Food and nutrition

• There are 7 food group

  1, Vitamins

  2. Minerals

  3. Fats

  4. Proteins

  5. Carbohydrates (starches and sugars)

  6. Water

  7. Fibre
• Test for reducing sugar 


  Method:

  1, Crush some food with a little water in a motor with a pestle

  2. Put some of the solution in a test tube

  3. Add a few drops of benedicts solution

  4. Put the test tube in a water bath

  5. Record your results

  6. Repeat for the other foods

  No sugar to lots of sugar- Blue -> Green -> Yellow -> Orange -> Brick red
• Test for starch 


  Method:

  1, Put a small drop of crushed food in a test tube

  2. Add 2 drops of iodine

  3. Record your results

  4. Repeat for the other foods

  If starch is present -> blue black

  No starch present -> yellow brown
• Test for protein (biuret test)


  Method:

  1, Crush food

  2. Add water

  3. Add sodium hydroxide - breaks protein into amino acids

  4. Add copper sulfate

  Protein present -> Lilac purple

  Protein absent -> Blue
• Test for fats/lipids (emulsion test)


  Method:

  1, Put a sample of food into a test-tube and add 1ml of ethanol

  2. Shake the test tube

  3. Add 2ml of water

  4. Record your results

  5. Repeat for the other foods

  Fat present -> white emulsion

  Fat absent -> colourless
• Simple carbohydrates (eg glucose and lactose )


  Sugars provide a readily available, instant source of energy and are found in sugary drinks, biscuits, cakes and fruit

  
• Complex carbohydrates (eg starch glycogen and cellulose )


  Sometimes, sugar molecules are linked together to form very long molecules called complex carbohydrates. These are insoluble and they are used as structural and storage materials

  
• Starch 


  Any food derived from plants will contain a lot of starch e.g. cereals, rice, potatoes, pasta, and bread. (Remember that plants produce glucose in photosynthesis, and when they want to store the sugars, they are linked together to form starch).
• Cellulose


  Is the building material of plant cell wall. It is a lot of sugar molecules linked together.
• Glycogen

  In animals, extra sugar is built up into complex molecules of glycogen. This is done in liver cells and is controlled by a hormone called GLUCAGON. Glycogen is stored either in the LIVER or in MUSCLE. When energy is needed, the glycogen is broken down to glucose and used in respiration
• Lipids (Fats) ( 2 forms)


  1, Fats - solid, usually from animals e.g. butter, dripping, lard. 2. Oils -liquid, usually from plants e.g. olive oil, castor oil.

  In the body, fats are stored in a layer under the skin. This acts as: an energy store, an insulator, protection of organs. They are made up of fatty acids and glycerol

  There are two main types of fat, saturated fat comes from animals, unsaturated fat comes from plants Too much saturated fatty acid increases your blood cholesterol, which can lead to heart disease and high blood pressure due to a narrowing of blood vessels.

  
• Proteins


  Proteins - made up of amino acids. When proteins are digested, amino acids are absorbed in our blood & are reassembled into different proteins the body needs

  Proteins are used to make structures of the body ie structural proteins and enzymes, hormones, antibodies ie functional proteins, they carry out certain jobs. Functional proteins have enzymes that work to build up and break down materials

  We need proteins for the raw materials for growth and repair. (structural proteins) Food from animals is the best source of protein but plants also contain protein

  
• Energy content of food

  1, Use a syringe to measure 20ml of water in a boiling tube and record in table.

  2. Clamp the boiling tube to the retort stand.

  3. Measure the temperature of the water with the thermometer and record it. 4. Choose a brand of crisp and find its mass using the balance. Record its mass in the table and impale it carefully on a mounted needle. 5. Hold it in the flame until it catches alight and put it under the boiling tube of water as shown, until it has burnt away completely. 6. Measure the temperature of the water again and record it.

  
• Energy content of food formula

  7. Repeat the procedure for the other crisps.

  8. Calculate and record the rise in temperature for each crisp.

  9. Calculate the energy released from each crisp by using this formula.