large quantities of rough endoplasmic reticulum
Plasma cells are specialized for antibody secretion and large quantities of these proteins are synthesized for export from the cells. In plasma cells, you would expect to find which of the following?
phosphorus, nitrogen, oxygen, carbon, and hydrogen (CHONP)
The five elements found in the highest frequency in biological systems are
The protein has quaternary structure.
Enzyme K has a total of 4 active sites. When you denature the molecule to study it's composition, you find that each active site occurs on a different polypeptide. Which of the following hypotheses does this observation support?
Red blood cells carry very large amounts of hemoglobin, which carries iron in its heme group. Iron is transported throughout the body bound to a protein called transferrin. When the transferrin-iron complex binds to the transferrin receptor on red blood cell precursors in the bone marrow, this complex is brought into the cells in vesicles. The pH inside these vesicles falls and the iron ions are released from the transferrin. The delivery of iron into cells via this mechanism is a result of:
speciﬁcity of enzymes binding to their substrate(s)
The lock-and-key analogy for enzymes applies to ______.
This cell likely manufactures large amounts of lipids, but not of proteins for export from the cell
You observe a cell under the microscope that exhibits very large amounts of smooth endoplasmic reticulum, but relatively small amounts or rough endoplasmic reticulum. Which of the following best describes this cell?
It is hydrophobic
Suppose you discovered a new amino acid. Its R-group contains only hydrogen and carbon atoms. Predict the behavior of this amino acid.
competitive inhibition; hydrophobic
HIV is the virus that causes AIDS. In the mid-1900's, researchers discovered an enzyme called protease; in this enzyme the amino acid residues at the active sites are highly hydrophobic. 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 was successful, it would be an example of _____; in designing a drug that would bind to the active site and jam it, researchers should use a(n) _____ molecule.
Physical conditions are identical for all groups tested.
What does it mean to say that experimental conditions are controlled?
internalizing the asbestos ﬁbers by wrapping them with extensions of the cell and drawing the ﬁbers
into the cell.
Montana is home to the site of a former asbestos mining operation that has been in the news for years as a Superfund clean-up site. Individuals mining asbestos in Libby as well as their families have experienced unusually high incidences of certain lung diseases. Asbestos fibers enter the body by way of the lung. There, phagocytic cells attempt to deal with the fibers by
the complex formed as covalent bonds are being broken and re-formed during a reaction
What is a transition state?
hydrogen bonds between sections of the polypeptide backbone
In a protein molecule, what type of interaction is directly responsible for the formation of secondary structure?
Eukaryotes tend to have more extensive membrane systems than bacteria and archaea.
Which of the following best describes members of the 3 domains of living things?
a change in both the protein's tertiary structure and its function
Because of the R groups on amino acids, a protein can be seen as a string of chemical groups with varying
reactivities along the polypeptide backbone. These chemical groups participate in a variety of chemical
bonds and molecular interactions, and are important in determining the conformation and function of a
protein. One of these types of bonds is a covalent, disulﬁde (-S-S-) bond which forms between two cysteine
residues that may be some distance from each other. If such a protein is placed under reducing conditions, a
disulﬁde bond is often reduced so that each of the sulfur atoms is now bonded to hydrogen atom (-S-H and
H-S-) rather than to each other. When such reduction of a disulﬁde bond occurs, what is most likely to happen?
D. C3H7OH and C2H5COOH are polar molecules.
Which of the following molecules is/are polar?
D) C3H7OH and C2H5COOH are polar molecules.
the composition of their side chains, or R groups
Twenty different amino acids are found in the proteins of cells. What distinguishes these amino acids one from another?
enzyme, substrate, product
You have isolated a protein, PFK, which acts as an enzyme in a reaction that adds a phosphate group to
fructose-6-phosphate (F6P) to form fructose-1,6-bisphosphate (FBP). When ATP binds to a regulatory site
on the enzyme, the reaction rate slows dramatically. ATP and F6P are involved in the reaction at the active
site. You graph the results of an experiment comparing the concentration of F6P with the rate of formation of FBP
in the presence of PFK. You notice that this graph is steep at low F6P concentrations, but levels off at high
F6P concentrations. What are PFK, F6P, and FBP, respectively?
The graph levels off when no more F6P can be bound to PFK because all of the active sites are
What is the most likely explanation for why the graph of F6P concentration vs. rate of FBP formation levels
One role of ATP in this reaction is to serve as one of the substrate molecules. What is another role of ATP in
The pH would be lowered because of the release of additional H+ into the solution.
The following is an important set of reactions found in biological systems.
First, there is the reaction between carbon dioxide and water to form carbonic acid: CO2 + H2O <--> H2CO3
Second, in aqueous solution, carbonic acid quickly dissociates to form a proton and the bicarbonate ion, as
follows: H2CO3 <--> H+ + HCO3
How would the second reaction affect the pH of the solution?
The characteristic can be passed on to offspring.
What does it mean to say that a characteristic of an organism is heritable?
The pH of human blood averages 7.4, and variation outside of the range 7.35-7.45 is considered abnormal.
Because human blood typically remains at a quite stable pH, we would expect that the ﬂuid portion of the
blood (the plasma)
primary, secondary, and tertiary
You are studying a protein that is shaped like a doughnut. This shape is a function of which level(s) of
acts as a base and gains a proton, giving it a positive charge; acts as an acid and loses a proton, giving it a negative charge
At the pH found in cells (about 7.0), the amino group on an amino acid _____ and the carboxyl group on an
amino acid _____.
in the cytoplasm; M-N-G
X-ray crystallographic analysis has been performed by Krzysztof Palczewski on the protein rhodopsin (depicted in
Figure 3.1), which is a light-sensitive protein found in species ranging from ancient bacteria (archaea) to humans. The
structure, in which each letter represents an amino acid, is characterized by a single polypeptide chain with several
alpha-helical segments that loop back and forth across the cell membrane seven times. A disulﬁde bond (-S-S-) can be
seen at the bottom of the third transmembrane segment. [Figure adapted from K. Palczewski et al.,Science 289 (2000):
In Figure 3.1, the location of the C-terminus is _____; the ﬁrst three amino acids of the protein are _____.
They are both capable of reproducing themselves.
Which of the following is NOT a characteristic that chloroplasts and mitochondria share?
The antibodies bind to cell adhesion proteins called cadherins
Treating dissociated cells with certain antibodies makes the cells unable to reaggregate. Why?
The membrane phospholipids of cold-adapted organisms will have more unsaturated hydrocarbon tails.
You have just discovered an organism that lives in extremely cold environments. Which of the following would you predict to be true about the phospholipids in its membranes, compared to phospholipids in the membranes of organisms that live in warmer environments?
the amount of branching that occurs in the molecule
What is the major structural difference between starch and glycogen?
A gap junction is a channel that connects adjacent cells. From substances listed, which one cannot pass through a gap junction?
The molecules responsible for cell-cell adhesion differed between the two species of sponge.
H. V. Wilson worked with sponges to gain insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted the cell-cell interaction, and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson observed that sponges reassembled into two separate species. The cells from one species did not
interact or form associations with the cells of the other species. How do you explain the results of Wilson's experiments?
Researchers tried to explain how vesicular transport occurs in cells by attempting to assemble the transport components. They set up microtubule tracks along which vesicles could be transported, and they added vesicles and ATP. Yet, when they put everything together, there was no movement or transport of vesicles. What were they missing?
The 20 amino acids serve as a signal sequence that directs the forming polypeptide to the endoplasmic reticulum, where they are cleaved off during processing.
Scientists have found that polypeptides that are normally synthesized in the endoplasmic reticulum are about 20 amino acids longer when they are synthesized by ribosomes not attached to the endoplasmic reticulum. What is/are possible explanations for the greater length of these polypeptides?
cytoskeletal proteins and proteins in the extracellular matrix
Integrins are integral membrane proteins. Among their other function, they are often attached to _____.
a transport protein that facilitates diffusion of a large molecule across cell membranes
GLUT-1 is an example of what?
part of the extracellular matrix
Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are _____.
their phosphate groups
What feature of mononucleotides provides the energy needed for polymerization when nucleic acids are formed?
It allows adjacent cells to adhere to one another.
What is the function of the middle lamella in plant cells?
The geometry of the bonds is different, and the shapes of enzyme active sites are highly specific.
Enzymes that readily break starch apart cannot hydrolyze the glycosidic linkages found in cellulose. Why is this logical?
Prokaryotic and eukaryotic flagella differ in their mechanism of movement and in the presence or absence of plasma membrane covering.
Flagella are found in both eukaryotic cells and prokaryotic cells. Despite the functional similarities of all flagella, scientists suspect that eukaryotic and prokaryotic flagella have evolved independently. Why don't they think there is a common evolutionary origin for prokaryotic and eukaryotic flagella?
They would be manufactured on free ribosomes in the cytoplasm.
Eukaryotic cells manufacture cytoskeletal proteins that help to maintain the cells' shapes and functions. What would you predict about these proteins?
They have polar heads and nonpolar tails; their polar heads are able to interact with water.
Lipids that form membranes have what kind of structure?
Ions cannot cross planar bilayers
In an experiment involving planar (flat) bilayers, a solution of table salt (sodium and chloride ions in water) is added on the left side of the membrane while pure water is added on the right side. After 30 minutes the researchers test for the presence of ions on each side of the membrane. The right side tests negative for ions. What can you conclude?
It forms a channel in the membrane.
Gramicidins are peptide antibiotics produced by certain species of bacteria and active against many other species of bacteria. These compounds increase the permeability to inorganic ions such as Na+. What is the most likely mode of action of a gramicidin?
a loss in cell-cell adhesion
Pemphigus vulgaris is a disease of humans in which the immune system reacts against and damages normal constituents of the body. In this disease, antibodies are produced against the cadherins of desmosomes. The blistering of the skin and mucous membranes characteristic of this disorder is probably a result of _____.
delivery of cargo vesicles to the lysosome from the Golgi apparatus
A particle circulating in the blood of a mammal comprises lipid associated with protein. The particle's protein binds to a receptor on the cell surface and, with the help of several other proteins, the particle and the receptor are brought into the cell enclosed in a membrane-bound vesicle. Through fusion of this structure with a lysosome, the vesicle delivers its contents to the lysosome. The receptor mentioned above is recycled back to the cell surface. The low pH environment of the
lysosome allows the lipid and protein particle to dissociate, with one of the lipid molecules, cholesterol, moving through a lipid bilayer into the cytosol. Which of the following are NOT
It lacks a nuclear localization signal (NLS)
What can you infer about a high molecular weight protein that cannot be transported into the nucleus?
30%, 30%, and 20%, respectively
If, on a molar basis, human DNA contains 20% C, what are the mole percents of A, T, and G?
Individual polysaccharide strands are joined by peptide bonds, a type of covalent bond
Peptidoglycan forms sheets that stiffen the cell walls of bacteria. How are these peptidoglycan sheets formed?
a covalent bond forms between the sugar of one nucleotide and the phosphate of a second
When nucleotides polymerize to form a nucleic acid _____.
the locations of their polar and nonpolar amino acids
Integral membrane proteins stay in membranes because of _____.
Rhodopsins are light-sensitive molecules composed of a protein (opsin) and retinal (derivative of vitamin A). Opsin is a membrane protein with several α-helical segments that loop back and forth through the plasma membrane. There are two classes of rhodopsins. According to Oded Beje, one class has relatively slow dynamics and is well suited for light detection. The second class has faster dynamics and is well suited for chemiosmosis-pumping of protons or chloride ions across cell membranes. Oded Beje was the first to report
on a rhodopsin (proteorhodopsin) found in the domain Bacteria. Proteorhodopsin consists of a single polypeptide chain. What is the highest level of structure found in this protein?
in the S phase of the cell cycle
Scientists isolate cells in various phases of the cell cycle. They ﬁnd a group of cells that have 1½ times more DNA than do G1 phase cells. The cells of this group are _____.
it explains how ATP is synthesized by a proton motive force
The chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because _____.
GDP is phosphorylated to produce GTP during formation of succinate
Substrate-level phosphorylation occurs when ATP or GTP is formed by the transfer of a phosphate group from a metabolic intermediate to ADP or GTP, respectively. A substrate-level phosphorylation occurs in the Krebs cycle when _____.
Protein function can change by binding of another molecule and some conformational changes to a
protein alter the protein's function but do not denature the protein.
ABC is a G protein coupled receptor that acts in cell signaling. When D binds ABC, the latter changes conformation and transduces the signal to the inside of the cell, altering the activity of a G protein. What can you say about the structure and/or function of the protein ABC?
Plant ECM is primarily carbohydrate in nature, whereas animal ECM contains large amounts of protein.
What is a major difference between the extracellular matrix (ECM) of a plant cell and the ECM of an animal cell?
The cell underwent repeated mitosis, but cytokinesis did not occur.
Some cells have several nuclei per cell. How could such multinucleated cells be explained?
Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common but when it does happen the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?
If at each step in the process many enzymes for the next step are phosphorylated, then the initial signal will be greatly ampliﬁed.
How does a phosphorylation cascade amplify a signal that binds to a cell surface receptor?
abnormally shaped RBCs
Spherocytosis is a human blood disorder associated with a defective cytoskeletal protein in the red blood cells (RBCs). Which of the following would you expect to be the consequence of such a defect?
Plant cells deposit vesicles containing cell-wall building blocks on the cell plate; animal cells form a
How is plant cell cytokinesis different from animal cell cytokinesis?
The following formula best describes what takes place during _____. 6CO2 + 12H2O + light energy ---> C6H12O6 + 6H2O + 6O2
water ions and small molecules can readily pass from one cardiac muscle cell to the next
Intercalated discs are cell-cell junctions found between cardiac muscle cells. One feature of these intercalated discs is that they contain a large number of gap junctions that help to coordinate the heartbeat by allowing _____.
the portion of the molecule that binds to the microtubular track along which the vesicle is being
Motor proteins such as kinesin require energy in the form of ATP. ATP hydrolysis results in a conformational change that allows the protein to move along microtubular tracks (pathways). What structural component of kinesin contains the ATP binding site and, therefore, changes shape to enable movement?
the parent cell must ﬁrst replicate its entire genome
A parent cell divides to form two genetically identical daughter cells in the process of mitosis. For mitosis to take place _____.
degradation of cyclin-dependent kinase
Which of the following would not be an effect of the mitosis-promoting factor (MPF) that is involved in moving a cell into M phase?
Homologous recombination, the exchange of segments of homologous chromosomes, takes place during which of the following processes?
It is probably an enzyme that works through allosteric regulation.
You have isolated a previously unstudied protein, identiﬁed its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites. One of these is large, apparently the bonding site for the large substrate; the other is small, possibly a binding site for a regulatory molecule. Based on this information, your best hypothesis for the function of this protein is that _____.
Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
What is the difference between a ribonucleotide and a deoxyribonucleotide?
Catabolic processes are activated that generate more ATP.
A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply
Cross talk allows cells to coordinate and modulate their responses to multiple signals the cell receives
Which of the following best describes the advantage(s) of "cross talk" in signal transduction pathways?
Photosynthesis stores energy in complex organic molecules; respiration releases the energy stored in
complex organic molecules.
Which of the following statements most accurately compares photosynthesis and respiration?
Scientists have found that extracellular matrix components may induce speciﬁc gene expression in embryonic tissues such as the liver and testes. For this to happen there must be direct communication between the extracellular matrix and the developing cells. Which kind of transmembrane protein would most likely be involved in this kind of induction?
6, 3, 3
The diploid number for Insect J is 6. During meiosis, there would be ___ chromosomes in the Metaphase I cell, ___ chromosomes in the Metaphase II cell, and ___ chromosomes in one cell following Telophase II and Cytokinesis. Hint: how many centromeres are there at each point?
They would contain large quantities of rough endoplasmic reticulum
The small intestine is the site of digestion and absorption of nutrients. A single layer of epithelial cells lines the small intestine. In the duodenum (the first section of the small intestine), these epithelial cells secrete large quantities of digestive enzymes. Which of the following features would you expect to find in these epithelial cells?
methionine, glycine, phenylalanine
Refer to Figure 15.5. If you had a mRNA for which the codons were read beginning from the start codon, which amino acids would be added (in order)? UCUGAUGGGCUUU...
concurrent transcription and translation
Which of the following occurs in prokaryotes, but not eukaryotes?
Snapdragons are flowers that come in a variety of colors including red, pink, and white. A series of crosses
with snapdragons having flowers of different colors produced the following results:
pink × pink: 27 pink, 13 red, 14 white
red × red: all red
white × white: all white
pink × white: 29 pink, 26 white
pink × red: 28 pink, 27 red
white × red: all pink
Based on the results, what is the most reasonable explanation for the inheritance of these flower colors?
It attaches to the amino acid.
Refer to Figure 16.3. What is the function of the ACC sequence at the 3' end?
It base pairs with the codon of mRNA.
Refer to Figure 16.3. What is the function of the highlighted AGU on the loop of the tRNA?
larger than; the same size as
A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is _____ the functional mRNA.
The microtubule-organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle. Specifically, it is known as which of the following?
Telomerase ensures that the ends of the chromosomes are accurately replicated and eliminates telomere shortening.
Bodnar et al. (1998) used telomerase experimentally to extend the life span of normal human cells. Telomere
shortening puts a limit on the number of times a cell can divide. How might adding telomerase affect cellular aging?
All of the above minimize errors in DNA replication in E. coli - proofreading activity of the epsilon subunit of DNA polymerase III, mismatch repair, nucleotide excision repair
Which of the following are important in reducing the errors in DNA replication in E. coli organisms?
the number of ribosomes
There should be a strong positive correlation between the rate of protein synthesis and _____.
missense mutation OR point mutation
The mutation resulting in sickle cell anemia changes one base pair of DNA and is an example of a _____.
2, 1, 3, 5, 4
Put the following steps of DNA replication in chronological order.
1. Single-stranded binding proteins attach to DNA strands.
2. Hydrogen bonds between base pairs of antiparallel strands are broken.
3. Primase binds to the site of origin.
4. DNA polymerase binds to the template strand.
5. An RNA primer is created.
A and B
In humans, ABO blood types refer to glycoproteins in the membranes of red blood cells. There are three alleles for this autosomal gene: IA, IB, and i. The IA allele codes for the A glycoprotein, The IB allele codes for the B glycoprotein, and the i allele doesn't code for any membrane glycoprotein. IA and IB are codominant, and i is recessive to both IA and IB. People with A type blood have the genotypes IAIA or IAi, people with type B blood are IBIB or IBi, people with type AB blood are IAIB, and people with O type blood are ii. If a woman with type AB blood marries a man with type O blood, which of the following blood types could their children possibly have?
Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc × AaBbCc, will produce an AaBbCc offspring?
one with carbon and hydrogen atoms only
Which of the following molecules would you expect to have the most free energy per gram?
DNA polymerase contains the template needed.
Semiconservative replication involves a template. What is the template?
the methyl-guanosine cap of a properly modified mRNA
What molecule or feature ensures that the correct amino acid is added with reading of a specific codon during translation?
a section of DNA that encodes information for building one polypeptide chain (one gene, one
Over time, as more knowledge is acquired, scientific definitions are modified to fit the existing observations. This has certainly been true for the definition of a gene. Which of the following definitions most accurately reflects our current understanding of the gene?
homologous chromosomes separate
Meiosis involves the creation of haploid cells from diploid cells. The haploid chromosome number is created when _____.