(U3) Practicals Flashcards
Describe the details of the Benedict’s test for reducing sugars. (2)
What are the colour changes for positive results?
- add an equal vol of Benedict’s reagent to the test solution
- heat to ~80ºC in a water bath
- Blue = -ve
- green —> yellow —> orange = partially positive
- brick-red ppt = +ve
Describe the details of the Benedict’s test for non-reducing sugars. (4)
What are the colour changes for positive results?
- test part of solution for reducing sugar (benedicts test 1)
- if none is present, hydrolyse by heating with HCl in a water bath
- once cooled, neutralise with NaHCO3
- test with Benedict’s reagent
- blue = -ve
- green —> yellow —> orange = partially positive
- brick-red ppt = +ve
Name a glucose specific test and state it’s colour changes
- clinistix strips
- pink to purple
How do you test for starch?
What are the colour changes?
- add iodine solution
- yellow-brown (-ve) to blue-black (+ve)
Outline the Biuret test
State the colour changes
- add equal volumes of KOH to the test sample
- then a few drops of CuSO4 solution
- shake
- Blue (-ve) to lilac/mauve (+ve)
How do you calculate Rf values during chromatography?
What number should the value always be less than?
- (Distance moved by solute / distance moved by solvent front) x 100
- less than 1
Describe how to conduct a belt transect (6)
- lay out a measuring tape down the area from zone A to E
- place a quadrat at regular intervals of 5m along the tape
- use a key to identify species
- calculate percentage cover
- repeat the process at a different area - increase reliability
- record results in a table & represent on a histogram
Describe how to conduct a random sample (8)
- lay out a 2 measuring tapes perpendicularly
- Find co-ordinates using a random number generator
- place a quadrat at random intervals of along the tapes
- use a key to identify and record types of plants
- calculate percentage cover of each species
- repeat the process at 10 or more different co-ordinates - get reliable average
- repeat in another area for comparison
- record results & represent on a bar chart
Describe how to conduct a line transect (3)
What is it used for?
1.
- Just count along a measuring tape e.g. every meter
- use a key to identify individual species types
- no quadrat
- Abundance calculation
Describe how to conduct a pitfall trap (4)
What is it used to sample?
- Dig a hole
- Place container into hole, flush with ground level
- Raise the lid (leaf) with rocks at each side
- Collect sample 24 hours later
- Ground invertebrates e.g. ground beetle
What solution is used to stain chromosomes in a root tip squash?
Acetic orecin
What substance can be used to absorb carbon dioxide in a respirometer?
Potassium / sodium hydroxide
State 2 precautions necessary when drawing a base line in chromatography
any 2 from
- use a pencil (as its insoluble)
- ensure solvent is below the base line
- wear gloves
Describe how to set up and develop a chromatogram to identify unknown amino acids
Include a safety precaution
(8)
Safety precaution: conduct in a fume cupboard
Setting up:
- fill base of tank with solvent
- draw base line in pencil above the solvent
- add a spot of the solution via a capillary tube to the baseline, concentrate by applying several times
- add spots of known amino acids for comparison
- wear gloves to avoid contamination
Developing:
- allow chromatogram to dry, then spray with ninhydrin
- heat with a hairdryer to develop the spots
Describe how to conduct a pooter (2)
What is it used to sample?
1.
- place tube without gauze over insect
- place tube with gauze into mouth and suck insect into pot
- Small invertebrates e.g. aphids
What device is used to measure wind speed?
Anemometer
What device is used to measure soil water content?
Soil moisture meter
What device is used to measure soil pH?
Soil pH meter
What device is used to measure light?
Lux meter
What device is used to measure soil temperature?
Soil thermometer
