1. Defense
Against
Infec.ous
Disease
IB
Bio
12

3. Assessment
Statements
Obj.
6.3.1
Define
pathogen.
1
6.3.2
Explain
why
an.bio.cs
are
effec.ve
against
bacteria
but
not
viruses.
3
6.3.3
Outline
the
role
of
skin
and
mucous
membranes
in
defense
against
pathogens.
2
6.3.4
Outline
how
phagocy.c
leucocytes
ingest
pathogens
in
the
blood
and
body
.ssues.
2
6.3.5
Dis6nguish
between
an#bodies
and
an#gens.
2
6.3.6
Explain
an.body
produc.on.
3
6.3.7
Outline
the
effects
of
HIV
on
the
immune
system.
2
6.3.8
Discuss
the
cause,
transmission
and
social
implica.ons
of
AIDS.
3
Command
terms:
hPp://i-­‐biology.net/ibdpbio/command-­‐terms/
Assessment
statements
from:
Online
IB
Biology
Subject
Guide

5. Bacteria
• Prokaryotes
(no
real
nucleus)
• Divide
by
binary
fission
Can
cause:
• Food
poisoning
(e.g.
Salmonella)
• Ear
and
eye
infec.ons
hPp://en.wikipedia.org/wiki/
• Cholera,
diarrhea
File:Ericson_Type_II_Conjunc.vi.s.JPG

6. Viruses
• Acellular
(non-­‐living?)
• Need
a
‘host’
cell
to
carry
out
func.ons
of
life,
including
reproduc.on
• Can
have
DNA
or
RNA
• Mutate,
evolve
and
recombine
quickly
Cause:
• Flu,
HIV/AIDS,
smallpox,
measles,
common
cold,
herpes,
ebola
The
1918
flu
epidemic
killed
between
50
and
130
million
people.
hPp://en.wikipedia.org/wiki/1918_flu_pandemic

7. Fungi
• Eukaryotes,
reproduce
with
spores
Cause:
• Athlete’s
foot,
mould,
ringworm
• Allergic
reac.ons
and
respiratory
problems
Image
from:
hPp://en.wikipedia.org/wiki/Athlete's_foot

8. Protozoa
• Simple
parasites
Cause:
• Malaria
• Leishmaniasis
• Toxoplasmosis
Leishmaniasis
image
from:
hPp://en.wikipedia.org/wiki/Leishmaniasis

9. Life
Cycle
of
Leishmania

11. 3
Main
Lines
of
Defense
1) Physical
barriers
– Skin,
mucous
membranes
2) Non-­‐specific
immune
system
– Phagocy.c
leukocytes
3) An.gen-­‐specific
immune
system
– Lymphocytes
(e.g.
B-­‐cells,
T-­‐cells,
Killer
cells)

13. hPp://apchute.com/lympha.c/inflam.html

14. Phagocy.c
Leucocytes
“ea.ng
cell”
“white
blood
cells”
Chemotaxis
(movement
in
response
to
chemicals)
aPracts
the
phagocytes
to
the
area
of
invasion
as
response
to:
• proteins
produced
by
the
pathogen
• phospholipids
released
by
damaged
cells
The
phagocyte
aPaches
to
the
pathogen’s
cell
surface
proteins
and
then
engulfs
it.
The
fluid
nature
of
the
plasma
membrane
allows
this
to
happen.
A
phagosome
forms.
This
is
a
vesicle
that
contains
the
pathogen.
Lysosomes
–
vesicles
of
diges.ve
enzymes
–
deposit
the
enzymes
into
the
phagosome.
The
diges.ve
enzymes
break
down
the
pathogen
and
the
waste
products
are
expelled
from
the
cell
by
exocytosis.
Review
opportunity:
• Plasma
membranes
and
vesicles
• Membrane
fluidity
and
fusion
• Endo-­‐
and
exo-­‐cytosis

15. Phagocy.c
Leucocytes
card
sort
game:
order
the
images
&
outline
the
processes
Images
from:
hPp://highered.mcgraw-­‐hill.com/sites/0072495855/student_view0/chapter2/anima.on__phagocytosis.html