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Chapter 7: Infection and disease 1
EL: To explore what a disease is and what causes them
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Study design – key knowledge

detecting ‘self’ and ‘non-self’ molecules: antigens and membrane receptors
– pathogens: non-cellular agents, cellular agents; controls;

physical and chemical barriers to infection in plants and animals;

immune response
– structure and overall function of the lymphatic system
– non-specific: inflammatory response; phagocytosis; blood clotting
– specific immune response: T-cell lymphocytes and cell-mediated
response; B-cell lymphocytes and humoral response, antigens and
antibodies; memory cells;

disorders of the immune response: autoimmunity; hypersensitivity, allergens
and allergic responses;

acquired immunity: natural, artificial including vaccines and antibody
serums.
Chapter 7: Pre-test
Question
What is a disease?
What is a pathogen
What is a cellular agent?
What is a non-cellular
agent?
Start of unit
End of unit
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Disease
 Any
condition that interferes with how an
organism or any part of it functions
 Can
be acquired through:
Genetic causes – inherited from parents
 Pathogens and parasites

+ Pathogens
 disease
causing organism or agent
(frequently but NOT always a MO)
 Non-cellular


Prion
virus
 Cellular




pathogens
pathogens
bacteria
fungi
protozoa
exo- and endo-parasites
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Nature of Disease
 Intensity of pathogenic effect: VIRULENCE
 Due to special characteristics of the pathogenic organism,
such as ability to produce toxins
 Individuals
level of susceptibility to pathogen:
RESISTANCE

Varies with age, state of health, immunity
 Some
pathogens are able to survive outside the host,
others are not
 Time
between infection and symptoms: INCUBATION
PERIOD

Depends on pathogen achieving sufficient numbers, reaching target
tissue, toxin accumulation etc
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Nature of Disease: Transmission
 Infective
agents can be transmitted from
one host to another by:
Direct contact
 Droplets in air breathed or sneezed by host
 Sexual contact (e.g. STIs)
 Contaminated food or water
 A carrying vector (e.g. rats carrying fleas)
 An injecting vector (e.g. mosquitoes carrying malaria
parasites)
 Injection with infected needles and syringes

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Non cellular pathogens: Viruses

A virus is a non-cellular agent composed of a protein
coat (capsid) and nucleic acid (RNA OR DNA)

Rely on living cells to function and replicate:



Not able to respire
OBLIGATE intracellular parasites
Often integrated into host chromosomes and replicated during cell
division

Highly specific to host cell or organism it infects (e.g.
adenovirus specific to lung cells
-> common cold)

All organisms on Earth are susceptible
to virus infection (e.g. bacteriophages)

http://www.youtube.com/watch?v=Rpj0emEGShQ
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Chicken pox
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Shingles
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Rubella
or
German
measles
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Mumps
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Cold sore
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Warts
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Verruca
+ Polio
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Small pox – a killer
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Non cellular pathogens: Prions
 Proteinaceaous
GENOME
infectious particles: NO
 Deviant
versions of a normal cell surface
protein that are transmissable
 Disease
caused by accumulation of abnormal
protease-resistant protein
 Diseases
include BSE
(or mad cow), CJD,
Kuru
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Cellular pathogens: Bacteria
 Prokaryotic
 Contain
organisms lacking organelles
circular DNA molecule
 Can
be classified according to metabolic
characteristics and/or shape
Round
Rod-shaped
Spiral
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Cellular pathogens: Bacteria
 Cell
wall contains PEPTIDOGLYCAN
and is chemically and
morphologically complex
 Can
have flagellum, capsules or
spores
 Reproduce
rapidly by binary fission in
favourable conditions
 http://www.youtube.com/watch?v=gE
wzDydciWc&NR=1
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Eye infection
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Leprosy
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Tetanus
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Plant blight
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NOB Activity 7.1 & 7.2
 One
group will set up activity 7.1 pg 58-59
(procedure 1-5)
 One
group will set up activity 7.2 part A pg
61-62 (procedure 1-8)
 One
group will set up activity 7.2 part B pg
63 (procedure 1-6)
 We
will make observations next lesson
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Homework – Chapter 7
 Quick
check qu 1-25
 Biochallenge
 Chapter
1
Review qu 2
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Reflection
 What
did you learn about infection and
disease today?
 What
was the most disgusting disease
today?
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Chapter 7: Infection and disease 2
EL: To examine our bacteria investigations
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Activity 7.1 & 7.2
Everyone will complete:
 Activity
7.1 pg 59, procedure 6-8, qu 1-7
 Activity
7.2 part A pg 63, procedure 9, qu 1-
8
 Activity
10-15
7.2 part B pg 63, procedure 7, qu
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Homework – chapter 7
 Quick
check qu 26-30
 Biochallenge
 Chapter
qu 2
review qu 4, 5, 6, 8
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Reflection
 Were
you surprised by the results of any of
the experiments and why?
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Chapter 7: Infection and disease 3
EL: To further explore the causes of disease
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Expected learning
 To
further explore the causes of disease
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Cellular pathogens: Fungi
 Eukaryotic heterotrophs
 break down organic matter by secreting enzymes and
other chemicals
 These chemicals are the main cause of the disease
 Primarily
moisture
terrestrial, but need
 Reproduce
 Cell
using spores
wall made of chitin
 Filamentous
moulds and
unicellular yeasts
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Athletes foot
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Oral Thrush
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Frogs – chytrid fungus
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Cellular pathogens: Protists
 Unicellular
 Very
eukaryotic organisms
diverse
 Usually
motile (i.e. flagella, cilia)
 Heterotrophic
 Reproduce
 May
sexually and asexually
have specialist life cycle
involving different hosts
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Protist Life Cycle
http://www.youtube.com/watch?v=Q_nCHDry0s8
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Endoparasites: worms
 Flat
and round worms may be parasitic, but
aren’t necessarily pathogenic
 Pathogenic
worms include tapeworms,
roundworms
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Endoparasites: worms
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Ectoparasites: arthropods
 Generally
parasitic, but aren’t necessarily
pathogenic
 Pathogenic
arthropods include head lice
and body lice
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Nelson Activity 5.2
 Complete
activity 5.2 and hand in
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Reflection
 Why
do you think parasites have evolved
such a complex life cycle?