‘An Experiment to investigate the effects of an active office schema on the recall of schema-consistent and schema-inconsistent objects in an incidental memory test’
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Summary of the entire investigation (150 words)
Chlorophyll, the green pigments responsible for the notable coloration in green vegetables. Light is absorbed and reflected through these pigments contained in tissues of green vegetables. Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product. This pigment is responsible for absorbing sunlight required to produce sugar molecules, and ultimately of all biochemical, in the plant.
Chlorophyll is found in the thylakoid sacs of the chloroplast. The chloroplast is a specialised part of the cell that functions as an organelle. Once the appropriate wavelengths of light are absorbed by the chlorophyll into the thylakoid sacs, the important process of photosynthesis can begin. When a chlorophyll molecule absorbs light energy, it becomes an excited state, which allows the initial chain reaction of photosynthesis to occur. The pigment molecules cluster together in what is called a photosynthetic unit. Several hundred-chlorophyll a and chlorophyll b molecules are found in one photosynthetic unit. A photosynthetic unit absorbs light energy. Red and blue wavelengths of light are absorbed. Green light cannot be absorbed through the chlorophyll allowing light to reflect, making the plant to appear green. Once the light energy penetrates these pigment molecules, the energy is passed to one chlorophyll molecule, called the reaction centre chlorophyll. When this molecule becomes excited, the light reactions of photosynthesis can proceed. With carbon dioxide, water, and the help of specialized enzymes, the light energy absorbed creates chemical energy in a form the cell can use to carry on its processes. Under neutral conditions, chlorophyll is a pigment that’s insoluble in water and gives food a pleasant green colour. However, when observable to heat and acidic conditions, chlorophyll becomes a composite known as pheophytin, which gives food a dull olive brown colour. Alternately, when chlorophyll is exposed to heat and alkaline conditions (not pictured), it becomes a different compound, known as chlorophyllin, which is water soluble and gives food a bright green colour. Since this change causes the pigment to become water soluble, the cooking water may turn bright green as well. Chlorophyll pigments give plants their green colour, and several changes happen when a green vegetable goes into boiling water. First, a brighter green colour develops, caused by the expansion of gases and their escape from spaces between plant cells. The breakdown of these rather cloudy pockets of gas reveals the bright-green chloroplasts within the cells. A second colour change occurs in response to acidic water: The magnesium ion in the centre of the chlorophyll molecule is changed with a hydrogen atom, causing the green to dull. Chlorophyll-a becomes grey-green pheophytin-a, and chlorophyll-b turns into yellowish pheophytin-b. If the boiling water is slightly alkaline, then chlorophyll stays greener. Fried vegetables change to a duller green colour when temperatures reach 140 degrees Fahrenheit. The heat damages chloroplasts, releasing natural cell acids to turn green into olive-green.
Chlorophyll a Chlorophyll b
The major chlorophylls in plants include chlorophyll a and chlorophyll b, which occur in the approximate ratio of 3:1. Chlorophyll a has a methyl group at the C-3 carbon, while a formyl group is bonded to the same carbon atom in chlorophyll b. In addition to structural differences between chlorophyll a and b, their thermal stabilities are also different. Chlorophyll retention has been used as a measure of quality in green vegetables. Blanching inactivates chlorophyllase and enzymes responsible for senescence and rapid loss of green colour. However, chlorophyll change is initiated by damaged tissue during blanching and other processing steps. Chlorophylls are susceptible to many chemical or enzymatic degradation reactions. The simultaneous actions of enzymes, weak acids, oxygen, light and heat can lead to the formation of many variations products. There is general agreement that the main cause of green vegetable discolouration during processing is the conversion of chlorophylls to pheophytins by the influence of ph. The green colour of vegetables turns to an olive green when placed in acidic conditions. Other improvements in colour have involved the production of the more heat-stable chlorophyllides. Alkalizing agents in blanch and brine solutions, such as sodium bicarbonate, hexametaphosphate, disodium glutamate, sodium hydroxide, and magnesium hydroxide, have been used to raise the pH of green vegetables and therefore, retain chlorophyll after processing. Since chlorophyll stability is known to be affected by pH and colour is one of the most important quality attributes of vegetables. Earlier research relied on the use of spectrophotometric and colorimetric techniques to determine the kinetic parameters of chlorophyll change in model systems of green vegetables. Modern instruments are essential to provide consistent measurements and quantitative data for colour which can be categorized into three broad types; visual systems, tristimulus colorimetry and spectrophotometry. In this study, the change of chlorophyll by pH was determined through using spectrophotometric parameters which measures colour by determining a reflection or transmission spectrum.
With the background information researched, the hypothesis is that at a low pH the chlorophyll pigments of Broccoli and Spinach will break down losing its colour and transforming into more paler olive green, whereas at a higher concentration of pH will retain chlorophyll of broccoli and spinach to a high standard.
Materials and Method
To determine the effects of pH on chlorophyll of Broccoli and Spinach, pH had to the independent variable therefore altering the concentration of pH consisting of chlorophyll pigments of Broccoli and Spinach allowed to obtain accurate results, also allowing to strictly follow the aim of the study. Variation of pH solutions included were; Acetic Acid (pH of), Water (Neutral – pH of 7), Ammonia (Basic – pH of 12).
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