Photosynthetic Pigments

BIOLOGY LAB REPORT
NAME :princess cucumber
TOPIC : 3.8 & 8.2 : PHOTOSYNTHETIC PIGMENTS
RESEARCH QUESTION

INTRODUCTION
The photosynthetic pigments are responsible for absorbing and trapping light energy the major pigments of photosynthesis are the chlorophylls. The two chlorophylls found in green plants are chlorophyll a and chlorophyll b. other pigments include carotenoids and phycobilins, sometimes referred to as accessory pigments. Carotenoids occur in all photosynthetic organisms, while phycobilins occur in the red algae and cyanobacteria.

HYPOTHESIS
VARIABLES
Variables | Methods to handle | Manipulated variable : | | Responding variable : | | Constant variable: 1. Volume of pure acetone 2. Molarity of | 1. |
Table 1 shows the variables in this experiment
APPARATUS & MATERIALS Apparatus/ materials | Quantity | Large boiling tube | 1 | Large test tube rack | 1 | Cork stopper with pin hook | 1 | Strip of filter paper (Goodman) | 1 | Capillary tube | 1 | Fresh spinach leaves | 10g | Fresh solnostemon hybrid leaves | 10g | Chromatography solvent (9:1 petroleum ether-acetone) | 3mL | Measuring cylinder (20mL) | 1 | Strainer | 1 | Acetone (100%) | 40mL | Calcium carbonate | As much as needed | Pestle and mortar | 1 | Electronic balance | 1 | Scissors | 1 | Ruler | 1 | Measuring cylinder (15mL) | 1 | Beaker (50mL) | 1 |
Table 2 shows the apparatus and materials used in this experiment
METHOD
Preparation of spinach pigment extract: 1. 10g of fresh spinach leaves ( without the veins ) is taken and is placed into a mortar. 2. A pinch of calcium carbonate is added into the mortar. The pestle is used to grind the leaves and calcium carbonate until it forms a paste 3. 20mL of pure acetone is added and the mixture is stirred until a dark green solution is formed 4. The concentrated pigment extract is separated using a strainer
Preparation of chromatogram: 5. A piece of filter paper is cut so that it is narrow enough to fit down a boiling tube without hitting the sides. The chromatography paper is cut as it should almost touch te tio of the boiling tube when suspended from the secure stopper hook 6. A capillary tube is used to make a dark spot of pigment extract on the paper, approximately 2.5 cm from the bottom tip. The electric hair dryer is used to dry the spot between applications. The darker your spot, the better your results. 7. 1.5mL chromatography solvent is added to the bottom of your boiling tube 8. The chromatography paper is placed straight into the boiling tube, th tip of the chromatography paper will be immersed, but not the pigment spot. 9. The stopper is secured and the chromatogram is allowed to run. When the solvent is within 2 cm of the top of the paper, the paper is removed and the point where the solvent front reached is marked with a pencil and is left to dry. 10. The solvent is disposed in the solvent waste container. 11. The pigments band are identified by their colours and relative positions on the chromatogram. The pigment’s front is marked with a pencil 12. The distance travelled by the solvent and each of the pigments are measured. The Rf values for each pigment is calculated and recorded. 13. The experiment is repeated using 10g of fresh solnostemon hybrid leaves

DATA COLLECTION
Qualitative Data 1. The spinach paste is a thick green solution 2. The solnostemon hybrid paste is a thick dark red solution 3. The acetone is a cool solution that evaporates as soon as it is in a small quantity 4.
Quantitative Data Data Processing Rf = the distance travelled by the pigments from original spot / the distance by the solvent

DISCUSSION

CONCLUSION AND EVALUATION

Limitations | Suggestions | | |
Table 5 shows the limitations and ways to overcome these limitations in this experiment
REFERENCE
Biology HL Student’s Handbook, 12th Edition, Page 194 - 196
Biology for the IB Diploma, Hodder Education, C.J.Clegg, page 44