B05) COMMUNICAL DISEASES
Phagocytes | Phagocytosis | Phagocytes engulf the pathogens and digest them. |
Lymphocytes | Antibody production | Specific antibodies destroy the pathogen. This takes time so an infection can occur. If a person is infected again by the same pathogen, the lymphocytes make antibodies much faster. |
Antitoxin production | Antitoxin is a type of antibody produced to counteract the toxins produced by bacteria. |
Immune system
Antigens (surface protein)
White blood cells are part of the immune system
Pathogens are identified by white blood cells by the different proteins on their surfaces ANTIGENS.
Human defence systems
Non-specific defence systems
The human body has several non specific ways of defending itself from pathogens getting in | | Nose | Nasal hairs, sticky mucus and cilia prevent pathogens entering through the nostrils. |
| Trachea and bronchus (respiratory system) | Lined with mucus to trap dust and pathogens. Cilia move the mucus upwards to be swallowed. | |
| Stomach acid | Stomach acid (pH1) kills most ingested pathogens. | |
| Skin | Hard to penetrate waterproof barrier. Glands secrete oil which kill microbes |
Pathogen | Disease | Symptoms | Method of transmission | Control of spread |
Virus | Measles | Fever, red skin rash. | Droplet infection from sneezes and coughs. | Vaccination as a child. |
Virus | HIV | Initially flu like systems, serious damage to immune system. | Sexual contact and exchange of body fluids. | Anti-retroviral drugs and use of condoms. |
Virus | Tobacco mosaic virus | Mosaic pattern on leaves. | Enters via wounds in epidermis caused by pests. | Remove infected leaves and control pests that damage the leaves. |
Bacteria | Salmonella | Fever, cramp, vomiting, diarrhoea. | Food prepared in unhygienic conditions or not cooked properly. | Improve food hygiene, wash hands, vaccinate poultry, cook food thoroughly. |
Bacteria | Gonorrhoea | Green discharge from penis or vagina. | Direct sexual contact or exchange of body fluids. | Use condoms. Treatment using antibiotics. |
Protists | Malaria | Recurrent fever. | By an animal vector (mosquitoes). | Prevent breeding of mosquitoes. Use of nets to prevent bites. |
Fungus | Rose black spot | Purple black spots on leaves. | Spores carried via wind or water. | Remove infected leaves. Spray with fungicide. |
Communicable diseases
Viruses | Bacteria (prokaryotes) | Protists (eukaryotes) | Fungi (eukaryotes) |
e.g. cold, influenza, measles, HIV, tobacco mosaic virus | e.g. tuberculosis (TB), Salmonella, Gonorrhoea | e.g. dysentery, sleeping sickness, malaria | e.g. athlete’s foot, thrush, rose black spot |
DNA or RNA surrounded by a protein coat | No membrane bound organelles (no chloroplasts, mitochondria or nucleus). Cell wall. Single celled organisms | Membrane bound organelles. Usually single celled. | Membrane bound organelles, cell wall made of chitin. Single celled or multi-cellular |
Pathogens
Pathogens may infect plants or animals and can be spread by direct contact, water or air
Viruses live and reproduce inside cells causing damage
Bacteria may produce toxins that damage tissues and make us fell ill
Pathogens are microorganisms that cause infectious disease
Detection and identification of plant diseases (bio only) | Detection | Identification |
Stunted growth | Reference using gardening manual or website, laboratory test for pathogens, testing kit using monoclonal antibodies. | |
Spots on leaves | ||
Area of decay | ||
growths | ||
Malformed stem/leaves | ||
Discolouration | ||
Presence of pests |
Nitrate ions needed for protein synthesis – lack of nitrate = stunted growth.
Magnesium ions needed to make chlorophyll – not enough leads to chlorosis – leaves turn yellow.
Plants have several ways of defending themselves from pathogens and animals
Physical | Mechanical |
Thick waxy layers, cell walls stop pathogen entry | Thorns, curling up leaves to prevent being eaten |
Chemical | |
Antibacterial and toxins made by plant | |