Nokea
"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.
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Which of the following is NOT true about multiple sclerosis (MS)
- A. Sex bias observed with males more at risk of developing the disease
- B. Incidence higher in northern countries
- C. Symptoms caused by demyelination of neurons
- D. EAE is an animal model for MS induced by injection with myelin
Correct Answer: A
Rationale: The correct answer is A: Sex bias observed with males more at risk of developing the disease. This statement is NOT true because MS actually has a sex bias towards females, with women being more at risk. This is due to hormonal, genetic, and immunological factors. The other choices are true: B is correct as MS is more common in northern regions, possibly due to environmental factors; C is correct since MS is characterized by demyelination of neurons leading to various symptoms; and D is correct as experimental autoimmune encephalomyelitis (EAE) is an animal model often used to study MS, induced by injecting myelin components to trigger an immune response.
Which of the following cells are 'professional' antigen presenting cells
- A. Neutrophils, dendritic cells, B cells
- B. B cells, T cells, dendritic cells
- C. Macrophages, B cells, dendritic cells
- D. Neutrophils, epithelial cells, dendritic cells
Correct Answer: C
Rationale: The correct answer is C: Macrophages, B cells, dendritic cells. Professional antigen-presenting cells are specialized immune cells that effectively present antigens to T cells. Macrophages, B cells, and dendritic cells are considered professional APCs because they express major histocompatibility complex (MHC) molecules and co-stimulatory molecules, allowing them to effectively activate T cells. Neutrophils and epithelial cells are not considered professional APCs as they have limited ability to present antigens to T cells. B cells and T cells are not APCs themselves, but B cells can act as APCs when they present antigens to T cells in the context of an immune response.
What is the main function of the Membrane Attack Complex (MAC)?
- A. Recruitment of neutrophils
- B. Phagocytosis activation
- C. Lysis of pathogens
- D. Enhancing cytokine production
Correct Answer: C
Rationale: The main function of the Membrane Attack Complex (MAC) is to lyse pathogens by creating pores in their cell membranes. First, MAC assembles on the pathogen's surface. Then, it forms a pore, disrupting the pathogen's membrane integrity, leading to cell lysis. This mechanism is crucial for the immune system to effectively eliminate pathogens.
Choice A (Recruitment of neutrophils) is incorrect because MAC is not involved in recruiting neutrophils. Neutrophil recruitment is typically mediated by other signaling molecules.
Choice B (Phagocytosis activation) is incorrect as MAC does not directly activate phagocytosis. Phagocytosis is a separate process involving the engulfment of pathogens by immune cells.
Choice D (Enhancing cytokine production) is incorrect because MAC does not directly enhance cytokine production. Cytokine production is mainly regulated by other immune cells and signaling pathways.
What is Louis Pasteur's main contribution to immunology?
- A. Development of the smallpox vaccine
- B. Discovery of phagocytosis
- C. Germ theory of disease and vaccine development
- D. Theory of innate immunity
Correct Answer: C
Rationale: Louis Pasteur's main contribution to immunology is the germ theory of disease and vaccine development. Firstly, Pasteur's germ theory revolutionized our understanding of infectious diseases by demonstrating that microorganisms are the cause. Secondly, he developed the concept of vaccination by creating vaccines for diseases such as rabies and anthrax, laying the foundation for modern immunology. The other choices are incorrect because:
A: Pasteur worked on the rabies vaccine, not the smallpox vaccine.
B: Phagocytosis was discovered by Metchnikoff, not Pasteur.
D: Pasteur did not propose the theory of innate immunity.
Which of the following are not found in Cyanobacteria?
- A. thylakoids
- B. gas vesicles
- C. chloroplasts
- D. heterocysts
Correct Answer: C
Rationale: The correct answer is C: chloroplasts. Cyanobacteria do not have chloroplasts because they are prokaryotic organisms and do not possess membrane-bound organelles like chloroplasts found in eukaryotic cells. Instead, they perform photosynthesis using thylakoids, which are membrane-bound compartments where photosynthesis occurs. Gas vesicles are also present in cyanobacteria and help regulate their buoyancy. Heterocysts are specialized cells that aid in nitrogen fixation, a process that allows cyanobacteria to convert atmospheric nitrogen into a form that can be used by the organism. Therefore, the absence of chloroplasts in cyanobacteria makes choice C the correct answer.