Is Chlorophyll Necessary for Starch Production? Experiment

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.

Hazard	Precaution
Inhalation of chemicals	Stand away from chemicals when pouring and point chemicals away from anyone or anything to avoid accidental inhalation.
Heat source (Bunsen burner or Hotplate)	Do not directly touch open flame or hot plate to avoid pain and severe skin and tissue damage. Turn off heat source if not in use or needed. Turn heat on low if moving around or looking away.
Shattering of glass (beakers/test-tubes/Petri dish)	Work over/on top of workbench to avoid accidental dropping of glass equipment. Let equipment cool down before washing with cool water.
Eye and skin contact with chemicals	Keep chemicals and containers with chemicals sealed to avoid tipping onto floor or on body parts. Avoid pouring with fingers or other body parts close to chemical.

 

Independent Variable/s	Dependant Variable/s	Controlled Variable/s	Control/s
Chlorophyll	Starch (formation)	Room Temperature Water Temperature Time Recorded	White part of Variegated Leaf

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

Diagram of leaf before experiment and label

Diagram of leaf after experiment and label areas where starch formed

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.

Hazard	Precaution
Inhalation of chemicals	Stand away from chemicals when pouring and point chemicals away from anyone or anything to avoid accidental inhalation.
Heat source (Bunsen burner or Hotplate)	Do not directly touch open flame or hot plate to avoid pain and severe skin and tissue damage. Turn off heat source if not in use or needed. Turn heat on low if moving around or looking away.
Shattering of glass (beakers/test-tubes/Petri dish)	Work over/on top of workbench to avoid accidental dropping of glass equipment. Let equipment cool down before washing with cool water.
Eye and skin contact with chemicals	Keep chemicals and containers with chemicals sealed to avoid tipping onto floor or on body parts. Avoid pouring with fingers or other body parts close to chemical.

Independent Variable/s	Dependant Variable/s	Controlled Variable/s	Control/s
Light	Starch (Formation)	Room Temperature Water Temperature Time recorded	Plant left with no light exposure.

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:

Leaf Tested	Colour of leaf after boiling in Ethanol and being covered in iodine solution
Leaf with exposure to sunlight
Leaf with no exposure to sunlight

Bibliography

Source

How is this source Reliable?

Brotherton, Judith, and Kate Mudie. Heinemann Biology Preliminary. Port Melbourne, Vic.: Pearson Australia, 2009. Print.	Heinemann Biology Preliminary 3rd Edition is a student study text book issued biology by the NSW Board of Studies (the curriculum authority instituted by the government) as compulsory means of learning biology in preliminary years.
http://Csip.cornell.edu,. ‘CSIP Student Inquiry Projects – Home’. N.p., 2006. Web. 14 Mar. 2015.	Information is less than 10 years old and has years of research and many scientists working on various projects around the world, must be recognised to post information (cannot be edited or altered by public means).
JA, Kaiser. ‘Light-Dark Regulation Of Starch Metabolism In Chloroplasts: II. Eff… – Pubmed – NCBI’. http://Ncbi.nlm.nih.gov. N.p., 2015. Web. 14 Mar. 2015.	A well-known and reputable American government organisation, backed by hundreds of years of research and evidence, as well as some of the best scientists in the world providing this information.
Togasaki, Bob, and Roger Innes. Sun Light And Green Plants Feed Us All!. 1st ed. Bob Togasaki, 2010. Web. 16 Mar. 2015.	Small information book put together by 2 scientists with information referenced and crosschecked from reputable sources such as Harvard university, Oxford university and more!