Biology 1

A balanced diet

Food Groups:

• cabohydrates to release energy
• fats to keep warm
• protein for growth, cell repair and cell replacement
• fibre for a smooth digestive system
• vitamins and mineral irons to keep everything healthy

Your body needs energy to fuel the chemical reactions in the body that keep us alive, these reactions are called your metabolism. The speed at which they occur is your metabolic rate.

Muscle needs more energy than fatty tissue, which means:

People with a higher proportion of muscle to fat in their bodies will have a HIGHER metabolic rate. Physically bigger people are likely to have a higher metabolic rate than smaller people. The bigger you are, the more energy your body needs to be supplied with (because of more cells)

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

Two main types of pathogens are- bacteria and viruses.

bacteria: very small cells, they reproduce rapidly inside your body. They make you feel ill by a) damaging your cells  b) producing toxins/poisens

viruses: these arent cells, they are tiny. They replicate themselves by invading your cells and using the cells machinery to produce many copies of themselves. The cell will then burst, releasing new viruses. Cell damage is what makes you feel ill.

Think of white blood cells as security guards, they constantly patrol every part of you by travelling in the blood, always looking for microbes. There are 3 stages to an attack on a microbe.

1. The white blood cells engulf the microbes and digest them

2. Every invading cell has unique molecules called antigens on its surface. When white blood cells come across these foreign antigens (ones they ont recognise) they start to produce proteins called antibodies to lock onto and kill the invading cells. The antibodies produced are specific t that type of antigen- they wont lock onto any different ones. These antibodies are produced rapidly and carried round the body to kill all similar bacteria/viruses. If the same illness occurs again, these antibodies will be produced again and the person will become naturally immune.