A-level OCR Biology A: Module 1 -
Practical skills
Chromatography - method
1. Pour 30cm³ of solvent into a 500cm³ beaker
2. Draw a line 2cm from the bottom of a piece of chromatography paper, this is the origin
3. Mark and label 10 dots, 2cm apart along the origin
4. Use capillary tubes to place samples on the appropriate dot
5. Roll the paper to form a cylinder and attach with a stapler, ensuring the edges don't overlap
6. Use a drying oven to completely dry the paper
7. Place the paper into the beaker so the origin is submerged and the paper isn't touching the
sides. Tightly cover with aluminium foil
8. Leave for 1-2 hours, then remove the paper and mark where the solvent reached. Set the
paper upside down to dry
9. Once dried, remove the staples and hang in a fume cupboard
10. Spray lightly and evenly with ninhydrin, leave to dry
11. Heat in an oven for 10 minutes until the spots have developed
12. Draw around the spots and measure the distance travelled. Measure solvent front
13. Calculate Rf value
Chromatography - equipment
- Safety goggles and disposable gloves
- Aluminium foil
- Pencil
- Ruler
- Staples / paper clips
- Capillary tube
- Chromatography paper
- 500cm³ beaker
- Oven
- Solvent (ammonia and propan-2-ol)
- Ninhydrin
- 5 related solutions inc. unknown
(e.g. 4 amino acids + unknown)
Chromatography - variables
Control - Solvent, time, temperature, developing technique
Dependent - Distance travelled
,Independent - Solution
Chromatography - notes
- Solvent front is the distance the solvent travelled
- Propan-2-ol is flammable
- Ninhydrin is an irritant, only use in fume cupboard
- Avoid contact with chemicals
- Rf is the ratio of the distance travelled to the solvent front
Stationary phase
The phase in chromatography on which the mobile phase and substances move.
E.g. chromatography paper
Mobile phase
The phase in chromatography that acts as the solvent and travels along the stationary phase.
E.g. water, propan-2-ol
Rf value
Distance moved by spot ÷ distance moved by solvent
Determining glucose concentration - method
1. Label 4 boiling tubes with glucose concentrations
2. Add 5cm³ of Benedict's solution to each
3. Add 0.5cm³ of glucose concentration to the respective tube
4. Stir with a glass rod
5. Place the tubes into a water bath at 80° for 2 minutes
6. Remove the tubes and allow to cool
7. FIlter the contents of each tube into a cuvette
8. Record the absorbance
Determining glucose concentration - equipment
- Safety goggles
- Labels, pen
- Distilled water
- Syringes
- Boiling tubes
- Tongs
- Beakers of varying sizes
, - Water bath
- Colorimeter
- Cuvettes
- Glucose solutions + unknown
- Benedict's solution
Determining glucose concentration - variables
Control - Temperature, time, volumes, colorimeter
Dependent - Absorbance
Independent - Concentration
Determining glucose concentration - notes
- You can't label the cuvettes, so you must remember which is which
- Don't get fingerprints on the cuvettes
- Use colour filters on the colorimeter for greater accuracy
- Be careful with the high temperature of the water bath
Colorimeter
A device used to measure light absorbance
Effect of substrate concentration on catalase - method
1. Make dilutions of hydrogen peroxide of 5 different concentrations
2. Put 10cm³ of dilution in each test tube, label with the concentration
3. Soak discs of filter paper in celery extract for 5 minutes
4. Remove the discs from the dilution and shake to remove drips
5. Put each disc in a test tube, pushing each one to the bottom. Start a timer
6. Time how long it takes for the disc to rise to the top
7. Repeat 3 times with each concentration
Effect of substrate concentration on catalase - equipment
- Safety goggles
- Test tubes
- 5cm³ syringes
- 1cm³ syringes
- Glass rods
- Forceps
- Stop clock
Practical skills
Chromatography - method
1. Pour 30cm³ of solvent into a 500cm³ beaker
2. Draw a line 2cm from the bottom of a piece of chromatography paper, this is the origin
3. Mark and label 10 dots, 2cm apart along the origin
4. Use capillary tubes to place samples on the appropriate dot
5. Roll the paper to form a cylinder and attach with a stapler, ensuring the edges don't overlap
6. Use a drying oven to completely dry the paper
7. Place the paper into the beaker so the origin is submerged and the paper isn't touching the
sides. Tightly cover with aluminium foil
8. Leave for 1-2 hours, then remove the paper and mark where the solvent reached. Set the
paper upside down to dry
9. Once dried, remove the staples and hang in a fume cupboard
10. Spray lightly and evenly with ninhydrin, leave to dry
11. Heat in an oven for 10 minutes until the spots have developed
12. Draw around the spots and measure the distance travelled. Measure solvent front
13. Calculate Rf value
Chromatography - equipment
- Safety goggles and disposable gloves
- Aluminium foil
- Pencil
- Ruler
- Staples / paper clips
- Capillary tube
- Chromatography paper
- 500cm³ beaker
- Oven
- Solvent (ammonia and propan-2-ol)
- Ninhydrin
- 5 related solutions inc. unknown
(e.g. 4 amino acids + unknown)
Chromatography - variables
Control - Solvent, time, temperature, developing technique
Dependent - Distance travelled
,Independent - Solution
Chromatography - notes
- Solvent front is the distance the solvent travelled
- Propan-2-ol is flammable
- Ninhydrin is an irritant, only use in fume cupboard
- Avoid contact with chemicals
- Rf is the ratio of the distance travelled to the solvent front
Stationary phase
The phase in chromatography on which the mobile phase and substances move.
E.g. chromatography paper
Mobile phase
The phase in chromatography that acts as the solvent and travels along the stationary phase.
E.g. water, propan-2-ol
Rf value
Distance moved by spot ÷ distance moved by solvent
Determining glucose concentration - method
1. Label 4 boiling tubes with glucose concentrations
2. Add 5cm³ of Benedict's solution to each
3. Add 0.5cm³ of glucose concentration to the respective tube
4. Stir with a glass rod
5. Place the tubes into a water bath at 80° for 2 minutes
6. Remove the tubes and allow to cool
7. FIlter the contents of each tube into a cuvette
8. Record the absorbance
Determining glucose concentration - equipment
- Safety goggles
- Labels, pen
- Distilled water
- Syringes
- Boiling tubes
- Tongs
- Beakers of varying sizes
, - Water bath
- Colorimeter
- Cuvettes
- Glucose solutions + unknown
- Benedict's solution
Determining glucose concentration - variables
Control - Temperature, time, volumes, colorimeter
Dependent - Absorbance
Independent - Concentration
Determining glucose concentration - notes
- You can't label the cuvettes, so you must remember which is which
- Don't get fingerprints on the cuvettes
- Use colour filters on the colorimeter for greater accuracy
- Be careful with the high temperature of the water bath
Colorimeter
A device used to measure light absorbance
Effect of substrate concentration on catalase - method
1. Make dilutions of hydrogen peroxide of 5 different concentrations
2. Put 10cm³ of dilution in each test tube, label with the concentration
3. Soak discs of filter paper in celery extract for 5 minutes
4. Remove the discs from the dilution and shake to remove drips
5. Put each disc in a test tube, pushing each one to the bottom. Start a timer
6. Time how long it takes for the disc to rise to the top
7. Repeat 3 times with each concentration
Effect of substrate concentration on catalase - equipment
- Safety goggles
- Test tubes
- 5cm³ syringes
- 1cm³ syringes
- Glass rods
- Forceps
- Stop clock
