Monday, February 27, 2012

IB Biology on EE Bacteria Transformation using plasmid and heat shock method

IB Biology EE on Transformation Experiment
Bacteria Transformation using heat shock method
Possible Research Questions?
  • How different salt solution affect transformation efficiency ?
  • How different temperature affect transformation efficiency?
  • How different incubation time affect transformation efficiency?





Click here to order transformation kit from Carolina for green fluorescent gene
Click here to order transformation kit from Carolina for E Coli/ampicillin plasmid
Sample EE report on effect of salt on transformation efficiency

Click here to view effect of temperature on transformation efficiency
Video on Transformation Experiment for IB EE Science

Thanks to all videos and pictures contributors for the above post

Thursday, February 23, 2012

IB Biology, Enzymatic decomposition of hydrogen peroxide by enzyme catalase

IB Biology on Enzymatic decomposition of hydrogen peroxide by enzyme catalase using disc and well method
Simple enzymatic study (Inaccurate)
  • Place 5ml hydrogen peroxide into well
  • Soak paper disc in well containing catalase
  • Place disc soak with catalase into well
  • Measure time for disc to float
  • H2O2 decomposes - produce O2
  • O2 will cause the disc to float
  • Rate = Time taken for disc to reach the surface


Video tutorial on decomposition of hydrogen peroxide using Disc method



Sample report for SL Biology using disc method

Accurate Method for Enzymatic study measured using Pressure or Oxygen sensor

  • Rate of decomposition = Change in pressure due to release of O2 gas released over time
  • Pressure sensor or Oxygen Sensor can be used
  • Initial rate will have to be used







Click here to view video on decomposition of hydrogen peroxide using pressure sensor
  • Make sure it is time based for 300s
  • Press collect button to obtain the base line pressure
  • Add catalase enzyme
  • Close cap and measure pressure



Tip when using Pressure sensor
  • Always collect the average rate for first 50s
  • Use linear regression to find the gradient for first 50s
  • If possible take instantaneous rate at time zero (Initial Rate)
  • Initial rate (time close to zero) is used because as time progresses, conc of H2O2 changes
  • To measure rate at certain H2O2 concentration - Initial rate must be use



Sample report on hydrolysis of starch using pressure sensor

Wednesday, February 22, 2012

IB Biology IA, on Hydrolysis of starch by enzyme amylase using colorimeter

IB Biology IA, Hydrolysis of starch using enzyme amylase for SL and HL 

1st Method (SL) using white tile and stop watch
How changing Temp/Salt conc affect the hydrolysis of starch by enzyme amylase?
Setup
  • Place 50ul iodine onto white tile
  • Add 10ul 0.1% enzyme into 1ml 1% starch
  • Pipette 50ul of enzyme/starch mixture onto white tile containing iodine
  • Repeat for every 30s interval until all starch is hydrolysed (iodine remains yellow)
  • Rate enzyme activity = 1/ Time taken to hydrolyse 1% starch
  • Assume conc of starch remains the same




Video Tutorial on hydrolysis of starch using white tile and stop watch

Sample report on Hydrolysis of starch for SL level

IB Biology on Hydrolysis of starch by enzyme amylase
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2nd Method (HL) --Abs vs Time using visible spectrophotometer
Starch + iodine will form blue black colouration (abs at 576nm )
Absorbance drop as starch digested, blue black turn colourless
Measure absorbance change over 120s, digestion of starch by amylase.
Research Question
How changing Temp/Salt conc affect the rate of amylase digestion of starch ( by monitoring the absorbance change over time)

Set up
1. 1ml 0.01% starch in cuvette
2. 40ul iodine (adjust vol) for a blue black
3. Set Abs at 576nm
4. Place cuvette in spec and set to Abs vs time
5. Add 10ul 1% amylase into cuvette
6. Start data collection immediately
7. Rate of digestion = Abs change over 120s








Video, Starch hydrolysis by amylase (Abs decrease over time)

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Treatment of amylase at different salt Concentration
Set up
1. 1ml 0.01% starch in cuvette
2. 40ul iodine (adjust vol) for a blue black
3. Set Abs at 576nm
4. Place cuvette in spec, set to Abs vs time
5. Add 10ul water to 10ul 1% amylase, (20ul total) and transfer to cuvette containing 1ml starch + 40ul iodine
6. Start data collection immediately
7. Rate of digestion = Abs change over 120s
Treatment of amylase at different Salt Concentration


8. Incubate enzyme at different salt conc for 10mins
9. After 10min repeat step 1 to 4, adding 20ul treated amylase and measure Abs over time.








Sample report on starch hydrolysis using visible spectrophotometer

Tips to make it work.
  • Starch must be freshly prepared and accurate
  • Volume iodine adjusted accordingly to get blue black colouration
  • Blue black colouration must be dilute so Beer's Lambert Law is obeyed
  • Trial and error needed to get the right starch/iodine solution for this study
  • Prepare a large stock of 0.01%starch/iodine and add 1 ml to cuvette instead of adding 1ml starch and 40ul iodine to cuvette ( pipetting error)
  • Make sure use Lugol's Iodine (I2+KI) as iodine will not work.

Tuesday, February 21, 2012

IB Chemistry, Biology on Scientific Theory, Hypothesis, Scientific Method

IB Chemistry, Biology on Scientific Theory, Hypothesis, Scientific Method


Science is based on evidence and for those who believed in Science which is a warranted knowledge - knowledge that is reliable and guaranteed on the basis of how it has been acquired.


Good trusted Science is whereby data are reliable, review and collected using Scientific methodology


Source taken from potholer54






Video on Scientific Theory, Hypothesis and Scientific Method

Video on Evolution Theory and Facts

Notes from slideshare on Scientific Theory and Hypothesis

Thanks to potholer54 and cdk007 for the above post

Saturday, February 18, 2012

IB Chemistry IA on Kinetics, Rate of reaction, Iodine clock reaction with H2O2 and peroxodisulphate measured using visible spectrophotometer

IB Chemistry, Chemistry IA, Kinetic, Iodine Clock, Visible Spectrophotometer
Conventional Way ( X cross Method )
  • Time for triiodide/starch to obscure a mark “X”.(subject to lots of Human Error)
Visible Spectrophotometer (Change in Absorbance at 608.7nm)
  • Time for triiodide/starch to form, causing an increase in absorbance.
Comparative study on both Methods can be done by students
...................................................................................................................................................
Iodine Clock Introduction.

H2O2 oxidises  into I3 and I3 will react with starch to form blue black.
H2O2 + 3 I  + 2 H+ → I3 + 2 H2O.
Triiodide formed will be reconverted to iodide by the thiosulfate. (Delaying mechanism) .
I3(aq) + 2 S2O32−(aq) → 3 I(aq) + S4O62−(aq)


Absorbance MUST increase immediately when blue black colouration forms.
Research Question?
How changing KI conc affect the rate ( by the sudden increase in absorbance ) over time.
Steps to follow
1. Prepare 2 fold serial dil for 0.1M KI
2. Add (0.5ml, 0.1M S2O3) , (0.5ml, 0.5M KI), (0.1ml 1% starch), (0.1ml, 0.1M HCI) into a cuvette.
3. Set visible spec at 608.7nm
4. Set data collection to 300s (Abs vs time)
5. Place cuvette containing solution in step 2
6. Add 1ml of 3%H2O2 and press collect button
7. Take time for absorbance to increase
8. See 2min video tutorial for clarification


Data done by IB students
Rate is measured by time it takes for an increase in absorbance using different KI Conc




Video, Iodine clock reaction using Visible Spectrophotometer

Advantage of Visible Spec and Tips to make it work
  • MUST produce a sharp increase in absorbance once blue black form
  • Reduce human error ( X method )
  • Micro volume is used, save reagents (total volume 2.5ml )
  • DO NOT NEED TO CALIBRATE but ensure wavelength at 608.7nm
  • MUST add H2O2 into cuvette and start data collection simultaneously
  • Sulphur clock may be adopted ( sulphur formation ) but may NOT BE ACCURATE cause sulpur formation may not produce a sharp increase in absorbance
Sample report of iodine clock using visible spectrophotometer

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Iodine Clock Reaction, Peroxodisulphate S2O82− and Potassium iodide, KI
Iodine is generated:
2I + S2O82− → I + 2SO42−
I + 2S2O32− → 2I + S4O62−
Same Method but using S2O82− as oxidising agent not H2O2
Steps to Follow
1. Prepare 2 fold serial dilution for 0.1M KI
2. Add 0.5ml 0.1M KI, 50ul 1% starch, 50ul 0.02M S2O3 into cuvette
3. Set visible spec at 608.7nm
4. Set data collection to 300s (Abs vs time)
5. Place cuvette containing solution in step 2
6. Add 0.5ml of 0.05M S2O82-and press collect 
7. Take time for absorbance to increase
8. See 2min video tutorial for clarification

IB Student data, Iodine clock with different conc KI
  • Visible spectrophotometric is accurate if it shows a sharp increase in absorbance
  • H2O2 is better compared S2O82-
  • Comparative study between X cross method, visible and light sensor can be investigate and error analysis can be done


Video, Iodine Clock using visible spectrophotometer
Sample report on iodine clock reaction using visible spectrophotometer

Thanks to all picture and video contributors for the above post

Thursday, January 19, 2012

IB Chemistry IA on the effect of RMM or hydrocarbon chain on its rate of evaporation of organic solvents

IB Chemistry IA on the effect of RMM or hydrocarbon chain on its rate of evaporation or boiling point of organic solvent
Experimental setup

  • Different alcohols are used. (Methanol, ethanol, propanol, butanol, pentanol )
  • Pipette 1 ml of solvent on to temp probe wrapped with cotton.
  • Close the lid to prevent any breeze
  • Triplicate runs performed for each solvent 
  • Compute the average rate of evaporation.







Video Tutorial on Chemistry IA on effect of RMM on its rate of evaporation.



Sample IA report for the above experiment
IB Chemistry IA on the effect of RMM on rate of evaporation of organic solvents
Research Questions using the above methodology

  • Does changing ethanol concentration (90, 80, 70, 60, 50)% affect its rate of evaporation
  • Does molar mass of hydrocarbon affect its rate of evaporation 
  • Does branching of alcohol (OH) gp, ( 1- propanol, 2 - propanol ) or ( 1- butanol, 2- butanol, 2 methyl propan 2 ol) affect the rate of evaporation
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