Is Chlorophyll Necessary for Starch Formation?

Published Date: 03 Oct 2016 Last Modified: 21 Sep 2017

Part A: Researching and Planning

Experiment 1: Is Chlorophyll necessary for starch formation? Finding out what is needed for plant cells to undergo photosynthesis, we need to test for the necessary factors in which starch forms. Glucose is what is stored as starch in the mitochondria which is broken down later as energy. It is believed that most plants need light, CO_2, chlorophyll and water to produce starch through photosynthesis.

We need to only use 2 different solutions to discover if Chlorophyll is necessary for the formation of starch; Ethanol (methylated spirits) and Iodine solution.

Aim – To determine whether Chlorophyll is necessary for starch formation.

Hypothesis – Chlorophyll is necessary for starch formation.

Materials:

• 100mL Beaker (250mL recommended if available)
• Tweezers/Forceps
• Scalpel
• Petri dish
• Iodine Solution
• Ethanol
• Bunsen burner
• Tripod
• Gauze mat Diagram 1.
• Test tube
• Water
• Variegated Leaves (different colour based on uneven distribution of chlorophyll)
• Matches
• Stopwatch/Timer (if available)

Method:

1. Set up and turn on equipment as shown in diagram 1.
2. Place variegated leaf inside of a beaker of boiling water for 2 minutes.
3. Remove leaf and cut a small square out of it. [OPTIONAL]
4. Place leaf into a test tube filled with Ethanol.
5. Place test tube of ethanol and leaf into a boiling water bath created using a beaker full of water for 2-3 minutes.
6. Remove leaf from test tube using tweezers and wash the leaves with water.
7. Place the leaf onto a petri dish containing Iodine solution; be sure to completely cover the leaf.
8. Observe the colour of the leaf after 3-5 minutes. If starch is present in the leaf, the leaf will should have changed into a blue-black colour.
9. Draw a diagram based on results, showing the areas in which starch is and is not present.
10. Repeat experiment and record and explain results for reliability.

Results Table

Experiment 2: Is light necessary for starch formation?

As [most] plants receive sunlight they constantly produce glucose and then move it outside of the chloroplast. However, plants cannot move the glucose out of the chloroplast as fast as it is synthesised. The plant then combines the glucose molecules [together] into a larger molecule called starch. Areas of a leaf that receive light are able to photosynthesize and in-turn are able to produce glucose (which becomes starch) while areas of a leaf that do not receive light should not be able to undergo photosynthesis and thus do not produce glucose ( starch). Iodine is a specific stain for starch, giving a blue-black colour if starch is present in the plant/leaf.

Aim – To determine whether light is necessary for starch formation.

Hypothesis – Light is necessary for starch formation.

Materials:

• Plant with exposure to [the] sun (light).
• Plant with no exposure to [the] sun (light).
• Bunsen Burner
• Tripod
• Gauze mat
• Matches
• Beaker
• Petri dish
• Tweezers/Forceps
• Aluminium Foil
• Water Diagram 1.
• Clips/Paper clips (to attach foil to leaves)
• Ethanol
• Iodine Solution
• Stopwatch/Timer (if available)

Method:

1. Set up and turn on equipment as shown in diagram 1.
2. Place 2 leaves inside a beaker of boiling water for 2 minutes.
3. Remove leaves and cut small squares out of each leaf.
4. Place small squares (leaves) into a test tube filled with Ethanol.
5. Place test tube of ethanol and leaves into a boiling water bath created using a beaker full of water for 2-3 minutes.
6. Remove leaves from test tube using tweezers and wash the leaves with water.
7. Place each square piece onto a petri dish containing Iodine solution.
8. Observe the colour of each leaf after 3-5 minutes. If starch is present in the leaf, the leaf will should have changed into a blue-black colour.
9. Record results in a table.
10. Repeat experiment, record and explain results for reliability.

Results Table:

Bibliography