Module 4 notes Flashcards
(37 cards)
1
Q
communicable diseases
A
- caused by pathogens: bacteria, viruses, protoctista and fungi
- pathogens cause harm through directly damaging tissue or through the release of toxins
2
Q
tuberculosis
A
- bacterial disease
- can infect humans, deer, cows, pigs and badgers
- transmitted through airborne droplets and more prevalent where people live im cramped conditions
- causes harm by damaging lung tissue and suppressing immune system
- cured using antibiotics and prevented through vaccination
3
Q
ring rot
A
- bacterial disease
- infects potatoes, tomatoes and aubergines
- damages leaves, tubers and fruit
- transmitted through infected tubers and micropropagation of plantlets from infected plants
- reduces crop of the plant and affects livelihood of farmers
4
Q
viruses
A
- non-living and aceullular
- smaller than bacteria
- consist of genetic material (DNA or RNA), a capsid (layer of protein surrounding genetic material) and attachment proteins
- viral replication occurs inside host cells and involves injection of nucleic acid into cell
- e.g. bacteriophage- virus that affects bacteria
5
Q
HIV/AIDS
A
- viral disease
- transported around in blood until it attaches to protein on T helper cells
- HIV positive is when person infected with HIV
- AIDS is when replicating viruses in T helper cells interfere with normal functioning of immune sustem
- with T helper cells being destroyed by virus, host is unable to produce and adequate immune response to other pathogens and is left vulnerable to infections and cancer
- HIV transmitted through direct contact through sharing/mixing of bodily fluids
6
Q
influenza
A
- viral disease
- infect the ciliated cells lining gas exchange surfaces
- young chilren, the elderly and anyone with a lowered immune system are at a higher risk of having severe symptoms or dying
- transmitted by airborne droplets when coughing and sneezing
7
Q
tobacco mosaic virus
A
- viral disease
- infects plants, mainly tobacco plants
- causes damage to leaves, resulting in mosaic pattern on them
- damages flowers and fruits
- damage prevents plant from growing
- transmitted when infected leaves touch healthy leaves or gardener’s use contaminated tools
- no cure, but resistant strains have been developed
8
Q
protoctista
A
- eukaryotes that exist as single-celled organisms or cells grouped into colonies
- very few are pathogenic, but the few that are cause extremely dangerous symptoms to hosts they infect
- pathogenic protoctista are parasites and are transmitted via a vector
9
Q
malaria
A
- protoctista diseases
- caused by Plasmodium and is spread to humans through mosquitoes
- reproduces both sexually and asexually, within mosquitoes and within human hosts
- passed from mosquitoes to humans when mosquitoes bite and take blood from humans
- in humans, infects red blood, liver and brain
- some preventative medicines but no vaccine or cure
10
Q
potato blight
A
- protoctista disease
- caused by fungus-like protoctista
- causes potato blight and tomato late blight
- has hyphae which enter plant and cause damage to leaves and fruit
- transmitted by spores which travel on wind or are transferred by animals and insects from one plant to another
- no cure, resistant strains have been developed
11
Q
fungi
A
- eukaryotes that cause many plant diseases
- can be either multicellular or single-celled
- pathogenic fungi are parasitic, releasing enzymes to digest host’s tissue (animals or plants)
12
Q
black sigatoka
A
- fungal disease
- infects bananas
- fungal hyphae cause damage to leaves, causing them to turn black preventing plant growth
- transmitted by spores from one plant to next through wind
- fungicides can kill fungus, and resistant strains have been developed
13
Q
athlete’s foot
A
- fungal disease
- only affects humans
- a type of ring worm that thrives in warm, damp regions between the toes
- causes skin to crack and to become scaly, causing itchiness and soreness
- transmitted by direct contact, e.g. wearing the same socks or shoes as an infected person
- cured using antifungal creams
14
Q
living conditions that make transmission more likely
A
- hot climates- increased heat provides more kinetic energy for chemical reactions and reproduction
- social factors (poverty/developing countries)- could result in poorer sewage infrastructure, a lack of fresh water and food, poorer sanitation and overcrowded living quarters. Medicines and vaccines being less readily available to prevent the spread
15
Q
2 modes of transmission
A
- direct
- indirect
16
Q
3 examples of direct transmission in animals
A
- direct contact- touching, kissing, contact with cuts in skin and sexual contact
- inoculation- animal bites, sharing needles and cuts in skin
- ingestion- drinking and eating contaminated water and food
17
Q
3 examples of indirect transmission in animals
A
- vectors- usually animals that pass the pathogen to humans, such as mosquitoes transmitting malaria
- droplets- pathogens transmitted in droplets of water, e.g. saliva and mucus expelled when sneezing
- fomites- dirty bedding, socks, and cosmetics are examples of inanimate objects that can carry and transmit pathogens
18
Q
example of direct transmission in plants
A
- direct contact- between different plants, e.g. ring rot, TMV, black sigatoka & blights
19
Q
2 examples of indirect transmission
A
- contaminated soil- pathogens and their spores can remain in the soil and infect the roots of subsequent plants
- vectors- wind, water, animals and humans can all carry pathogens and spores from one plant to another
20
Q
plant responses
A
- barriers to prvent entry, such as bark or waxy cuticles
- antibacterial chemicals and proteins as a defence against bacterial infections. Can repel insects (vectors) and kill pathogens
- physical defences to prevent pathogens from spreading between their cells, such as producing callose
21
Q
animal responses
A
- have primary and secondary line of defence against pathogens
- primary line of defence is non-specific
- secondary line of defence is a specific response to antigens
22
Q
primary defences in animals
A
- skin is a physical barrier and contains skin flora (healthy microorganisms), which outcompete pathogens for space and resources on the skin
- blood clots will form if the skin is cut to form a new barrier
- mucous membranes line many body tracts. The mucus produced traps pathogens and the cilia sweep the mucus away from the lungs
- lysozymes are hydrolytic enzymes which digest pathogens
- expulsive reflexes, such as sneezing, coughing and vomiting, are mechanisms to force pathogens out of the body
- inflammation occurs in localised areas where damage to cells is detected. It causes the area to become red, hot, sore, itchy and swollen. When cells are damaged, this triggers mast cells to release histamines and cytokines
- histamines cause blood vessels to dilate and therefore more blood is flowing in this area. The increased temeperature from blood can kill pathogens. Histamines also make the walls of blood vessels more permeable so more white blood cells can be delivered to the site of damage
- cytokines attract phagocytes, which can engulf and destroy pathogens
23
Q
phagocytosis
A
- phagocytes (macrophages and neutrophils) travel in the blood and squeeze out of capillaries to engulf and digest pathogens
- non-specific response
24
Q
process of phagocytosis
A
- damaged cells and pathogens release cell-signalling chemicals (cytokines) that attract the phagocytes to the site of infection
- an opsonin protein can attach to pathogens to mark them and make it easier for neutrophils and macrophages to engulf them
- phagocytes have receptors which can attach onto chemicals on the surface of pathogens
- tha phagocyte then engulfs the pathogen into a vesicle to create a phagosome
- withing the phagocytes, there are lysosomes whcih contain hydrolytic lysozyme
- the lysosome fuses with the phagosome to expose the pathogen to the lysozyme. The lysozyme hydrolyses the pathogen and any soluble useful molecules are abosrobed into the cytoplasm of the phagocyte
- the phagocytes will present the antigen of the digested pathogen on their surface- they are then called antigen-presenting cells
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2 types of lymphocytes involved in second line of defence
- B lymphocytes (B cells)
- T lymphocytes (T cells)
- both are created by bone marrow stem cells, but B cells mature in bone marrow whereas T cells mature in thymus
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cell-mediated response (T-cells)
- receptors on T cells bind to antigens on antigen-presenting cells (APCs)
- causes T cell to divide rapidly by mitosis (clonal expansion)
- APCs are cells that present a non-self antigen on their surface
27
examples of antigen-presenting cells
- infected body cells- presenting viral antigens on their surface
- macrophage- engulfed and destroyed a pathogen presenting the antigens on their surface
- cells of a transplanted organ- different shaped antigens on their surface compared to your self-cell antigens
- cancer cells- abnromal-shaped self-antigens
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process of cell-mediated response
1. once a pathogen has been engulfed and destroyed by a phagocyte, the antigens are positioned on cell surface- this is now called an APC
2. T helper cells have receptors on their surface which can attach to antigens on APC
3. once attached, interleukins are produced which activates T helper cells to divide by mitosis to replicate and make large number of clones
4. cloned T helper cells differentiate into different cells:
- T helper cells and produce interleukins to activate B lymphocytes
- some produce interleukins to stimulate macrophages to perform more phagocytosis
- T memory cells for that shaped antigen
- T killer cells (cytotoxic T cells)
- T regulator cells which suppress immune response to ensure cell-mediated response only occurs when pathogens are detected
29
T killer cells
* destroy abnormal or infected cells
* release a protein, perforin, which embeds in the cell surface membrane and makes a pore (a hole) so that any substances can enter or leave the cell and this causes cell death
* most common in viral infections because viruses infect body cells. Body cells are sacrificed to prevent viral replication
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humoral response (B cells)
- T helper cells stimulate B cells by producing interleukins
- this initiates the humoral response, which involves antibodies
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antibodies
- globular, quaternary proteins that have binding sites complementary in shape to antigens
- made up of 4 polypeptide chains, 2 heavy polypeptide chains and 2 ligh polypeptide chains
- binding site is variable region, where antibody binds to a complementary-shaped antigen
- rest of antibody is constant region
- when an antigen binds to an antibody it is described as an antigen-antibody complex
- the hinge region of the antibody gives it flexibility when binding to mutliple pathogens
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3 ways antibodies work in the humoral response
- agglutination
- marking pathogens
- acting as anti-toxins
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agglutination
the clumping together of pathogens to make it easier for phagocytes to locate and engulf them
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marking pathogens
* act as an opsonin when an antibody-antigen complex has been formed
* the antibodies are marking the antigen making them more susceptible to phagocytosis
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acting as anti-toxins
antibodies can bind to toxins, preventing them from entering cells and causing harm
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humoral response process
- activated T helper cells bind to B cells with complementary antibody to antigen- clonal selection
- this B cell is activated by the release of interleukins from the T helper cell
- the B cells rapidly divide by mitosis to make clones which differentiate into either memory B cells or plasma cells- clonal expansion
- the plasma cells produce antibodies which attach to the antigens on the pathogen to help destroy them by agglutination and marking them for phagocytes
- this is the primary immune response ( the first time the body has encountered this pathogen/antigen)
- the B memory cells remain in the blood after infection and can rapidly produce large amounts of antibodies if there is reinfection with the same pathogen
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