Biology.

Carbohydrates and Fats-Provide the energy you need to stay alive and be active.

Protiens,Vitaminsand minerals-Your body uses to grow and replace damaged cells and tissues.

By eating a varied diet you are more likely to get everyhing you need to keep your body healthy.

Malnutrition happens when you eat the wrong amount of each type of nutrient; either too uch or too little. Deficiency diseases can occur when are avoided by eatingthe right kinds of food .

The more exercise you do, the more energy you need.

Many chemical reactions take place in your body, these reactions release the energy from your food.

Your metabolic rate is the speed at which your body uses that energy.

The higher your metabolic rate, the more energy you use.As you exercise your body builds up muscle tissue.Regular exercise also increases your metabolic rate.

Your body uses some of its fat stores to replace the energy that it uses.Exercise increases the propportion of muscle to fat in the body,which in turn increases metabolic rate.

Everybody has a diffrent metabolic rate.It depends on many factors including in heritance and how you live your life. Your metabolic rate decreases with age.

Cholesterol is a fatty substance transported by the blood. We all need some cholesterol to keep our body cells functioning normaly.Blood cholesterol level depends on the amount of fat in the diet.It is also affected by inheritance.People with high cholesterol levels are at increased risk of developing diseases of the heart and blood vessels.

Bacteria and viruses make you ill by releasing poisonous chemicals called toxins or by preventing your cells form working properly.

You might get symptoms such a s a headache, fever or feeling sick.

Once bacteria is inside you they can multiply rapidly. Viruses multiply by entering the cells in your body. They use the chemicals inside the cell to make copies of themselves. The new viruses burst out of the cell ready to invade the other body cells. This damages or even destroys the cell. 

Your body has different ways of protecting itself against pathogens. White blood cells are specialized cells that defend your body against pathogens. There are several different types of white blood cell.

Some injest: take into the cell any pathogens that they come accross in your body. Once the pathogen is inside the cell, the white blood cell releases enzymes to  digest and destroy it.

Other white blood cells release chemicals called antibodies which destroy pathogens. 

A particular antibody can only destry a particular bacterium or virus. So white blood cells learn to make many different types of antibody,

White blood cells also produce antitoxins. These are chemicals that prevent the toxins made by the pathogens from poisoning your body. 

Once your white blood cells have destroyed a type of pathogen, you are unlikely to develop the same disease again. This is because your white blood cells will recognise the pathogen the next time it invades your body and produce the right antibodies very quickly to kill the pathogen before it can affect you. 

This makes you immune to the disease!

If you have a sore throat you may take throat lozengers to relieve the pain. The sore throat is a symptom caused by a pathogen that has infected your body. This medicine helps you relieve the symptom but will not kill the pathogen. 

Antibiotics  are medicines that help cure diseases caused by bacteria. You take antibiotics to kill the bacteria that gets inside your body.Doctors use many diffrent antibiotics to treat people. penicillin was the first antibiotic to be discovered.

Antibiotics can not kill viruses. Because vairuses live and reproduce inside body cells. it is difficult to develop medicines the kaill viruses without damagingbody cells and tissues.