Infection and Response - AQA Biology GCSE

Overview

• Focus on communicable diseases caused by pathogens: viruses, bacteria, protists, fungi.
• Pathogens can spread via direct contact, water, or air.

Types of Pathogens

Viruses

• Very small, invade cells to replicate, causing cell damage and illness.

Bacteria

• Multiply rapidly through binary fission, produce cell-damaging toxins.

Protists

• Some are parasitic, using hosts to cause damage.

Fungi

• Single-celled or have hyphae structures, produce spores for spreading.

Spread of Diseases

• Direct Contact: Includes touching infected surfaces, bodily fluids, skin contact.
• By Water: Through contaminated water.
• By Air: Pathogens carried in droplets from coughing, sneezing, talking.
• Control Measures: Hygiene improvement, reducing contact, removing vectors, vaccination.

Viral Diseases

Measles

• Symptoms: Fever, rash; can lead to pneumonia, encephalitis.
• Spread: Droplet infection.
• Prevention: Vaccination.

HIV

• Symptoms: Flu-like initially; leads to AIDS.
• Spread: Sexual contact, bodily fluids.
• Prevention: Condoms, not sharing needles, antiretroviral drugs.

Tobacco Mosaic Virus

• Affects plants, causing leaf discoloration.
• Spread: Contact/insects.
• Prevention: Hygiene, pest control.

Bacterial Diseases

Salmonella

• Symptoms: Fever, cramps, vomiting, diarrhea.
• Spread: Raw meat, unhygienic conditions.
• Prevention: Vaccination of poultry, hygiene.

Gonorrhea

• Symptoms: Discharge, pain urinating.
• Spread: Unprotected sex.
• Prevention: Condoms, antibiotics.

Fungal Diseases

Rose Black Spot

• Symptoms: Black spots on leaves, reduces photosynthesis.
• Spread: Water/wind.
• Prevention: Fungicides, removal of infected leaves.

Protist Diseases

Malaria

• Symptoms: Fevers, shaking.
• Spread: Female Anopheles mosquitoes.
• Prevention: Insect nets, removing stagnant water, antimalarial drugs.

Human Defence System

• Non-Specific Defences: Skin, nose, trachea, bronchi.
• Specific Immune System: Phagocytosis, antibodies, antitoxins.

Vaccination

• Involves exposure to dead/inactive pathogen.
• Builds immunity.
• Reduces spread - herd immunity.

Antibiotics and Painkillers

• Antibiotics kill bacteria, not viruses.
• Overuse can lead to resistance.
• Painkillers treat symptoms, not causes.

Drug Discovery and Development

• Initial discovery in plants/microorganisms.
• Modern synthesis by chemists.
• Testing: Preclinical (cells, animals) and clinical (volunteers, patients).

Monoclonal Antibodies

• Produced by hybridoma cells from mice lymphocytes and tumor cells.
• Uses: Pregnancy tests, hormone level monitoring, disease treatment.

Plant Disease

• Detection: Stunted growth, spots, decay, discoloration.
• Ion deficiencies: Nitrate and Magnesium.

Plant Defence Responses

• Physical: Waxy cuticle, cell walls, dead cells.
• Chemical: Poisons, antibacterial compounds.
• Mechanical: Thorns, mimicry, drooping leaves.