Infection and response：练习题

Human non-specific defense systems act as the first line of protection against pathogens. Which of the following correctly explains how the stomach contributes to this defense mechanism?

The process of drug discovery and development involves rigorous testing. During the clinical trial phase, why are very low doses of the drug administered to healthy volunteers at the very start of the trial?

Antibiotics have significantly reduced deaths from infectious bacterial diseases. Why are antibiotics ineffective against viral pathogens such as the HIV virus?

Tobacco mosaic virus (TMV) is a significant plant pathogen. Which of the following statements best explains why an infection of TMV results in stunted growth of the affected plant?

A student investigates the immune system's response to a specific pathogen. Which statement correctly identifies the function of antitoxins produced by white blood cells?

A student observes a pattern of discolouration on the leaves of a tomato plant. Name the viral pathogen likely responsible for this and describe how it reduces the plant's growth.

Explain why antibiotics can be used to successfully treat a Gonorrhoea infection but cannot be used to cure Measles.

Explain how the chemical process of vaccination prevents a person from developing symptoms if they are later exposed to the same live pathogen.

When a pathogen enters the human body, the immune system is triggered to defend against disease.

(a) Describe three ways in which white blood cells help to defend the body against pathogens. (3)

(b) Gonorrhoea is a bacterial disease that was previously treated easily with penicillin. Explain why it is now much more difficult to treat certain strains of this bacterium. (2)

(c) New drugs must undergo extensive testing. Describe the three main stages of a clinical trial that occur after a drug has passed preclinical testing in a laboratory. (3)

The development of new drugs is a rigorous process designed to ensure safety and effectiveness before a medicine is licensed for public use.

(a) A scientist discovers a potential new drug from a plant extract. Before clinical trials can begin, the drug must undergo preclinical testing. Describe what is involved in this stage and identify the three specific factors being tested. (3)

(b) In Phase 1 clinical trials, the drug is administered to a small group of healthy volunteers. Explain the scientific reason for using healthy individuals rather than patients in this initial phase. (2)

(c) To prevent bias in results, clinical trials often use a double-blind protocol with a placebo. Explain how these two methods combined ensure that the observed effects are due to the drug itself rather than psychological factors or researcher expectations. (3)