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Biology KS3
Biology Y9 B2-B2.8
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Year 9 > Biology KS3 > Biology Y9 B2-B2.8
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Cards (88)
Pathogens
Organisms that cause
disease
Four major types of pathogen
Bacteria
Fungi
Protozoa
Virus
How
pathogens
cause illness
Toxins
Reproduction
Immune response
How pathogens are spread
Direct
contact
Indirect
contact
Food
and
water
Airborne
droplets
Insect
bites
Natural defences
Physical
and
chemical
barriers (First Line)
Non-specific
defences (Second Line)
Pathogen-specific
defences (Third Line)
Tuberculosis
(TB)
Infectious disease caused by the bacteria
Mycobacterium tuberculosis
, attacking the
respiratory
system
Infectious diseases usually decline as
living conditions
and standards of
healthcare
improve
Painkillers
can relieve the symptoms of an infection but do not kill the
pathogen
Invasion of pathogen
1. Pathogen
enters body
2.
Immune system
mounts
attack
3. Pathogen
reproduces
and makes
toxins
Lymphocytes
Type of
white blood cell
found in blood or lymph nodes, made by
bone marrow
, including T-lymphocytes and B-lymphocytes
Antibodies
Special
Y-shaped
proteins produced by
B-lymphocytes
in response to antigens, binding to and labelling pathogens for destruction
Delayed
response
It takes a
few days
to produce enough
antibodies
to destroy the pathogen
Active immunity
Memory cells remain after pathogen is
destroyed
, recognizing the pathogen if it re-infects and mounting a
quicker
, more effective immune response
Vaccines
Contain a small amount of dead or weakened pathogen particles, stimulating antibody and
memory
cell production without making the person
ill
MMR
vaccination rates used to be high, but fell following a media scare story about a speculative link between MMR and
autism
Independent expert scientists re-examined the original research and found no evidence of a link between the MMR
vaccine
and
autism
If 95% of children had the
MMR
jab the diseases could be wiped out in the UK, this is called
herd immunity
Antibiotics
Drugs used to treat
bacterial
infections, either
bactericidal
(kill bacterial cells) or bacteriostatic (slow bacterial growth/reproduction)
Antibiotics
are effective against
prokaryotic
cells but generally leave human cells unharmed
Antibiotic resistance
Bacteria
with resistance to an
antibiotic
have an advantage and can survive and reproduce, giving rise to a population of resistant bacteria
Antibiotic resistance
is evolving
faster
than the development of new antibiotics
Mutations of bacterial pathogens produce new
strains
, some of which may become immune to
antibiotics
The evolution of antibiotic resistance is an example of
natural selection
Methicillin-resistant Staphylococcus aureus (
MRSA
) is becoming
common
in hospitals and can cause
life-threatening
infections
Methods to prevent and control antibiotic resistance
Antibiotics should only be
prescribed
when
needed
Patients should
finish
the complete
course
of antibiotics
Introduction of
infection
control in
hospitals
Pathogen
A
microorganism
that can cause a
disease
Pathogens can be passed on from one person to another. Diseases caused by pathogens are known to be
COMMUNICABLE
DISEASES
Types
of pathogens
Viruses
Bacteria
Fungi
Protists
Viruses
Not considered as
living organisms
as they cannot
survive
outside a host
Bacteria
Prokaryotes that do not contain
mitochondria
and produce
toxins
Fungi
Can be single or multicellular, cell wall made from
chitin
, have
thread-like
structures called hyphae
Single
cellular fungus
YEAST
Multicellular fungus
MUSHROOM
Protists
Single
celled eukaryotic organisms,
may be parasitic and can cause
malaria
Viruses
reproduce
rapidly inside host cells until they
burst
open
Viruses are too small in size to observe under the light microscope. To see a virus we would need a special microscope called an
Electron Microscope
We do not have any
slides
of viruses under the
microscope
Bacteria
and protists can be observed under the
light
microscope
Pathogens can cause
communicable diseases
Not all diseases are
infectious
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