Biology.

Carbohydrates release energy.                                                                                 Fats help you keep warm and release energy.                                                Protein is for growth, cell repair and cell replacement.                                          Fibre keeps everything moving smoothly through the digestive system.           Vitamins and Mineral ions keep the skin, bones and everything else super healthy!     

Metabolism is the chemical reactions that happen in your body to keep you alive. they need energy.  The speed in which they take to occur is your metobolic rate.    Resting metabolic rate can vary.  People with a higher proportion of muscle to fat in their bodies will have a higher metabolic rate. 

Regular exercise can boost your resting metabolic rate because it builds muscle. 

Eating too much can lead to obesity.. 

Excess carbohydrates or fat in the diet can lead to obesity.  Obesity is common in developed countries. Hormonal problems can lead to obesity, though the usual cause is a bad diet, overeating and lack of exercise. 

Arthiritis (inflammation of the joints), type 2 diabetes (inability to control blood sugar levels), high blood pressure and heart diesease. It is also a risk factor for some kinds of cancer.

Too much saturated fat in your diet can increase your blood cholesterol level.

Eating too much salt can cause high blood pressure and heart problems. 

Eating too little can cause problems...

Suffereing from lack of food is common in developing countries. 

The effects of malnutrition vary depending on what foods are missing from the diet. Problems include slow growth, fatigue (tiredness), poor resistance to infection and irregular periods in women. 

Deficiency diseases are caused by a lack if vitamins or minerals. E.g. Lack of vitamin C can cause scurvy. 

Exercise is important as well as a balanced diet. People who exercise regularly are usually healthier than the lazy people that don't. 

It increases the amount of energy used by the body and decreases the amount stored as fat. It also buillds muscle so it helps to boost your metabolic rate. People who exercise are less likely to suffer from health problems such as obesity. 

Sometimes people can be fit but not healthy. For example, you could be physically fit and slim, but malnourished at the same time because your diet is not balanced.

Inherited factors!

It's not just about what you eat or how much exercise you do - your health can depend on inherited factors too. 

Some people may inherit factors that affect their metaboloic rate, e.g. some inherited factors cause an underactive thyroid gland, which can lower the metabolic rate and cause obesity. 

Other people may inherit factors that affect their blood choloesterol level. Choloesterol is a fatty substance that's esential for a good health. Some inherited factors increase blood cholesterol level, which increases the risk of heart disease.

Microorganisms that enter the body and cause disease are called pathogens.  Pathogens cause infectious diseases - diseases that can easily spread. 

Bacteria                                                                                                                      Very small cells (about 1/100th the size of your body cells) which can reproduce rapidly inside your body.                                                                                           They make you feel ill by doing two things. a) damaging your cells, b) producing toxins. (poisions)  

Viruses. (They are NOT cells)                                                                                    They're tiny (about 1/100th the size of a bacterium)                                                  They replicate themselves by invading your cells and using the cells machinery to produce many copies of themselves. The cell will then burst, releasing the new viruses.  This cell damage is what makes you ill. 

Your skin, hairs and mucus in your respiratory tract (breathing pipework) stop a lot of nasties getting inside your body. 

To try and prevent microorganisms getting into your body through cuts, small fragments of cells (called platelets) help blood clot quickly to seal wounds. If the blood contains low numbers of platelets then it will clot more slowly. 

If something does get through, your immune system kicks in. The most important part is the white blood cells. They travel around the blood and crawl into every part of you constantly patrolling for microbes.                                                     

White blood cells have three ways of attacking microbes:

Consuming them.                                                                                                 White blood cells can engulf foreign cells and digest them. 

Producing Antibodies.                                                                                        Every invading cell has unique molecules (called antigens) on its surface. When your white blood cells come across a foreign antigen they will start to produce proteins called antibodies to lock onto and kill the invading cells. The antibodies produces are specific for that type of antigen. Antibodies are then produced rapidly and carried around the body to kill all simillar bacteria or viruses.  If it happens again, the white blood cells will rapidly produce antibodies to kill it. The person will be naturally immune to the pathogen and won't get ill. :-)

Producing Antitoxins.                                                                                                 These counteract toxins produced by the invading bacteria.

Vaccinations protect us from future infections. 

They involve injecting small amounts of dead or inactive microorganisms. These carry antigens, which produce antibodies to attack them - even though the microorganism is harmless. For example, the MMR vaccine containes weakened versions of the viruses that cause measles, mumps and rubella. 

Some vaccinations "wear off" over time. So booster injections may need to be given. 

PROS                                                                                                                      They have helped control lots of infectious diseases that were once common in the UK (e.g. polio, measles, rubella...).                                                                       Big outbreaks of diseases - called epidemics - can be prevented if a large percentage of the population is vaccinated.

CONS                                                                                                                      Vaccines don't always work - sometimes they don't give you immunity.                    You can sometime have a bad reaction to a vaccine (e.g swelling, fever....) 

Some drugs just relieve symptoms - others cure the problem 

Painkillers (e.g aspirin) are drugs that relieve pain. They do not tackle the cause of the disease, they just help to reduce the symptoms.                                       

Antibiotics (e.g. penicillin) work differently - they actually kill (or prevent the growth of) the bacteria causing the problem without killing yuor own body cells. Different antibiotics kill different types of bacteria so it is important to be treated with the right one.                                                                                                            

Antibiotics don't destroy viruses (e.g. flu or cold viruses). Viruses reproduce using your own body cells which makes it very difficult to develop drugs that destroy just the virus withouut killing the body's cells. 

Bacteria can mutate - sometimes the mutations cause them to become resistant to (not be killed by) an antibiotic. 

If you have an infection, some of the bacteria might be resistant to antibiotics. This means that when you treat the infection, only the non-resistant strains will be killed.  

The individual resistant bacteria will survive and reproduce and the population of the resistant starin will increase. This is an example of natural selection.                      

The resistant strain could cause a serious infection that can't be treated by antibiotics. E.g. MRSA causes serious wound infections and is resistant to the powerful antibiotic methicilin. 

To slow down the rate of development of resistant strains, it's important for doctors to avoid over-prescribing antibiotics. 

You can investigate antibiotics by growing micro organisms in the lab. 

You can test the actions of antibiotics or disinfectants by crowing cultures of micro organisms:

Micro organisms are grown (cultured) in a "culture medium". This is usually agar jelly containing the carbohydrates, minerals, proteins and vitamins they need to grow.                                                                                                                       Hot agar jelly is poured into shallow round plastic dishes called Petri dishes.       When the jelly's cooled and set, inoculating loops (wire loops) are used to transfer micro organisms to the culture medium. The micro organisms then multiply.        Paper discs are soaked in different types of antibiotics and placed in the jelly. Antibiotic-resistant bacteria will continue to grow around them but non-resistant strains will die                                                                                                       The Petri dishes, culture medium and inoculating loops must be sterilised before use, e.g. the  inoculating loops are passed passed through a flame. If equipment isn't sterilised, unwanted micro organisms in the culture medium will grow and affect the result.