Paper 3- Practical Flashcards
MIDRIB:
ROOT:
STEM:
Formula for microscopy
Image/ Actual size= Magnification
What are standardised variables
-variables that are kept constant e.g temperature, pH e.t.c
HOW TO CARRY OUT SERIAL DILUTION:
-In the case where there’s a solution (Beaker S) that has 5% amylase with 10cm3 of water, state the concentration of water, the percentage of amylase and how much has been taken to be added.
TEST TUBE A:- 2.5% Amylase
-5cm3 from Beaker S
-5 cm3 of water
TEST TUBE B:- 1.25% Amylase
-5cm3 from tube A
-5cm3 of water
TEST TUBE C:-0.625% Amylase
-5cm3 from tube B
-5cm3 of water
*ALL TEST TUBES HAVE 10cm3
Examples of sources of errors
- Uncertainty in measuring equipment (subjective measures)
- Human errors in working out
- struggles with standardising (hot bath at same temperature for all)
Examples of improvements of errors
- Using better equipment (colorimeter)
- Repeating the experiment and taking the mean
- Less dependance of human judgement
Simple dilution formula
Concentration (1) X Volume (1) =Concentration (2) X Volume (2)
Describe the reducing sugar food test
- BENEDICTS REAGENT
-Theres the use of boiling water - results are:
BLUE- No reducing sugar
GREEN- Low concentration
YELLOW- Medium concentration
RED/ORANGE- High concentration
Describe the Non-reducing sugar
*BENEDICTS REAGENT
- Break the disaccharide glycosidic bond FIRST! (Enzyme OR Acid)
- Results are: No colour change RED. (after change)
Describe the starch food test
*IODINE
-Results:
BLUE/ BLACK- Starch is present
YELLOW- Starch is not present
Describe the food test for proteins
*BIURET REAGENT
-Results
PURPLE- Protein is present
LIGHT BLUE- No protein
Describe the food test for Lipids
*ETHANOL
- Shake vigorously!
Results:
CLOUDY- Lipids are present
CLEAR- No lipids
How to calibrate a microscope
1) Place the stage micrometer on the stage of the microscope
2) the stage micrometer = 0.1mm however the eye piece graticule is unknown.
3)Align the stage micrometer and eye piece graticule
4) Find out where they align and count how many divisions from e.p.g have been measured
5)Remove the stage micrometer and place the cell back, align the cell with the eye piece graticule and see how many divisions it covers
