CCEA GCSE Biology 2.6 Health, Disease, Defence Mechanisms and Treatments Exam Questions

About CCEA GCSE Biology 2.6 Health, Disease, Defence Mechanisms and Treatments

Health, Disease, Defence Mechanisms and Treatments is the final and one of the broadest topics in CCEA GCSE Biology Unit 2. It covers how pathogens cause and spread disease, how to grow microorganisms safely using aseptic technique, and how the body and plants defend themselves. You also need to explain vaccination, how antibiotics work and why resistance develops, and how new drugs are tested. The topic ends with non-communicable diseases such as heart disease, stroke and cancer. The prescribed practical investigates the effect of antibiotics or chemicals on bacterial growth. Examiners often ask about memory cells and secondary response graphs, aseptic steps and clinical trials.

What you need to know

• Communicable disease Pathogens such as bacteria, viruses and fungi cause disease and spread through air, water, food, direct contact or vectors. Bacteria can release toxins; viruses reproduce inside cells and damage them. Hygiene, isolating patients and controlling vectors reduce spread.
• Aseptic technique and the practical Sterilise the inoculating loop in a flame, work near a Bunsen flame, lift the Petri dish lid only slightly, then tape the lid on but do not seal it fully and incubate at about 25 °C. Antibiotic or antiseptic discs on a bacterial lawn produce clear zones of inhibition; a larger clear zone means a more effective substance.
• Body defences The skin, mucus, cilia, stomach acid and blood clotting stop pathogens entering. Phagocytes engulf and digest pathogens. Lymphocytes produce antibodies that are specific to the antigens on a pathogen, and some become memory cells.
• Vaccination A vaccine contains dead or weakened pathogens or their antigens. Lymphocytes make antibodies and memory cells, so if the real pathogen enters later the secondary response is faster and larger and the person does not become ill. High vaccination rates protect the population.
• Antibiotics and drug development Antibiotics kill bacteria or stop them growing but do not work on viruses. Overuse leads to resistant strains such as MRSA, so patients should finish the course and doctors should not prescribe them unnecessarily. New drugs are tested on cells and animals, then in clinical trials on healthy volunteers and patients, often using placebos and double blind trials.
• Plant defences Plants have physical defences such as cell walls and a waxy cuticle, and chemical defences such as antibacterial substances.
• Non-communicable disease Risk factors for heart disease and stroke include smoking, high fat diets, obesity, lack of exercise and high blood pressure. Cancer is caused by uncontrolled cell division (mitosis) forming a tumour; malignant tumours can spread. Treatments include surgery, radiotherapy and chemotherapy.

Common mistakes in 2.6 Health, Disease, Defence Mechanisms and Treatments

• Saying antibiotics can treat colds or flu. These are caused by viruses, which antibiotics do not affect.
• Writing that antibodies kill all pathogens. Each antibody is specific to one antigen, so it only works against one type of pathogen.
• Stating that a vaccine gives you the disease. It contains dead or weakened pathogens or antigens that cannot cause illness.
• Sealing the Petri dish completely. Taping it fully could allow anaerobic, possibly harmful, bacteria to grow.
• Incubating cultures at 37 °C in school. Use about 25 °C to reduce the risk of growing human pathogens.

Try three 2.6 Health, Disease, Defence Mechanisms and Treatments exam-style questions