5.9-5.15 Preventing and Identifying Disease Flashcards
(15 cards)
Describe how some plants defend themselves against attack from pests and pathogens by physical barriers
Examples of plants’ physical barriers:
- A thick cellulose cell wall, which is impermeable to many pathogens
-A thick waxy cuticle on the surface of the leaf, which acts as a barrier to most pathogens
Describe how plants defend themselves against attack from pests and pathogens by producing chemicals
-Cells of some plants can produce antimicrobial chemicals, proteins and enzymes.
-Some plants can release compounds that attract larger insects than the pests, which feed on the pests and stop them eating the plant.
-Often, we can extract antimicrobial compounds from these plants for use in drugs such as antibiotics.
Describe the method of identifying plant diseases that is observation including signs of disease.
Visible symptoms may include changes in growth, change in colour or blotching of leaves, or lesions (areas of damage on stem or leaves). Symptoms can be checked against photos or other information to suggest a cause.
Describe the method of identifying plant diseases that is distribution analysis.
This looks at where the damaged plants occur. Flooding, drought or lack of a soil nutrient will create similar symptoms in all the plants in the area. Diseases that spread by wind will affect plants over a wide area, though most obviously where the wind first reaches the crop and are likely to follow the direction of wind travel. Soil pathogens are usually only found in small areas, and so create an obvious pattern of damaged plants.
Describe the method of identifying plant diseases that is sending samples to a lab for testing.
The tests should allow a diagnosis to be made for the problem. Tests can include trying to grow a pathogen from damaged crop plants or using technology to identify the presence of genetic material from a pathogen. Soil samples can also be sent in to be tested for nutrients and toxins. A report will be sent in about observations made.
Describe how the physical barrier of skin protects the human body from pathogens.
-Skin is an effective physical barrier as it is very thick over most of the body so pathogens can usually only cross this barrier through wounds or by an animal vector that pierces the skin.
Describe how the physical barriers of cilia protects the human body from pathogens.
Ciliated cells are specialised to move substances like mucus across their surfaces. This helps to carry dust and pathogens away, either out of the body or into the throat where they enter the digestive system.
Describe how the physical barriers of mucus protects the human body from pathogens.
Produced by goblet cells in the airway, mucus traps bacteria and other pathogens before they reach the lungs and cause infection
Describe how the chemical defence of lysozymes protects the human body from pathogens
Lysozome is secreted in tears, on the conjunctiva, saliva, mucus and vaginal fluid. It helps to protect the thinner surfaces of the body. Lysozyme is an enzyme that breaks down the cell walls of some types of bacteria, it kills the pathogens or makes them inactive.
Describe how the chemical defence of hydrochloric acid protects the human body from pathogens
Some of the cells lining the stomach secret hydrochloric acid, reducing the pH of the stomach contents to about 2. At that acidity, many pathogens are destroyed.
How does the immune system attack a pathogen (through lymphocytes)?
-Pathogens have antigens on the surface that are unique to them.
-A lymphocyte with antibodies on its surface that match the antigens on a pathogen will attach to the pathogen.
-This activates the lymphocyte.
-This lymphocyte divides over and over again to produce identical clones.
-Some of the lymphocytes secrete large amounts of antibodies.
-The antibodies stick to the antigens and destroy the pathogen.
-Other lymphocytes remain in the blood as memory lymphocytes, ready to respond immediately if exposed to the same antigen.
Describe phagocytes.
White blood cells which are attracted to pathogens. They surround them in the blood, bind to them and engulf them. They do this to all pathogens so are non-specific.
Explain the body’s response to immunisation using an inactive form of a pathogen
The pathogen contains a specific antigen. White blood cells release complementary antibodies to the specific antigen. They attach and clump pathogens together. White blood cells engulf the pathogens. Phagocytosis occurs.
Upon a secondary infection the antibodies can be produced much quicker, so the pathogen can be destroyed and the symptoms are not felt.
What are the advantages of immunisation?
-They have eradicated many diseases (e.g. smallpox) and reduced the occurence of many.
-Epidemics can be prevented through herd immunity where a large proportion of the population is immunised so the spread of the pathogen is reduced as there are less people to catch the disease from.
What are the disadvantages of immunisation?
-They are not always effective in providing immunity
-Bad reactions can occur in response to vaccines (although very rare)
