Nokea
Which of the following does not describe defensins?
- A. They disrupt pathogen membranes by penetrating them and disrupting their integrity
- B. They function as opsonins
- C. They are amphipathic, that is they have hydrophobic and hydrophilic regions
- D. They are contained in neutrophil granules
Correct Answer: B
Rationale: The correct answer is B: They function as opsonins.
Rationale:
1. Defensins disrupt pathogen membranes by penetrating them (A), not by functioning as opsonins.
2. Defensins are amphipathic (C), having hydrophobic and hydrophilic regions, which aid in membrane disruption.
3. Defensins are contained in neutrophil granules (D), contributing to their role in the immune response.
Summary:
Choice B is incorrect because defensins do not function as opsonins, which are molecules that enhance phagocytosis of pathogens by immune cells. Choices A, C, and D correctly describe aspects of defensins' mechanism of action and localization.
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What does the presence of carcinoembryonic antigens (CEAs) and α-fetoprotein (AFP) on cell membranes indicate has happened to the cells?
- A. They have shifted to more immature metabolic pathways and functions
- B. They have spread from areas of original development to different body tissues
- C. They produce abnormal toxins or chemicals that indicate abnormal cellular function
- D. They have become more differentiated as a result of repression of embryonic functions
Correct Answer: A
Rationale: The presence of CEAs and AFP indicates that cells have reverted to more immature metabolic pathways, characteristic of cancerous transformation.
When a patient is undergoing brachytherapy, what is it important for the nurse to be aware of when caring for this patient?
- A. The patient will undergo simulation to identify and mark the field of treatment
- B. The patient is a source of radiation and personnel must wear film badges during care
- C. The goal of this treatment is only palliative and the patient should be aware of the expected outcome
- D. Computerized dosimetry is used to determine the maximum dose of radiation to the tumor within an acceptable dose to normal tissue
Correct Answer: B
Rationale: Patients undergoing brachytherapy emit radiation, requiring safety measures for healthcare providers.
Which of the following restriction endonucleases produce fragments with blunt ends?
- A. Sacl
- B. EcoRI
- C. Smal
- D. HindIII
Correct Answer: C
Rationale: The correct answer is C: Smal. Smal is a restriction endonuclease that cuts DNA at specific sequences, producing fragments with blunt ends. Smal recognizes the sequence CCCGGG and cuts between the two C's on both strands, resulting in blunt-ended fragments.
Explanation for incorrect choices:
A: Sacl - Sacl produces sticky ends, not blunt ends.
B: EcoRI - EcoRI produces sticky ends with overhangs.
D: HindIII - HindIII also produces sticky ends with overhangs.
In summary, Smal is the only enzyme among the choices that generates DNA fragments with blunt ends.
What is the primary function of platelets?
- A. Producing hormones
- B. Transporting oxygen and carbon dioxide
- C. Clotting and sealing damaged blood vessels
- D. Protecting the body from foreign substances
Correct Answer: C
Rationale: Platelets primarily function in clotting and sealing damaged blood vessels. Firstly, when a blood vessel is injured, platelets rush to the site to form a plug, preventing excessive bleeding. Secondly, platelets release clotting factors to initiate the coagulation cascade, leading to the formation of a stable blood clot. This process is crucial for wound healing and preventing blood loss. Platelets do not produce hormones (choice A), transport gases (choice B), or protect the body from foreign substances (choice D). These functions are carried out by other components of the body's systems.
Patients with rheumatoid arthritis typically have pain:
- A. With activity.
- B. Upon awakening.
- C. Late in the evening.
- D. All day without remission.
Correct Answer: B
Rationale: Rheumatoid arthritis often causes morning stiffness and pain upon awakening due to inflammation and lack of movement during sleep. Pain tends to improve with activity as joints warm up.