Chapter 4 : Biological Molecules Flashcards
State the chemical elements making up carbohydrates.
Carbon, Hydrogen and Oxygen.
These are in the ratio 6:12:6 or C6H12O6.
These form substances like glucose which is changed to glycogen in animals, and starch in plants, or cellulose, which makes up plant cell walls.
State the chemical elements making up Fats.
Carbon, Hydrogen and Oxygen.
These form glycerol and fatty acids. which form lipids.
Lipid molecules contain less Oxygen than carbohydrate molecules.
State the chemical elements making up Proteins.
Carbon, Hydrogen, Oxygen and Nitrogen. some proteins also include sulfur.
These form amino acids, which make up Proteins.
What is the colour change in the iodine solution test for starch?
Orange–brown or just brown, to blue–black.
What is the colour change in the Benedict‘s solution test for reducing sugars?
Blue to orange–red.
What is the colour change in the Biuret reagent test for proteins?
Blue to purple.
What is the result of the Ethanol emulsion test for fats and oils/lipids?
A white emulsion when poured into water.
What is the result of the DCPIP test for Vitamin C?
A colour change from purple to colourless.
What are the pairings of bases in DNA?
A – T and G – C.
Describe the structure of DNA.
- Double stranded and coiled to form a double helix.
- Each strand contains bases.
- Bonds between pairs of bases hold the strands together.
- The bases always pair up in the form A to T and G to C.
Describe, in steps, the iodine solution test for starch.
- Select foods for the test, eg. potatoes, rice, bread
- Cut foods up with KNIFE.
- Take small piece of each food and place on different WHITE TILES.
- Add drop or two of IODINE. DROPPER.
- Repeat process for each food.
- Construct table of 3 columns, stating, Food, Observation, Conclusion respectively.
If solution stays brown – test is negative. If it turns blue–black, test is positive.
KNIFE. IODINE. DROPPER. WHITE TILE.
When recording the colour change in a food test, do you state the colour seen even if the result is negative or do you state that there is no change, in your result.
State colour that you see.
Describe, in steps, the Benedict‘s solution test for reducing sugars.
- Cut up food samples into pieces, eg. lemons, milk, bananas
- Set up water bath at 80 degrees celsius.
- Put food pieces in boiling test tubes, and add a little water and shake to to dissolve any sugar in the food.
- Add enough Benedict‘s solution cover the food and shake to mix.
- Stand test tube in beaker with boiling water.
- As mixture of food and Benedict‘s solution heat up take note of the colour change.
- Repeat with other food samples.
Staying blue – negative result. Turning orange–red – positive.
TEST TUBES. BENEDICT‘S SOLUTION. BUNSEN BURNER. TRIPOD STAND. WIRE GAUZE. KNIFE, BEAKER. THERMOMETER.
Describe, in steps, the Ethanol test for fats and oils.
- Cut a selection of foods into small pieces and keep them separate.
- Add food sample to CLEAN test tube, and add a little ethanol. Shake the tube to dissolve any fats or oils in the food.
- Take another clean test tube and put distilled water in it.
- Pour ethanol from the first tube into the second, carefully, WITHOUT LETTING THE FOOD GET IN.
Positive result is a white emulsion in the water.
KNIFE. TEST TUBES. ETHANOL. DROPPER. DISTILLED WATER.
Describe, in steps, the Biuret test for proteins.
- Set up test tube with positive result and test tube {using water} with negative results of colour comparison.
- Cut food samples into small pieces eg, cooked egg white, milk, beans
- Put cut pieces of first food, add some Biuret reagent to test tube.
- Shake to mix.
- Repeat for other food samples.
Blue to violet change in colour is positive result.
DROPPER, SEVERAL CLEAN TEST TUBES. KNIFE.
