module 7 Flashcards
(36 cards)
what is disease/ infectious disease
A disease is any condition that impairs the normal
functioning of an organism
Infectious diseases: these have a causative agent, called a
pathogen, and are usually contagious, meaning they can
spread between individuals y
- The common cold (caused by a virus)
- Tetanus (caused by bacteria)
- Hair lice (caused by a small parasitic insect
types of pathogens non living
Prion - NON LIVING
- Misfolded protein; Mutated protein that’s shape allows it
to unwind healthy protein and turn it into prions.
- The smallest pathogen
- Made up of amino acids, polypeptide
- Non-cellular
- Can’t be treated
- They DO NOT reproduce but can spread, they rewrite
healthy protein
e.g mad cows disease
Virus - NON-LIVING
- A protein capsule containing DNA or RNA; capsids have
unique proteins to enter cells on the surface
- They can replicate inside living cells
- Non-cellular, infects living things
- Treated with antivirals + vaccines
- Must use a host mechanism to reproduce (no ribosomes)
e.g. covid 19, chickenpox
what is a pathogen?
A foreign entity that invades the host with the
intention to cause harm and produce a disease.
- Pathogens are biological agents that cause disease or illness in a host organism. They live and reproduce at the
expense of the host and release toxins, damage tissue or outcompete other microflora for nutrients.
- Something becomes pathogenic when it causes disease or impairs the health of an organism.
Types of pathogens - living
bacteria -
- Single cell, prokaryotic organism
- Has a cell wall; unicellular-one cell colonies
- It reproduces asexually and replicates inside the hosts,
stealing nutrients and secretes toxins (plasmid
replication); DNA is in plasmid during replication/DNA
usually in spaghetti ball → DNA present but no nucleus
- 3 Shapes: cocus, bacillus,spirillum
- Treated with antibiotics by destroying cell wall
e.g. tetnus
Protozoan -
LIVING
- Single celled eukaryotic organism with no cell wall
- heterotrophic (eats other organisms for nutrients).
- It replicates sexually which leads to higher genetic
variations
e.g Malaria
Fungi -
LIVING
- Eukaryotic cell with cell walls, DNA inside a nucleus
- Unicellular or multicellular
- Undergo both asexual and sexual reproduction, releasing
spores into the environment
- Heterotrophs
e.g thrush, tinea/athletes foot
Macroparasite -
LIVING
- Visible to the naked eye
- Ecto (outside the body) and Endo (inside the body)
- No cell wall
- Sexual reproduction
- Multi-cellular, specialised tissues that perform specific
functions, and eukaryotic
- Can cause secondary infection
e.g ticks, tapeworms, lice
transmission of pathogens
direct contact -
Physical contact between one host and another person; infected person to host. Occurs when an
infected individual touches or exchanges bodily fluids with another individual
➢ Exchange of bodily fluid; kissing, sexual contact, biting
➢ Skin to skin contact
➢ Blood transmission
indirect contact -
Contactless transmission; does not require physical contact and has an intermediate mode of
transmission.
➢ Sneezing
➢ Coughing
➢ Breathing; airborne transmission
vector transmission -
Requires a living third organism in order to transmit the disease. Organism does not have the
disease but is able to pass it on. Usually spread by a blood-sucking insect including: mosquitos,
ticks, and fleas.
➢ Eg. Mosquitos are able to spread malaria but do not have the disease
vehicle transmission
A non-living object that is able to carry an agent; indirect transmission of an infectious agent to
a host via inanimate objects
➢ Food
➢ Water
Fomites are long-living surfaces, objects or materials that are able to carry/transmit diseases
➢ Clothes
➢ Utensils
➢ Furniture
what is an epidemic?
An epidemic is a widespread occurrence of an infectious disease in a community or region at a particular time, exceeding what is normally expected
SPONTANEOUS GENERATION
The spontaneous generation theory states that living organisms could come into existence through non-living matter.
Eg. Maggots came from rotting meat, rats came from garbage, and disease was caused by a mysterious toxic air called
miasma. Due to society’s belief in this theory, when microbes were first observed in the blood of people suffering
disease, the microbes were thought to have been created through disease.
Pasteur and Koch’s work is central to the currently accepted germ
theory which highlights that infectious diseases are caused by the
presence and actions of specific pathogens within the body.
KOCH POSTULATES
After his experiments, he was able to state a series of steps that are
needed to identify the microorganism responsible for a particular disease;
Koch’s Postulates:
1. All infected hosts must contain the suspected organism; the
pathogen must be associated or responsible for all causes of the
disease.
2. The pathogen must be able to be isolated from the affected host
and grown in a pure culture; grow on agar
3. A healthy, unaffected host must be introduced to the cultured
pathogen and it must result in the new host developing the same
disease/symptoms; use some sort of medium to transfer.
4. The pathogen must be able to be isolated from the newly affected
host and shown to be the same pathogen (e.g. same
characteristics) that was isolated from the original affected host.
Koch’s postulates can be used to identify the causative organism of an infectious disease from the suspected host.
The symptoms of the disease are carefully identified and then the blood of the infected is examined to determine
possible causative organisms. Identification of the organism in more sufferers will surely confirm the causative
organism.
LOUIS PASTEUR
The role of Pasteur in identifying disease was that he disproved the theory of spontaneous generation and showed that
microorganisms came from pre-existing organisms.
HIS EXPERIMENT
His experiments showed that microorganisms came only from other microorganisms and that genuinely sterile
solution remains lifeless indefinitely unless contaminated by living creatures. Pasteur showed that air carried
microbes by filtering air through a gun-cotton filter. Microscopic examination of the gun-cotton revealed that it
contained many microbes. He then conducted experiments to show that the microbes that seemed to appear on
food/water were growing from airborne microbes that caused contamination.
Pasteur disproves the spontaneous generation theory through the use
of a swan-necked flask to show that microbes arise from other
microbes rather than non-living matter. A meat broth was poured into
both flasks and boiled to terminate all the microbes. One of the
swan-necks was removed and both were left to sit out for weeks. The
flask with the swan-neck did not develop any microbial colonies
whereas the flask without the wan-neck had microbial colonies
formed on the surface of broth.
The experimental result supports Pasteur’s proposal that
microbes or germs did not arise from spontaneous generation.
agricultural diseases
plant -
Potato Blight -
A fungus-like microorganism that
causes the serious potato and
tomato disease
→ a rapidly spreading, watery rot
of leaves which soon collapse,
shrivel and turn brown
Panama Disease -
A soilborne fungal disease that
enters through the roots and
starves the plant of water and
nutrients, causing the plant to
wilt and die
Signs and symptoms:
- Yellow on the lower and older
leaves
- Edges turn brown
how to treat - Manage the movement of soil,
water and plant material
entering and exiting the farm
- Use fungicides to eradicate
potato blight fungus
- Spray plants with a
preventative treatment
animal -
Foot and mouth
disease - Virus disease that spreads
between farms → Transmission
through infected animals,
inhalation, consuming and
direct contact
Signs and symptoms:
- Excessive nasal discharge or
salivation
- Reluctance to move, eat or
drink
- Drop in milk production
- Blisters on the feet, mouth or
mammary glands
- Depression
treatment -
No specific treatment, but
conventional methods of
treating infected animals
involve the use of antibiotics.
Because there is a large number
of FMD virus strains, it is hard to
maintain effective levels of
vaccination and herd immunity
is challenging
pathogen adaptions for entry and transmission
Appressorium - Specialised infection cells;
flattened, enlarged hyphal
tips that adhere to surfaces
and facilitate the penetration
of fine hyphal pegs through
cell walls
e.g Fungi
➢ Rust, powdery
mildews, blast
diseases
function -
Direct transmission of fungi by allowing it to breach the intact cuticles of their plant hosts through the use of enzymes
to digest the cuticle and plant cell wall.
Anopheles transmission
The bite of the anopheles
mosquito transmits the
Plasmodium parasite to man
e.g Protozoa
➢ Malaria
function -
The anopheles mosquito acts as a vector for the disease by transmitting the disease to individuals through their
saliva when they bite them, breaking the skin and by passing an organism’s layer of defence.
Horizontal (same generation) gene transfer - Non-vertical transfer of genetic material between different species; a process that includes the spread of antibiotic resistance genes
among bacteria fueling
pathogen evolution
Horizontal transfer = viruses are
transmitted among individuals of the same generation and not up/down generations.
–> EG. brother to brother.
NOT father to son
e.g Bacteria
➢ HPV
function :Indirect through food and water OR direct through an infected person or animal. The movement of genetic information across normal mating barriers between more or less distantly
related organisms.
– Bacteria absorbs useful DNA from
another dead bacteria
immune system first line:
first line -
physical - Skin, Mucus
membrane (The mucus membranes are on the surface of the respiratory, digestive, reproductive and urinary
tracts. They produce a thick, protective layer of mucus, which is able to trap pathogens and antigens.) , Cilia (Cilia are tiny, hair-like projections from cells lining the air passages They vibrate or move in an upright
direction, resulting in mucus (containing trapped
pathogens) being propelled to the throat which can be
coughed or sneezed out.) ,
chemical:
Substances such as stomach acid, alkali conditions in the small intestine and enzymes in the tears
and mouth all act to destroy pathogens.Fluids are routinely secreted from the sweat glands, hair follicles and open passages in the body. Brown, grey or yellow waxy secretions made in the ear canal by ceruminous and sebaceous glands
located on the outer part of the ear canal and used to trap dust and other particles
antigens
Antigens are molecules (usually proteins) which the host recognise as being foreign and initiate the adaptive immune
response (e.g. the production of antibodies to destroy the antigens) and innate immune response (e.g. phagocytosis);
Any foreign material that will trigger an immune response.
The human body constantly gets attacked by foreign invaders, causative agents, that are able to cause infections and
diseases. These invaders range from living microbes, such as bacteria, fungi, parasites, and viruses, to nonliving
toxins, chemicals, and drugs. Despite this, the body has a number of external and internal defences that are able to
prevent these invaders from entering and causing harm.
immune system 2nd line
INFLAMMATION RESPONSE
This response is nonspecific, meaning that it does not attack
specific pathogens but generally acts to get rid of all or any
pathogens. The inflammatory response is initiated by the infected
cells releasing chemicals, known as histamines and prostaglandins,
acting on blood vessels and causing vasodilation (dilation of blood
vessels).
This results in higher levels of blood flow through the site of infection
meaning the infected area is supplied with extra blood, making the
area red and swollen with an increased temperature in the region.
Due to the increase in temperature, it slows the rate at which
pathogens reproduce their enzymes and proteins that are required
for the pathogen’s invasion, survival and successful reproduction.
Additionally, as the blood vessels dilate, histamines also increase the permeability of capillaries which allows more
white blood cells to leave the blood vessels and move to the damaged tissue
immune system 2nd line
PHAGOCYTOSIS
Phagocytosis is the process whereby phagocytes attack foreign substances
(pathogens and invading particles) by engulfing and destroying them.
Phagocytosis occurs when an organism succeeds in passing the first line of
defence and enters the deeper tissues.
Phagocytes, such as macrophages and neutrophils, are a type of leukocyte that
engulfs other materials. They circulate around the body, cleaning up dead cells
and killing pathogens that arrive on the skin and mucous membranes. They are
able to change their shape to flow around bacteria and other foreign particles.
The phagocytes completely enclose the invading bacteria within their cell, where
they are broken up by cellular enzymes.
1. The phagocyte, a macrophage or neutrophil, attracts and binds to the foreign material
2. The phagocyte surrounds and engulfs the foreign material and forms a phagosome
3. The phagosome moves deeper into the cell and fuses with a lysosome, forming a phagolysosome; this
lysosome contains digestive enzymes that is able to break down the microbe or antigen
4. Within this structure, the enzymes will break down the foreign materials into smaller pieces, leading to the
destruction of ingested cells.
5. The small waste fragments are expelled from the phagocyte by exocytosis
Following this, the decomposed matter derived from the antigen is let out by the phagocyte.
immune system 2nd line
LYMPH SYSTEM
The lymphatic system is a one-way system that transports lymph from the tissues to the
subclavian veins where lymph is returned to the bloodstream. The role of this system is to filter
and return intercellular fluid to the blood using lymph nodes connected by lymph vessels. The
lymph nodes have the ability to filter and trap antigens. Essentially, the lymph nodes facilitate
the lymphocytes to bind with antigen and initiate an adaptive response.
immune system 2nd line
CELL DEATH TO SEAL OFF PATHOGEN
When the body is unable to neutralise an antigen, a chronic inflammation
involving both macrophages and lymphocytes may occur. This reaction
forms a cluster of cells called a granuloma in which a central core of dead
tissue is surrounded by layers of macrophages, then lymphocytes, then
fibre cells which produce a tough outer wall.
This will seal off the pathogen. Since the pathogens are deprived from food
supply by being contained in the granuloma, it will die. The death of
antigens and pathogens prevents the transmission of the disease to
healthy cells.
immune system third line antibodies
antibodies - Antibodies (immunoglobulins) are proteins that are produced in
response to the presence of an antigen in the body, playing a
critical role in the immune system’s defence against infection and disease. When the appropriate B cells are activated, they form plasma cells that produce antibodies, the antigen binding site which matches the shape of the antigen they are specific for. These antibodies seek out the antigen and bind to a part of it, forming the antibody-antigen complex, causing the deactivation of the
antigen.
immune system third line
T CELLS AND CELL MEDIATED IMMUNITY
Helper T-Cells -
These T-cells become activated by antigen-presenting cells (APC) and stimulate the cloning of
specific B and cytotoxic killer T cells by the secretion of cytokines - a hormone that alerts the body
that it is under attack, a chemical signal.
Cytotoxic Killer T-cells -
These cells attack and destroy foreign cells, infected host cells and abnormal ‘self’ cells, by moving to the site of infection and binding to infected cells, releasing cytotoxins; initiating apoptosis (the process of programmed cell death) suppressor
T-Cells -
(OFF)
These cells collaborate with the cytotoxic killer cells to suppress the “killing rate” after the pathogen
has been eliminated, stopping the immune response when the antigen is destroyed; they turn the immune response off after the infection has been defeated
Memory
T-Cells (ON) -
These cells remain in the body and reactivate quickly with subsequent exposure to the same antigen; circulate the host in preparation for antigen response
- When they find specific antigens, they produce a small amount of cytokines
immune system third line
B cells
Memory B-Cells -
These cells remain in the body and reactivate quickly when they recognise the antigen, which then
produces a small amount of cytokines. This will stimulate the growth of specific plasma B-Cells
➢ recognise, remember and respond
Plasma
B-Cells -
These cells are responsible for producing antibodies that have a surface receptor protein that are
capable of binding to the antigen activated by the Helper T-Cell; ultimately giving rise to the
antibodies via B-Cell activation. These antibodies that are produced by the plasma cells are secreted
into the lymph and blood to bind with an antigen.
➢ Use protein synthesis to produce antibodies
Innate Immunity - second line of defence
Innate immunity is present from birth, unlike acquired immunity which is “learnt” from exposure to pathogens. Innate
immunity provides a non-specific, immediate response to pathogens where the cells involved recognise a limited
number of antigens. This immunity retains no “memory” of exposure to a pathogen, and therefore provides no ongoing
protection from continued exposure to the same microbe.
Acquired Immunity - third line of defence
During the first exposure to an antigen, the adaptive immune system must “learn” how to attack and destroy a
pathogen. Once a “memory” of a pathogen has been obtained, a secondary exposure will result in a much more rapid
response, meaning the individual has acquired immunity.
secondary exposure
