B1 Revision Guide

B1 Revision Guide

B1 Revision – Healthy Bodies

Diet and Exercise

·         Components in a balanced diet –

o    Carbohydrates – the main source of energy.

o    Fats – important for energy storage and forms the main part of cell membranes.

o    Proteins – important for growth and repair.

o    Vitamins and minerals – to keep healthy – eg vitamin A for good vision and calcium for bones.

o    Water – maintains fluid levels to prevent dehydration.

o    Fibre – indigestible and maintains a healthy digestive system.

·         Malnutrition – occurs when a balanced diet is not maintained – can include being overweight or underweight, or lacking a particular vitamin or mineral (deficiency disease).

·         Metabolism –

o    Metabolic rate – the speed at which your body uses energy released from food in chemical reactions.

o    Basal metabolic rate - the rate at which you use energy at rest.

o    A higher muscle to fat ratio due to exercise increases metabolic rate.

o    Metabolism decreases with age.

o    Metabolic rate is affected by inherited factors.

·         Cholesterol – a fatty substance that increase risk of diseases of the heart and blood vessels – the level of cholesterol depends on inheritance and the amount of fat in the diet.

Pathogens

·         Pathogens are microorganisms (bacteria/viruses/fungi) that cause diseases.

·         Bacteria and viruses spread through the air, food, water and by touch, as well as through the placenta when a woman is pregnant.

·         Pathogens make us ill by releasing toxins (poisonous chemicals), causing symptoms such as headaches, fever and feeling sick.

·         Bacteria can double in numbers rapidly

·         Viruses enter your cells and use chemicals inside the cell to make copies of themselves before they burst out and infect other cells.

·         Important discoveries about pathogens –

o    Ignaz Semmelweiss – concluded that fewer women died of ‘childbed fever’ when doctors handling dead bodies washed their hands with chlorinated soap before delivering babies

o    Louis Pasteur – proved that there were germs in the air that carried disease.

·         Antiseptics – chemicals used to clean wounds to prevent entry of microorganisms into the body.

·         Disinfectants – chemicals used on surfaces to kill pathogens.

Defence against Disease

·         Some white blood cells ingest pathogens – they take them into the cell and digest them with enzymes.

·         Other white blood cells make antibodies – chemicals that attach to pathogens and destroy them, or antitoxins that prevent toxins from poisoning the body.

·         Specific antibodies are made for specific pathogens – so a flu antibody would destroy the flu virus, but not the measles virus.

·         If you are infected with the same pathogen again, your white blood cells can produce the right antibodies much faster as they recognise the pathogen – this kills the pathogen before it causes symptoms, so you…