B1.1:Keeping Healthy


B1.1.1:Diet and Metabolic Rate


  • Carbohydrates (e.g. pasta, rice) - gives and releases energy 
  • Lipids (e.g. butter, oily fish) - insulates the body, releases energy and protects the organs 
  • Protein (e.g. meat, beans) - growth, cell repair and cell replacement 
  • Vitamins (e.g. fruits and vegetables) - keeps skin, bones and bood healthy  
  • Minerals (e.g. milk, meat) - keeps skin, bones and blood healthy 
  • Fibre (e.g. cereal, bread) - helps digest food and keeps the digestive system healthy
  • Water (e.g. cucumber, watermelon) - used for cells, tissues and hydration

METABOLISM - All the chemical reactions which take place in the body

METABOLIC RATE - The rate at which the chemical reactions are going

What does metabolic rate depend on?

  • amount of exercise
  • proportion of muscle to fat in the body
  • inherited factors
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B1.1.2:Factors Affecting Health

Eating too much and a lack of exercise can lead to obesity (being 20% or more over the maximum recommended body mass) which can then result in arthritis, diabetes, high blood pressure.  A high cholesterol level in the blood can result in high risks of heart disease.

CHOLESTEROL - A waxy substance present in animal tissues only

  • it helps strengthen your cell membrane
  • the body uses it to make sex hormones and vitamin D

Statins reduce the amount of cholesterol made in the body by inhibiting the enzyme involved in making cholesterol.

Eating too little can lead to malnourishment which causes slow growth, feeling fatigue and a poor resistance to infection.

MALNOURISHMENT - A condition in which you don't have the right balance of foods to stay healthy

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B1.1.2:Deficiency Diseases

DEFICIENCY DISEASES - A disease caused by a lack of a certain nutrient in the diet e.g. a vitamin or a mineral


  • Vitamin A can cause blindness
  • Vitamin C can cause scurvy which makes the gums bleed
  • Vitamin D can cause rickets, which makes the legs bow outwards in growing children


  • Iron can cause anaemia which affects the red blood cells making you feel weak/tired
  • Calcium can cause weak bones/teeth
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B1.1.3:Evaluating Information on Food & Lifestyle

What classifies a food as being unhealthy?

  • A high saturated fat content - eating too much saturated fat can raise your blood cholesterol level
  • A high sodium/salt level - eating too much salt can lead to a high blood pressure
  • A high energy content - eating too many high energy foods can lead to obesity

The energy in food is usually measured in kilojoules (kJ) or calories.

How does lifestyle affect your health?

e.g. a person who eat too much fat or carbohydrate and doesn't do much exercise will increase their risk of obesity meaning they will also increase their ridk of developing health problems.

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B1.1.3:Evaluating Diet

How to evaluate information on diet?

e.g. slimming products (Diet Pills) or slimming programmes (The Atkins Diet)

  • check if it has been reviewed by other scientists so they seem reasonable to experts
  • check if the results are from an independent study (not connected with another company) as they are less likely to be biased 
  • check the sample size - larger samples are bettter as they are more representative of the population as a whole
  • check if the results have been reproduced by other scientists as they are more likely to be believable

Diet and slimming products will only work if you:

  • eat less fat or carbohydrate (so that you take in less energy) OR
  • do more exercise (so that you use more energy)
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B1.1.4:Fighting Disease

Pathogens (bacteria and viruses) cause infectious diseases:

  • Bacteria are very small living cells which reproduce rapidly. They make you feel ill by producing toxins and damaging cells.
  • Viruses are not cells. They replicate themselves by invading your cells and using the cells' machinery to produce many copies of themselves. The cells burst, realeasing new viruses. The cell damage makes you feel ill.

How are pathogens transferred from person to person?

  • droplet infection - sneezing, coughing
  • direct contact - touch, STD's
  • contaminaed food and drink - salmonella
  • break in the skin - cuts, needles

The body's defences:

  • skin - small fragments of cells help blood clot quickly to seal wounds
  • mucus - sticky mucus in breathing pipework traps pathogens to prevent reaching the lungs
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B1.1.4:The Immune System

  • When you are infected with a microbe it takes a few days to produce the right antibody to fight off the infection.
  • After the delay in the making of antibodies in about 5 days your body starts producing white blood cells with the antibodies.
  • In 10 days the maximum amount of white blood cells is reached.
  • Through this period you still feel unwell as the antibodies fight off the microbe.
  • Some antibodies stay in the body in case the microbe comes back making the body immune to the infection.

ANTIBODIES - Made by white blood cells to destroy bacteria/pathogens

How do white blood cells defend the body?

  • ingesting microorganisms - phagocytes engulf pathogens and digest them
  • producing antitoxinsneutralise the toxins produced by the invading bacteria
  • producing antibodies - destroy the pathogens by punching holes and sticking them together


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VACCINATION - The injection of dead or inactive microorganisms to provide immunity against a particular pathogen

  • When you are injected with a vaccine you are injected with a dead/weakened pathogen which means they will not reproduce.
  • Antigens are found in the dead pathogen and are foreign to the body.
  • If something is foreign to the body the white blood cells produce antibodies which destroy the antigens.
  • If you are re-infected the antibodies will remember how to create antibodies and will produce rapidly making your body immune to the infection.

ANTIGENS - Chemicals that are on the outside of cells e.g. bacteria

e.g. MMR - Mumps, Measles and Rubella vaccine contains weakened versions of the viruses in only one vaccine.

PROS - controls lots of infectious diseases, prevents epidemics (big outbreaks of diseases)

CONS - don't always give immunity, bad reactions (swelling, fever) 

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ANTIBIOTIC - A drug used to kill or prevent the growth of bacteria

Antibiotics kill bacteria not viruses as viruses live in our cells meaning we would have to destroy the cell to get rid of the pathogen.

PAINKILLER - A drug that relieves pain

Painkillers do not kill the pathogens but make us feel better while our immune system or antibiotics kill the pathogens.

Antibiotic Resistance:

Bacteria can mutate. Mutations cause bacteria to be resistant to an antibiotic.

e.g. Resistant strains of bacteria like MRSA (methicillin-resistant Stapylococcus aureus). MRSA causes serious wound infections and is resistant to the powerful antibiotic, methicillin.

When you treat an infection, only the non-resistant strains of bacteria will be killed meaning the individual resistant bacteria will survive and reproduce, therefore increasing the population of individual resistant bacteria.

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B1.1.7:Investigating Antibiotic Action

CULTURE - A population of one type of microorganism that's been grown under controlled conditions

A culture medium is a liquid substance containg nutrients needed for microorganisms to grow

How to culture microorganisms on a culture medium?

  • Heat agar jelly to kill unwanted microorganisms
  • Pour the hot agar jelly into a petri dish (shallow round plastic dish)
  • Use inoculating loops (wire loops) to transfer microorganisms to the culture medium so they can multiply
  • Soak paper discs in different types of antibiotics and place them on the jelly
  • Antibiotic-resistant bacteria will grow around them but non-resistant strains will die

To avoid contamination the petri dish, culture medium and inoculating loop should be sterelised. The petri dish should also have a lid to stop any microorganisms in the air contaminating the culture.

Bacterial cultures are kept at 25°C in school labs to prevent harmful pathogens from growing.

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B1.1.8:Fighting Disease in the Past


  • Doctor from Austria who worked in the 1840's
  • Noticed that huge numbers of women were dying after childbirth
  • Believed that doctors were spreading disease on their unwashed hands
  • Told doctors to wash their hands in an antiseptic every time they entered a ward - as a result he cut the death rate from 12% to 2%
  • Antiseptic solution killed bacteria on doctor's hands yet he didn't know this because the existance of bacteria was discovered 20 years later
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