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produced by gram negative bacteria
lipopolysaccharide embedded in the cell surface membrane
component embedded in the outer phospholipid of the cell membrane is toxic
salmonella
s. entera invades cells lining the intestinal wall. upon lysis, endotoxins are released which cause inflammation and results in diarrhoea
s. typhi invades the body via the lymphatic system once ingested and invades body cells once spread around the body via the lymph - when endotoxins are released typhoid fever is caused
staphylococcus
haemolysins: polypeptides that become integrated in cell membranes of host cells, creating pores which cause the cells to lose water and ions
superantigens: polypeptides that stimulate immune cells and cause massive release of cytokines into the blood, which can cause toxic shock syndrome - high fever, low blood pressure, coma, multiple organ failure
occurs when the recipient has a weak immune system
bacteria secretes hydrolytic enzymes into the host’s cells and digests them
energy source is cholesterol - component of cell membrane
cavities appear in lung tissue, blood vessels are broken down, and fluid collects as bacteria digest cells
t-cells: immune cells produce signals that stimulate bacterial killing by macrophages
a TB -infected macrophage
‘caseous necrosis’: characteristic crumbly core material containing dead cells
growth of bacteria is restricted in the lungs
bacteria is engulfed by macrophages in the alveoli and bronchioles
granuloma is formed
macrophages kill the bacteria but few survive as a latent infection that could result in infection years later
variety of stem rust fungus discovered in uganda in 1999
devastating crops of wheat in east africa, the middle east, and asia
has the potential to cause worldwide food scarcity
computer model predicts it will reach india, one of the world’s largest producers of wheat
85% of the worlds population depend on wheat as their only sources of energy
60% of the worlds population depend on wheat as their main source of dietary protein
secretes digestive enzymes from its hyphae onto the material on which it is growing
enzymes digest chemicals in the stem and the fungus absorbs the products of this digestion
weakens the stem, often causing the plant to fall over
makes mechanical harvesting impossible
uses nutrients that would otherwise be stored in the plant’s seeds
reduces the harvest
breaks the outer epidermis of the stem
increases the rate of water loss from the plant
makes the plant more susceptible to infection by other plant pathogens
kill stem rust fungus
usually expensive - reduces their availability to poor farmers in africa and asia
can damage delicate ecosystems
associations between plant roots and fungi are vital to the roots’ efficient absorption of inorganic ions from soil
stem rust fungus depends on the barberry plant to complete its life cycle
north america has an ongoing barberry eradication programme, but spores are carried to north america by the wind from southern american states and mexico
spore dispersal occurs over very large distances
eight short strands of RNA - segmented genome
surrounded by protein capsid
envelope with outer protein layer and inner lipid layer
glycoproteins project through the envelope and cover the surface of the virus
H glycoproteins help the virus particle enter a cell of the host
N glycoproteins allow newly formed virus cells to escape from a cell of the host
influenza enters lungs through inhaled air droplets
enters epithelial cells lining the bronchus and bronchioles by endocytosis
replication of the virus occurs in the host cells
toxins are released as the host cell lysis - brings about many of the symptoms of influenza, can cause secondary infection
a novel virus strain, unfamiliar to human immune systems, must reach human hosts from its point of origin
the virus must be able to replicate in humans and cause disease
the virus must be efficiently transmitted between humans
spanish flu 1918-19
asian flu 1957-58
hong kong flu 1968-69
sporozoites infect cells in the liver and rapidly divide to form thousands of daughter cells called merozoites
infected liver cells lose and their merozoites are released into the blood
merozoites enter red blood cells, where they digest the haemoglobin as a food source
each merozoite undergoes several cell cycles to produce 8-32 new red blood cells
the red blood cell bursts releasing the new merozoites, which infect other red blood cells
each red blood cell that bursts produces toxins produced during the breakdown of its contents by the merozoites, which cause the symptoms of malaria - raised body temperature, intense fever symptoms, and a swollen spleen
not possible to drain large lakes, which are also breeding grounds for mosquitoes
some people earn their living, or derive their main food source, from wetlands
successful drainage might involve inter-governmental co-operation, which is not always possible
the areas are vast, much larger than areas treated in europe, and would often involve co-operation between different governments or areas occupied by warring groups
insecticide would damage other wildlife, including beneficial insects
cheap and effective, as most mosquitoes bite during the night
however mosquitoes that bite during the day are emerging in many areas where malaria is endemic
since releasing more insects in order to reduce the number of insects is counter-intuitive, local groups of people are reluctant to accept its use
large-scale, and effective, education programmes are needed to convince people to accept such programmes
a vaccine would have to be suitable for use with babies and young children, since malaria is most severe during the first years of life
pharmaceutical companies need to charge for their products
countries in which malaria is endemic are often poor and could not afford country-wide vaccination programmes
plasmodium shows great antigenic variability, making the production of an effective vaccine difficult
t cells bind to antigen presenting cell
activated t helper cell is formed that releases cytokines
release of cytokines stimulates the activated t cell to divide repeatedly to form a clone
the intact pathogen that has been inactivated (stop it causing infection) or attenuated (reducing ability to cause infection)
purified components of the pathogen that have been found to have antigenic properties but do not cause disease
toxoids - modified toxins - to develop active immunity against toxin-based diseass
genetically engineered dna - which can be desgined to stimulate particular target cells of the immune system
attract more phagocytes to the site of infection
binding to, and forming pores in, the surface membranes of foreign cells, leading to the lysis of these cells
binding to surface membranes of foreign cells, aiding the attachment of a phagocyte to a foreign cell
proteins are called opsinins - cause opsonisation
produce new types of cell that directly replace those affected by disease
generate new types of cell that can be used in the laboratory to test the effectiveness and safety of new drugs, reducing need for animal and human experimentation
scientists do not know how to control the differentiation of pluripotent stem cells
two genes that produce ips cells are oncogenes
conversion of adult cells to ips cells is currently slow and the success rate is very low
growing cells for therapies will require specialist systems and research centres, so access to therapies may be limited to areas with suitable facilities
the safety aspects of introducing pluripotent stem cells into recipients must be trialled
clinical trials take a long time and are expensive
primers: short lengths of single-stranded DNA that are complementary to the base sequence of part of the 3’ ends of the strands of target DNA to be copied
free DNA nucleotides, each with an adenine, cytosine, guanine, or thymine base
thermostable DNA polymerase
separate chains of double stranded DNA with known end sequences by heating to 95oC
make primer that matches the end sequences of the DNA fragment to be copied. cool to 45oC to allow the primer to stick each strand
add heat tolerant taq polymerase and nucleotides, and heat to 75oC
resistance to glyphosate, a commonly used weed killer that would also affect the soya plant
resistance to pests, including fungi, nemotade worms, and insects
tolerance to drought and to soil salinity
the balance of fatty acids, increasing the percentage of oleic acid and reducing the percentage of linoleic acid
during cooking, linoleic acid is more easily oxidised to produce trans fats that oleic acids - trans fats are harmful to human health
production of active pharmacological ingredients - molecular pharming
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