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Flashcards · 8461 · Topic 3
Infection and response flashcards
18 cards on Topic 3, subtopics 4.3.1 to 4.3.3. Pick a subtopic or study them all.
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4.3.1 Communicable diseases
- Pathogen: definition, the four types, and how bacteria and viruses make us ill
- A microorganism that causes infectious disease: viruses, bacteria, protists, fungi. Bacteria reproduce rapidly and may release toxins that damage tissues. Viruses live and reproduce inside cells, causing cell damage.
- Measles and HIV: spread and control
- Measles (virus): inhaled droplets from sneezes and coughs; fever and red rash; controlled by vaccinating young children. HIV (virus): sexual contact or exchange of body fluids such as blood; attacks immune cells; antiretroviral drugs.
- Tobacco mosaic virus and rose black spot
- TMV (virus): mosaic discolouration of leaves. Black spot (fungus): purple or black leaf spots, spread by water or wind; fungicides and removing affected leaves. Both reduce photosynthesis, so less glucose for growth.
- Salmonella and gonorrhoea
- Salmonella (bacterium): in food; fever, cramps, vomiting, diarrhoea; UK poultry vaccinated. Gonorrhoea (bacterium): sexual contact; thick yellow or green discharge, pain on urinating; antibiotics (many strains penicillin-resistant), condoms.
- Malaria: pathogen, vector, symptoms and control
- Caused by a protist; the mosquito is the vector. Recurrent episodes of fever; can be fatal. Control: stop mosquitoes breeding, and use mosquito nets.
- Non-specific defences of the human body
- Skin: barrier. Nose: hairs and mucus trap particles. Trachea and bronchi: mucus traps pathogens and cilia move it away from the lungs. Stomach: hydrochloric acid kills pathogens.
- Three ways white blood cells defend the body
- Phagocytosis (engulf and digest pathogens); producing antibodies (bind to a specific pathogen); producing antitoxins (neutralise bacterial toxins).
- How does vaccination work?
- Small amounts of a dead or inactive pathogen stimulate white blood cells to produce antibodies. If the live pathogen enters later, white blood cells respond quickly with the right antibodies. If most people are immune, spread falls.
- Antibiotics vs painkillers
- Antibiotics (e.g. penicillin) kill infective bacteria inside the body, not viruses; specific bacteria need specific antibiotics, and resistant strains are a concern. Painkillers treat symptoms only and kill no pathogens.
- Testing a new drug: the stages
- Preclinical testing on cells, tissues and live animals; then clinical trials on healthy volunteers and patients, starting with very low doses, then finding the optimum dose. Double blind trials with a placebo; results peer reviewed.
4.3.2 Monoclonal antibodies (biology only) (HT only)
- How are monoclonal antibodies produced?Higher
- Mouse lymphocytes are stimulated to make an antibody and combined with a tumour cell to form a hybridoma cell, which divides and makes the antibody. A single hybridoma is cloned, and the antibody collected and purified.
- Monoclonal antibodies: what are they?Higher
- Antibodies produced from a single clone of cells. They are specific to one binding site on one protein antigen, so they can target a specific chemical or specific cells in the body.
- Four uses of monoclonal antibodiesHigher
- Pregnancy tests; measuring levels of hormones and other chemicals in blood, or detecting pathogens; locating or identifying specific molecules in a cell or tissue with a fluorescent dye; treating some diseases, such as delivering a drug or radioactive substance to cancer cells.
- Why are monoclonal antibodies not as widely used as was first hoped?Higher
- They create more side effects than expected.
4.3.3 Plant disease (biology only)
- Plant deficiency signs: nitrate and magnesium ions
- Nitrate (for protein synthesis): stunted growth. Magnesium (for chlorophyll): chlorosis, yellow leaves.
- Signs of plant disease, and ways to identify the causeHigher
- Signs: stunted growth, spots on leaves, areas of decay, growths, malformed stems or leaves, discolouration, pests. Identify by a gardening manual or website, a laboratory test of the infected plant, or testing kits containing monoclonal antibodies.
- Physical, chemical and mechanical plant defences
- Physical: cellulose cell walls, a tough waxy cuticle, layers of dead cells such as bark. Chemical: antibacterial chemicals, poisons that deter herbivores. Mechanical: thorns and hairs, leaves that droop or curl when touched, mimicry.
- Aphids as plant pests
- Aphids are insects that feed on phloem sap, taking sugars from the plant and weakening it.