What is the primary function of bacterial ribosomes?

Correct Answer: A

Rationale: The correct answer is A: Synthesize proteins. Bacterial ribosomes are responsible for translating mRNA into proteins through a process called translation. Ribosomes do not generate ATP (choice B), produce DNA (choice C), or synthesize lipids (choice D). These processes are carried out by other cellular components such as mitochondria for ATP production, DNA polymerase for DNA replication, and enzymes for lipid synthesis. The primary function of bacterial ribosomes is protein synthesis, making choice A the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Chrysophyta. Diatoms are classified under the division Chrysophyta due to their unique characteristics, such as possessing a cell wall made of silica (siliceous frustule) and containing chlorophyll a and c for photosynthesis. Chrysophyta includes golden-brown algae, which diatoms are a part of. Rhodophyta (B) includes red algae, Chlorophyta (C) includes green algae, and Phaeophyta (D) includes brown algae. These choices are incorrect as they do not align with the specific characteristics and classification of diatoms within the kingdom Protista.

Correct Answer: B

Rationale: The correct answer is B: Mycelium. Mycelium refers to the network of branching filaments that form the main body of a fungus. When fungi grow on solid media, they develop a visible mass of mycelium. Hyphae (A) are the individual filaments that make up mycelium. Spores (C) are reproductive cells produced by fungi. Columella (D) refers to a specialized structure found in some fungi but is not related to the colonies grown on solid media. Therefore, the correct term for the colonies of fungi on solid media is mycelium.

Correct Answer: B

Rationale: The correct answer is B: Mycobacterium tuberculosis. Acid-fast bacteria have a unique cell wall component called mycolic acid, making them resistant to decolorization by acid-alcohol during staining. Mycobacterium tuberculosis is acid-fast, as it retains the stain due to its high lipid content. Streptococcus pyogenes (A), Clostridium perfringens (C), and Bacillus subtilis (D) do not possess mycolic acid in their cell walls, so they are not acid-fast.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani and Bacillus anthracis. Both bacteria produce exotoxins that damage host tissues. Clostridium tetani produces tetanospasmin, which causes muscle rigidity in tetanus. Bacillus anthracis produces anthrax toxins, leading to tissue damage and systemic effects. Explanation: - Choice B (Escherichia coli and Pseudomonas aeruginosa) primarily cause infections through other mechanisms and do not produce exotoxins that damage host tissues. - Choice C (Streptococcus pneumoniae and Listeria monocytogenes) are known for causing infections but not primarily through exotoxins that damage host tissues. - Choice D (Salmonella typhi and Mycobacterium tuberculosis) cause diseases through different mechanisms and do not produce exotoxins that directly damage host tissues.

Correct Answer: D

Rationale: The correct answer is D because antigens can be composed of lipids, proteins, or polysaccharides. Antigens are molecules that can elicit an immune response in the body. They can be diverse in their chemical composition, leading to the recognition and response by the immune system. Therefore, the correct choice is D as antigens can be any of these chemical components. Choices A, B, and C are incorrect because they each represent a possible chemical composition of antigens, but the flexibility of antigens to be made up of any of these components makes D the most accurate choice.

Correct Answer: C

Rationale: The correct answer is C because antibacterial chemotherapeutics need to be maximally toxic to microorganisms, not lead to allergic reactions, be stable, and have a wide spectrum of activity to effectively treat bacterial infections. A is incorrect because maximum toxicity to bacteria can lead to harmful side effects in the body. B is incorrect because rapid disintegration and insolubility in water would hinder the drug's effectiveness. D is incorrect because the basic requirements for antibacterial chemotherapeutics are outlined in option C.

Correct Answer: B

Rationale: The correct answer is B because the term "infectious process" refers to all biological processes that occur after the attachment and penetration of microbes into the host organism, regardless of whether there are clinical manifestations. This includes the colonization, multiplication, and spread of the microorganisms within the host. Explanation: A: Incorrect because it only mentions the attachment and penetration of microbes into the microorganism, missing the subsequent processes. C: Incorrect because it is too specific, stating that the penetration of microbes always manifests clinically, which is not always the case. D: Incorrect because there is a correct answer, which is B, as explained above.

Correct Answer: A

Rationale: Step 1: Giardiasis is caused by Giardia intestinalis, which is a well-known protozoan parasite. Step 2: Protozoans are single-celled eukaryotic organisms commonly found in water sources. Step 3: Giardia intestinalis infects the intestine, causing symptoms like diarrhea and abdominal cramps. Step 4: Bacteria (Choice B) are prokaryotic organisms, different from protozoans. Step 5: Fungi (Choice C) are also eukaryotic but are not responsible for causing Giardiasis. Step 6: Viruses (Choice D) are not cellular and cannot independently cause Giardiasis. In summary, the correct answer is A (protozoan) because Giardia intestinalis is a protozoan parasite specifically known to cause Giardiasis, while the other choices (Bacterium, Fungus, Virus) do not match the characteristics of the