Food tests and enzyme basics Flashcards
Test for Glucose/ reducing sugars
- Place food sample in a test tube.
- Add enough Benedict’s solution for sample to turn blue.
- Heat test tube in a boiling water bath for 5 minutes.
- Take the test tube out and observe the colour.
Positive result is from blue to orange/ brick red.
Safety precautions for reducing sugars test
Handle test tube with tongs.
Wear safety goggles and heatproof gloves.
Tie hair, wear a lab coat. Goggles.
Test for Starch
- Place food sample in test tube.
- Add a few drops of iodine to the food sample.
- Observe the colour.
Positive result is from orange/brown to blue/black
Test for Protein
- Place food sample in test tube.
- Add drops of Biuret solution to the food sample.
- Observe colour.
A positive result is from blue to violet/purple
Test for fat
Place food sample into test tube. Add ethanol to the sample and shake. Add water and also shake.
Positive result is colourless to milky white emulsion.
Enzyme for starch
amylase
Enzyme for proteins
protease
Enzyme for lipids
lipase
Starch is broken down into
simple sugars/glucose
Proteins are broken down into
amino acids
Lipids are broken down into
fatty acids and glycerol
Relationship between rate of reaction and temperature with enzymes
Rate of reaction increases with temperature at 40oC. After 40oC collisions are too violent and the active site is denatured.
Relationship between rate of reaction and pH.
All enzymes have an optimum pH. At extremes of pH the active site can change shape causing the enzyme to become denatured. Reaction cannot take place and the change can be irreversible.
Describe the structure of DNA.
Double helix shape. Sugar-Phosphate backbones. Phosphate and a nitrogenous base. ATCG.
