Human Nutrion

• Carbohydrates

  Contain carbon, hydrogen and oxygen atoms

  Starch and glycerol are large complex sugars which are made up of many smaller units such as maltose of glucose joined together in a long chain.
• Proteins


  Contain carbon, hydrogen, oxgyen and nirtogen atoms

  Protiens are made from long chains of amino acids
• Lipids


  Contain hydrogen, carbon and oxygen atoms

  Each lipid is made from 3 fatty acid and 1 glycerol
• How to prepare a food sample

  1) Get a piece of food and break it up using a pestle and mortar.

  2) Transfer the ground up food to a beaker and add some distilled water.

  3) Give the mixture a good stir with a glass rod to dissolve some of the food.

  4) Filter the solution using a funnel lined with filter paper to get rid of the solid bits of food.
• Benedict's test


  For glucose

  1) 5cm3 of sample

  2) water bath at 75c

  3) add Benedict's solution

  4) leave for 5 minutes

  5) green > yellow > brick red ( in increasing concentrations of glucose)
• Iodine test


  For starch

  1) 5cm3 of sample

  2) add some iodine and gently shake

  3) if it contains starch the sample will turn blue/black

  4) if not it will stay browny-orange
• Biuret Test


  For proteins

  1) 2cm3 of sample

  2) add 2cm3 of biuret solution and shake gently

  3) if it contains protein it will change from blue to pink/purple
• Sudan III test


  For lipids

  1) 5cm3 of sample

  2) add 3 drops to test tube and shake gently

  3) if it contains lipids the top layer will be bright red.
• Where are carbohydrates found and what is their use?


  Pasta, rice, sugar

  Provide energy
• Where are proteins found and what are they used for?


  Meat, fish and dairy

  Growth and repair

  Energy in emergencies
• Where are lipids found and what is their use?


  Butter and oily fish

  Provide energy, act as an energy store and also provide insulation
• Where is vitamin A found and what is its use?

  Liver

  Improve vision and keep skin and hair healthy
• Where is vitamin C found and what is its use?

  Fruit (oranges)

  To prevent scurvy
• Where is vitamin D found and what is its use?


  Eggs or sunlight

  Needed for calcium absorption
• Where is calcium found and what is its use?

  Milk and cheese

  To make bones and teeth
• Where is iron found and what is its use?


  Red meat

  Used to make haemoglobin
• Why do we need water?


  Every bodily function relies on water

  We need a constant supply of water to replace water that is lost through urinating, breathing and sweating
• Why do we need fibre?

  It aid the movement of food through the gut

  Can be found in wholemeal bread and fruit.
• What groups of people require different energy levels


  More active people need more energy

  Children and teenagers need more energy as the need to grow more

  Pregnant women need more energy and they need to provide energy for the baby to develop
• Energy from food practical


  1) weigh a small amount of food and skewer it on a mounted needle

  2) add a set volume of water into a boiling tube

  3) measure the temperature of the water and then set fire to the food using a Bunsen Bruner flame.

  4) hold the alight food under the boiling tube until it goes out. Keep doing this until the food won't relight as all the energy has been used up

  5) then measure the temperature of the water again.
• Calculate the amount of energy in joules

  Energy in food = mass of water x temperature change x 4.2
• Calculate the amount of energy in joules per gram


  Energy per gram of food = energy in food / mass of food
• The role of bile


  1) It is produced by the liver stored in the gallbladder and released in the small intestine.

  2) It neutralises the HCl from the stomach so enzymes in the small intestine can work properly. These enzymes work best in alkaline conditions

  3) It also emulsifies fats which gives them a bigger surfaces area for the lipase enzymes to work on which makes digestion faster.
• What is peristalsis?


  A wave of muscular contraction that moves food along
• Role of mouth in digestion


  Teeth break down food

  Salivary glands produced amylase enzymes in the saliva
• Oesophagus


  Muscular tube which moves ingested food to the stomach
• What is the role of the liver in the digestive system

  It produces bile
• What is the role of the gallbladder in digestion?

  stores bile
• What is the role of the stomach in digestion?

  1) it breaks down food with muscular walls

  2) produces pepsin, protease enzyme

  3) produce hydrochloric acid that a) kills bacteria and b) create optimum pH for pepsin.
• What is the role of the pancreas in the digestive system?

  Produces protease, amylase and lipase enzymes
• What is the role of the small intestine in digestion?

  1) produces protease, amylase and lipase enzymes to complete digestion.

  2) absorbs nutrients into the body

  3) first part is the duodenum and the second part is the ileum
• What is the role of the large intestine in digestion?

  1) also called the colon

  2) absorbs excess water
• What is the role of the rectum in digestion?

  stores faeces
• How are villi adapted for absorption?


  - thin walls, only one cell thick for quick absorption

  - large surface area, each villi has its own mircovilli as well

  - good blood supply close to the surface for quick absorption

  - lacteal for absorbing fats
• What are goblet cells?


  cells that secrete mucus and help move food down the small intestine