Biology

A healthy diet

A healthy diet contains the right amounts and proportions of NUTRIENTS and energy that the body needs to stay healthy.

A person who does not eat a balanced diet may become MALNOURISHED. So what we eat can affect our health.

Possible effects include:

• being very overweight or underweight
• defficiency diseasescaused by too little of a nutrient
• conditions such as Type 2 diabetes.

Controlling mass

Metabolic rate

METABOLIC RATE is the rate at which all the chemical reactions are carried out in the body.

Metabolic rate is affected by many factors:

• how much muscle you have
• how much exercise you do
• some INHERITED FACTORS (factors in your genes)

A man usually has a higher metabolic rate than a woman of the same mass, because muscle cells use lots more energy than other cells, including fat cells.

The body gains energy by eating food. Energy is EXPANDED (used) during exercise. The balance between energy taken in and energy expanded affects your mass.

Remember: the correct scientific word for your 'weight' is mass.

Lifestyle and disease

LIFESTYLE is the way we live, including what we eat and what we do, which affects how active we are. Lifestyle factors can harm health and lead to disease.

Exercise and disease

 A person who exercises regularly is more likely to stay healthy than a person who doesn't.

Benefits of exercise

(teeny thierry)

• Better weight control
• Better health

Pathogens and infection

Micro-organisms that cause disease are called PATHOGENS. Pathogens include some bacteria and viruses. When a few pathogens INFECT us (get inside out bodies) they can reproduce very rapidly. Large numbers of pathogens can make us ill.

Bacteria are much smaller than our cells.

The immune system

The body has different ways of protecting itself against pathogens.

The IMMUNE SYSTEM helps to protect the body against pathogens. WHITE BLOOD CELLS are part of the immune system.

Immunisation

IMMUNISATION means to make someone immune to a disease.

Vaccination

VACCINATION is a way of making someone immune to a disease by giving them a VACCINE. The MMR VACCINE is given to children to make them immune to measles, mumps and rubella for the rest of their lives.

A vaccine contains a small amount of a dead or inactive form of a pathogen.

The vaccine causes white blood cells to make antibodies, in the same way they would if the body was infected by live pathogens.

If the live pathogen infects you later, your immune system remebers how to destroy it.

Treating diseases

Some medicines, such as painkillers, only treat SYMPTOMS of disease. They do not kill pathogens. Other medicines help you by killing the pathogens.

A symptom is the result of disease, such as feeling pain or having a high temperature. It is not the cause of the disease.

Using antibiotics

• ANTIBIOTICS are medicines that kill bacterial pathogens inside the body.
• Specific bacteria are only killed by a specific antibiotic, so the correct antibiotic must be used.
• Deaths from bacterial diseases have greatly decreased where antibiotics are used.

Penicillin is an example of an antibiotic.

Antibiotic resistance

Remember that antibiotics do not cause bacteria to become resistant, nor does failing to finish a course of antibiotics.

Cultures

The action of disinfectants and antibiotics can be studied using cultures of micro-organisms. Other micro-organisms from the air and surfaces can easily contaminate cultures when they are being prepared. Several techniques can help prevent this.

 Sterlising dishes and culture media

STERILISATION kills micro-organisms.

• Petri dishes can be sterilised by autoclaving or heating to a high temperature.
• Culture media (the substance that the micro-organisms hrown on, such as nutrient agar) are sterilised by heating to a high temperature.

Sterilising innoculation loops