Lesson 5: Food groups and tests Flashcards
What are the 3 main food groups?
- Carbohydrates
- Proteins
- Fats
What are the 2 forms carbohydrates come in?
- Starch (made up of glucose)
- Sugar (made up of sucrose)
Where are carbohydrates found?
What are they needed for?
- Found in pasta and bread
- Needed for energy (for chemical reactions and movement.)
Where are proteins found?
What are they needed for?
- Found in meat and beans
- Needed for growth and repair
Where are fats/lipids found?
What are they needed for?
- Found in cheese and oils
- Needed for energy (long- term store.)
- Insulate body
- Protect organs
How do you test for starch?
- To test for starch use Iodine.
- Add iodine to food sample in spotting tile.
- If starch is present, iodine turns from orange-> blue/black
- If starch isn’t present, there is no change.
- As a safety pecaution, wear goggles.
How do you test for sugar?
- To test for sugar use Benedict’s solution.
- Add food solution to test tube - - Add drops of benedict’s solution and heat in water bath for 5 mins. (from kettle.)
- If sugar is present, Benedict’s turns from blue-> red
- If sugar isn’t present, there is no change.
- As a safety precaution, wear goggles.
How do you test for protein?
- To test for protein use Biuret’s solution
- Add food to testube of Biuret and shake.
- If protein is present, Biuret’s wil turn from Blue -> purple/ lilac colour
- If protein isn’t present, there is no change.
- As a safety precaution, wear goggles.
How do you test for lipids/ fats?
- To test for lipids/ fats use ethanol + water.
- Add food solution to testube
- Add few drops of ethanol.
- Add a few drops of distilled water
- Shake solution gently.
- If fat is present, ethanol + water will change from clear and colourless to cloudy white.
- If fat isn’t present, there is no change.
- As a safety precaution, wear goggles.
Where is water found?
What is water needed for?
Found in normal drinking water/ fruits.
Needed for:
- Regulate temperature
- Chemical reactions
- Replace water that is wasted by sweating, breathing, urinating.
- Carry substances around body
- Remove waste substances
What is the difference between fats and lipids?
- Fats don’t include liquids
- Lipids include liquids
True or False…
Glucose/ sucrose are complex carbs.
- False. They are simple molecules (monomers.)
What is the best way to prepare a food sample?
1.) Grind food with pestle and mortar
2.) Add distilled water in excess
3.) Filter the solution to remove food.
What is a qualitative test?
One that is based on observing changes.
No numbers
What are the 3 different colours Benedict’s can change?
What do these mean?
1.) Green = small amount of sugar
2.) Yellow = quite a bit of sugar
3.) Brick- Red = A lot of sugar present
Give 1 disadvantage of these Food Tests.
- Can’t tell exact amount of food.
True or False. Benedict’s solution works for all sugars.
- False. Benedict’s only works for reducing sugars.
Give an example of a reducing sugar.
- Glucose.
Give an example of a non- reducing sugar.
- Sucrose
For which food test do we not filter out the food particles when preparing the sample?
WHY??
- Lipids
Lipid molecules will stick to filter paper so you won’t see any change.
Give a MAJOR safety precaution when working with ethanol.
- Ethanol is highly flammable
- Make sure no naked flames are present
Q: Suggest an appropraite piece of equipment you can use to measure small volumes of reagants precisely.
- Measuring cylinder
What is a safety precaution for all chemicals used?
- Wear goggles, irritants.
What do you do differently when you test for lipids than the others?
- Don’t filter out solution of food + distilled water.
- Lipid molecules bind to paper.
Q.)
Give 1 other use of glucose in the body other than respiration.
- Converted into glycogen.
fWhy is Biuret’s solution dangerous?
- Copper sulphate: poisonous
- Sodium hydroxide: corrosive.
