Biology - Topic 3 Infection and Response

What is a pathogen?

A microorganism that causes infectious disease.

Name the four major pathogen groups.

Bacteria, viruses, fungi and protists.

What is a communicable disease?

An infectious disease that can pass between organisms.

Name three routes by which pathogens spread.

Air, water and direct contact (including body fluids).

How do bacteria cause illness?

They reproduce and may produce toxins that damage tissues.

How do viruses cause illness?

They enter and reproduce inside living cells, damaging them.

How can handwashing reduce infection?

Removes microorganisms and reduces transfer between people.

How can vaccination reduce transmission?

Fewer susceptible hosts means pathogens spread less readily.

How can isolation help control disease?

Limits contact between infected and uninfected people.

What is a vector?

An organism that carries and transmits a pathogen.

What pathogen causes measles?

A virus transmitted in droplets from coughs and sneezes.

What are typical symptoms of measles?

Fever and red skin rash; serious complications can occur.

How is measles commonly prevented?

Vaccination to develop immunity.

How does HIV spread?

Exchange of infected body fluids, including blood and sexual contact.

What does HIV attack if untreated?

Cells of the immune system; advanced infection can cause AIDS.

How can HIV be controlled medically?

Antiretroviral drugs slow viral replication.

What does tobacco mosaic virus (TMV) do to plants?

Causes leaf discolouration, reducing photosynthesis and growth.

How is Salmonella usually transmitted?

Eating contaminated food or food prepared unhygienically.

Name symptoms of Salmonella food poisoning.

Fever, stomach cramps, vomiting and diarrhoea.

How can spread of Salmonella be reduced?

Proper food hygiene and vaccinating poultry.

What type of pathogen causes gonorrhoea?

A bacterium spread through sexual contact.

Name possible symptoms of gonorrhoea.

Pain on urinating and an unusual yellow/green genital discharge.

Why is gonorrhoea harder to treat than before?

Antibiotic-resistant strains have emerged.

How can gonorrhoea transmission be reduced?

Barrier contraception and appropriate antibiotic treatment.

What causes rose black spot?

A fungus causing black/purple leaf spots and premature leaf loss.

How can rose black spot be controlled?

Fungicides and removing/destroying infected leaves.

What type of pathogen causes malaria?

A protist carried by mosquitoes.

Why are mosquitoes important in malaria transmission?

They act as vectors transferring the parasite between humans.

How can malaria spread be reduced?

Mosquito nets and reducing mosquito breeding sites.

What symptom is characteristic of malaria?

Recurring fever; untreated infection can be fatal.

How does the skin protect against pathogens?

It forms a physical barrier and produces antimicrobial secretions.

How does the nose help block pathogens?

Hairs and mucus trap particles and microorganisms.

How do trachea and bronchi remove pathogens?

Mucus traps them; cilia move mucus toward the throat.

How does the stomach defend against pathogens?

Hydrochloric acid kills many swallowed microorganisms.

What is phagocytosis?

White blood cells engulf and digest pathogens.

What are antibodies?

Proteins that bind to specific antigens on pathogens.

What do antitoxins do?

Neutralise toxins released by bacteria.

How does vaccination create protection?

Exposes immune system to antigens so memory cells respond faster later.

What is herd immunity?

High population immunity reduces the spread of infectious disease.

Why do antibiotics not treat viral infections?

Viruses use host cells and lack the bacterial targets of antibiotics.

What are antibiotics used to treat?

Bacterial infections; specific antibiotics target susceptible bacteria.

Why is antibiotic resistance a problem?

Resistant bacteria survive and treatments become less effective.

What do painkillers do in infectious disease?

Relieve symptoms; they do not kill pathogens.

What naturally occurring source led to penicillin?

Penicillium mould, observed by Alexander Fleming.

Which plant originally provided digitalis?

Foxglove plants.

Which plant originally provided aspirin-related medicine?

Willow.

What three aspects are checked when testing new drugs?

Toxicity, efficacy and effective dose.

What is preclinical drug testing?

Testing on cells, tissues and sometimes animals before human trials.

What happens in early clinical trials?

Healthy volunteers or patients receive low doses to check safety.

What is a placebo?

Inactive treatment used as a comparison in a clinical trial.

What is a double-blind trial?

Neither participant nor assessor knows who received the drug until afterwards.

Why use a control group in clinical trials?

To distinguish the drug's effect from other influences.

What are monoclonal antibodies?

Identical antibodies from one cell clone, specific to one antigen binding site.

How are monoclonal antibodies produced?

Fuse antibody-producing mouse lymphocytes with tumour cells to form hybridomas.

What is a hybridoma?

A fused cell that divides repeatedly and produces one specific antibody.

How are large quantities of one antibody obtained?

Clone a single hybridoma cell, grow it and purify its antibodies.

How do pregnancy tests use monoclonal antibodies?

They bind specifically to the hormone hCG in urine.

How can monoclonal antibodies help diagnose disease?

Bind specific antigens or hormones so they can be detected.

How can monoclonal antibodies target cancer cells?

Deliver attached drugs or radioactive material to target antigens.

What is one drawback of monoclonal antibody treatments?

They can cause significant adverse side effects.

Name three signs of plant disease.

Stunted growth, leaf spots, rotting, discolouration or malformed leaves.

How may a plant pathogen be identified?

Reference guide, laboratory test or antibody-based test kit.

What deficiency causes chlorosis in plants?

Magnesium ion deficiency; less chlorophyll can be made.

What deficiency causes stunted growth?

Nitrate ion deficiency, reducing amino acid/protein synthesis.

Why are nitrate ions important for plants?

Used to make amino acids and proteins for growth.

What is one physical plant defence against pathogens?

Tough cell walls, waxy cuticle or protective bark.

What is one chemical plant defence?

Antibacterial chemicals or poisons that deter herbivores.

What is one mechanical plant defence against herbivores?

Thorns, hairs, leaf curling or mimicry.

How does a waxy cuticle protect plants?

Creates a protective barrier and reduces water loss.