Practicals

Question 1

Prac 7:
Why should you draw the solvent front immediately?

Answer 1

Solvent rapidly evaporates so the end point will not be visible shortly after the experiment
This value is needed to calculate Rf values

Question 2

Prac 7:
Why should you measure the Rf value from the middle of the pigment?

Answer 2

Pigment value is spread out.
Measuring from the middle is a way of standardising measurements you are taking to allow for comparisons

Question 3

Prac 7:
Why does the paper need to be vertical in the tube?

Answer 3

To ensure that the pigments travel straight upwards and avoids them running off the paper and being washed off.

Question 4

Prac 7:
What colours are these pigments
- Chlorophyll a
- Chlorophyll b
- Carotene
- Xanthophyll
- Phaeophytin

Answer 4

• Chlorophyll a = blue / green
• Chlorophyll b = yellow / green
• Carotene = orange
• Xanthophyll = yellow
• Phaeophytin = grey

Question 5

Prac 8:
Explain how chemicals which inhibit the decolourisation of DCPIP could be used as weed killers

Answer 5

Rate of the light-dependent decreases meaning less ATP and NADPH produced therefore rate of light-independent reaction decreases meaning that less GP can be converted into triose phosphate.