Natwerk Designs

Help Designing Experiment for Photosynthesis?

I need ideas. I need to design a scienctific experiment to determine the effect of one of the variable which is temperature, wavelength of light, or light intensity. How would I measure it, and the expected result, plus control.

Public Comments

1. Okay, first a little info on the nature of photosynthesis---From the book, THE HANDY BIOLOGY ANSWER BOOK, ISBN 1-57859-150-3 WHAT IS THE FUNCTION OF CHLOROPLASTS? Chloroplasts ... functional units ... photosynthesis takes place ... green plants use light energy ... synthesis of organic molecules from carbon dioxide and water ... oxygen released as a by-product. ... contain the green pigment chlorophyll ... traps light energy .... ... chloroplasts ... bigger than any other organelle except the nucleus .... WHAT ARE THE MAIN COMPONENTS OF CHLOROPLASTS? Chloroplasts have outer and inner membranes .... ... have a closed compartment of stacked membranes ... called grana .... A chloroplast may contain one hundred or more grana, and each granum may contain a few to several dozen disk-shaped ... thylakoids that contain chlorophyll on their surface. The fluid that surrounds the thylakoid is called stroma. HOW MANY CHLOROPLASTS ARE IN PLANT CELLS? Unicellular algae may only have one large chloroplast ... plant leaf cell may have between 20 and 100. WHY IS LIGHT IMPORTANT FOR LIVING ORGANISMS? ... photosynthesis .... Light ... energy is contained in packets called photons. The energy of a photon is inversely proportional to the wavel-length of the light---the longer the wavelength, the less energy per photon. Sunlight ... spectrum of colors present in light. WHAT IS PHOTOSYNTHESIS? ... process by which plants use energy ... from light ... make food molecules from carbon dioxide and water. Photosynthesis is a dual-staged process .... ... light-dependent reaction ... first steps of photosynthesis. ... light energy derived from sunlight is converted to chemical energy. Oxygen (O2) is produced as a waste product .... The steps of the second stage ... carbon-fixation reactions ... Calvin cycle. ... a series of reactions that assemble sugar molecules from carbon dioxide (CO2) and the energy-containing products of the light reactions. Carbon fixation ... conversion of carbon dioxide (CO2) into organic compounds. HOW DO CHLOROPLASTS WORK? Chloroplasts ... capture solar energy to perform photosynthesis, the reduction of carbon dioxide to simple carbohydrates. ... series of reactons ... result in the chemical splitting of water and ... release of oxygen .... During the light phase, chlorophyll molecules absorb energy from light and their electrons become energized. The exicited electrons pass energy from one chlorophyll molecule to another, resulting in ... ATP and ... nucleic acid-type carrier ... NADPH. This molecule carries the electrons to the next stage of photosynthesis, the dark phase. The dark reactions manufacture sugars using the energy ... from NADPH and ATP. The conversion of carbon dioxide ... in the atmosphere into carbon atoms in living organisms ... called carbon fixation. HOW ARE PLANT CELLS ABLE TO USE LIGHT TO PRODUCE SUGARS? Plant cells use chloroplasts to convert light energy to chemical energy (sugar). These chloroplasts ... likely to have originated as free-living bacteria .... The energized electrons are used to build and rearrange a number of different molecules. .... DO PLANT CELLS REALLY PRODUCE OXYGEN? Yes, plant cells produce oxygen throught ... photosynthesis. Splitting water molecules to harvest their electrons causes the release of oxygen. By submerging a small piece of an aquatic plant in a beaker containing water, one can actually see the oxygen bubbles produced. HOW DO THE TWO FORMS OF CHLOROPHYLL, CHLOROPHYLL a AND CHLOROPHYLL b, PARTICIPATE IN PHOTOSYNTHESIS? ... light is absorbed by pigments .... Chlorophyll a ... primary pigment ... in all photosynthetic organisms except photosynthetic bacteria. ... carotenoids and chlorophyll b absorb light that chlorophyll a cannot absorb ... extend the range of visible light useful for photosynthesis. ------------------------------ Now that we have some "BASICS" of photosynthesis established, you can think about experiments. Here is a pretty good reference source: PHOTOSYNTHESIS http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html Why don't you design an experiment where you place a leaf sample in ionic solution (under a light source) and try to measure the electron flow as photosynthesis occurs? Maybe you could vary the light source brightness and see if that has an effect upon electron current flow. The control might be a similar leaf placed in a beaker of water, non-ionic, and see if electron current flow could be measured with change in light source intensity. Good luck.
2. When designing an experiment you need to determine what problem you want to solve....What is the effect of _____ on _________? As such, you need to identify the dependent and independent variables of the experiment. For example, "What is the effect of light on plant growth"? You then should develop a hypothesis and support your hypothesis with fact or prior knowledge. For example, "If you reduce the amount of light a plant receives, then the plant will not grow as much because plants need light for photosynthesis". You would then design an experiment to test your hypothesis. You would have a control group (plant in normal light) and an experimental group (plant in dark/reduced light). The two groups would have to contain the same type of plant, age of plant, type of soil, amount of soil and water, same temperature, type of pot etc....these are your controlled variables or constants. These things are identical in both your experimental and control groups. You would then measure the plant growth of both groups over time and record your data. You would use your data to support or reject your initial hypothesis. I would recommend this experimental design for middle school or 9th/10th grade science students. However, it can be modified to meet the needs of any student.