1. What is the role of viral surface proteins in the molecular basis of infectious disease? Provide examples

and explain their significance in host-cell interaction.

Answer: Viral surface proteins play a crucial role in the molecular basis of infectious diseases. For instance,

the hemagglutinin protein of the influenza virus facilitates viral attachment and entry into host cells. The

surface protein spike (S protein) of SARS-CoV-2 enables viral entry into human lung cells via binding to

ACE2 receptors. Understanding the significance of viral surface proteins helps in designing targeted

therapeutics and vaccines.

2. Discuss the molecular mechanisms of antibiotic resistance in bacteria. How does the acquisition of

resistance genes impede treatment of infectious diseases?

Answer: Antibiotic resistance in bacteria arises from various molecular mechanisms such as mutation or

horizontal gene transfer. For instance, the acquisition of resistance genes through plasmids or transposons

allows bacteria to produce enzymes that inactivate antibiotics or alter their target sites. This impedes

treatment as the effectiveness of antibiotics is reduced, leading to persistent infections and limited treatment

options.

3. Describe the molecular basis of host defense mechanisms against viruses. How does the innate immune

response recognize and eliminate viral pathogens?

Answer: The innate immune response acts as the first line of defense against viral pathogens. Pattern

recognition receptors (PRRs) located on host cells can recognize molecular patterns unique to viruses, such

as viral nucleic acids or viral proteins. This recognition triggers the production of interferons and other

cytokines, which activate antiviral pathways, inhibit viral replication, and recruit immune cells to eliminate

the viral infection.

4. Explain the role of virulence factors in the pathogenesis of infectious diseases. Provide examples and

describe their molecular mechanisms.

Answer: Virulence factors are molecules produced by pathogens that contribute to the development and

severity of infectious diseases. For example, bacterial toxins such as cholera toxin and pertussis toxin

disrupt host cell signaling and immune responses. The molecular mechanisms of virulence factors often

involve binding to host cell receptors, modifying intracellular signaling pathways, or evading immune

surveillance, ultimately facilitating pathogen survival and dissemination.