The Efficiency of Chloroplast - Essay Example

Bio Comprehensive Essay Plants are the primary producers. They are the primary source of food of animals. They can produce there own food called starch from the process they do called photosynthesis. Photosynthesis is only possible if the ingredients are complete. Among these ingredients needed are sunlight, water, and carbon dioxide. There are organs of plants that are responsible for absorbing these ingredients. The cell responsible for the absorption of light is is the chloroplasts. The structure of these organelles is composed of double modified membrane where it houses the chlorophyll, proteins, and lipids. Its inner layer invaginates and form thylakoid disks that are arranged in stacks called "grana" where chlorophyll is concentrated and so with other pigment absorbing organs. The membranes are very much important in the process of photosynthesis of plants because it is where the organelles responsible for absorbing light (chlorophyll in chloroplast) are suspended or being housed One way to measure the efficiency of chloroplast when it is intact is through Fluorescence. This will be able to measure the chlorophyll in the flourimeter. The spectrum of fluorescence is different to that of absorbed light, with the peak of fluorescence emission being of longer wavelength than that of absorption. Therefore, fluorescence yield can be measured by exposing a leaf to light of defined wavelength and measuring the amount of light re-emitted at longer wavelengths. When transferring photosynthetic material from the dark into the light, an increase in the yield of chlorophyll fluorescence happens over a time period of around 1 s. This increase has then been explained as a consequence of reduction of electron acceptors in the photosynthetic pathway, downstream of PSII, notably plastoquinone and in particular, QA. Once PSII absorbs light and QA has accepted an electron, it is not able to accept another until it has passed the first onto a succeeding electron carrier (QB). During this period, the reaction centre is said to be 'closed'. At any point in time, the occurrence of a fraction of closed reaction centers leads to an overall reduction in the efficiency of photochemistry and so to a matching increase in the yield of fluorescence. Our body part is made up of cells. These cells multiply in a process called cell division. If the division of the cells is having irregularities in number tumors develops. There will be too numerous divisions of cells. But what triggers human malignant cancers is due to mutations of both signal transduction pathways and in the mechanisms that control the cell cycle. Signal transduction responses are responsible for gene activation, manufacturing of metabolic energy, and cell movement. It has something to do with the cell activity. It has even something to do with the modification of the cell skeleton. Since it is responsible for gene activation it leads to gene expression as proteins. Gene activation leads to further effects, since genes are expressed as proteins, many of which are enzymes, transcription factors or other regulators of metabolic activity. Because transcription factors can activate still many genes in turn, an initial stimulus can trigger via signal transduction the expression of whole suite of genes and a panoply of physiolgical events. When there is a mutation of the pathway the expresion of genes also mutates. This mutation may lead to cancers. There sequence is sometimes affected by the mutation. In every expresion like GUC for example when mutated may lead to GUA and this does not mean the same as what GUC codes for. To determine a patient with cancer caused by mutation of the tranduction signal pathway, you can conduct mutation analysis. With this, you can be able to trace if the patient's cancer is cause mainly of his/her signal transduction being mutated. Enzymes are catalysts. Mostly of these are protein based. Enzymes attach temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they decrease the amount of activation energy needed and thus speed up the reaction. Enzymes activity is affected with pH level, temperature, and even concentration of substances. There are mechanisms work to make enzyme activity well coordinated with the cell and work also efficiently. It binds and anchors to the membrane, mitochondria, and endoplasmic reticulum and in the nuclear envelop. They are fitted with a harmonious relationship with these organelles to work efficiently. To control the activity of enzymes there are Feedback inhibition, Inactive precursors, and Precursor activation. If there are enzymes that are there but not needed in the cell or are absent in the cell but are needed, these enzymes are turned on or off through transcription of genes. Phosphofructokinase is an important regulatory enzyme in glycolysis. It is an allosteric enzyme made of 4 subunits and controlled by few activators and inhibitors. This gives way to a exact control of glucose and the other monosaccharides galactose and fructose going down the glycolysis pathway. This enzyme breaks down what is considered the first "committed" step of glycolysis, since it is not only non changeable to its original form, but also deu to the original substrate is forced to proceed down the glycolytic pathway after this step. Before this enzyme's reaction, glucose-6-phosphate can potentially travel down the pentose phosphate pathway. PFK converts fructose 6-phosphate and ATP to fructose 1,6-bisphosphate and ADP. The enzyme has two sites with different affinities for ATP which is both a substrate and an inhibitor. PFK-1 is inhibited by its product, ATP and from the TCA, citrate. It is activated by high-levels of AMP, and the most potent activator is fructose-2,6-bisphosphate, which is produced by PFK-2 from the same substrate. An experiment can be conducted for PFK. You need to have a 15 grams of plant tissue from plant leaf (use spinach). With the use of mortar and pestle grind the leaf together with the 30ml extraction solution (5mM MgCl2, 5mM DTE, and 1mM EDTA adjusted to pH 7.7 with NaHCO3) containing 3 grams of PVP. Filter the solution with the use of cheese cloth, centrifuge then the supernatant should be fractioned with ammonium sulfate by dropwise addition of saturated solution of pH 8. the salt concentration should be first brought to 20% saturation and the resultant precipitate be removed by centrifugation. Further ammonium sulfate addition were designed to increase the concentration in the preparation of small increments, after each addition precipitated protiens should be collected by centrifugation and dissolve in 1 to 2 ml of extraction solution. When sample is available, add to separate lenghts of dialysis tubing and dialyse together for 3 hours in one litre of of a solution consisting of 5mM imidazole-HCl, 1mM MgCl2, 1mM DTE, and 0.5 mM EDTA (pH 7.7). Chloroplast will be isolated by homoginizing 8 grams of leaves for 5 seconds in 40 ml of the isolation medium. Homogenate should be filtered by Miracloth and centrifuge at 2500 grams for 80 seconds, then collect the pellets of chloroplast. Chloroplast extracts will then be resuspended and broken in 10 ml solution containing 0.2 g PVP and the suspensions should be combined and centrifuged at 22000 g for 20 mins, the supernatant should be taken as extract of soluble chloroplast components. PFK should be assayed. The reaction should be initiated by the addition of ATP and the activity then will be calculated from the change in extinction of 340 nm measure witht the UNICAM SP1800 spectrophotometer. The result of the activity will show that ammonium frationation ofan extract from leaves (spinach) will produce two fraction of of PFK actvity, the first stimulated by inorganic phosphate and the second inhibited by inorganic phosphate. In this activity you can conclude that most leaves contains PFK activity in the chloroplasts as well as in the cytoplasm. Work Cited: Wikipedia Encyclopedia (2006). 13 May 2006. Kelly, G. (1977). Chloroplast PFK (vol. 60(2), pp. 290-294. Plant Physio. http://www.pubmedcentral.gov/pagerender.fcgiartid=542598&pageindex=1#page Meshinchi, S., et. Al. (2003). Neoplasia (vol. 102, pp 1474-1479). American Society of Hematology. http://www.bloodjournal.org/cgi/content/full/102/4/1474 Read More