homework for test (jan 2025) Flashcards
what chemical elements are present in arbohydrates?
CHO
what chemical elements are present in proteins?
CHON
what chemical elements are present in lipids?
CHO
what are the monomers of carbohydrates?
simple sugars (eg glucose)
what are the polymers of carbohydrates?
starch and glycogen
what is the monomer of proteins?
amino acids
what are the monomers of lipids?
fatty acids and glycerol
how do you test for lipids?
- place a small food sample in a test tube
- add roughly equal amount of ethanol and mix well
- add roughly equal amount of water (1:1:1) and mix well again
- if the mixture turns milky, fat is present
how do you test for starch?
- take a small sample of food and place it in a well on a spotting tile
- add 10 drops of iodine solution/a roughly equal amount of iodine to food
- if starch is present, the iodine changes from orange to black/blue
how do you test for glucose?
- place a small sample (approx. 2cm^3) of food in a test tube
- then add 1cm^3 of Benedict’s solution, or enough for it to appear blue
- then heat in an 85 degree celcius water bath for 5 minutes
- if the mixture turns from blue to green/yellow/orange/brick red then sugar is present
how do you test for proteins?
- place a small food sample in a test tube
- add a roughly equal amount of Biuret solution or enough for the pale blue colour to be seen
- if the mixture turns from blue to mauve/purple, proteins are present
what is the role of enzymes?
they are biological catalysts in metabolic reactions
what is the practical to investigate how enzyme activity is affected by changes in temperature?
- place single drops of iodine solution in rows on the spotting tiles
- label a test tube with the temperature to be tested (eg. 10 degrees celcius)
- use cold water from the tap and hot water from the kettle to prepare a water bath at that temperature, and keep it at that temperature for the test using a thermometer
- use a syringe to place 2cm^3 of amylase into the test tube, then place it in the water bath for 5 minutes
- use another syringe to add 2cm^3of starch solution to the amylase solution (leaving the test tube in the water bath) start the stop watch and mix using the pipette
- after 30 seconds, use the pipette to squirt one drop of iodine solution into the first drop of iodine, the squirt the rest of the pipette back in the test tube. the iodine solution should turn blue/black
- after another 30 seconds, drop another drop of the solution into the next iodine drop
- repeat step 7 until the iodine stays orange
- count how many iodine drops you used, each equals 30 seconds of reaction time
- repeat 1-9 for each temperature (eg 20, 30, 40, 50, 60)
- repeat each temperature 3 times and work out a mean
what is the practical to investigate how enzyme activity is affected by changes to the pH?
- Test tube of Starch solution is placed in Water bath of set temperature (30 - 40°C as optimum temperature of Amylase is approximately 37°C)
- Solution of Amylase enzyme is added into test tube of Starch solution
- Immediately after, buffer solution of set pH is added which will maintain reaction mixture at set pH
- Pipette is used to add droplets of mixture into wells on tile
- A few drops of Iodine solution is added
- Process is repeated in increments of 10 seconds until Iodine turns orange, indicating that Starch has completely broken down into Glucose
- Time taken for Starch to be completely broken down is compared to that of each respective pH (time taken for Iodine solution to turn orange with each respective pH of buffer solution)
