Basic Immunology Notes (Temasek JC IP Year 3 Biology)

Question-and-answer flashcards covering infectiousness, pathogens, transmission, bacterial and viral structures, vaccines, antibiotics, immune cells, and immunity concepts from the notes.

What is the difference between infectious and non-infectious diseases?

Infectious diseases can spread from person to person and are caused by pathogens (bacteria, viruses, protozoa, fungi, worms); non-infectious diseases cannot be spread and may be inherited or due to factors like malnutrition, pollution, or lifestyle.

Name examples of pathogens that cause infectious diseases.

Bacteria, viruses, protozoa, fungi, and worms.

List the main ways infectious diseases can be spread.

Airborne droplets/droplet nuclei, direct contact, contaminated food and water, and disease vectors.

What is the difference between a sign and a symptom?

A sign can be observed or measured (e.g., fever, rash); a symptom is described or felt by the patient (e.g., fatigue, headache).

Describe the structural features of typical bacteria (prokaryotes).

Unicellular, no nucleus or membrane-bound organelles, circular DNA, cell wall of peptidoglycan, plasmids, 70S ribosomes, reproduce by binary fission.

What are the common shapes of bacteria?

Bacillus (rod-shaped), Coccus (spherical), Spirillum (spiral).

List key differences between prokaryotic and eukaryotic cells.

Size (

What are viruses and where do they reproduce?

Obligate intracellular parasites that reproduce only inside a host cell; they cannot multiply outside a living host.

What is the size range of viruses?

From about 10 nm (tiny viruses) to about 500 nm (largest viruses).

State two living and two non-living characteristics of viruses.

Living: can acquire/use energy, reproduce inside a host, evolve. Non-living: non-cellular, no own metabolism or cellular machinery, cannot grow, move, respire, or excrete on their own.

What does host specificity mean for viruses?

Viruses infect specific types of organisms and specific cells, due to interactions with host cell surface proteins.

What are the basic components of a virus?

Genetic material (DNA or RNA) enclosed in a protein coat (capsid); some have an envelope; enclosed material forms the nucleocapsid.

What is the virion?

The active infectious form of a virus outside a host cell.

What is the influenza virus envelope protein involved in cell entry?

Hemagglutinin (HA) spikes on the viral envelope help attach to host cells.

How is influenza transmitted and what are typical symptoms?

Spread by respiratory droplets and contact with contaminated surfaces; incubation about 1 day; symptoms include high fever, sore throat, congestion, dry cough, and headache.

What is neuraminidase and why is it targeted by antivirals?

Neuraminidase helps release new virions from infected cells; antivirals inhibit neuraminidase to prevent viral spread.

What is the pneumococcal disease and its pathogen?

Pneumococcal disease is caused by Streptococcus pneumoniae; can cause ear infections, pneumonia, meningitis, and sepsis.

Describe the transmission route of Streptococcus pneumoniae.

Spread by respiratory droplets and droplet nuclei and by contaminated surfaces; inhaled into alveoli.

What are common diagnostic tests for pneumococcal disease?

Blood test, urine test, sputum test, chest X-ray, spinal tap (lumbar puncture for CSF).

What is the general approach to treating pneumococcal disease?

Take antibiotics (effective against bacteria, not viruses); pneumococcal vaccination; avoid close contact; cough etiquette; hand hygiene.

What is a vaccine and how does it work?

A vaccine contains an agent resembling a pathogen (antigen) that stimulates B lymphocytes to differentiate into plasma B cells producing antibodies, providing immunity.

What are memory B cells and plasma B cells?

Plasma B cells secrete antibodies; memory B cells persist to rapidly respond to future infections by the same pathogen.

Outline the mode of action of vaccines (basic steps).

Antigen enters body; binds to B cell receptor; B cell differentiates into plasma and memory B cells; plasma B cells secrete antibodies; antibodies bind pathogens; memory B cells provide long-term immunity.

What are antibodies and what do they do?

Proteins secreted by B lymphocytes that bind to specific antigens, neutralize pathogens, or mark them for destruction by phagocytes.

What are the main leukocytes involved in immunity and their primary roles?

Lymphocytes (B cells -> plasma/memory; antibody production); Neutrophils (phagocytosis; short-lived); Macrophages (phagocytosis; long-lived in tissues).

What is the process of phagocytosis?

Phagocytes have receptors that recognize microbial molecules, attach to the microbe, engulf via receptor-mediated endocytosis, and digest.

What are the two main immunity classifications (active vs passive, natural vs artificial)?

Active immunity: immune response to antigen producing antibodies; long-lasting. Passive immunity: antibodies provided directly; short-term.

What are natural and artificial immunity?

Natural immunity: gained through infection (active) or from mother via placenta/breast milk (passive). Artificial immunity: gained via vaccination (active) or antibodies injected (passive).

Why are antibiotics ineffective against viruses?

Viruses lack their own metabolic machinery and ribosomes; they rely on host cell systems, so antibiotics targeting bacterial processes do not affect viruses.

List common antibiotic mechanisms of action.

Inhibition of cell wall synthesis (e.g., penicillin); disruption of cell membrane; inhibition of bacterial 70S ribosomes; inhibition of enzymes for folic acid synthesis; inhibition of DNA replication.

How can antibiotic resistance arise and spread?

Mutations from mutagenic exposure confer resistance; antibiotic exposure kills susceptible bacteria; resistant survive and multiply, passing resistance to offspring.

How can antibiotic resistance be mitigated?

Complete prescribed course; avoid misuse/overuse; use antibiotics only when necessary.

What is a disease vector? Give an example.

An organism that transmits a pathogen between hosts; e.g., Anopheles mosquito transmitting malaria.

What is a pathogen’s nucleocapsid?

The combination of the viral genome (nucleic acid) and its protein capsid.

What is the term for viruses that carry a lipid envelope?

Enveloped viruses.