AQA GCSE Food Preparation and Nutrition: Revision Guide

Key learning: What you must know about WATER What water does in the body (its functions) • Controls body temperature • Needed for chemical reactions in body • Removes waste products from body • Keeps mucous membranes moist and healthy • Keeps skin moist and healthy • Needed for all body fluids • Found in all body cells • Heat is removed from the body by sweating • Waste products leave the body in urine (made in the kidneys) and faeces (made in the large intestine) • Water controls the concentration of substances (e.g. sodium) in the blood Main sources of water in the diet • Drinking water (tap water) • Naturally found in many foods – milk, milk products, fruit, vegetables, meat, fish, eggs • Added to many foods – soup, sauces, pastries, breads, boiled rice, pasta, beans, pulses, etc. • Tap water is good quality and safe to drink in the UK and much cheaper than bottled water • Discarded plastic water bottles have a major impact on environmental sustainability and pollution What happens if you do not have enough water (dehydration) • You become thirsty • A headache often starts • Dehydration – the urine becomes very dark in colour • You feel weak and sick • The body overheats • You become confused • The blood pressure and heart rate change • Headaches may be caused because the blood has become too concentrated • The colour of urine is a good indicator of dehydration: • Chemical reactions in the body may be affected • If the body rises above 37°C, this is dangerous • The brain becomes affected by lack of water • The volume of the blood decreases which affects the blood pressure and heart rate What happens if you have too much water • Substances in the blood become over-diluted • Vital organs in the body start to fail, e.g. heart, kidneys • May cause death • It is a rare cause of death, but it has happened to some people who have done a lot of exercise then had a lot of water to drink in one go What is the recommended amount of water per day • In the UK: 1–2 litres of water or other fluids a day (6–8 average glasses) • More water will be needed in hotter climates and when doing a lot of physical activity What you must know about water In your answers, you need to know how to explain: Further information you can add to extend your answers: Good Good Fair Dehydrated Dehydrated Very dehydrated Severe dehydration 1 2 3 4 5 6 7 Hydrated: the body has enough water Dehydrated: the body does not have enough water Key terms you should try to use in your answers 6 Water Book-link: 1.1.6 Water, pages 36–37 332 Chapter 1: Nutrients : Water