Human Nutrition

• • Carbohydrates are made up of simple sugars.
  • Carbohydrate molecules contain elements of carbon, hydrogen and oxygen.
  • Starch and glycogen (large, complex carbohydrates) are made up of maltose units joined in a long chain.
• • Proteins are made up of long chains of amino acids.
  • They all contain carbon, nitrogen, hydrogen and oxygen atoms.
• • Lipids (fats and oils) are built from fatty acids and glycerol.
  • Lipids contain carbon, hydrogen and oxygen atoms.
• The Benedicts test is for glucose where you add about 10 drops of Benedict's solution to the food sample and leave in a water bath set at 75 degrees for 5 minutes.

  If positive then.the solution will change from blue to green to yellow to brick red.
• Iodine solution is the used to test for starch. You should add a few drops of iodine and gently shake the tube to mix the contents. yellow - negative blue/black - positive
• The Biuret test is used to test for proteins. A positive result is when the solution changes from blue to purple.
• Carbohydrates are found in pasta, rice , sugar and they provide energy.
• Lipids are found in butter, oily fish and they provide energy, act as an energy store and provide insulation.
• Proteins are found in meat and fish. They are needed for growth and repair of tissue and to provide energy in emergencies.
• Vitamin A is found in liver and helps to improve vision and keep your skin and hair healthy.
• Vitamin C is found in citrus fruits e.g. oranges and is needed to prevent scurvy.
• Vitamin D can be found in oily fish, eggs and fortified milk and is needed for calcium absorption.
• Minerals = calcium (milk and cheese) are needed to make bones and teeth.

  Minerals = iron (red meet) are needed to make haemoglobin for healthy blood.
• Dietary fibre are found in wholemeal bread, fruit and they aid the movement of food through the gut.
• • The amount of energy depends on factors.
  • Activity level = more active people need more energy than less active people
  • Age = children and teenagers need more energy than older people. As they need more energy to grow and are generally more active.
  • Pregnancy = pregnant women need more energy as they have got to provide extra energy for their babies to develop.
• Food can be burnt to see how much energy it contains.

  1. Weigh a small amount of food and then place into a test tube. Add a set volume of water to the boiling tube. Measure the temperature of the water and then set fire to the food using a bunsen burner. Hold the burning food under the boiling tube until it goes out and keep doing this until the food won't catch fire again. Then measure the temperature of the water again.
• 2. Then use the formula energy in food (j) = mass of water (in g) x temperature change x 4.2.
• 3. then you can use the formula every per gram of food (j) = energy on food (j) / mass of food (g)
• 1. Starch, proteins and fats are big molecules that are too big to pass through the walls of the digestive system and they are insoluble.
• • Sugars ,amino acids, glycerol and fatty acids are much smaller molecules. They are soluble and can pass easily through the walls of the digestive system.
• Digestive enzymes break down the big molecules into smaller ones.
• Amylase converts starch into maltose.

  Maltase converts maltose into glucose.
• Proteases converts protein into amino acids
• Lipases converts lipids into glycerol and fatty acids.
• • Bile = produced in the liver, stored in the gall bladder before its released into the small intestine.
  • the hydrochloric acid in the stomach makes the pH too acidic for the enzymes in the small intestines to work. Bile (alkaline) neutralises the acid and makes conditions alkaline so the enzymes can work best.
  • Bile also emulsifies the fat, it breaks the fat into tiny droplets which give a bigger surface area of fat for lipase to work on- digestion is faster.
• There is muscular tissue all there way down the alimentary canal (your whole digestive track)

  The job is to squeeze boluses through your oesophagus.

  The waves of circular muscle contractions are called peristalsis.
• MOUTH

  • salivary glands in the mouth produce amylase enzyme in the saliva
  • teeth break down food, giving a larger surface area
• OESOPHAGUS

  • boluses move to the stomach via peristalses contractions.
• liver= bile produced + gall bladder = bile is stored
• STOMACH

  • it pummels the food with muscular walls.
  • it produces protease and pepsin
  • it produces hydrochloric acid as it kills bacteria and gives the optimum pH for protease to work.
• PANCREAS

  • produces protease, amylase and lipase which are then released into the small intestine.
• LARGE INTESTINE

  • its where excess water is absorbed from the food.
• SMALL INTESTINE

  • releases protease, amylase and lipase to complete digestion
  • this is where the nutrients are absorbed out of the alimentary canal into the body
  • the first part is duodenum and the last part is the ileum
• RECTUM

  • last part of the large intestine
  • this is where the faeces are stored before they exit through the anus.
• Villi in the small intestine help with absorption, villi are good as they have a large surface area, they are one cell thick and have a good blood supply to assist quick absorption.