IA on effect of pH on the rate of diffusion of pigment (betalain) from beetroot, measured using visible spectrophotometer.

1. Effect of pH on the rate of diffusion of pigment (betalain) from beetroot, measured using visible spectrophotometer.
Beetroot cut into slices with a scapel and borer.
Pigment betalain will diffuse out once cell membrane is ruptured.
pH (1, 4, 5, 7, 9) will be used, to destroy the plasma membrane.
Red pigment measured using colorimeter.
Initial and final abs taken over 3 mins.
Ave rate diffusion calculated.
Betalain structure giving it red colorization
pH buffer (1, 4, 5, 7, 9)
Procedure:
3 slices beetroot placed in well.
2.6ml of diff pH buffer was added.
After 15s of mixing, ini abs was taken.
Final abs was taken after 3 min.
Rate of diffusion – Change of abs over 3 mins
-ve control – Beetroot with only water added.

2. Go to expt – press calibrate Insert cuvette (red pigment), press collect
Insert a blank containing water
Press stop, and click on rainbow icon. Select abs vs time. λ max at 528nm will
be automatically chosen
Abs vs time
Effect of pH on the rate of diffusion of pigment (betalain) from beetroot, measured using visible spectrophotometer.

3. 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
1 4 5 7 9 -ve control
Rate
of
diffusion
pH
pH vs rate of diffusion
Change of abs over time were plotted.
Rate of diffusion seems to be the highest for pH 1.
Might be due to the denaturation of cell membrane at pH 1, and
thus leakage of red pigment out from cell.
pH buffer Initial
abs
Final abs Rate of
diffusion/
absmin-1
1 0.420 0.642 0.740
4 0.307 0.406 0.033
5 0.350 0.430 0.027
7 0.337 0.490 0.051
9 0.290 0.380 0.030
-ve control 0.465 0.600 0.045
–ve control with other pH seems to be relatively the same
Duration is 3 mins. Only pH 1 is significantly higher.
Effect of pH on the rate of diffusion of pigment (betalain) from beetroot, measured using visible spectrophotometer.
No significant diff at diff pH

4. Why transition metals ion complexes have diff colour?
Transition Metal – Colour Complexes
Colour you see is BLUE – Blue reflected/transmitted to your eyes
- Red/orange absorbed (complementary colour)
Colour you see is Yellow – Yellow reflected/transmitted to your eyes
- Violet absorbed (complementary colour)
complementary colour
Blue
transmitted
Wave length - absorbed
Wave length - absorbed
Visible
light
Visible
light
Yellow
transmitted
absorbed