Module 2 Practicles Flashcards
2.1.1
How to prepare a stained temporary mount of onion epidermis
Use the forceps to peel of a thin layer of onion epidermis
Place onto the centre of the microscope slide, not folded over
Add two drops of iodine solution to cover
Use a mounted needle to lower coverslip at 45 degrees
2.1.1
How to prepare a stained temporary mount of cheek cells
Use a marker to put a small dot in the middle of the bottom of the slide
Use a cotton bud to remove cells from the inside of the cheek
Rub the cotton bud on the centre of the slide
Dispose of cotton bud in beaker of disinfectant
Add two drops of methylene blue, use a mounted needle to lower a coverslip at 45 degrees
2.1.1 How to calibrate arbitrary eyepiece graticule measurement with a stage micrometer
Lowest power objective lens
Clip stage micrometre onto stage
Focus, move so that eyepiece graticule and stage micrometre are lined up
Record how many eyepiece graticule units (EPGUs) correspond to 1000 micrometres (micrometers/EPGUs)
Repeat for other magnifications
2.1.1
Calculating specimens size from EPGU
Replace stage micrometer with specimen
line up a suitable cell with eyepiece graticule scale
Count how many EPGUs fit into the cell
Convert using conversion number
2.1.2
Identifying mystery substances using biochemical tests:
Iodine test - Starch
Emulsion test - Lipids
Biuret test - Proteins
BEnedicts test - reducing sugars
Acid hydrolysis - non-reducing sugars
2.1.2
Idoine test
Add sample to spotting tile
Add a few drops of iodine solution
Positive result - orange/brown to blue/black
2.1.2
Emulsion test
Add equal amounts of ethanol and sample to test tube
Add a bung, shake vigorously
Add equal amount (same as one sample volume) of water
Positive - colourless to cloudy emulsion
2.1.2
Biuret test
Add equal amounts of sample and biuret solution
Positive - From blue to purple/lilac
2.1.2
Benedict’s test
add equal volume of sample and benedict’s reagent
Heat in water bath for two minutes
Positive - from blue to green/orange/red - qualative
2.1.2
Acid hydrolysis (after negative benedict’s test)
Add 2cm of sample solutions and 1cm of HCL
Boil in water bath for 1 minute
Neutralise with NaHCO3 powder (sodium bicarbonate)
Effervescence will occur
Check pH
Carry out benedict’s test
Positive - from blue to green/orange/red - qulaative
2.1.2
Finding concentration of glucose in urine using a colourimeter
Label test tubes with 0.32, 0.16, 0.08, 0.04, 0.02, 0.01 M
Carry out a serial dilution of glucose solution
Carry out benedict’s test for reducing sugars of all solutions
Label and fill cuvette tray with solutions, and one with distilled water
Make sure cuvette tray is set to 0.0 and filter is set to 680nm
Use colourimeter to find absorbance of each
Plot a calibration curve, and use this to find the concentration of the unknown
2.1.2
Investigation using paper chromatography and ink
Draw a horizontal line in pencil 1.5cm from base of chromatography paper
Place dots equidistant from one another, label in pencil
Roll paper into cylinder, avoiding overlaps, hold in place with paper clips
Add water to a depth of 1cm
Add cylinder
Wait until the water approaches the top of the paper, mark this level in pencil
Allow to dry
Use a ruler to measure distance from origin to solvent front
Measure distance from origin to top of each pigment spot
Calculate Rf value ( distance moved by pigment/distance moved by solvent front)
2.1.2
Investigation using paper chromatography and amino acids
Put 10ml of solvent into beaker, cover with petri dish
Place a 10cm by 10cm piece of chromatography paper onto a white tile, dray a 2cm line from the top, this is the handling region
Draw a line 1cm from the bottom in pencil
Place amino acids spots, using a cocktail stick equidistance from one another, label in pencil
Remove the handling area, roll into cylinder and hold with paper clip
Replace the petri dish lid, and leave until solvent rises 2/3rds of the way up the paper.
Remove and mark solvent front in pencil
Dry paper
Lay flat in fume cupboard, spray with ninhydrin spray and leave to settle
Pick up and put in over at 110 degrees for 1-2 minutes
Calculate Rf value
2.1.3
Extraction of DNA from a strawberry
Crush strawberry with 20cm3 of DNA extraction buffer (detergent (disrupts phospholipid bilayer) and salt (Neutralises charge))
Strain into beaker using tea strainer and muslin
Add 1cm3 of protease enzyme
Pour filtrate into a boiling tube
Add 5cm3 of ice cold ethanol, by tilting boiling tube at 45 degrees, rolling ethanol down the sides
Let stand for 5 minutes
Remove with inoculating loop
2.1.4
Investigation into the effect of substrate concentration on enzyme activity
Grind 2cm of potato cylinder with 5cm of distilled water to make a smooth paste
Place 10cm of H2O2 (hydrogen peroxide) into test tube
Using forceps, dip a filter paper disc into enzyme suspension, tap of excess
Drop filter paper disc into the hydrogen peroxide solution and measure the time taken for the disc to rise
Remove disc and discard
2.1.5
Effect of ethanol concentration on membrane permeability
Label 5 test tubes with 0, 20, 40, 60, 80, and 100% ethanol concentration
Collect 5 beetroot cylinders and trim to 5cm
Rinse under tap and pat dry
Add 1 cylinder to each test tube
Swirl tubes once and remove cylinders
Pour remaining liquid into cuvette tray, filling an extra with distilled water
Use a colour filter with green filet (520nm) to measure absorbance (Au)
Plot a graph
2.1.5
Determine water potential by measuring change in mass
Label boiling tubes, 0, 0.2, 0.4, 0.6, 0.8, and 1 mol dm-3
Place 30cm3 distilled water in each tube, along with 30cm3 of appropriate salt solution
Use a cork borer and scalpel to create 6 potato cylinders, 5cm long
Divide filter paper into 6 sections, labelled
Blot dry each cylinder
Record mass of each cylinder
Add to appropriate cylinder
Leave for 45 minutes
Remove cylinders from the test tubes, and place back onto filter paper
blot dry
Reweigh, calculate percentage change
2.1.6
Light microscopes and studying mitosis
Remove root tips
Place in suitable stain
Gently squash on a glass slide, using a coverslip
Use a microscope to observe cells undergoing mitosis
Create a biological drawing - label
Biological drawing rules:
Sharp pencil
Clear, continuous lines
No shading/colouring
Accuracy
Label magnification and scale
Take up more then half the page
Title
Biological drawing label rules:
Sharp pencil
Label all relevant structures
No arrow heads
Do not cross over other label lines
Labels written horizontally
Biological drawing label, contents:
Shape
Size
Colour
Hairiness
