Biology Review Flashcards
Hyperbaric oxygen may be used as a treatment for certain types of bacterial infections. In this therapy, the patient is placed in a chamber in which the partial pressure of oxygen is significantly increased, increasing the partial pressure of oxygen in the patient’s tissues. This treatment is most likely used for infections with:
A. obligate aerobic bacteria.
B. facultative anaerobic bacteria.
C. aerotolerant anaerobic bacteria.
D. obligate anaerobic bacteria.
D. Obligate anaerobes cannot survive in the presence of oxygen and would likely be killed by such a therapy, treating
the infection. The other types of bacteria listed can all survive in the presence of oxygen, so infections involving these
bacteria would likely not be treated using this therapy.
Which of the following does NOT describe
connective tissue cells?
A. They account for most cells in muscles, bones, and tendons.
B. They secrete substances to form the extracellular matrix.
C. In organs, they tend to form the stroma.
D. In organs, they provide support for epithelial cells.
A. While bones and tendons are composed predominantly of connective tissue cells, muscle tissue is considered a differ-
ent tissue type. Other examples of connective tissue include cartilage, ligaments, adipose tissue, and blood. Connective tissue often secretes substances to form the extracellular
matrix, such as collagen and elastin, eliminating (B). (C) and (D) are essentially identical and can both be eliminated: in organs, connective tissue often forms the support structure for epithelial cells, called the stroma.
Which of the following types of nucleic acid could form the genome of a virus?
I. Single-stranded RNA
I. Double-stranded DNA
Ill. Single-stranded DNA
A. I only
B. II only
C. I and Il only
D. I, IL, and IlI
D. In a virus, the nucleic acid can be either DNA or RNA and-in both cases–can be either single- or double-stranded. Therefore, all of the types of nucleic acids
listed here could be used for a viral genome, making (D) the correct answer.
The theory of spontaneous generation states that living organisms can arise from nonliving material, In 1859, Pasteur demonstrated that no organisms
emerged from sterilized growth media, weakening the theory of spontaneous generation and supporting which tenet of cell theory?
A. All living things are composed of cells.
B. The cell is the basic functional unit of life.
C. Cells arise only from preexisting cells.
D. Cells carry genetic information in the form of DNA.
C. The process of sterilization kills all living cells. A lack of cellular growth in these conditions supports the idea that
cells can only arise from preexisting cells, matching (C). By contrast, since this experiment did not directly visualize the
cells, nor did it analyze the genetic material, (A), (B), and (D) can be eliminated.
Mitochondrial DNA is:
I. circular.
I. self-replicating.
Ill. single-stranded.
A. I only
B. Il only
C. I and II only
D. Ill, and Ill
C. Mitochondria are thought to have evolved from an anaerobic prokaryote engulfing an aerobic prokaryote and establishing a symbiotic relationship; therefore, mitochondrial DNA, or mDNA, is likely to be similar to bacterial DNA.
Both mDNA and bacterial DNA are organized into a single circular chromosome of double-stranded DNA that can replicate during binary fission. Therefore, Statements I and Il are correct, while Statement III is incorrect.
Which of the following is NOT a function of the smooth endoplasmic reticulum?
A. Lipid synthesis
B. Poison detoxification
C. Protein synthesis
D. Transport of proteins
C. The smooth endoplasmic reticulum is involved in the transport of materials throughout the cell, in lipid synthesis, and
in the detoxification of drugs and poisons. Proteins from the rough ER can cross into the smooth ER, where they are secreted into cytoplasmic vesicles and transported to the Golgi apparatus. However, protein synthesis is not a function of the smooth ER, but rather of the free ribosomes or
the ribosomes associated with the rough ER. (C) is therefore the correct answer,
What is the main function of the nucleolus?
A. Ribosomal RNA synthesis
B. DNA replication
C. Cell division
D. Chromosome assembly
A. The nucleolus (not to be confused with the nucleus ) is a dense structure within the nucleus where ribosomal RNA (rRNA) is synthesized. (A) is therefore the correct answer.
Which of the following organelles is surrounded by a single membrane?
A. Lysosomes
B. Mitochondria
C. Nuclei
D. Ribosomes
A. Lysosomes are vesicular organelles that digest material using hydrolytic enzymes. They are surrounded by a single membrane. Both mitochondria and nuclei are surrounded by double membranes, eliminating (B) and (C). Ribosomes
must not be surrounded by membranes because they are found not only in eukaryotes but also in prokaryotes, which
lack any membrane-bound organelles. This eliminates (D).
Which of the following is NOT a difference that would allow one to distinguish a prokaryotic and a eukaryotic cell?
A. Ribosomal subunit weight
B. Presence of a nucleus
C. Presence of a membrane on the outside surface of the cell
D. Presence of membrane-bound organelles
C. Some of the main differences between prokaryotes and eukaryotes are that prokaryotes do not have a nucleus, while eukaryotes do, eliminating (B); prokaryotes have ribosomal subunits of 30S and 50S, while eukaryotes have ribosomal subunits of 40S and 60S, eliminating (A); and
prokaryotes do not have membrane-bound organelles, whereas eukaryotes do, eliminating (D). The presence of a membrane on the outer surface of the cell could not distinguish a prokaryotic cell from a eukaryotic one because both gram-negative bacteria and animal cells share this feature. Thus, (C) is the correct answer.
Which of the following does NOT contain tubulin?
A. Cilia
B. Flagella
C. Microfilaments
D. Centrioles
C. Tubulin is the primary protein in microtubules, which are responsible for the structure and movement of cilia and flagella, eliminating (A) and (B). Centrioles organize microtubules into the mitotic spindle, eliminating (D). Microfilaments are not composed of tubulin, but rather actin, making (C) the correct answer.
Herpes simplex virus (HSV) enters the human body and remains dormant in the nervous system until it produces an outbreak after exposure to heat, radiation, or other stimuli. Which of the following
statements correctly describes HSV?
A. While it remains dormant in the nervous system, the virus is in its lytic cycle.
B. During an outbreak, the virus is in the lysogenic cycle.
C. Herpes simplex virus adds its genetic information to the genetic information of the cell.
D. The herpes simplex virus contains a tail sheath and tail fibers.
C. Viruses can exist in either the lytic or lysogenic cycle; they may even switch between them. During the lytic cycle, the virus’s DNA takes control of the host cell’s genetic machinery, manufacturing numerous progeny. In the end, the host cell bursts (lyses) and releases new virions, each capable of infecting other cells. In the lysogenic cycle, viral DNA is added to the host cell’s genome, where it can remain dormant for days or years. Either spontaneously or as a result of environmental circumstances, the provirus can reactivate and enter a lytic cycle. Thus (A) and (B) are incorrect because the terms are reversed. (D) describes features of
bacteriophages, which are viruses that infect bacteria-not the human nervous system. (C) accurately describes how HSV operates during the lysogenic cycle, making it the correct answer.
Resistance to antibiotics is a well recognized medical problem. Which mechanisms can account for a bacterium’s ability to increase its genetic variability and thus adapt itself to resist different antibiotics?
I. Binary fission
I. Conjugation
Ill. Transduction
A. Iand Il only
B. I and Ill only
C. Il and III only
D. I, IL, and III
C. Bacterial cells reproduce by binary fission, an asexual process in which the progeny is identical to the parent. Therefore, binary fission (Statement I) does not increase genetic variability. Conjugation can be described as sexual mating in bacteria; it is the transfer of genetic material between two bacteria that are temporarily joined. Transduction occurs when fragments of the bacterial chromosome accidentally become packaged into viral progeny produced during a viral infection and are introduced into another bacterium by the viral vector. Therefore, both conjugation and transduction (Statements II and III) increase bacterial genetic variability.
A bacterial cell is noted to be resistant to penicillin. The bacterium is transferred to a colony that lacks the fertility factor, and the rest of the colony does not become resistant to penicillin. However, the penicillin-resistant cell has also started to
exhibit other phenotypic characteristics, including secretion of a novel protein. Which of the following methods of bacterial recombination is NOT likely to account for this change?
A. Conjugation
B. Transformation
C. Transduction
D. Infection with a bacteriophage
A. A bacterial cell that does not rapidly cause a phenotypic change in the rest of the colony is likely not Ft, meaning that this cell is not able to form a sex pilus for conjugation, making (A) correct. The expression of new phenotypic characteristics indicates that this bacterium may have acquired genetic material from the environment through transformation. (B), or transduction (which occurs via bacteriophage infection), (C) and (D).
In Alzheimer’s disease, a protein called the amyloid precursor protein (APP) is cleaved to form a protein called beta-amyloid. This protein has a 3-pleated sheet structure and precipitates to form plaques in the
brain. This mechanism of disease is most similar to which of the following pathogens?
A. Bacteria
B. Viruses
C. Prions
D. Viroids
C. Prions are infectious proteins that cause misfolding of other proteins. Prions generally cause a shift toward 3-pleater sheet conformations, causing decreased solubility and increased resistance to degradation. This ultimately leads to disease. This mechanism is very similar to the one described here for Alzheimer’s disease, making (C) the correct answer.
After infection of a cell, a viral particle must transport itself to the nucleus in order to produce viral proteins. What is the likely genomic content of the virus?
A. Double-stranded DNA
B. Double-stranded RNA
C. Positive-sense RNA
D. Negative-sense RNA
A. A virus that requires transport to the nucleus in order to produce viral proteins likely requires use of nuclear RIVA polymerase in order to create mRNA that can be translated to protein. Therefore, only DNA viruses need to be trans. ported to the nucleus to produce viral proteins, eliminating all answer choices but (A).
