The nurse is caring for a patient with an infection. Which immunoglobulin should the nurse understand is produced first when an infection occurs?

Correct Answer: D

Rationale: Step-by-step rationale for why IgM is the correct answer: 1. IgM is the first immunoglobulin produced in response to an infection. 2. It is the largest immunoglobulin and is effective in agglutinating pathogens. 3. IgM activates the complement system to enhance immune response. 4. IgG is produced later in the immune response and provides long-term immunity. 5. IgD and IgE have specific roles but are not the initial immunoglobulins produced in response to infection.

Correct Answer: d

Rationale: The correct answer is D because in prokaryotes, 50s and 30s ribosomal subunits combine to form the 70s ribosome, which is necessary for protein synthesis. Firstly, ribosomes are composed of two subunits, and in prokaryotes, these are the 50s and 30s subunits. Secondly, these subunits come together during translation to form the functional ribosome. Therefore, these ribosomal subunits are indeed necessary for protein synthesis in prokaryotes. A: Incorrect. Translation can begin before transcription is finished in prokaryotes due to their lack of a nuclear membrane. B: Incorrect. Messenger RNA in prokaryotes is co-linear with the DNA template as they do not undergo RNA splicing like eukaryotes. C: Incorrect. In prokaryotes, the ribosomal RNA present is the 16s, 23s, and 5s, not 28s.

Correct Answer: D

Rationale: The correct answer is D because in the electron transport chain, protons (H⁺) are pumped across the membrane to create a proton gradient. This gradient is utilized by ATP synthase to produce ATP. Therefore, protons go into solution outside the cytoplasmic membrane. Choices A and B are incorrect because protons do not simply stay in the cytoplasm or get taken back by NAD and FAD. Choice C is incorrect as protons do not directly form water when carried by cytochromes.

Correct Answer: C

Rationale: Rationale for Answer C: 1. Allergen exposure triggers B cells to produce IgE antibodies specific to the allergen. 2. IgE antibodies bind to mast cells sensitizing them. 3. Upon re-exposure to allergen, allergen binds to IgE on mast cells. 4. This triggers release of histamine and other chemicals causing allergic symptoms. Summary: - Choice A: Incorrect because B cells do not produce IgE antibodies before allergen exposure. - Choice B: Incorrect because IgE antibodies are produced by B cells, not the other way around. - Choice D: Incorrect because histamine is released after allergen binds to IgE on sensitized mast cells.

Correct Answer: C

Rationale: The correct answer is C because methylation of DNA typically results in the inhibition or slowing down of transcription. Methylated DNA attracts proteins that bind to it, preventing transcription factors from accessing the DNA and initiating transcription. This interference with the transcription process leads to gene silencing or reduced gene expression. A: DNA unwinding in preparation for protein synthesis is unrelated to DNA methylation. B: Continuous replication is not a typical consequence of DNA methylation. D: Methylation does not directly induce protein synthesis but rather affects transcription by influencing gene expression.