Topic 3 - Infection and Response

Flashcards covering the key concepts related to pathogens, diseases, and the immune response.

Pathogen

Microorganisms that cause disease in their host.

Bacteria

Produce toxins that harm cells and tissues, leading to illness.

Virus

 Invade host cells, reproduce inside them, destroying the host cells.

Protist

 Live on or in a host organism and cause damage.

Fungi

Penetrate living tissues, causing diseases.

How Pathogens Are Spread

• Water: Pathogens spread through contaminated water.

• Air: Airborne droplets from coughs/sneezes spread pathogens.

• Direct Contact: Touching contaminated surfaces spreads pathogens.

Good Hygiene Practices

• Practice good hygiene (e.g., regular handwashing).

• Ensure safe food handling and storage.

• Use barrier methods (e.g., condoms) during sexual activity.

• Vaccinate to prevent specific infections.

• Quarantining  for 2 weeks

Measles

• Cause: Virus

• Spread: Airborne

• Symptoms: Red skin rash and fever.

• Treatment: Vaccine

• Prevention: Children vaccinated when young.

HIV

• Cause: Virus

• Spread: Sexual contact or exchanging bodily fluids.

• Symptoms: Flu-like symptoms, attacks lymph nodes and immune cells.

• Treatment: Antibiotics.

• Prevention: Condoms

Tobacco Mosaic Virus (TMV)

• Cause: Plant Virus

• Spread: Contact or contaminated tools

• Symptoms: A distinct mosaic pattern visible on leaves, discolouration of leaf limiting photosynthesis and stunting growth.

• Management: Using resistant plant varieties, proper sanitation of tools, removing and destroying infected plants.

Salmonella

A type of bacteria that causes fever and vomiting, usually through contaminated food or water.

Gonorrhoea

• Cause: Bacteria

• Symptoms: Thick yellow discharge, pain when urinating

• Spread: Sexual Contacts

• Treatment: Antibiotics

• Prevention: Condoms, regular screening.

Rose Black Spot

• Cause: Fungus

• Symptoms: Black/purple dots on leaves.

• Spread: In water and wind.

• Treatment: Fungicides or removing infected leaves.

Malaria

• Cause: Protist, mosquito is the vector

• Symptoms: Repeating fever that can be fatal.

• Spread: Infected mosquito bite

• Treatment: Mosquito nets and insecticides.

Body’s Non-Specific Defences Against Pathogens

• Skin: Acts as a barrier to pathogens; platelets form a scab when wounded.

• Nose hairs and mucus: Trap pathogens, removed by sneezing or blowing the nose.

• Trachea and bronchi: Produce mucus to trap pathogens.

• Stomach acid (HCl): Kills pathogens in food or mucus.

Phagocytosis

The process by which phagocytes engulf and digest pathogens.

Lymphocytes

• Antigens: Pathogens have specific molecules called antigens that lymphocytes use to detect pathogens.

• Antibody Production: Lymphocytes produce antibodies with specific shapes to bind to the antigens on the pathogens.

• Function of Antibodies: Binding of antibodies causes pathogens to bind together, making them easier for phagocytes to ingest.

Memory Cells

• Memory Cells: Lymphocytes that remain in the blood after an infection. If infected by the same pathogen later, memory cells quickly produce antibodies to destroy it before symptoms appear.

• Antitoxins: Lymphocytes may produce antitoxins to neutralize toxic substances produced by pathogens, preventing cell and tissue damage, stopping symptoms, and helping the individual feel better.

Vaccines

• Definition: Vaccines contain dead or weakened pathogens with antigens that trigger immune responses, causing lymphocytes to produce antibodies.

• Antibodies produced quickly (on reinfection) - Killing pathogen faster

Advantages of vaccine

• Benefits: Reduce disease spread, create herd immunity, and prevent epidemics

Disadvantages of vaccine

• Side Effects: Vaccines can cause side effects such as swelling or fever.

• Effectiveness: Vaccines don’t always work.

Painkillers

• Painkillers like paracetamol treat symptoms but don't cure the disease. 

Antibiotics

• Function: Antibiotics stop or slow bacterial growth, curing bacterial diseases but not viruses.

Why don’t antibiotics treat viruses

Antibiotics can’t treat viruses as they live inside the host cells, difficult to target virus cells only

Antibiotic Resistance

• Cause: Antibiotic resistance occurs when bacteria mutate to resist antibiotics, making them harder to treat.

• Reason: Caused by overusing antibiotics

Difference Between Antibiotics and Painkillers

• Antibiotics: Kill bacteria. Painkillers: Treat symptoms (like pain) but don’t kill pathogens

Medicines from Plants

• Penicillin: Antibiotic came from Penicillium (fungus).

• Aspirin: A painkiller derived from willow.

• Digitalis: A heart drug that originates from foxgloves.

Why It’s Hard to Develop Antiviral Drugs

•  Viruses live inside host cells, so targeting them without harming body cells is difficu

Herd Immunity

• When a large portion of a population is vaccinated, it reduces disease spread and protects those who can't be vaccinated.

Monoclonal Antibodies

• Uses: Used in diagnosis (e.g., pregnancy tests), research, and cancer treatment.

Monoclonal Antibodies - Production

1. A mouse is injected with an antigen, triggering an immune response.

2. Lymphocytes produce specific antibodies but don’t divide easily.

3. Lymphocytes are fused with tumour cells, forming hybridomas that divide rapidly.

4. Hybridomas produce large amounts of identical antibodies, which are collected and purified.

Monoclonal Antibodies - Cancer

• Cancer Cells: Cancer cells have unique tumour markers.

• Functions:
  

  • Detect cancer cells to help locate and treat them.

  • Deliver anticancer drugs directly to cancer cells.

  • Trigger the immune system to attack cancer cells.

  • Block chemicals that make cancer cells divide rapidly.

Drug Testing Process

• Preclinical Trials

  • Test on cells, tissues, and live animals.

  • Assess toxicity, dosage, and efficacy.

• Clinical Trials

  • Phase 1: Test on healthy volunteers & patients (low doses).

  • Monitor for safety and side effects.

  • Phase 2 & 3: Find optimum dosage and confirm efficacy.

• Double-Blind Trials

  • Patients randomly assigned to drug or placebo groups.

  • Neither doctor nor patient knows who receives the real drug.

• Peer Review

  • Ensures accuracy and prevents false claims before publication.

Physical Defenses

• Waxy Cuticle: Barrier to stop pathogens from entering.

• Cell Walls: Protect against microorganisms.

• Dead Cells Around Stem: Act as a barrier to pathogens (e.g., bark).

Chemical Defenses

• Antibacterial Chemicals: Plants produce antibacterial chemicals to kill bacteria.

• Poison: Plants produce poison to deter herbivores

Mechanical Defenses

• Thorns/Hairs: Stop animals from eating them.

• Drooping/Curling Leaves: Knock insects off when touched.

• Mimicry: Plants may mimic withering to trick animals into not eating them.

How Plant Diseases Are Detected and Identified

• Symptoms: Stunted growth, leaf spots, rotting.

• Identification: Testing kits using monoclonal antibodies (mABs), lab analysis

Magnesium Deficiency

• Function: Needed for chlorophyll, necessary for photosynthesis.

• Symptoms: Yellow leaves (chlorosis).

Nitrate Deficiency

• Function: Needed to make proteins for growth.

• Symptoms: Stunted growth