• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Testing Starch in a (Variegated) Leaf - Lab Report

Extracts from this document...

Introduction

Aim: To test various leaves for the presence of starch Hypothesis: After the iodine reagent is added, the green areas on the leaf, where starch is supposedly present, will turn to a blue-black colour - the positive test for starch. Method: 1. Obtain your leaf and cut a small sample of your leaf; 2. Immerse the leaf samples in hot water for 1-2 minutes (depending on the size of the leaf samples) 3. Remove the leaf samples from the hot water and keep them carefully to one side. 4. Half fill a boiling tube with alcohol and place the tube in hot water until bubbles start to form in the alcohol. 5. Place the leaf samples in the hot alcohol for about 5 minutes. 6. ...read more.

Middle

Repeat experiment 11. Write observations 12. Draw conclusions Safety Procedures: * Handle the hot water bath with care * The alcohol is highly flammable; handle the test tube with care * Keep all flammable items away from the experiment. * Small samples were taken of the experiment, so that the experiment could be replicated (repeated). * The leaf was placed in hot water to remove the waxy covering (the cuticle), and to break the cell membranes, and stopping all chemical processes. * Since chlorophyll dissolves in alcohol (solvent), the alcohol is first heated as it works best at higher temperatures. * The leaf samples were placed in the hot alcohol so they could be decolourised. ...read more.

Conclusion

Conclusion: From the experiment, we can now conclude that the starch and chlorophyll was present in the same place. When the chlorophyll uses sunlight to produce glucose (as well as other products), the glucose is converted into starch for storage of sugars. This starch was present in the places of the chlorophyll, the green pigment. Also we can conclude that starch is only present when chlorophyll is present. Evaluation: The leaf was boiled to break the cell membranes, and to stop chemical processes. Although there may not have been sufficient time for this to happen, and thus the cell membranes may have just been partially broken. All of the chlorophyll from the leaf sample may not have dissolved in the alcohol, the solvent. A small amount may have remained in the leaf sample. - Rohan M ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a teacher thought of this essay

3 star(s)

This report on the starch test on leaves adequately describes the method and likely outcome of the test for green leaves grown in the light.

GCSE exam questions very rarely ask for this method but focus on investigations where the plant has been denied one factor required for photosynthesis. The writer does mention that a positive result was achieved only for the green areas of the leaf and the essay would have benefited from a discussion of variegation in plants where leaves have both green and white areas.

The writer's method is a little vague in places and would be difficult to repeat since exact details of size and temperature are omitted.

3 stars

Marked by teacher Ross Robertson 26/04/2013

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Green Plants as Organisms essays

  1. Marked by a teacher

    Biology lab - transpiration

    5 star(s)

    jelly, a fan, lamp, spray bottle, a scale, calculator, and a plastic bag. Exercise 9B: Structure of the Stem The materials needed for this exercise were a nut-and-bolt microtome, single-edge razor blade, plant stems, paraffin, 50% ethanol, distilled water, 50% glycerin, toluidine blue O stain, a microscope slide and cover slip, pencil, paper, and a light microscope.

  2. Marked by a teacher

    Year 11 Module B4 Revision notes. Plants, photosythesis, biomass and the carbon cycle.

    4 star(s)

    Water flow through plants Root hairs take in water by osmosis Root hairs give the plant a large surface area for absorbing water from the soil. There is usually a higher concentration of water in the soil than the plant so water is drawn into the root hair cell by osmosis.

  1. Marked by a teacher

    Science Investigation Into What Affects The Rate That An Aspirin Dissolves At In Water

    3 star(s)

    Surface Area I also think this investigation worked well and produced reliable results. The method was very simple, but worked well and produced clear results that enabled me to answer the original question. I think my results were quite accurate as I repeated each experiment three times for an average,

  2. Marked by a teacher

    Investigate which surface of a leaf loses more water by transpiration.

    3 star(s)

    However, both of the possible reasons that they don't are probably because of the size and weight of leaf 4. The first possibility is that the leaves can lose as much water as they want through just one surface and water stored in layers of cells on the opposite side

  1. Marked by a teacher

    transpiration lab

    3 star(s)

    The reason that an increase in temperature will cause an increase in transpiration rate is because an increase in temperature will cause more water to evaporate from the cell walls inside the leaf. This will increase the water potential gradient between the leaf interior and the outside air causing water

  2. GCSE Biology - Photosynthesis Coursework

    Here, it was in fact at a light intensity of around 950 when it seems that another factor such as temperature or carbon dioxide concentration has become a limiting factor. In my main experiment therefore, it will not be necessary to take readings above this point.

  1. Testing a leaf for starch experiment

    Conclusion: From the experiment we can now conclude starch and chlorophyll were present in the same place. The green leaf which contained chlorophyll tested positive for starch while the yellow leaf containing no chlorophyll tested negative for starch. Discussion: Photosynthesis is the process whereby chlorophyll uses sunlight to produce glucose which is then converted to starch.

  2. An Investigation into Water Loss from Plants.

    All leaves must be approximately the same size and all from the same bush to ensure continuity. * 20 test tubes: To place the shoots in and hold them in water to ensure they have a continuous supply of water.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work