Edexcel GCSE Biology: Communicable Diseases

Edexcel GCSE Biology: Communicable Diseases - Paper 2

Understanding Communicable Diseases

Communicable diseases, also known as infectious diseases, are caused by pathogens that can spread from one person to another. These pathogens can be bacteria, viruses, fungi, or protists.

1. Bacteria

• Structure: Single-celled organisms without a nucleus. They have a cell wall, cell membrane, cytoplasm, and a circular strand of DNA.
• Reproduction: Bacteria reproduce asexually by binary fission, which quickly creates large populations.
• Disease Examples:
  • Food poisoning: Caused by bacteria like Salmonella and Campylobacter.
  • Tuberculosis: Caused by the bacterium Mycobacterium tuberculosis.
  • Pneumonia: Some types are caused by bacteria.
• Treating bacterial infections: Antibiotics target specific processes in bacterial cells, disrupting their growth and killing them.

2. Viruses

• Structure: Smaller than bacteria, viruses consist of a protein coat surrounding genetic material (DNA or RNA).
• Reproduction: Viruses cannot reproduce on their own. They invade host cells, using the host's cellular machinery to replicate themselves.
• Disease Examples:
  • Flu (influenza): Caused by influenza viruses.
  • HIV (human immunodeficiency virus): Weakens the immune system, making individuals vulnerable to other infections.
  • Common cold: Caused by a variety of viruses.
• Treating viral infections: Antibiotics are ineffective against viruses. Antiviral medications are sometimes available, but they can be difficult to develop.

3. Fungal Pathogens

• Structure: Eukaryotic organisms with a cell wall, cell membrane, and a nucleus. They can be single-celled (yeasts) or multicellular (moulds).
• Reproduction: Fungi reproduce both sexually and asexually.
• Disease Examples:
  • Athlete's foot: Caused by a fungus that infects the skin on the feet.
  • Ringworm: Caused by a fungus that infects the skin, causing a circular rash.
  • Thrush: Caused by a fungus that infects the mouth and throat.
• Treating fungal infections: Antifungal medications are used to treat fungal infections.

4. The Human Immune System

The human immune system defends against pathogens through a series of defenses:

• Non-specific defenses:
  • Skin: A physical barrier that prevents pathogens from entering the body.
  • Mucus: Traps pathogens in the respiratory system.
  • Cilia: Tiny hair-like structures that sweep mucus and trapped pathogens out of the respiratory system.
  • Stomach acid: Kills pathogens in the digestive system.
  • White blood cells: Phagocytes engulf and destroy pathogens, while lymphocytes produce antibodies.
• Specific defenses:
  • Antibodies: Proteins that bind to specific antigens on pathogens, marking them for destruction.
  • Memory cells: Lymphocytes that remember specific pathogens, allowing for a faster and more effective response to future infections.

5. Vaccinations

Vaccinations introduce weakened or inactive forms of pathogens into the body, stimulating the immune system to produce antibodies and memory cells without causing disease. This provides long-lasting immunity against specific diseases.

6. Preventing the Spread of Communicable Diseases

• Hygiene: Handwashing, covering coughs and sneezes, and proper food hygiene.
• Isolation: Separating infected individuals from others to prevent the spread of disease.
• Treatment: Prompt treatment with appropriate medications to prevent the spread of disease and reduce complications.

Exam Information:

• Paper 2: This paper assesses your understanding of communicable diseases and the human immune system. Expect questions on:
  • The structure and reproduction of pathogens.
  • The different types of communicable diseases and their symptoms.
  • The role of the immune system in defending against pathogens.
  • The importance of vaccination and other methods of disease prevention.
• Practice Past Papers: Familiarize yourself with the exam format and question types by working through past papers.
• Review Key Terms: Understand the definitions of key terms related to communicable diseases and the immune system.

Remember: This is just a starting point for your study. Refer to your textbook, online resources, and consult with your teacher for a more detailed understanding of communicable diseases.