Communicable diseases Flashcards
1
Q
Describe pathogens
A
- organisms that cause disease
- the organism they live in is called a host
- a host body creates a good habitat in which microorganisms can live
- live by taking nutrition from their host, but also causing damage in the process- can be considerable
- 4 types- bacteria, fungi, viruses, protoctista
2
Q
Describe bacteria
A
- in prokaryotae kingdom
- smaller cells than eukaryotic
- can reproduce rapidly- up to every 20 mins in right conditions
- once in host body, can reproduce rapidly
- presence can cause disease by damaging cells or releasing waste products and/or toxins that are toxic to the host
- ## in plants, the bacteria often live in the vascular tissues and cause blackening and death of these tissues
3
Q
Examples of diseases caused by bacteria- including characteristics
A
- tuberculosis- affects many parts of body- killing the cells and tissues- lungs most often infected
- Bacterial meningitis- infection of the meningis- the membranes that surround the brain and spinal cord become swollen- can cause damage to brain and nerves
- ring rot (plants)- ring of decay in vascular tissue of a potato tuber or tomato, accompanied by leaf wilting
4
Q
Describe fungi
A
- can cause a variety of disease in both plants and animals
- common fungal infections in which the fungus luves in the skin of an animal where its hyphae, which form a mycelium, grow under the skin surface
- the fungus can send out special reproductive hyphae, which grow to the surface of the skin to release s[pres- causes redness and irritation
- in plants, the fungus iften lives in the vascular tissue, where it can gain nutrients
- the hyphae release extracellular enzymes, such as cellulase, to digest the surrounding tissue which causes decay
- leaves will often become mottled in colour, curl up and shrivel before dying
- fruit and storage organs, such as tuvers ([potatoes) will turn black and decay
5
Q
Describe fungi
A
- can cause a variety of disease in both plants and animals
- common fungal infections in which the fungus luves in the skin of an animal where its hyphae, which form a mycelium, grow under the skin surface
- the fungus can send out special reproductive hyphae, which grow to the surface of the skin to release s[pres- causes redness and irritation
- in plants, the fungus iften lives in the vascular tissue, where it can gain nutrients
- the hyphae release extracellular enzymes, such as cellulase, to digest the surrounding tissue which causes decay
- leaves will often become mottled in colour, curl up and shrivel before dying
- fruit and storage organs, such as tuvers ([potatoes) will turn black and decay
6
Q
Examples of diseases caused by fungi- including characteristics
A
- black sigatoka (bananas)- causes leaf spots on banana plants reducing yield
- ringworm (cattle)- growth of fungus in skin with spore cases erupting through skin to cause a rash
- Athletes foot (humans)- growth under skin- particularly between the toes
7
Q
Describe viruses
A
- can cause many diseases in plants and animals
- invade cells and take over the genetic machinery and other orgalles of the cell
- then cause the cell to manufacture more copies of the virus
- host cell eventually bursts, releasing many new viruses which will infect healthy cells
8
Q
Examples of diseases caused by viruses- including characteristics
A
- HIV/AIDS- attacks cells in the immune system and compromises the immune response
- influenza- attacks respiratory system and causes muscle pains and headaches
- tobacco mosaic virus- causes mottling and discoloration of leaves
9
Q
Describe protoctista
A
- usually cause harm by enterinh hos cells and feeding on the contents as they grow
- the malarial parisite plasmodium has immature forms that feed on the haemoglobin inside red blood cells
10
Q
Examples of diseases caused by protoctista - including characteristics
A
- blight (potatoes and tomatoes)- affects both leaves and potato tubers
- malaria- parisite in the blood that causes headache and fever and may progress to coma and death
11
Q
stages of a pathogens life cycle
A
- travelling from 1 host to another (transmission)
- entering the hosts tissues
- reproducing
- leaving the hosts tissues
12
Q
2 types of pathogen transmission- define
A
- direct- passing a pathogen from one host to another with no intermediary
- indirect- passing a pathogen from one host to another via a vector (an organism that carries a pathogen from one host to another)
13
Q
4 means if direct transmission with factors that affect these
A
- direct physical contact, such as touching a person who is infected or touching contaminated surfaces(including soil) that harbour the pathogen
- e.g. HIV, bacterial meningitis, ringworm, athletes foot
- Hygiene- washing hands regularly- especially after tuning the toilet. Keeping surfaces clean- especially door handles etc- cleaning and disinfecting cuts and abrasions. Sterilising surgical instruments, using condoms during sexual intercourse
- faecal-oral transmission- usually by eating food or drinking water contaminated by the pathogen
- e.g. cholera, food poisoning
- using human sewage to fertiliuse crops is a common practice in some parts of the world. Treatment of waste water and drinking water can reduce risk. Thorough washing and cooking/preoaraton of fresh food.
Droplet infection in which the pathogen in carried in tiny water droplets in the air
- e.g. tuberculosis, influenza
- catch it- bin it- kill it- cover mouth while coughing/sneezing- use a tissue and ensure its disposed of correctly
- transmission by spores- resistant stage of pathogen- can be carried in air or reside in surfaces or in soil
- e.g. anthrax, tetanus
- use of a mask, washing skin after contact with soil
14
Q
Social factors which can affect direct pathogen transmission
A
- overcrowding (many people sleeping/living in one house)
- poor ventilation
- poor health- particularly if a person has HIV/AIDS as they are more likely to contact other diseases
- poor diet
- homelessness
- living/working with people who have migrated from areas where a disease is more common
15
Q
describe indirect transmission
A
- transmitted by a vector which may be used by organism to gain access to the primary host
16
Q
Describe an example of indirect transmission
A
Transmission of malaria:
- person with maria
- has gametes of plasmodium in blood
- female anopheles mosquito (vector) sucks blood
- plasmodium develops and migrates to mosquitos salivary glands
- an uninfected person is bitten
- plasmodium migrates to liver
- plasmodium migrates to blood- the person now has malaria and cycle repeats
17
Q
Describe direct transmission in plants, and what happens once the pathogen has entered the plant
A
- pathogens present in the soil- infect plants by entering the roots- especially if these have been damaged as a result of replanting, burrowing or movement because of a storm
- many fungi produce spores as a means of sexual or asexual reproduction- may be carries in the wind- airborne transmission
Once inside:
- pathogen may infect all the vascular tissue
- pathogens in the leaves are distributed when the leaves are shed and carry the pathogen back to the soil- can grow and infect another plant
- pathogens can also enter fruit/seeds- distributed with the seeds- many/all offspring infected
18
Q
Describe indirect transmission in plants
A
- often occurs as result of insect attack
- spores or bacteria become attached to a burrowing insect, such as a beetle- attacks an infected plant
- then attacks another plant- pathogen is transmitted to uninfected plant- beetle is acting as vector
- e.g. fungus that causes Dutch Elm disease is carried by the beetle Scolytus multistriatus
19
Q
What is a factor that can affect transmission in plants and animals
A
Climate:
Many protoctists, bacteria and fungi can grow and reproduce more rapidly in warm and moist conditions
- therefor, they tend to be more common in warmer climates
- in cooler climates, these pathogens may be damaged or even killed by cold winter weather- will definitely reduce their ability to grow and reproduce
- greater variety of disease in warmer climates- animals and plants living in these regions more likely to become infected
- climate change- tropical diseases may become more common in Europe
20
Q
Why are plants vulnerable to communicable disease
A
- Plants manufacture sugars in photosynthesis and convert those
sugars to a wide variety of compounds such as proteins and oils. - Therefore they represent a rich source of nutrients for many organisms such as bacteria, fungi. protoctists, viruses, insects and
vertebrates.
-The bacteria, fungi, protoctists and viruses may be pathogenic, and the insects and vertebrates may act as vectors to help transmit these pathogens
21
Q
Summarise how plants defend against disease
A
- do not have an immune system comparable with animals
- have developed a wide range of structural, chemical and
protein-based defences which can detect invading organisms and
prevent them from causing extensive damage - includes passive and active
22
Q
What are passive plant defenses
A
- defences present before infection, and their role is to prevent entry and spread of the pathogen.
- includes physical barriers and chemicals.
23
Q
Describe physical, passive plant defenses
A
- Cellulose cell wall - physical barrier, most plant cell walls contain a variety of chemical defences
that can be activated when a pathogen is detected. - Lignin thickening of cell walls - lignin (a phenolic compound)
is waterproof and almost completely indigestible. - Waxy cuticles - prevents water collecting on the cell surfaces. Since pathogens collect in water and need water to survive, the absence of water is a passive defence.
- Bark - most bark contains a variety of chemical defences that
work against pathogenic organisms. - Stomatal closure - stomata are possible points of entry for
pathogens. Stomatal aperture is controlled by the guard cells.
When pathogenic organisms are detected, the guard cells will
close the stomata in that part of the plant. - Callose - large polysaccharide that is deposited in the sieve tubes at the end of a growing season. It is deposited around the sieve plates and blocks the flow in the sieve tube. This can prevent a pathogen spreading around the plant.
- Tylose formation - a balloon-like swelling or projection that fills the xylem vessel. When a tylose is fully
formed, it plugs the vessel and the vessel can no longer carry watre. Prevents the spread of pathogens through the heartwood. The tylose contains a high concentration of chemicals such as terpenes that are toxic to pathogens .
24
Q
Describe plant passive chemical defences
A
- plant tissues contain a variety of chemicals that have anti-pathogenic properties
- include terpenoids, phenols, alkaloids and hydrolytic enzymes
- some of these chemicals, such as the terpenes in tyloses and tannins in bark are present before infection
- however, because the production of chemicals requires a lot of energy, many chemicals aren’t produce till a plant detects an infection
25
Q
What is active defence in plants
A
- when pathogens attack, specific chemicals in their cell walls can be detected by the plant cells- these chemicals include specific proteins and glycolipids
- the plant responds by fortifying the defences already present
- includes increasing the physical defenses and producing defensive chemicals
26
Q
Describe types of active defence in plants
A
- cell walls become thickened and strengthened with additional cellulose
- deposition of callose between the plant cell wall and cell membrane near the invading pathogen. Callose deposits are polysaccharide polymers that impeded cellular penetration at the site of infection. Strengthens the cell wall and blocks plasmodesmata
- oxidative bursts that produce highly reactive oxygen molecules capable of damaging the cells of invading organisms
- an increase in the production of chemicals
27
Q
Name Chemicals that are used in plant defence
A
- terpenoids
- phenols
- alkaloids
- defensive proteins (defensins)
- hydrolytic enzymes
28
Q
Describe how terpenoids work (plant defence)
A
- A range of essential oils that have antibacterial and antifungal properties.
- They may also create scent, for example, the menthols and menthones produced by mint plants.
29
Q
Describe how phenols work (plant defence)
A
- These also have antibiotic and antifungal properties
- Tannins found in bark inhibit attack by insects
- These compounds bind to salivary proteins and digestive enzymes such as trypsin and chymotrypsin, deactivating the enzymes
- Insects that ingest high amounts of tannins do not grow and will eventually die- helps to prevent the transmission of pathogens.
30
Q
Describe how alkaloids work ( plant defence)
A
- Nitrogen-containing compounds such as caffeine, nicotine, cocaine, morphine, solanine
- give a bitter taste to inhibit herbivores feeding
- also act on a variety of metabolic reactions via inhibiting or activating enzyme action
- Some inhibit protein synthesis.
- If the plant can reduce grazing by larger animals, then it will suffer less damage that can allow pathogens to enter the plant.
31
Q
Describe how defensive proteins (defensins) work (plant defence)
A
- These are small cysteine-rich proteins that have broad anti-microbial activity
- appear to to act upon molecules in the plasma membrane of pathogens, possibly inhibiting the action of ion transport channels
32
Q
Describe how hydrolytic enzymes work (plant defence)
A
- found in the spaces between cells
- include chitinases (which break down the chitin found in fungal cell walls), glucanases (which hydrolyse the glycosidic bonds in glucans) and lysozymes (which are capable of degrading bacterial cell walls).
33
Q
Describe 2 other ways plants defend against disease
A
- necrosis- deliberate cell suicide- a few cells are killed to save the rest of the plant- by killing cells surrounding the infection, the plant can limit the pathogens access to water and nutrients and therefor stop it spreading further around the plant. Necrosis is brought about by intracellular enzymes that are activated by injury- these enzymes destroy damaged cells and produce brown spots on leaves or dieback
- Canker- a sunken necrotic lesion in the woody tissue such as the main stem or branch- causes death of the cambium tissue in the bark
34
Q
What are primary defences
A
- Stop pathogenic organisms entering the body of their host.
- evolution has selected hosts adapted to defend themselves against such invasions
- non specific as will prevent the entry of any pathogen
35
Q
Name the main human primary defences
A
- skin
- blood clotting and skin repair
- Mucous membranes
- Coughing and sneezing
- inflammation
- others
36
Q
Describe the skin as a primary defence
A
- the body is covered by skin- the main primary defence
- outer layer of the skin is called the epidermis, consists of layers of cells
- most of these cells are called keratinocytes- these cells are produced by mitosis at the base of the epidermis- then migrate out to the surface of the skin- as they migrates, they dry out and the cytoplasm is replaced by the protein keratin
- this process is called keratinisation and it takes about 30 days
- by the time the cells reached the surface, they are no longer alive
- the keratinised layer of dead cells act as an effective barrier to pathogens
- eventually, the dead cells Slough off
37
Q
What must happen when an abrasion or laceration damages the skin and why
A
- the skin is only protective if it is complete
- say open the body to infection- the body must prevent excess blood loss by forming a clot, making a temporary seal to prevent infection, and repairing the skin
38
Q
What is involved in blood clotting
A
- calcium ions and at least 12 clotting factors
- many of the clotting factors are released from platelets and from damaged tissue- these factors activate an enzyme cascade
39
Q
Describe the enzyme cascade of blood clotting
A
- damage to blood vessel wall exposes collagen and releases clotting factors
- platelets in the blood bind to the collagen and to release clotting factors
- a temporary platelet plug is formed
- the clotting factors cause inactive thrombokinase in blood to lead to active thrombokinase (an enzyme)
- this causes prothrombin in blood, with the help of Ca2+ ions, to convert to active thrombin (an enzyme)
- this turn soluble fibrinogen in plasma to turn to insoluble fibrin
- these fibres attach to platelets in the plug
- red blood cells and platelets also get trapped
- all leads to blood clot
40
Q
What happens once a blood clot has formed
A
- it begins to dry out and form a scab
the scab shrinks as it dries, drawing the sides of the cut together - this makes a temporary seal, under which the skin is repaired
- the first stage is the deposition of fibrous collagen under the scab
- stem cells in the epidermis then divide by mitosis to form new cells, which migrate to the edges of the cut and differentiate to form new skin
- new blood vessels grow to supply oxygen and nutrients to new tissues
- the tissues contract to help draw the edges of a cut together so that the repair can be completed
- ask the new skin is completed, the scab will be released
41
Q
Which areas in the body are at risk of infection and why
A
- the Airways, lungs and the digestive system
- certain substances, such as oxygen and the nutrients in our foods, must enter our blood
- the exchange surface is where this occurs must be thinner and are less well protected from pathogens
- the air and foods that we take in from our environments may harbour microorganisms
- theerfor, these areas are protected by mucous membranes
48
Q
What attaches to the antigen on the surface of a molecule, describe this
A
- opsonins
- protein molecules
- type of antibody
- some not very specific- can attach to variety of pathogenic cells
- role is to enhance the ability of phagocytic cells to bind and engulf the pathogen
51
Q
Describe neutrophils
A
- most common phagocytes
- multilobed nucleus
- manufactured and matured in bone marrow
- travel in blood, often squeeze out into tissue fluid
- short lived but released in large numbers as result of infection
- large numbers of lysosomes
- engulf and digest pathogens
- usually die soon after ingesting a few pathogens
- dead neutrophils may collect in area of infection, to form pus
54
Q
describe macrophages
A
- larger cells
- kidney shaped nucleus
- manufactured in bone marrow
- travel in blood as monocytes before settling in body tissues
- many found in lymph nodes where they mature into macrophages
- dendritic cells (type of macrophage) found in more peripheral tissues
58
Q
Diagram of specific immune response
A
67
Q
Describe the structure of an antibody
A
- Y- shaped
- Have 2 distinct regions- one constant region which is the same in all antibodies (it may have a site for the easy binding of phagocytic cells), and one variable region which has a shape specific to the shape of the antigen
- 4 polypeptide chains- 2 x light and 2 x heavy
- disulphide links hold polypeptides together
- there is a hinge region to allow flexibility so molecule can grip more than one antigen
70
Q
Describe how agglutinins work
A
- because each antibody molecule has two identical binding sites it is able to cross link pathogens by binding an antigen on one pathogen with one binding site and then an antigen on another pathogen with its other binding sites
- when many antibodies perform this cross linking they clump together (agglutinate) pathogens
- has two advantages- the agglutinated pathogens are physically impeded from carrying out some functions, such as entering host cells, and the agglutinated pathogens are readily engulfed by phagocytes. This is particularly effective against viruses.
74
Q
primary vs secondary response, graph
A
- primary rises slower and reaches lower concentration than secondary
