The Effect of PeerTutoring and Computer Assisted Tutoring on Thesis

The Effect of PeerTutoring and Computer Assisted Tutoring on Standardized Math Scores - Thesis Example The purpose of this action research study is to determine the value of tutoring strategies in augmenting mathematical studies for junior high school students. My purpose is to study the results of two types of tutoring programs used with adolescent groups. The two tutorial groups are computer assisted instruction and peer-tutoring. Raul Yzaguirre School for Success (RYSS) is an urban charter school with a majority-minority Hispanic student population. RYSS is a Title I school with 100% of the students receiving free and reduced lunch. I am currently teaching Language Arts for the eighth grade while obtaining my administration internship. The purpose of the study is to discover the best available strategy to aid RYSS students in the improvement of their standardized test scores for mathematics. The administrative team at RYSS has approved a tutoring program for summer school students. Tutoring fits into the larger context of education because (a) tutoring helps students who are struggling while allowing them to engage in a challenging, rigorous learning experience; (b) tutoring assists students in moving toward grade level achievement, and (c) tutoring builds successful students so that they move from success to succes

GDP of the United States Assignment Example | Topics and Well Written Essays - 2500 words

GDP of the United States - Assignment Example The United States economy, with regard to recent trends, therefore, should be going forward and getting better. However, the United States is trying to recover due to the fact that the trend is not going as expected, and the question of why America down remains to be answered (Cobb, 1995) is. As regards to above trends in the current account as a percent of united states GDP, of 1980-2010, it is clear that the GDP rates keep fluctuating as it did in past recessions in the United States. According to the Bureau of Economic Analysis (BEA), the real gross GDP recorded an annual increase rate of 1.8 percent in the third quarter of 2011 (News Release, 2011). This trend of increase from the second to the third quarter has been a notable release by the Bureau of economic analysis. The second quarter of the year 2011 saw the real GDP increase by 1.3 percent. The gross domestic product refers to the output of goods and services that labor and property located in the United States produce (News Release, 2011). In the United States, the gross domestic product (GDP) growth rate is an essential component of the economy. For this case, the future of the economic activity is predicted by the yield curve slope and the spread between the interest terms (News Release, 2011). This is because the shifts of the slope are key determinants and indicators of high and low GDP growth. In determining GDP, there are three different approaches, which must carry out similar results. Therefore, the â€Å"total value of production†, the â€Å"total value of income† and the total value of expenditure should reflect equilibrium or simply be equal (News Release, 2011). The first method involves deriving a residual value and is referred to as the production approach (Krugman, 2001). Production approach involves taking an estimate of each industry’s gross output from other industries, and this is used to derive each industry’s residual value.

Karl Marx- Manifesto of the Communist Party Essay

Karl Marx- Manifesto of the Communist Party - Essay Example ried on an uninterrupted, now hidden, now open fight, a fight that each time ended, either in a revolutionary constitute of society at large, or in the common ruin of the contending classes† (Marx). Accordingly, Karl Marx viewed societal structures as comprising effectively two components; namely the â€Å"bourgeoisie and the proletariat† in asserting that â€Å"our epoch, the epoch of the bourgeoisie, possesses, however this distinct feature: it has simplified class antagonisms. Society as a whole is more and more splitting up into two great hostile camps, into two great classes directly facing each other - bourgeoisie and proletariat† (Communist Manifesto, 1848). To this end, the underlying proposition of the Communist Manifesto is that the social class struggle under the capitalist social paradigm, whilst creating oppression of the â€Å"proletarians†, ultimately lends itself to the demise of capitalism through revolution. Indeed, Linklater posits that â€Å"the structure of world capitalism guaranteed the emergence of the first authentically universal class which would liberate species from the consequences of estrangement between states and nations† (In Devetak et al, 2007 66). Moreover, Larson et al refer to the argument that socialists embraced the task of working class mobilisation and that â€Å"the perspectives which socialist theorists can be divided are revolutionary trade union activity and revolutionary transformation of capitalist society (Larson et al, 38). On the one hand, if we consider this in terms of the contemporary socio-economic framework; continuous evolution of social structures and demise of entrenched class barriers would suggest that Marx’s â€Å"bourgeoisie and proletariat† class model may be redundant and therefore should be viewed as solely contextually in terms of the socio-political backdrop influencing Marx’s theory at the time (Bottomore 23). For example, Bottomore highlights that â€Å"changes in working class politics during

The Spread of Islam in the Middle East Essay Example for Free

The Spread of Islam in the Middle East Essay The Muslim Perspective   Islam is the religion of all prophets of God, including Adam, Abraham, Lot, Moses, Jesus, and Muhammad.   Born in Mecca, Muhammad is known among Muslims as the final messenger of God to have brought a divine book on earth for the guidance of humanity.   Moreover, he is the reviver of Islam, rather than its founding father.   Ã‚  Ã‚  Ã‚   At the time of Muhammad’s birth in Mecca, Arabia was going through a period called the Age of Ignorance.   The followers of Abraham’s faith had turned to idol worship, and turned the Holy Ka’aba into a house of idols which they circumambulated naked.    Tribal feuds were very common; bloodshed was not rare.   Moreover, the society of Arabia at the time looked down upon women so much so that its people buried their baby girls alive.   Crime flourished, and there was no hope of bringing justice into the existing order.   Ã‚  Ã‚  Ã‚   Muhammad grew up among idol worshippers, who referred to him as Sadiq (Truthful) and Amin (Trustworthy).   At the age of forty, the man was visited by Archangel Gabriel who informed me about the new message of God to be revealed to Muhammad in order to revive the faith of Abraham once again. This message was the same as that received by the messengers before Muhammad.   The most important tenet of the faith was that there is no god except Allah (translated in Arabic as The God); and nobody else has any right to be worshipped.   The rest of the Ten Commandments were also included as the basic principles of faith.   Humanity, through Muhammad’s revival of Islam, was reminded to do good deeds, to stop killing unlawfully, to honor the parents, to stay away from adultery and fornication, and to expect final judgment and the afterlife in either heaven or hell.   Ã‚  Ã‚  Ã‚   With its social ills, the society of Arabia required reform at the time that Muhammad received the message of God.   Many people, upon hearing Muhammad’s message in Mecca, embraced Islam.   The prophet also sent some of his followers to other cities of Arabia in order to spread the message.   Once again, he was joined by a lot of people who embraced the faith and accepted him as a God-sent guide on earth.   Ã‚  Ã‚  Ã‚   Muhammad was also visited by some of the people from Medina, previously known as Yathrib.   These people wholeheartedly accepted Islam, before Muhammad moved to their city faced by severe trials in Mecca.   Such trials were posed by the idol worshippers of Mecca who insisted on continuing to worship idols as well their practices from the Age of Ignorance.   Even when Muhammad had moved to Medina, the idol worshippers of Mecca kept on harassing him and his followers.   This led to various battles between the forces of God and Muhammad, and those of the infidels.   Ã‚  Ã‚  Ã‚   Muhammad and his followers were often victorious on the battlefield.   Although they lost much at the same time, their main force was Allah who never let them give up in the face of trials.   By the time Muhammad conquered Mecca, the Muslims alongside Muhammad had become a tremendous power. As a matter of fact, the prophet of God conquered Mecca without bloodshed.   The awe that he had inspired in his enemies was enough to allow him and his followers a peaceful reentry into the city of the Ka’aba.   Many of Muhammad’s enemies also embraced Islam.   Historians inform us that even his enemies were thoroughly impressed by Muhammad’s personality, and especially his sense of forgiveness.   Ã‚  Ã‚  Ã‚   Muhammad expired soon after the conquest of Mecca.   His followers, having spent time with a great role model, continued to fight battles against the infidels who provoked them.   Furthermore, the prophet’s followers continued to move to far and distant places to spread the message of Islam.   Ã‚  Ã‚  Ã‚   Muhammad’s followers entered many lands in the Middle East as conquerors and rulers.   After settling in new lands in the Middle East, they showed by example the humane treatment of peoples that Muhammad himself had shown them.   Countless people embraced Islam in the Middle East, although they were never forced to do so, given that Islam prohibits the use of force to spread the message of God.   Ã‚  Ã‚  Ã‚   Muslim conquests were always for the cause of God’s faith.   Hence, Umar, one of the four chiefs or caliphs of Islam after Muhammad, took Muslim armies to invade Palestine and Mesopotamia.   Muslim armies under Umar also won a crushing victory over the Byzantines.   This paved the way for them to conquer Egypt and Syria.   Following a victory over the Sassanid Empire, Umar and his followers also overwhelmed the Persians in Mesopotamia. The Non-Muslim Perspective Although Muhammad had a great personality, his faith was essentially spread by the sword.   Muhammad only claimed that he was God’s messenger by taking notes from the Holy Bible.   Moreover, his followers conquered many lands because they were greedy for power.   People in the Middle East who came to be ruled by Muslim invaders had no choice but to accept Islam, given that the Muslims inspired fear into the non-Muslims.

Media, Sexuality And Teenagers

Media, Sexuality And Teenagers Youths living in the 21st century spend inordinate amounts of time with the media. They laugh with characters who are funny; they viciously attack and destroy evil creatures as they play their favorite video games; they see advertising for candy, makeup, and even liquor; they listen to rap lyrics about sex and violence; and they interact with people all over the world online. Needless to say, it is a completely different social world than the one their parents and grandparents faced during childhood and therefore, the effect media has on teenagers is overpowering. In constant contact with the media, Teenagers today are faced with often conflicting and confusing messages about how they are supposed to behave sexually. While adults, schools, and religious institutions are still reluctant to provide sexuality education for adolescents, the mass media is not at all reticent, portraying sexual behavior as riveting, common in everyday life, emotionally and physically risk free. Undoubtedly , the sexuality presented in the media has had a significant effect on the behavior of modern day teenagers, making the confusion between media and reality and the perception that teens have on reality. Considering the effect media has on adolescents. First of all, it must be recognized that over time, the amount of sexual content that is shown in the media has increased remarkably at a swift rate. Media and its leniency to what may or may not be shown or heard publicly have increased a great amount over the years. A study showed that Pornography is big business, generating $13 billion just in the U.S. in 2006 (IT Facts, 2007). Although sex magazines have greatly declined in circulation since the mid-1990s, that drop has been more than compensated for by video sales and rentals, cable and pay-per-view TV, and especially the explosive growth of Internet pornography, producing over 20% of the total revenue in 2006. (Bryant 305) Even the media that is meant for children is being tampered with and contaminated with information that most children do not and should not know. The book, Children, Adolescents, and the Media states that On television each year, American children and teenagers view nearly 14,000 sexual references, innuendoes, and behaviors, few of which (less than 170) involve the use of birth control, self-control, abstinence, or responsibility. (Strasburger 213) Adolescents today have too easy access to the variety of media and therefore, are more susceptible to any inappropriate or sexual content than their parents. There are four major sources of media that children and teenagers are exposed to. These are the shows that they view on television, the music, the games, and the Internet. When adolescents are exposed to this various media, they have a tendency to choose media and interact with it based on who they are or who they want to be at the moment. The assumptions of media uses are similar to gratifications theory, which suggests that media consumers come to the media with different needs and motives and that what they take away from the media will depend on why they came to it. (Brown 9) Moreover, what those adolescents learn also varies according to the adolescents sense of self-identity and lived experience. Since these teenagers are undergoing the crucial moment in their lives, shaping their own ego and identity and extremely vulnerable to all this tremendous amount of information from the media, what they choose to absorb from the media and what is sensational and stimulus in the media can be very influential. The exaggerated or distorted image of sex in the media is omnipresent and detrimental to adolescents who are not fully prepared to distinguish betwe en reality and situation that can only happen an unreal world, such as television show. One of the most influential media that affects teenagers is television. Many studies have documented televisions ability to transmit information and to shape attitudes. Television influences adolescents perception of social behavior and social reality. Television may offer teenagers a guideline for sexual behavior that they might not be able to observe anywhere else. Television stations such as Disney Channel, Nickelodeon or even Cartoon Network have been intensified and marketed in a way so that older children would continue to watch these channels. By doing this, the younger children who have initially always watched the shows are exposed to things that they shouldnt be experiencing. The most recent content analysis of television found that more than 75% of prime-time kids shows on the major networks contain sexual content, but only 14% of incidents include any mention of the risks or responsibilities of sexual activity or the need for contraception. This figure rises to 27% for sh ows depicting or implying intercourse. (Kunkel, Eyal, Finnerty, Biely, Donnerstein) Television is definitely one of the sources of media which convey wrong image of sex. Television has a tremendous impact on the behavior of children and teenagers over time by giving them improper knowledge of sex. The media and the amount of sexual and violent content that is allowed to be shown not only on childrens stations but on stations that are meant to be viewed as families have increased a lot. An example of this is just the commercials that are advertised on television. Even on channels such as Nickelodeon, advertisements that are shown are not necessarily appropriate for children. It is known that Nickelodeon guides children towards MTV by featuring artists whose music and actions are inappropriate for young children in concerts and in Kids Choice Awards. (McEntire) A major part of television is also music channels, such as MTV and many more. These channels are the most universally watched channels by teenagers both male and female. On these channels, there are not only reality shows in which they show characters as violent and show sex as accepted, but the re are many music videos which show many images of sex and violence. An example of reality shows on music channels are The Real World and Laguna Beach on MTV, or shows such as Jersey Shore, in which the main character was a girl who was known because of being a stripper and having pictures on MySpace with revealing clothes. On VH1 there are shows such as Flavor Flave in which a retired rapper is perused by many young women or I Love New York where a young, ignorant acting female is trying to be won over by many men. In these shows, there are many illustrations of promiscuous actions that were not necessarily sex, but may have led up to sex by what is shown in the show. However, music videos by themselves are a serious issue with the media. A surprising amount of illustrations of sex are shown in music videos, which were reported in the article by McEntire that said, The average music video contains 93 sexual situations per hour. This includes eleven scenes actually depicting interco urse or oral sex. (McEntire) These numbers are alarming, and to know that these are the programs that almost all teenagers view on a daily basis is upsetting. As Television has become increasingly sexually explicit, Music plays a large part in the media affecting teenagers and their behavior. Many different types of music, such as Rap, Hip Hop, and Rock music are mainly directing its sales to the younger generation of people. The lyrics of these songs portray sex and violence. In many of these songs, they downgrade the worth of women and promote violence as it should be accepted. When the younger generation listens to these messages, as it is played repeatedly they begin to believe that it is the way that they should act, and lose sight of reality. In these songs, they also encourage the use of illegal substances to the younger generation such as drugs or Alcohol. An article proves that As the popularity of music among youth grows, the number of teens who are becoming more violent, more sexually active and who are experimenting which drugs is steadily increasing. (Keshan) Teenagers who listen to large amount and genres of music are less li kely to be affected by the messages depicted in the music but those who mainly listen to one type of music are more likely to take in the message given out in this music. The particular genres of Rap, Hip-Hop and Rock and Roll have a large impact on the behavior of young females, especially those of the African-American and His panic races. A study shows that Girls who watch 14 hours or more of rap music videos are more likely to engage in unsafe sex with multiple partners and get a STD. (McEntire) Just like most teenagers never take off their head phones playing their favorite music, video games are played by all ages of children, from little toddlers who are starting out learning letters or how to count to the older teenagers who play games with more detail and different situations. Video games over time have gotten more violent with content that is not appropriate for teenagers. From games of racing and sports such as football or baseball, to games that involve shooting and killing as if it was normal. These games do not only affect the behavior of teens, but they desensitize the future generations and how they depict violence. Furthermore, the worst thing is that they include sexual images such as naked women and strippers roaming a town or even raping scene as a mission. These games provoke teenagers to have strong desire to try out those distorted sexual images in reality. Grand Theft Auto is a game that is popular among teenagers, especially boys. A study depicts that Gr and Theft Auto: Vice City, a video game rated M, was the best selling game among teens in 2002. In the game, players can simulate having sex with a prostitute and then killing her. (Greenspan) This is just one example of many ways that violence and sexuality can be shown in multiple different video games. These games are mainly marketed to males, between the ages of 13 and 17 who would be more likely to go out and ask for a game containing violence or cars. Although this game is marked as M for mature, many parents wouldnt know or check for the rating of a video game when purchasing the game for their child. Although adolescents enjoy their pastime playing video games, the largest source of information that teenagers spend most of their time doing would to be the internet. With search engines such as Google, it is possible to find any information that may want to be discovered, whether it is appropriate or not. However, this exposure to inappropriate content is not always by the free will of the person sitting behind the screen. According to a study shown in 2006 à ¢Ã¢â€š ¬Ã‚ ¦.increased proportions of youth internet users were encountering unwanted exposures to sexual material and online harassment, but decreased proportions were receiving unwanted sexual solicitations (Online Victimization of Youth) which basically means that while being on sites that they had business being on, ads and pop-ups that were not necessarily appropriate appeared on the screen. This is the case on many children sites, such as Nickelodeon.com or NickJr.com. These advertisement and pop-ups which are mostly ab out pornography and mortgage increase teenagers curiosity and lead them to explore those inappropriate sites. All these contents in television, music, game, and internet, enhancing adolescents lust and injecting wrong perception of sex into teens affect the behavior of them and eventually lead to social catastrophe. A study manifests that Teens who see and hear a lot about sex in the media may be more than twice as likely to have early sexual intercourse as those who are rarely exposed to sexual contentà ¢Ã¢â€š ¬Ã‚ ¦ and à ¢Ã¢â€š ¬Ã‚ ¦12 to 14-years old exposed to the most sexual content in movies, music m magazines, and on television were 2.2 times more likely to have had sexual intercourse when re-interviewed two years later than their peers who had a lighter sexual media diet. (Lagorio) This has agitated the mindsets of young children, primarily in America. Teen pregnancies over the past 10 years have been largely affected by the change in censorship in the media. As the amount of sexual content increased in the media, the amount of teen pregnancies or children having children has elevated proportionally. With the portrayal of teenagers having children in shows such as The Secret Life of an American Teenager in which the main character is a girl who is pregnant, the idea of teenage girls getting pregnant is becoming more accepted and more common. This girl carrying a child in the television show is only depicted as a fifteen years old, and although she is carrying a child she still maintains a child-like innocence herself, which emphasizes the fact that she is only a child carrying another chilled. This however, is not only the case in television shows. Many girls between the ages of 14 and 17 are turning out pregnant, although it is obvious that they arent capable of supporting a child on their own. Since the statistic of young girls h aving babies has skyrocketed, many public school systems have felt the need to add Daycare Units into the schools so that they can promote the teenage mothers staying in school, and having free care for their child while they continue to get an education. This all comes back to the media, which is unmonitored for the most part, and promotes messages of sex, and becoming caught in a sensual moment, which would result in a lack of protection because of no preparation. When sex is illustrated in many television shows, they make it as though the couple has sex without needing protection such as condoms. All these uncensored information from the media bring out a huge social consequence in a long term. The media, at large, does have an effect on the beliefs and behaviors of teenagers over a long period of time. In a society that limits access to sexual information, teenagers will look to the media for answers to their questions. More important, the media may have a strong effect on teens without their even being aware of it, especially those whose parents do not instill in them a strong sense of family values. Although many adolescents try to get answers from the media about sex, unfortunately the media answers to these questions are usually not the healthy or accurate answers. Hence, in order to prevent any further tragedy befalling to teenagers, immediate solution has to be made. One of the possible solutions that would grant youth a healthier view of sex and sexuality is that widespread advertising of birth control in mainstream media. Advertising birth control represents one means of increasing teenagers access to it. Such advertising needs to address the risks of pregnancy, not merely the superficial difference that birth control pills can make. Unless new products such as the morning-after pill are widely advertised, teenagers will not know about them or use them. Comparative studies between the United States and Europe make it clear that countries that promote the use of birth control via advertising, sex education classes, and programming are rewarded with lower rates of teen pregnancy. (Strasburger 254), yet the media remain resistant. Given that eight studies now prove that making birth control available to teenagers does not increase the risk of early sexual intercourse, there is no longer any excuse to withhold access to it. Like advertising birth control, second solution would be having a greater responsibility and accountability of mainstream media for producing healthy and accurate messages about sex and sexuality. Entertainment industry executives need to realize that, their product is educating American children and teenagers, since media have become one of the most important sources for sexual information for young people today. Besides reforming mainstream media, middle and high schools should not underestimate the sex education and inform students the fallacy in the media. This would be resulted in teenagers being less likely to overestimate sexual activity among their peers and more aware of the truth about sex and sexual imagery in the media. Third key to protect teenagers from the unhealthy information from media is to execute more and better counter advertising. Only the National Campaign to Prevent Teen and Unwanted Pregnancy has engaged in long term efforts to counterprogram through the media. Although no clear data exists about this organizations success, several successful efforts involving counter advertising against tobacco and illicit drugs with teens as the target audience through the media have been demonstrated. Fourth solution would be having a greater sensitivity of parents to the influence of the media on adolescents. Many parents often seem not to see the impact of media on their children and teenagers. The most important steps that parents can take are to set rules about TV viewing, monitor what shows are being watched, and keep TV sets out of the bedroom. The last possible solution is to conduct better research on getting statistics on the effect of the media. Considerably more research needs to be funded, use a variety of methods and a variety of populations, and will need to take into account developmental, gender, and ethnic differences. School systems and parents need to grant access to researchers, and foundations need to fund such efforts. Foundations need to recognize media research as a new and much needed priority. Society needs to accept the fact that teenagers should be able to give consent for such research on their own and that parents can be informed about ongoing studies explaining the research. Although it is apparent that the medias negative effect on teenagers is catastrophic, we can take these resolutions discussed above and make adolescents prepared for unhealthy information from the media and enlighten them that some of sex and sexuality expressed in the media are false. Work Cited Brown, jane, Steele, Jeanne, and Walsh-Childers, kim. Sexual teens, sexual media: investigating medias influence on adolescent. Mahwah, New Jersey: Lawrence Eribaum Associates, Inc. Publishers Bryant, Jennings, and Mary Oliver. Media Effects: Advances in Theory and Research. 3rd ed. New York, NY: TaylorFrancis, 2009. Greenspan.Sam. How the Silver Screen Affects Your Teen. 2004, 10 Feb 2010 Hart, Eileen. Teens, Sex, and Media. 2002, 15 Jan 2010 Lenhart, Amanda. Teens and Social Media. 19 Dec 2007 InternetAmerican Life Project. 17 Feb 2009 Lagorio, Christine. Media May Promt Teen Sex. 03 Apr 2006 17, Feb 2009 McEntrie, Teresa. The Prevalence And Effects of Sex In The Media. 2002 Strasburger, victor. Children, Adolescents, and the Media. Thousand Oaks, California: SAGE Publications, inc, 2009.

The Ethics of Nanotechnology Essay -- Nanotechnology Science Research

The Ethics of Nanotechnology Introduction Imagine a world in which cars can be assembled molecule-by-molecule, garbage can be disassembled and turned into beef steaks, and people can be operated on and healed by cell-sized robots. Sound like science fiction? Well, with current semiconductor chip manufacturing encroaching upon the nanometer scale and the ability to move individual atoms at the IBM Almaden laboratory, we are fast approaching the technological ability to fabricate productive machines and devices that can manipulate things at the atomic level. From this ability we will be able to develop molecular-sized computers and robots, which would give us unprecedented control over matter and the ability to shape the physical world as we see fit. Some may see it as pure fantasy, but others speculate that it is an inevitability that will be the beginning of the next technological revolution. Laboratories, such as the Stanford Nanofabrication Facility (SNF), have already been researching nanofabrication techniques with applications in fiber optics, biotechnology, microelectromechanical systems (MEMS), and wide variety of other research fields relevant to today's technology. MEMS, "tiny mechanical devices such as sensors, valves, gears, mirrors, and actuators embedded in semiconductor chips", are particularly interesting because they are but a mere step away from the molecular machines envisioned by nanotechnology. MEMS are already being used in automobile airbag systems as accelerometers to detect collisions and will become an increasing part of our everyday technology. In 1986, a researcher from MIT named K. Eric Drexler already foresaw the advent of molecular machines and published a book, Engines of Creation, in ... ...searchers in this field put together an ethical set of guidelines (e.g. Molecular Nanotechnology Guidelines) and follow them, then we should be able to develop nanotechnology safely while still reaping its promised benefits. References Drexler, K. Eric Engines of Creation. New York: Anchor Books, 1986. Drexler, K. Eric Unbounding the Future. New York: Quill, 1991. Feynman, Richard P. There's Plenty of Room at the Bottom. 03 March 2002. http://www.zyvex.com/nanotech/feynman.html The Foresight Institute. 03 March 2002. http://www.foresight.org/ Institute for Molecular Manufacturing. 03 March 2002. IMM.org National Nanotechnology Initiative. 03 March 2002. http://www.nano.gov/ Thibodeau, Patrick. "Nanotech, IT research given boost in Bush budget". 03 March 2002. (April 11, 2001) CNN.com [Definitions]. 03 March 2002. Whatis.com

Light Reactions and Plant Pigments

The Effect of Light Reactions on Plant Pigmentation Alyssa Martinez AP Biology 4th pd E. Perkins Abstract In this lab, we were to separate pigments and calculate Rf  values using plant pigment chromatography, describe a technique to determine the photosynthetic rate, compare photosynthetic rates at different light intensities using controlled experiments and explain why rate  of photosynthesis varies under different environmental conditions. In the second part of the lab, we used chloroplasts extracted from spinach leaves and incubated then with DPIP and used the dye-reduction technique. When the DPIP is reduced and becomes  colorless, the resultant increase in light transmittance is measured over a  period of time using a spectrophotometer. If pigments are separated, then Rf values can be determined. Introduction Paper chromatography is a  useful technique for separating and identifying pigments and other molecules from cell extracts that contain a  complex mixture of molecules. As solvent moves up  the  paper, it carries along any  substances dissolved in it. The more soluble, the further  it travels and vice-versa. Beta carotene is  the most abundant carotene in plants and is  carried along near the solvent front since it is very soluble and  forms no hydrogen bonds with cellulose. Xanthophyll contains oxygen and is found further from the solvent front since it  is less soluble in the solvent and is  slowed down by hydrogen  bonding to cellulose. Chlorophyll a is  primary photosynthetic pigment in plants. Chlorophyll a, chlorophyll b, and carotenoids capture light energy and transfer it to  chlorophyll a at the reaction center. Light is  part of a continuum of radiation or energy waves. Shorter wavelengths of energy have greater amounts of energy. Wavelengths of light within the visible spectrum of  light power  photosynthesis. Light is absorbed by leaf  pigments while electrons within each photosystem are boosted to a higher energy level. This energy level is  used to produce ATP and reduce  NADP to NADPH. ATP and  NADPH are then used to  incorporate CO2 into organic molecules. In place of  the electron accepter, NADP, the compound DPIP  will be substituted. It changes chloroplasts from blue to colorless. Methodology Obtain a 50 ml graduated cylinder which has about 1 cm of solvent at the bottom. Cut a piece of  filter paper which will be long enough to reach the solvent. Draw a line about 1. 5 cm from the bottom of the paper. Use a quarter to extract the pigments from spinach leaf cells and place a small section of leaf on top of the pencil line. Use the ribbed edge of the coin to crush the leaf cells and be sure the pigment line is on top of the pencil line. Place  the chromatography  paper in the cylinder and cover the cylinder. When the solvent is about 1 cm from the top of the paper, remove the paper  and immediately mark the location of the solvent front before it evaporates. Mark the bottom of each pigment band and measure the distance each pigment migrated from the  bottom of the pigment origin to the bottom of the separated pigment band and record the distances. Then, turn on the spectrophotometer to warm up the instrument and set the wavelength to 605 nm. Set up an incubation area that  includes a light, water flask, and test tube rack. Label the cuvettes 1, 2, 3, 4, and 5, respectively. Using lens tissue, wipe the outside walls of each cuvette. Using foil paper, cover the walls and bottom of cuvette 2. Light should not  be permitted inside cuvette 2 because it is a control for this experiment. Add 4 mL of distilled water to cuvette 1. To 2, 3, and 4, add 3 mL of distilled water and  1 mL of DPIP. To 5, add 3  mL plus 3 drops of distilled water and 1mL of DPIP. Bring the spectrophotometer to zero by adjusting the amplifier control knob until the meter reads 0% transmittance. Add 3 drops of unboiled chloroplasts and cover the top of cuvette 1 with Parafilm and invert to mix. Insert cuvette 1 into  the sample holder and adjust the  instrument to 100% transmittance. Obtain the unboiled chloroplast suspension, stir to mix, and transfer 3 drops to cuvette 2. Immediately cover and mix cuvette 2. Then remove it from the foil sleeve and  insert it into the spectrophotometer's sample holder, read the percentage transmittance, and record it. Replace cuvette 2 into the foil sleeve,  and place it into the incubation test tube rack and turn on the flood light. Take and record additional readings at 5, 10, and 15  minutes. Mix the cuvette’s contents before each reading. Take the unboiled chloroplast suspension, mix, and transfer 3 drops to cuvette 3. Immediately cover and mix cuvette 3 and insert it into the spectrophotometer's sample holder, read the percentage transmittance, and record. Replace cuvette 3 into the incubation test tube rack. Take and record additional readings at 5, 10, and  15 minutes. Mix the cuvette's contents just prior  to each readings. Obtain the boiled chloroplast suspension, mix, and transfer 3 drops to cuvette 4. Immediately cover and mix cuvette 4. Insert it into the spectrophotometer's sample holder, read the percentage transmittance, and record it. Replace cuvette 4 into the incubation test tube rack and take and record additional readings at 5, 10, and  15 minutes. Cover and mix the contents of cuvette 5 and insert it into the spectrophotometer's sample holder, read the percentage transmittance, and  record. Replace cuvette  5 into the incubation test tube rack and take and record additional readings at 5, 10, and 15 minutes. Results Table 4. 1: Distance Moved by Pigment Band (millimeters) Band Number| Distance (mm)| Band Color| | | | | | | | | | | | | | | | Distance Solvent Front Moved ____ (mm) Table 4. 2: Analysis of Results __ = Rf for Carotene (yellow to yellow orange) __ = Rf for Xanthophyll (yellow) __ = Rf for Chlorophyll a (bring green to blue green) __ = Rf for chlorophyll b (yellow green to olive green) Table 4. 4: Transmittance (%) Time (minutes) Cuvette| 0| 5| 10| 15| 2 Unboiled/Dark| | | | | 3 Unboiled/Light| | | | | Boiled/Light| | | | | 5 No Chloroplasts/ Light| | | | | Analysis of Results Graph Discussion Chromatography  is  a  technique  used  to  separate  and identify pigments and other molecules from cell extracts that contain a complex mixture of molecules. This can be used to identify the pigments that are used in the  process of  photosynthesis. Photosynthesis is the process by which plants use light energy to produce chemical  energy in the form of food. This is where plant pigments come into play because they are the reason why the plant is able to absorb light. Chlorophyll a is one such  pigment. These pigments along with many others are contained in organelles known as chloroplasts. One of the problems encountered during the course of this lab included human error when using the spectrophotometer. The student made slight errors when setting the transmittance to the required levels. On a few occasions, the group accidentally introduced light into a cuvette where the variable being tested was the absence of light. This might have caused some error when taking measurements of the percentage  of transmittance. This resulted in skewed data, which meant that the experiment had to be repeated once more. During the first part of the  lab, the group made an error by allowing some part of the pigment  to be in the solvent. This did alter our results in the end. Topics for Discussion 4A: Plant Pigment Chromatography 1. What factors are involved in the separation of the pigments? The factors involved in the separation of the  pigments  from the  spinach plants  are the pigments’ solubility in the solution, how much they bind to the paper based on their chemical structure, and the size of the pigment particles. . Would you expect the Rf value of a pigment to be the same if a different solvent were used? Explain. No I would not expect the Rf values to be different because the pigments will dissolve differently in different types of solvents. For example, chlorophyll b is very soluble in hydrophobic solutions, so if the crushed spinach cells on the paper were put in a hydrophobic s olution, the chlorophyll b would move the highest and probably be right on the solution front, while the other pigments will move much less. 3. What type of chlorophyll does the reaction center contain? What are the roles of the other pigments? Chlorophyll a is in the reaction center, and the other pigments are able to absorb light from the other wavelengths that chlorophyll a cannot absorb light from, and then they transfer the energy harvested from the other wavelengths to the chlorophyll a, providing more energy to be used in photosynthesis. 4B: Photosynthesis/The Light Reaction 1. What is the function of DPIP in this experiment? DPIP is the electron acceptor in this experiment (instead of NADP which is what is normally used in plants). The electrons boosted to high energy levels will reduce the DPIP, which will change its color from blue to clear as more high energy electrons are absorbed by it. 2. What molecule found in chloroplast does DPIP â€Å"replace† in this experiment? It replaces NADP molecules that are found in chloroplasts. 3. What is the source of the electrons that will reduce DPIP? The electrons come from the photolysis of water. 4. What was measured with the spectrophotometer in this experiment? The light transmittance was measured, which really was the measure of how much the chloroplasts reduced the DPIP 5. What is the effect of darkness on the reduction of DPIP? Explain. Darkness will restrict any reaction to occur. 6. What is the effect of boiling the chloroplasts on the subsequent reduction of DPIP? Explain. By boiling chloroplasts, we denature the protein molecules, ending the reduction of DPIP. 7. What reasons can you give for the difference in the percent transmittance between the live chloroplasts that were incubated in the light and those that were kept in the dark? The percent transmittance grew to steadily higher numbers as the experiment progressed because the light reaction was able to occur. However, the dark cuvettes had stable levels of transmittance because light is necessary to excite electrons, which, in turn, reduces the DPIP. 8. Identify the function of each of the cuvettes. Cuvette 1: Used as the control Cuvette 2: Used to observe the rate of photosynthesis without light Cuvette 3: Used to observe the rate of photosynthesis with light Cuvette 4: Used to observe the rate of photosynthesis in boiled chloroplasts Cuvette 5: Used to observe the rate of photosynthesis