Nokea
A patient with a pH of 7.29 has metabolic acidosis. Which value is useful in determining whether the cause of the acidosis is an acid gain or a bicarbonate loss?
- A. PaCO2
- B. Anion gap
- C. Serum Na+ level
- D. Bicarbonate level
Correct Answer: D
Rationale: Bicarbonate levels help differentiate between acid gain (low bicarbonate) and bicarbonate loss (normal or high anion gap).
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"Hamburger disease" is caused by
- A. Helicobacter pylori
- B. Salmonella typhimurium
- C. A strain of E. coli
- D. Shigella flexneri
Correct Answer: C
Rationale: The correct answer is C: A strain of E. coli. "Hamburger disease" is commonly caused by E. coli O157:H7, a strain of Escherichia coli bacteria found in undercooked ground beef. This strain can lead to severe foodborne illness. Helicobacter pylori (Choice A) is associated with stomach ulcers, not hamburger disease. Salmonella typhimurium (Choice B) and Shigella flexneri (Choice D) are both known to cause food poisoning, but they are not typically linked to hamburger disease specifically. In this case, the unique association between E. coli O157:H7 and undercooked ground beef makes Choice C the correct answer.
Innate behaviors are
- A. under strong genetic control
- B. performed in virtually the indifferent way by all individuals of a species
- C. Sociobiology
- D. the environment
Correct Answer: A
Rationale: The correct answer is A because innate behaviors are indeed under strong genetic control. These behaviors are instinctual and are genetically programmed in organisms. This genetic control ensures that all individuals of a species exhibit these behaviors consistently. Choice B is incorrect because while innate behaviors may be performed similarly by individuals of a species, there can still be variations. Choice C, Sociobiology, is incorrect as it is a branch of biology that studies social behavior in animals. Choice D, the environment, is incorrect as innate behaviors are not primarily influenced by the environment but rather by genetic factors.
Epithelial cells at mucosal sites have barrier functions exerted through several mechanisms. These mechanisms do not include:
- A. Secretion of mucins
- B. Secretion of antimicrobial peptides
- C. Phagocytosis of microbes
- D. Tight junctions
Correct Answer: C
Rationale: The correct answer is C: Phagocytosis of microbes. Epithelial cells primarily act as a physical barrier to prevent the entry of microbes. Phagocytosis is a function of immune cells, not epithelial cells. A: Secretion of mucins helps trap pathogens. B: Secretion of antimicrobial peptides aids in defense. D: Tight junctions form a physical barrier between cells. Therefore, phagocytosis is not a direct mechanism exerted by epithelial cells at mucosal sites.
Before the patient receives a kidney transplant, a crossmatch test is ordered. What does a positive crossmatch indicate?
- A. Matches tissue types for a successful transplantation
- B. Determines paternity and predicts risk for certain diseases
- C. Establishes racial background and predicts risk for certain diseases
- D. Cytotoxic antibodies to the donor contraindicate transplanting this donor’s organ
Correct Answer: D
Rationale: A positive crossmatch indicates the presence of preformed cytotoxic antibodies against the donor, contraindicating transplantation.
Which enzyme catalyzes the addition of deoxynucleotides to the 3'OH ends of DNA molecules?
- A. Phosphohydrolase
- B. T4 DNA ligase
- C. Terminal deoxynucleotidyl transferase
- D. DNA endonuclease
Correct Answer: C
Rationale: The correct answer is C: Terminal deoxynucleotidyl transferase (TdT). TdT catalyzes the addition of deoxynucleotides to the 3'OH ends of DNA molecules. It does so by adding nucleotides in a template-independent manner, making it crucial for generating diversity in immune cell receptor genes.
A: Phosphohydrolase - This enzyme is not involved in adding deoxynucleotides to DNA ends.
B: T4 DNA ligase - This enzyme catalyzes the joining of DNA fragments, not the addition of deoxynucleotides.
D: DNA endonuclease - This enzyme cleaves DNA internally, not involved in adding deoxynucleotides to DNA ends.