cytoplasm of the cell
C) Embedded in the cell membrane
D) Outside the cell as part of the extracellular matrix.
Refer to the diagram of a molecule below when answering questions 14 - 19:
Referring to the above picture, answer questions
14a. ON THE DIAGRAM, label sugar’s carbon atoms from 1’ to 5’
14b. When monomers of this type are polymerized, they will form nucleic acids. The nucleic acid
elongates (grows) when a new monomer is attached. ON THE DIAGRAM circle the carbon atom to
which the next monomer would attach.
14c. ANSWER THIS AND ALL REMAINING QUESTIONS ON THE SCAN SHEET. THIS
QUESTION SHOULD BE ANSWERED AS #14 ON YOUR SHEET.
This type of sugar (from diagram) is:
A) Glucose
B) Fructose
C) Deoxyribose
D) Ribose
15. This sugar would be classified as a:
A) Ketose
B) Triose
C) Pentose
D) Hexose
16. The nitrogenous base on this monomer is a(n):
A) Pyrimidine
B) Purine
17. Which of the following bases could be complementary to the base on the monomer in the diagram?
A) Uracil
B) Thymine
C) Guanine
D) Adenine
18. A nucleic acid made out of this type of monomer would be:
A) Single-stranded
B) Double-stranded
19. Which of the following would be the most likely function of such a nucleic acid?
A) Storage of hereditary information
B) A temporary copy of a gene (transcript)
C) Storage of energy
D) Structural element of a cell
20. In cells, the activity of enzymes is often regulated by other molecules. Which of the following is true
regarding regulation?
A) If the product of a reaction is abundant, regulatory molecules will denature the enzyme,
causing it to stop producing the product.
B) If the product of a reaction is abundant, the cell will cease making the product and use the
reactants in different chemical reactions.
C) If the product of a reaction is abundant, the cell will need to make even more of the product.
D) None of the above
21. Regulation of an enzyme’s function can occur through inhibition. Which of the following best
describes allosteric inhibition?
A) Regulatory molecule binds to the products of a reaction, preventing release from the enzyme’s
active site
B) Regulatory molecule binds to the reactants of a reaction, preventing them from entering the
enzyme’s active site
C) Regulatory molecule binds to the enzyme at a site other than active site, changing the shape of
the active site of the enzyme
D) Regulatory molecule binds to active site of the enzyme preventing the reactants from entering
the active site
22. HIV is the virus that causes AIDS. In the mid-1990s, researchers discovered an enzyme in HIV called
protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into
the active site and block it. If this strategy for stopping HIV infections were successful, it would be an
example of what phenomenon?
A) allosteric regulation
B) vaccination
C) poisoning
D) competitive inhibition
23. Which of the following observations is the strongest argument in favor of the hypothesis that protein
structure and function are correlated?
A) Enzymes tend to be globular in shape.
B) Proteins function best at certain temperatures.
C) Proteins have four distinct levels of structure and many functions.
D) Denatured (unfolded) proteins do not function normally.
24. How can phosphorylation drive an endergonic reaction?
A) It raises the potential energy of the reactant molecule(s), making subsequent reactions
exergonic.
B) It stabilizes the transition state of the reaction.
C) It adds needed heat to the reactants so they have sufficient energy to complete the reaction.
D) It raises the activation energy of the reaction.
25. A strand of DNA has the following sequence: 5’-ATACGACT-3’. What is the sequence of the
complementary strand?
A) 5’-ATACGACT-3’
B) 5’-TATGCTGA-3’
C) 5’-TCAGCATA-3’
D) 5’-AGTCGTAT-3’
26. Now consider a strand of DNA with the following sequence: 5’-GCTACGCG-3’, and a second strand
with the sequence: 5’-ATACGACT-3’. Imagine that each DNA molecule is double-stranded, thus each
sequence above has a complementary strand. Which DNA molecule would most easily denature?
A) The molecule containing the sequence 5’- GCTACGCG -3’, due to weaker phosphodiester
bonds in the sugar-phophate backbone of the molecule
B) The molecule containing the sequence 5’- ATACGACT -3’, due to weaker phosphodiester
bonds in the sugar-phophate backbone of the molecule
C) The molecule containing the sequence 5’-GCTACGCG-3’, due to less hydrogen-bonding
between complementary strands
D) The molecule containing the sequence 5’- ATACGACT -3’, due to less hydrogen-bonding
between complementary strands
27. Imagine 2 nucleic acids which contain the following sequences: 5’-ATACGTACGTTA-3’ and 5’AUACGUACGUUA-3’. Which of these molecules might catalyze chemical reactions?
A) The one containing 5’-ATACGTACGTTA-3’
B) The one containing 5’-AUACGUACGUUA-3’
28. In the context of chemical evolution, DNA's structure is interesting because it suggests a possible
copying mechanism. What about DNA's structure facilitates copying?
A) DNA always goes from 5' to 3'.
B) The nitrogenous bases are located on the inside of the double helix.
C) It has the same number of purines and pyrimidines.
D) The strands of the double helix are complementary.
29. Although DNA is the main hereditary material in all life-forms, it lacks one important characteristic of
being a candidate for the first life-form. Why have researchers rejected the idea that DNA was found in the
first life-form?
A) Because it has only four different bases, it does not carry enough information; therefore, it
cannot adapt and evolve.
B) The type of sugar found in DNA is much too complicated to have been present early in Earth's
history.
C) It does not function as a catalyst
D) It is not stable enough to have withstood early Earth's harsh atmosphere.
30. Which of the following is not true about RNA?
A) RNA is less stable than DNA.
B) RNA is more reactive than DNA.
C) RNA functions primarily as a catalyst in present-day cells.
D) RNA could theoretically serve as a template for its own synthesis.
31. Cellulose and glycogen have different structure. What accounts for the structural difference between
these molecules?
A) Cellulose is made of β glucose subunits, allowing hydrogen bonding between adjacent strands
B) Cellulose is made of alternating α and β glucose subunits, allowing hydrogen bonding between
adjacent strands
C) Strands of cellulose branch, strands of glucose are linear
D) Celluose is made of galactose subunits, glycogen is made of glucose subunits
32. When an insect is crushed, it creates a crunching sound. This is due to the crushing of a structural
carbohydrate. What carbohydrate is the most likely source of this sound?
A) cellulose
B) glycogen
C) peptidoglycan
D) starch
E) chitin
33. Which functional group(s) is/are found in carbohydrates?
A) phosphate
B) carbonyl
C) hydroxyl
D) A and B
E) B and C
34. A carbohydrate is found on the outer surface of a cell, attached to a protein. What is the most likely
function of this carbohydrate?
A) This carbohydrate is an energy source.
B) This carbohydrate is a cofactor for an enzyme that is involved in cell transport.
C) This carbohydrate is acting as some sort of signal to other cells.
D) This carbohydrate is helping to anchor some protein to the cell membrane.
35. Chitin is a structural carbohydrate that is found in the cell walls of fungi. It forms a rigid wall around
the cell. Yeasts are single-celled fungi. Given what you know about other types of cells, you should expect
to find yeast in which of the following environments?
A) Isotonic solutions
B) Hypertonic solutions
C) Hypotonic solutions
36. In a cold environment, cell membranes become less fluid, and therefore, less permeable. Imagine that
you have just discovered a new archaea that lives in an extremely cold climate (such as pockets within ice).
Which of the following would you predict to be true about the phospholipids in its membranes?
A) Their hydrocarbon tails will be short and saturated.
B) They will have extremely long hydrocarbon tails.
D) They will interact extensively with cholesterol.
C) Their hydrocarbon tails will be short and highly unsaturated.
37. The hydrocarbon tails of the phospholipids in this archaea’s membrane (from previous question) will
be made of which of the following lipids?
A) Cholesterol
B) Isoprene chains
C) Fatty acids
D) Waxes
38. Which type of molecules most easily move across a membrane?
A) ions, like chloride (Cl-)
B) small, hydrophobic molecules, like N2
C) small, uncharged polar molecules, like water
D) large polar molecules, like glucose
39. Calcium (Ca2+) is an important ion in cell signaling (particularly inside the cell). Suppose calcium
concentration is greater outside the cell than inside the cell. Ca2+ will move into the cell by:
A) simple diffusion across the membrane
B) facilitated diffusion through a channel protein
C) endocytosis
D) transport through a Ca2+ pump protein
40. The process above will be:
A) Active, requiring energy
B) Active, requiring no energy
C) Passive, requiring energy
D) Passive, requiring no energy
41. Within the cell, calcium is stored inside the smooth ER. It is released in response to secondary
messengers. At the termination of a signaling event, the calcium is returned to the smooth ER. This will be
accomplished by:
A) simple diffusion across the membrane
B) facilitated diffusion through a channel protein
C) transport through a Ca2+ pump protein
D) endocytosis
42. At room temperature, the cell membrane has the consistency of olive oil. Cooling the membrane
________ its fluidity and ________ its permeability.
A) decreases; decreases
B) increases; increases
C) increases; decreases
D) decreases; increases
43. Which of the following represents a major difference between prokaryotic cells and eukaryotic cells?
A) Prokaryotes are unable to carry out aerobic respiration, a process that requires a complex innermembrane system.
B) Prokaryotes do not possess ribosomes
C) Eukaryotic cells have membrane bound organelles
D) Prokaryotes use RNA in storage of hereditary information
E) Prokaryotes lack any inner membrane structures.
44. What is the function of the nuclear pore complex?
A) communicates with components of the endomembranal system
B) synthesizes and repairs DNA, the unit of genetic information
C) assembles ribosomes from raw materials that are synthesized in the nucleus
D) regulates movement of materials across the nuclear membrane
45. Green algae are single-celled organisms. They share many characteristics with plant cells, such as
being surrounded by cellulose cell walls. Some algae move with flagella, but due to the cell wall, algae will
not move by “cell crawling”. Amoebae are also single-celled organisms, but are more like animal cells.
They lack a cell wall and move by crawling. Comparing these two organisms, which of the following might
you most reasonably expect:
A) more mitochondria in algae
B) more actin beneath the cell membrane in amoebae
C) centrioles in algae but not amoebae
D) Absence of intermediate filaments in algae
46. Liver cells play an important role in the detoxification of chemicals. Comparing a liver cell with a
blood cell, you might expect to find a higher density of ___________ in liver cells.
A) Peroxisomes
B) Golgi stacks
C) Mitochondria
D) Lysosomes
47. You have a distant cousin, age 4, who is always tired and fatigued and is not able to play games and
sports like other healthy children. He is most likely to have an enzyme deficiency or defect associated with
which intracellular organelle?
A) mitochondria
B) peroxisomes
C) Golgi stacks
D) lysosomes
48. Plant cells are typically exposed to a hypotonic environment. Therefore, you would expect:
A) the plasma membrane to exert outward force on the cell wall
B) no contact between the cell wall and the cell membrane
C) a microscopic space between the plasma membrane and the cell wall
D) occasional contact between the plasma membrane and the cell wall
49. Within mitochondria, the reduction of O2 (during cellular respiration) can result in formation oxygen
free-radicals. These free-radicals can oxidize molecules in the membrane, and destroy the mitochondrion.
As a result, we have a high turn-over of mitochondria. We make new ones, and destroy the old ones. What
organelles are needed within a cell to destroy an old, defective mitochondrion?
A) peroxisomes
B) cytoskeletal proteins
C) phagosomes
D) lysosomes
50. Spherocytosis is a defect in red blood cells that is caused by a defective cytoskeletal protein used to
make intermediate filaments. What do you suspect is one consequence of defective cytoskeletal proteins in
red blood cells?
A) insufficient energy supply in the cell
B) abnormal cell shape
C) adhering of blood cells to blood vessel walls, causing the formation of plaque
D) a lack of cellular proteins available to transport oxygen
51. Turgor pressure occurs when ________.
A) solute concentration is higher inside the cell than outside, so that water enters the cell by
osmosis.
B) solute concentration is higher inside the cell than outside, so that water leaves the cell by
osmosis
C) solute concentration is the same inside the cell and outside, so that water pushes on the cell
wall
D) solute concentration is lower inside the cell than outside, so that water enters the cell by
osmosis
52. Human growth hormone is a protein produced by cells in the anterior pituitary gland. If you looked at
one of these cells with an electron microscope (to better see cell structures) you might expect to find that
the space within the cell is:
A) dominated by rough ER
B) dominated by mitochondria
C) dominated by smooth ER
D) dominated by actin filaments
53. Receptors for human growth hormone would be located:
A) On the surface of only certain types of cells in the body
B) On the surface of all cells in the body
C) Inside the cytoplasm of each cell in the body
D) Inside the cytoplasm of only certain types of cells
54. Given the nature of human growth hormone receptors, it is expected that:
A) Reception of the hormone would induce transcription of a single gene
B) Reception of the hormone could induce the transcription of many genes
C) The signal strength would not be amplified within the cell
D) Both A and C
55. Occasionally, when high levels of a hormone are produced for a long period of time, we become less
sensitive to the hormone. This happens because cells become less responsive to the hormone. How can
cells become less responsive to a hormone?
A) They reduce the number of receptor proteins for the hormone
B) They increase the number of receptor proteins for the hormone
C) The nuclear pore complex prevents messenger molecules from entering the nucleus
D) High concentrations of the hormone inhibit enzymes that produce secondary messengers
(allosteric inhibition)
56. In some stratified epithelial tissues and in muscle tissue, cells are held together by strong, yet flexible
connections. These connections leave spaces between adjacent cells and allow one cell to move (a little)
relative to another, while still maintaining a strong connection between the cells. These cells are held
together by:
A) tight junctions
B) plasmodesmata
C) gap junctions
D) desmosomes
57. Blood calcium levels are regulated by two hormones, parathyroid hormone and calcitonin. When blood
calcium levels rises, calcitonin is released; it binds to receptors in osteocytes and, through signal
transduction, results in an increase in calcium deposition in bones, effectively lowering blood calcium.
When blood calcium decreases, parathyroid hormone is released, binds to receptors on osteoclasts, and
causes dissolution of calcium phosphate, releasing calcium into the blood. Imagine a patient has high
levels of blood calcium, causing severe muscular pain and putting the patient at risk of paralysis. What
might be causing the elevated blood calcium levels?
A) defective receptors for calcitonin
B) defective receptors for parathyroid hormone
C) inadequate production of parathyroid hormone
D) B and C, only
E) All of the above
58. Suppose a hormone receptor is associated with a G-protein. When the hormone binds to the receptor,
what does the G-protein do?
A) Binds to the receptor, phosphorylating the receptor
B) Splits ATP and uses the energy to catalyze a reaction (acts as an enzyme)
C) Releases from the receptor, migrates to an enzyme, and phosphorylates the enzyme
D) Releases from the receptor and migrates to the nucleus, inducing transcription of a gene
Chapter 9: Cellular Respiration and Fermentation
1. The metabolic pathway glycolysis is active when cellular energy levels are ________; the regulatory
enzyme phosphofructokinase is ________ by ATP.
A) high; activated
B) low; activated
C) high; inhibited
D) low; inhibited
2. In eukaryotes, the energy of electrons as they pass through protein complexes serves to pump
(translocate) protons to the intermembrane space in the mitochondrion. How does this help the
mitochondrion to produce energy?
A) The protons receive electrons from the NAD + and FADH+ to form H2, a source of energy for the
cell.
B) The protons pick up electrons from the electron transport chain on their way through the inner
mitochondrial membrane.
C) The hydrogen ions (protons) are transferred to oxygen in an energy-releasing reaction.
D) The translocation of protons sets up the electrochemical gradient that drives ATP synthesis in the
mitochondria.
3. Both aerobic and anaerobic respiration have glycolysis as a first series of steps. What is the NET
outcome of glycolysis?
A) Production of 2 ATP
B) Production of 36 ATP
C) Production of 2 NADH
D) Production of 2 ATP and 2 NADH
E) Production of 30 ATP and 6 NADH
4. At what step(s) in glycolysis is ATP needed?
A)
B)
C)
D)
E)
Conversion of glucose to glucose 6-phosphate
Conversion of glucose 6-phosphate to fructose 6-phosphate
Conversion of fructose 6-phosphate to fructose 1,6-bisphosphate
A and B only
A and C only
The Krebs Cycle. Below is a diagram of the Krebs Cycle. The Roman numerals I, II, and III represent
missing names of organic acids. Letters refer to steps in the Krebs Cycle. Use the diagram to answer the
questions 5 - 7.
Acetyl-CoA
citrate
isocitrate
III.oxaoxaloacetate
A
E
I.α ketoglutarate
malate
B
II. fumarate
Succinyl CoA
D
succinate
C
5. The missing names for the organic acids are:
A) I. Fumarate, II. Oxaloacetate, and III. α-ketoglutarate
B) I. Oxaloacetate, II. Fumarate, and III. α -ketoglutarate
C) I. α -ketoglutarate, II. Fumarate, and III. Oxaloacetate
D) I. α -ketoglutarate, II. Oxaloacetate, and III. Fumarate
6. At which step(s) is FADH+ molecules reduced to FADH2? (choose all that apply)
A) Step A
B) Step B
C) Step C
D) Step D
E) Step E
7. At which step(s) is ATP produced? (choose all that apply)
A) Step A
B) Step B
C) Step C
D) Step D
E) Step E
8. In the electron transport chain, the molecule ubiquinone (Q) has what function(s)?
A) Transports electrons to protein complex III
B) Transports protons from the mitochondrial matrix to the intermembrane space
C) It oxidizes water to O2
D) Both A and B
E) Both A and C
9. How does FADH2 differ from NADH?
A) Electrons donated by FADH2 result in transport of 2 protons to intermembrane space, Electrons
donated by NADH result in transport of 3 protons to intermembrane space
B) Electrons donated by FADH2 result in transport of 3 protons to intermembrane space, Electrons
donated by NADH result in transport of 2 protons to intermembrane space
C) Electrons donated by FADH2 to the electron transport chain result in greater production of ATP
than electrons donated by NADH.
D) None of the above
10. Protons pass from the intermembrane space to the mitochondrial matrix through the ATP synthase
complex, resulting in the production of ATP. Why do these protons pass through the ATP synthase
molecule?
A) There is a concentration gradient with a higher concentration of protons in the intermembrane
space than in the mitochondrial matrix
B) Protons cannot diffuse through the mitochondrial membrane
C) The ATP synthase molecule includes a transmembrane proton channel
D) All of the above
E) None of the above