Diseases, Pathogens & Lifestyles 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? OrganismExamples of organism Bacteria Cholera, tuberculosis, pneumococci, staphylococcus etc Virus Influenza, small pox, Hepatitis, papillomavirus, HIV, H5N1 etc Fungi Athletes foot, thrush, ring worm etc OtherProtozoa (Malaria) etc

Diagram of Bacterial Cell Note bacterial cell also covered in other syllabus areas

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. Probability Risk Consequence Risk FluHIGHLOW Lightning strikeLOWSEVERE

Measurement of risk – scale of 0-100% 0% % (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 non- smokers” 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, direct sunlight

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 – ’

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.