Transcript Evidence 14.docx

Contents
Microbes
Describe what are microbes?
Describe the structure of bacteria
and viruses
How do bacteria and viruses
reproduce?
Summary quiz
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Starter activity
• Match the correct keyword to the definition
Pathogen
Infection
Disease
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causes damage to the individual’s
vital functions or systems.
the invasion and multiplication of
pathogenic microbes in an
individual or population.
a micro-organism that has the
potential to cause disease.
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Infection and disease
What is a pathogen?
• A pathogen is a micro-organism that has the potential to cause
disease.
What is an infection?
• An infection is the invasion and multiplication of pathogenic
microbes in an individual or population.
What is disease?
• Disease is when the infection causes damage to the individual’s
vital functions or systems.
An infection does not always result in disease!
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Disease
• What is communicable?
 Communicable - able to be passed from one
person to the other
• What is non communicable?
 Non-Communicable - can’t be passed on from
one person to another
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What causes disease?
Why do people become ill?
People who lead very unhealthy lifestyles sometimes
become ill but it is also clear that people can become ill
despite leading a healthy lifestyle. Why?
Therefore, rather than something being wrong with that
person, perhaps something else changes the normal state
of the body and causes disease.
These were eventually discovered to be…
MICROBES
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Microbes
As the name suggests, they are microscopic organisms.
They can only be seen
using a microscope.
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Microbes
The two kinds of microbe that we will be dealing with are:
BACTERIA
VIRUSES
Now it is important at this point to remember what it
means to be living organism.
A living organism must be able to demonstrate that it
can perform the seven life processes.
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The seven signs of life
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Microbes
The reason for looking back to these 7 characteristics is
because although bacteria can perform all of these life
processes, viruses cannot reproduce on their own.
Does this mean
that viruses are
non-living?
This question is still hotly debated!
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Micro-organisms are made from cell
• They are very small – so usually ONE cell
• Cells are the smallest unit of life – they can
carry out the 7 characteristics of life
• Two types of cell:
– Prokaryotic
– Eukaryotic
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Prokaryotes
• Prokaryotes are the
oldest, simplest, and
most abundant forms of
life on earth.
– abundant for over 2
billion years before the
appearance of eukaryotes
– 5,000 different kinds
currently recognized
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Prokaryotic cells
• Single cell organisms
• Two main types: bacteria and archaea
• Relatively simple structure
Figure 1-7a
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Bacteria
• These are tiny
single celled
organisms that
cause a range of
illnesses
Activity: Name some diseases caused by bacteria
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Staphylococcus causing skin
infections
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Bacteria
 As the bacteria breed successfully they begin to
affect the body
 Symptoms of infection appear
 Symptoms caused by remains of dead bacteria
or substances released by the living bacteria
(toxins)
 Toxins may cause fever
 Bacteria may directly damage body cells
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Fungi - eukaryotes
• Can be single-celled
organism to a 3.5mile-wide
mushroom.
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Fungi
• These are tiny organisms that can cause a
range of infections
• They release digestive chemicals onto the
surface of the person they grow on.
 Activity: Name some diseases caused by
fungi
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Athletes Foot
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Fungi (yeast that causes
thrush)
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Viruses – living?
• Not a cell!
• Viruses can’t:
– eat,
– excrete wastes,
– move around on their
own,
– reproduce (unless they
are inside another
organism’s cells)
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Viruses
• Viruses are the smallest
type of disease causes
micro-organism
• They reproduce by
taking over cells of the
body and making these
cells produce new
viruses.
 Viruses do not produce toxins but cause disease
by damaging the cells they enter
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What diseases do these viruses cause?
– Rhinovirus attacks cells in nose and throat
– HIV attacks cells of immune system
– Herpes Simplex
 Can you think of any other diseases caused by a
virus
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Protoctista - eukaryotes
• Can be single-celled to
multi-celled
• They’re not plants, animals
or fungi
• Protoctistas fall into four
general subgroups:
unicellular algae, protozoa,
slime moulds, and water
moulds
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Protozoa
 This are single celled animal-like creatures
 Cause diseases such as:
 Malaria – transmitted through mosquito bites
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Contents
Microbes
Describe what are microbes?
Describe the structure of bacteria
and viruses
How do microbes reproduce?
Summary quiz
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A single bacterium
Bacteria can be different shapes but this diagram can
represent them.
cell wall
cell
membrane
cytoplasm
loose genetic
material
present in animal cells
absent from animal cells
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Structure of a bacteria
Cytoplasm
Cell Wall
– multi-layered structure-circular chromosome of DNA
- few organelles
- 2 distinct types
- food storage granules
- slimy capsule surrounds cell wall
Flagella
Cell Membrane
-one or more projection
– bilayer with proteins
from cell wall
floating in it
-Allow the bacterium to move
-controls what goes in and out of
in liquids
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Bacterium
So, the bacterium shares some structural characteristics
with an animal cell but shows important differences. The
most obvious differences are:
the absence of a distinct nucleus
the presence of a cell wall
The other major difference is the size of the cell.
To get an idea of how small these cells are, remember
that the human body consists of approximately 100
million animal cells.
Bacteria cells are 10-1000 times smaller than
animal cells.
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Bacterium
If we wanted to measure a single bacterium, its length
would range from:
1
1
mm to
1000
mm
20
If a full stop is 1mm wide how many bacteria could you
line up along it?
Between 1000 and 20 bacteria would fit on a full stop!
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Virus
Now let’s consider the structure of the virus.
injection
tube
protein
coat
loose genetic
material
tail plate
Absent in animal cells
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Viruses - how small?
Viruses are very different to bacteria
because they do not have a cellular
structure and are much smaller.
Bacteria are 100 times smaller than a human cell.
Viruses are 1000 times smaller than a bacteria.
So how small are viruses compared to a human cell?
100 000 times smaller!
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Viruses and tennis balls!
Here’s another way to think about the size of viruses...
If a common cold virus was
the size of a tennis ball,
how big would a nose be?
A. the size of a supermarket
B. the size of Birmingham
C. the size of Wales
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Viruses – living or not?
If viruses are such tiny microbes,
how do they cause so much havoc?
Viruses need to hijack a host cell,
like a human body cell, in which to
live and make more viruses.
Viruses cannot function if they are
outside of a host cell.
Some scientists say that viruses are not ‘alive’ because of
how they reproduce. Would you say a virus was living or not?
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Virus and bacterium properties
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Contents
Microbes
Describe what are microbes?
Describe the structure of bacteria
and viruses
How do bacteria and viruses
reproduce?
Summary quiz
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Contents
Microbes
Describe what are microbes?
Describe the structure of bacteria
and viruses
How do bacteria and viruses
reproduce?
Summary quiz
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Bacteria reproduction
Bacteria can reproduce quickly and independently .
One bacterium can divide into two new bacteria
every 20 minutes!
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Bacteria reproduction
This means that if 1 bacterium enters your body
at 8.00am, 4 hours later, you would have 4096
bacteria within your body!
Do viruses reproduce in the same way as bacteria?
No!
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Virus reproduction
Viruses need a host cell to reproduce within.
This is a body cell, which will provide the machinery, and
chemicals the virus requires to make copies of it.
host cell
e.g. a human body cell
virus
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Virus replication
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The process of host cell infection
Therefore the virus not only infects the body; it
also infects the body cells.
1. Approach
The virus
approaches
the host cell
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2. Attachment
The virus secures
itself to the surface
of the host cell.
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The process of host cell infection
3. Insertion
The virus injects its
genetic material
through the
injection tube and
into the host cell.
4. Replication
The genetic
material makes
multiple copies of
itself.
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The process of host cell infection
5. Assembly
New viruses are
assembled using
chemicals from the
host cell. The
original virus dies
and breaks down.
It is at this stage that the viruses within the host cell
can remain dormant. In other words, they sit within the
cell without killing it or breaking out. With some viruses
such as HIV, this period can last a number of years.
This is why people can remain infected with HIV
without realizing they are infected.
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Virus reproduction
CELL LYSIS
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Student task
• USE BIOVIEWERS AND OBSERVE
SOME SLIDES.
• DRAW 2 BACTERIAL, VIRUS,
PROTOZOA AND FUNGI CELLS AND
WRITE ABOUT THEM USING THE
BOOKLETS
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Common illnesses
Most people have suffered from at least one of these illnesses:
VIRUSES
BACTERIA
Influenza (flu)
Food poisoning
Mumps
Sore throats
Chickenpox
Tuberculosis (TB)
Smallpox
Tetanus
Polio
Cholera
Rabies
Typhoid
German measles
Whooping cough
So, how do these microscopic organisms actually cause
illness in such a complex and relatively enormous
organism like a human being?
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Virus reproduction - what’s the order?
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Virus reproduction - explain it!
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Microbes quiz
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