Transcript Diseases, Pathogens & Lifestyles AQA AS Biology

Diseases, Pathogens & Lifestyles
AQA AS Biology
Syllabus objectives – full available on
Moodle
What is Disease?
• A malfunction that affects good health
• Not a single thing – rather a description of
certain symptoms of either:
– Mental
– Physical
– Or both
What pathogens are important?
Organism
Examples of organism
Bacteria
Cholera,
tuberculosis,
pneumococci, staphylococcus etc
Virus
Influenza, small pox, Hepatitis,
papillomavirus, HIV, H5N1 etc
Fungi
Athletes foot, thrush, ring worm
etc
Other
Protozoa (Malaria) etc
Note bacterial cell also covered in other syllabus areas
Diagram of Bacterial Cell
Diagram of fungal hyphae
Chitin
Cytoplasm contains
glycogen storage
granules.
How do pathogens cause disease?
• Pathogens need to penetrate an organisms
interface (a boundary linking 2 systems) with
the environment
• The bodies interfaces are generally moist
•
Although being moist is very important for
entry of molecules (covered in cell membrane
transport & lungs), it also makes it easy for
pathogens to enter.
What are the main examples of the
bodies interface with the
environment?
• gas exchange system (include
nose/throat/lungs) & digestive
system.
• Open wounds (caused by
cuts/abrasions/bites) or
puncture injury.
• Sexual and urinary cavities
• Septicaemia (entry and
establishment of bacteria in
blood).
How does the body prevent entry of
pathogens?
1. Physical Barrier – e.g. intact skin / epithelial cells
2. Mucous layer – sticky barrier – difficult to
penetrate (e.g. Mucus from goblet cells in the
trachea – looked at during lungs)
3. Production of enzymes – break down pathogens
(e.g. lysozyme – looked at during phagocytosis)
4. Stomach acid – produced for protease activity
(the break down of proteins – looked at during
digestion) – but also very effective at killing
many microorganisms we ingest.
How do pathogens cause disease?
1. Damaging the host
Prevents tissues functioning properly by tissue/cellular
disruption
E.g. virus prevent DNA/RNA & protein synthesis by host
cells
2. By producing toxins
Most successful pathogenic bacteria produce toxins
E.g. (looked at in detail later) Vibrio cholera causes
cholera by producing a toxin causing excessive loss of
water from the lining of the intestines.
Disease can be caused by a:
• SINGLE CAUSE
e.g. Malaria
• MULTI-FACTORIAL
e.g. Heart disease
Also, lifestyle & genetic factors
are very important in
determining whether disease
occurs
Are you attacked by an Army or a
single Assassin?
1. Army – e.g. Gastroenteritis bacteria
Some pathogens only cause damage when in large
numbers. I.e. some gastroenteritis bacteria will
divide every 30 minutes – but will not show disease
symptoms until in sufficient numbers – thus
vomiting & diarrhoea are not seen for 24 hours.
2. Assassin – e.g. Typhoid bacterium
Typhoid fever is a disease that can be caused
when numbers of Typhoid bacteria are
relatively small.
Summary questions on Pathogens so
far:
1. What is a pathogen?
2. Why are the digestive and respiratory systems
often the sites of entry for pathogens?
3. In which two ways do pathogens cause disease?
1. –
2. –
4. Suggest one reason why oral antibiotics are not
normally used to treat gastroenteritis and other
diarrhoeal diseases?
Summary answers on Pathogens so far:
1. An infectious agent that causes disease in its
host e.g; viruses, bacteria, fungi, etc.
2. The digestive and respiratory systems are moist
and delicate interfaces that enable specific
molecules to cross into the body from the
external environment.
3. Pathogens cause disease by;
1. – Damaging the host.
2. – Producing toxins.
4. Antibiotics would be digested so made inactive
in the stomach.
Label the parts of a bacterial cell.
Labels
A - Stiff rod-like flagellum.
B - Slime capsule.
C - Peptidoglycan (Murein) cell wall.
D - Plasma membrane (phospholipid bilayer).
E - Protoplasm.
F - Plasmid (small circle of DNA).
G - Circular ‘Naked’ DNA (Nucleoid)
H - Ribosomes (Smaller and simpler than eukaryotic
ribosomes)
Lifestyle and Health
• Many disorders result from an individual’s
lifestyle and the decisions they choose
• E.g. 1 - SMOKING (a choice) is reported to
increase the risk of lung cancer & emphysema
• E.g. 2 - Inappropriate or excess exercise can
lead to osteoarthritis
• E.g. 3 - over eating of inappropriate foods can
lead to increased risk of heart disease
What is a risk?
• “a measure of the probability that damage to
health will occur as a result of a given hazard”
The two important concepts of risk to consider
are:
– The probability a hazard will occur?
– What are the consequences if that hazardous
event occurs?
E.g.
Flu
Probability
Consequence
Risk
Risk
HIGH
LOW
LOW
SEVERE
Lightning
strike
Measurement of risk – scale of 0-100%
0% - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - 100%
(No harm will occur)
(harm will certainly occur)
You also need a time scale
• E.g. telling someone death is a 100% risk is
meaningless because we will all die at some point
in time. Telling them they have 100% risk in the
next month is altogether a different matter!
Why is Risk relative to external
factors?
• Assessing risk can be a difficult task
Because there are so many factors to consider
E.g. let us consider a statement made on
SMOKING
“smokers may be 15x more likely to
develop lung cancer than nonsmokers”
To understand this, we need to know many
more factors. E.g.
• Time period over which this occurs?
• How do numbers of cigarettes smoked affect
the figure?
What else can you think about?
Examples
• stress / age / gender / alcohol intake / lifestyle
/ geography etc....?
Should we always trust statistics in
newspapers and advertising?
• Beware of media statistics being MISLEADING
– they want to sell newspapers / obtain
ratings – always ask to see actual data before
being judgmental (part of your development
of becoming an independent and critical
scientist!)
RISK FACTORS & CANCER
• Cancer is where cells divide and grow
uncontrollably due to errors in the cell cycle
regulation (looked at later during mitosis &
cell cycle)
• Cancer is not a single disease, likewise, does
not have a single cause. Some factors are
beyond our individual control (e.g. genetics
and age)
Other factors ARE in our control –
these are what we call LIFESTYLE
CHOICES
• Lifestyle can expose us to environmental
carcinogenic factors (carcinogenic means
causes cancer )
• It is thought that HALF of people in UK could
have avoided getting disease by avoiding
negative lifestyle choices!
What are examples of specific lifestyle
factors contributing to cancer?
- Smoking
- Directly or passive
- Diet
- Want Low fat, high fibre,
fruit/veg etc
- Obesity
- Increases risk
- Physical activity
- Want regular exercise
- UV light
- E.g.
sunbeds,
sunlight
direct
Analysis & interpretation of data
Recognising correlations & causal
relationships
• It is very important you develop skills in data
analysis and interpretation in all areas of AQA
biology. The following example is to work
through in class, then please print out and
complete the Booklet ‘Analysis &
Interpretation of Data – 2012-01’
Scatterplot of mortality vs. smoking,
with regression line
• A scatter plot of the data shows a moderately
strong linear association, with a correlation.
• Abstract: Government statisticians in England
conducted a study of the relationship between
smoking and lung cancer. The data concern 25
occupational groups and are condensed from data on
thousands of individual men. The explanatory variable
is the number of cigarettes smoked per day by men in
each occupation relative to the number smoked by all
men of the same age. This smoking ratio is 100 if men
in an occupation are exactly average in their smoking,
it is below 100 if they smoke less than average, and
above 100 if they smoke more than average. The
response variable is the standardized mortality ratio for
deaths from lung cancer. It is also measured relative to
the entire population of men of the same ages as those
studied, and is greater or less than 100 when there are
more or fewer deaths from lung cancer than would be
expected based on the experience of all English men.
Read the abstract and examine the
scatter plot before answering
questions.
1. What is mortality (rate)?
2. How many occupational groups are in this study?
_______
3. Does the graph above present enough evidence to
state that smoking causes people to die of cancer?
4. What is the explanatory (independent/manipulated)
variable?
5. The response (dependent) variable the standardized
mortality ratio for deaths from lung cancer.
6. Describe the correlation.
Answers from the Abstract.
1. Deaths (rate must be in a given time period).
2. The data concern 25 occupational groups (count the
number of points on the graph).
3. data shows a moderately strong linear association,
with a correlation. Not cause.
4. The explanatory (independent/manipulated) variable
is the number of cigarettes smoked per day by men in
each occupation relative to the number smoked by all
men of the same age.
5. The response (dependent) variable is the standardised
mortality ratio for deaths from lung cancer.
6. Data shows a moderately strong linear association.