Ap Biology Notes Cellular Communication Essay Example for Free

Ap Biology Notes Cellular Communication Essay Cell-to-cell communication is essential in multicellular organisms. They must communicate to coordinate activities such as growth and development, and reproduction. In addition unicellular organisms communicate with each other. Signals may use light, or touch but we will focus on chemical signals. 1. External signals are converted to responses within the cell a. Evolution of cell signaling i. In yeast a cells and ÃŽ ±cells both secrete chemicals, which can only be received by the alternate type yeast. This signals the two cells to join via fusion 1. The process by which the signal on the surface of the cell is converted to a series of steps by the cell in response is called a signal transduction pathway ii. Signal transduction pathways are very similar in yeast and in complex multicellular organisms 2. This leads scientists to believe that this pathway evolved first in ancient prokaryotes b. Local and long distance signaling iii. Local signaling 3. Adjacent cells of plants and animals may communicate through cell junctions a. Signaling substances dissolved in the cytoplasm travel between cells i. Plants = plasmodesmata ii. Animals = gap junctions 4. Animal cells may use the following b. Cell-to-cell recognition iii. Direct contact between membrane-bound cell-surface molecules iv. Important in embryonic development and immune response c. Paracrine signaling v. Uses local regulators which are released and travel only a short distance to nearby cells vi. Ex. Growth factors target nearby cells to grow and divide d. Synaptic signaling vii. Electrical signal along a nerve cell triggers a chemical release across a synapse to trigger response in target cell viii. Ex. Nerve cells iv. Long- distance signaling 5. Both plants and animals use hormones e. Animals (endocrine signaling) cells release hormones which travel in the circulatory system to target cells f. Plants hormones travel in vessels or by diffusion through the air as gas g. Hormones vary in size and shape 6. Nervous system signals can also be long distance c. The three stages of cell signaling: A preview v. Reception: when the target cell detects a signaling molecule. The signaling molecule binds to a receptor protein on the target cell’s surface vi. Transduction: After binding the receptor protein is changed in some way, this converts the signal to a form that will bring about a specific cellular response 7. May occur in a single step or a series of changes vii. Response: The transduced signal triggers a specific cellular response. 8. Catalysis of an enzyme, rearrangement of the cytoskeleton, activation of a specific gene 2. Reception: A signaling molecule binds to a receptor protein, causing it to change shape d. To ensure signals are sent to the correct cell signaling molecules act as a ligand. viii. Ligand- molecule that specifically binds to another (usually larger) molecule ix. The receptor protein then usually changes shape x. May be located on the membrane or inside the cell e. Receptors in the plasma membrane xi. Water-soluble signaling molecule binds to receptor on the membrane causing it to change shape or aggregate. f. Intracellular Receptors xii. Found in cytoplasm or nucleus of target cells 9. Signaling molecule must be hydrophobic enough or small enough to pass through the plasma membrane h. Steroid hormones, thyroid hormones, nitric oxide | Examples| Pathway| Other| G-Protein Coupled Receptors| Yeast mating factors, epinephrine, hormones, neurotransmitters| 1. signaling molecule binds to the g-protein receptor 2. receptor changes shape and the cytoplasmic side binds to the inactive G protein 3. GTP then displaces to form GDP and activates the protein 4. Activated G protein diffuses along the membrane to an enzyme altering the enzyme to trigger the next step| Bacteria such as whooping cough, botulism and cholera disrupt this pathway| Receptor Tyrosine Kinases| Enzymes that catalyze the transfer of phosphate groups| 1. binding of two signaling molecules to two tyrosine chains causes the two to associate with each other forming a dimer 2. dimerization activates the tyrosine kinase region to add a phosphate from and ATP to each tyrosine in the polypeptide 3. each tail can now bind to and activate a different specific relay protein within the cell| One receptor may activate ten+ pathways. Absence can result in cancer| Ion Channel Receptors| Nervous system| 1. signaling molecule binds to the ion channel in the membrane 2. protein changes shape creating a channel through the membrane 3. specific ions can now flow through the membrane which may cause a change in the cell or trigger another pathway| Some ion gated channels are controlled by change in voltage rather than binding of a ligand| g. Intracellular Receptors xiii. Ex. Testosterone 10. Hormone passes through the plasma membrane 11. Testosterone binds to a receptor protein in the cytoplasm activating it 12. The hormone-receptor complex enters the nucleus and binds to a specific gene 13. The bound protein acts as a transcription factor, stimulating the transcription of the gene into mRNA 14. The mRNA is translated into a specific protein 3. Transduction: cascades of molecular interactions relay signals from receptor to target molecules in the cell h. Protein phosphorylation and dephosphorylation xiv. Proteins can be activated by the addition of a phosphate group (often broken off of ATP or GTP) 15. Phosphates are transferred from ATP to a protein by a general group of enzymes known as protein kinases i. Phosphorylation often causes the protein to change shape j. This happens because the added phosphate group interacts with polar or charged amino acids within the protein xv. Protein phosphatases are enzymes that remove phosphate groups from a protein 16. Mechanism for turning off signal transduction 17. These also allow for turning off and reusing pathways i. Small molecules and ions as second messengers xvi. Molecules other than proteins act as second messengers 18. Small and water soluble such as ions k. This allows them to rapidly spread throughout the cell via diffusion 19. Second messenger refers to anything after the first messenger which is the extracellular signaling molecule that binds to the membrane 20. Most common second messengers are cyclic AMP and Ca+2 xvii. Cyclic AMP as a second messenger in response to the hormone epinephrine 21. Epinephrine binds to receptor molecule protein activates adenylyl cyclase which can catalyze the synthesis of many molecules of cAMP l. Adenylyl cyclase catalyzes the conversion of ATP into cAMP ix. cAMP usually activates a serine/threonine kinase known as protein kinase A which phosphorylates many other proteins m. cAMP is converted back to AMP by phosphodiesterase xviii. Calcium ions and inositol tripohosphate 22. Increasing calcium concentration causes responses such as muscle contraction, secretion of substances, and cell division in animals, and greening in response to light in plants 23. Calcium is usually in high concentrations outside of the cell and in the ER but in low concentrations in the cytosol 24. Pathway n. Signaling molecule binds to receptor   o. Phospholipid pinches off membrane IP3 is released as second messenger p. IP3 binds to receptor on ER causing protein channel to open q. Ca+2 is released into cytosol 4. Response: Cell signaling leads to regulation of transcription or cytoplasmic activities j. Nuclear and cytoplasmic responses xix. Pathways lead to the regulation of one or more cellular activities 25. Regulate protein synthesis r. Turning specific genes on or off (calls for the synthesis of mRNA from DNA) 26. Regulate protein activity s. Cause a shape change to turn a protein on or off 27. Regulate overall shape change of cell 28. Release of mating factors 29. Cell division k. Fine-tuning of the response xx. Signal amplification 30. Enzyme cascades amplify effects by increasing the product at each step t. Enzymes stay active long enough to work on multiple products before becoming inactive xxi. The specificity of cell signaling and coordination of the response 31. Different types of cells are programmed to respond to only certain types of signals u. Some cells will respond to the same signals but in different ways v. This is because different cells have different collections of proteins xxii. Signaling efficiency: scaffolding proteins and signaling complexes 32. Scaffolding proteins increase the efficiency of the response w. A large protein with multiple protein kinases attached x. Decreases the time of the response because diffusion between proteins is not needed 33. Pathways are not linear, in fact the same protein may act in multiple pathways 34. Relay proteins serve as branch points where the signal may go in one of two directions xxiii. Termination of the signal 35. Each step in the pathway lasts only a short time, this makes the proteins ready for a new signal 36. When the signaling molecule leaves leave the receptor it reverts to its inactive form and the relay molecules follow

Freedom of Speech in Cyberspace -- Argumentative Persuasive Internet E

Freedom of Speech in Cyberspace: Government Restrictions on Content in the United States of America (this essay is missing the url of each source cited) "Information wants to be free. The Internet fosters free speech on a global scale."[1] Introduction The Internet provides a gateway for an individual to speak freely and anonymously without being targeted to what he or she said. With this said, one of the biggest issues concerning the Internet today is freedom of speech. The issue of free speech on the Internet has been a topic of discussion around the world within the past years. It is a unique communication medium and is powerful than the traditional media[2]. Because the Internet can not be compared equally to other mediums of communication, it deserves the utmost freedom of speech protection from the government. The restriction of speech on the Internet takes away from individual's rights and freedom from experiencing the Internet's benefits and uses. Information found on the Internet is endless and boundless and this poses the question, "should the government be allowed to regulate the information and content being transmitted or posted online?" Free Speech on the Internet Free speech on the Internet is a very controversial subject and has been the key problem surrounding the Internet today. The attempt to regulate and govern the Internet is still pursued by government officials. This subject has been intensified due to terrorist attacks against the United States and around world within the past years. The government believes that by regulating the Internet, it will protect the general public from criminal actions and eliminate the exposure of children to pornography or vulgar language. Senator Jim Exon of ... ...eved 27 April 2004. Rosenthal, Elisabeth. "China Lists Controls To Restrict the Use Of E-mail and Web." The New York Times, 27 January 2000. Retrieved 26 April 2004. Smith, Craig, "Tough New Rules Don't Faze Chinese Internet Start-Ups," The New York Times, 4 October 2000. Retrieved 26 April 2004. Stewart, William. Key Internet Features - Freedom of Speech. Living Internet. Retrieved 20 April 2004. Unknown Author. An Overview of the Communications Decency Act (CDA). Center for Democracy & Technology. Retrieved 26 April 2004. Unknown Author. Communications Decency Act. Electronic Privacy Information Center. Retrieved 26 April 2004. Unknown Author. Communications Decency Act. Wikipedia. Retrieved 25 April 2004. Unknown Author. Introduction to Ethics. Engineering Handbook. Retrieved 20 April 2004.

Essay a Note on the Institution of Al-Hisbah and Its Economic Functions

These Short Essays are partial fulfillment of Paper IE1001 of Part 1 of Certified Islamic Finance Professional (CIFP) [DRAFT V0. 5] INCEIF Student Name: Mustafa Aydemir Student ID: 1200279 Bismillahirrahmanirrahim Essay (4) A note on the institution of al-Hisbah and its economic functions in today’s economy. A short Essay by Mustafa Aydemir There are various controlling mechanisms in Islam. Allah swt is overseeing his entire creation; Self-discipline and control by a person self; a persons supervising another person; and the accountability system elaborated in this essay, namely Hisbah.Forbidding the wrong is a divinely imposed obligation on every Muslim. In other words, an executive power of the law of Allah (swt) in vested in each and every one follower of the Islamic faith. This concept points out that it is not only a right but a duty on a single Muslim to issue orders lenient to Gods law, and to do everything in his capacity that they are followed (Cook, 2001). It is the second statement of the Islamic doctrine ‘al-amr bil-maruf wa nahy an al-munkar’ that can can be considered the foundation of Hisbah.It is derived from the Quran verses â€Å"Commanding right and forbidding wrong† (3-110), (3-104), (7-157), (9-71). Beside being an individual obligation of a Muslim to actively seeking the rightful and actively removing the prohibited, Hisbah is a spiritual institution under the power of the state that appoints citizens to carry out the responsibility of enjoining what is right, whenever people start to neglect it, and forbidding what is wrong, whenever people start to engage in it.It is aiming to safeguard a nation from deviance, protect Iman (faith), and ensure the well-being of all people in both spiritual and matters in our daily life according to the Islamic law. It is common knowledge of a Muslim that Allah has made it obligatory to all believers to command well and prevent wrongdoing to the extent of his or her knowledge and capabilities. The following Quranic verse describes: â€Å"Let there arise from you a group calling to all that is good, enjoining what is right and forbidding what is wrong. It is these who are successful. (3:104) Furthermore, the following hadith highlights: â€Å"On the authority of Abu Sa'eed al-Khudree (radiAllaahu anhu) who said : I heard the Messenger of Allaah (sallAllaahu alayhi wa sallam) say : Whosoever of you sees an evil, let him change it with his hand; and if he is not able to do so, then [let him change it] with his tongue; and if he is not able to do so, then with his heart – and that is the weakest of faith. (Al Sahih al Muslim)† Hisbah is a religious institution that may be one of the formal departments of a Muslim state.The institution would be specialized in fulfilling the aforementioned obligatory task of enjoining what is right and forbidding what is wrong. The Hisbah is the structured means of carrying out this duty. In today’s economy, Hisbah may be organized around monitoring and ultimately trying to safeguard the limits set by Shariah from being violated as an enforcement agency. Consequently, the execution of Hisbah is protecting the well-being of the society as well as ensuring public safety from committing sins, similar to Federal Bureau of Investigation (FBI).The obvious question to be answered weather an elected government would takeover the coordination of Hisbah. Hence, the role of the state in the economy to safeguard life and property of all individuals within its boundaries would be supported and accompanied by Hisbah. The role of the state was continuously discussed and studied in Islamic thoughts since the early days (Chapra, 1995) . One of which, the Hisbah institution could be a department under the Economic ministry to watch over markets and ensure stability, fairness and prevent unlawful trade practices.What is good for individuals may be applied to economic activities by the Hisbah institution. (INCEIF Lecture Notes). The advantage of Hisbah in particular is highlighted in all its power within Islamic financial institutions. It includes monitoring a financial institution through a rigorous Shariah governance framework. But even a marketplace and manufacturing are of concern to make sure that Shariah-compliance is given. The work of a Shariah Supervisory Board may be considered as Hisbah, or at least affiliated to it.A Shariah committee is appointed to oversee tasks of enjoining what is right and forbidding what is wrong through Shariah audits, training and advisory activities required to ensure compatibility of an Islamic financial institution with Islamic law. Hisbah in terms of accounting and auditing activities to ensure Shariah-compliance in every industry sector maybe tested in a pilot project if it would ultimately help to improve the well being of all people and hence support Maqasid al Shariah.The bigger the motivation of Muslims are to implementing Islamic values , and the more effective socio-economic institutions are in creating a fair equilibrium between resources and their claims, the smaller will be the role of the state (coordinating Hisbah) will have to play in the economy. We all must take inspiration from what the Qur'an says: And if they strive in Our Cause. We will certainly guide them to Our Ways. For Allah is undoubtedly with those who strive for the good (29-69).

The, The Eyes Of The Beholder - 1558 Words

â€Å"Beauty lies in the eyes of the beholder.† This renowned quote was said by Plato, attempting to clarify that there is no universal beauty. Unfortunately, in today’s society, humankind has forgotten the meaning of this, and consequently have become obsessed with what society deems as beautiful or ideal. In the movie Rebecca, directed by Alfred Hitchcock, Maxim de Winter, as well as many other characters experience the negativity that comes with conforming to society’s ideology. The media portrays how the so-called perfect man and woman both look and act. Society also pressures people to hastily find their one true love. Nowadays, people have trouble expressing individuality; the standards that are currently present restrict many lives today. Throughout media, both men and women alike, experience society’s push for impractical ideas of the perfect person; there are some who expect the opposite gender to appear and behave in an unreasonable or romanticized fashion. The effects that accompany this crooked concept are primarily negative and rarely, if at all, beneficial to society as a whole. Men and women both endure certain industries ideas of how the perfect body looks. While individuals should aspire to maintain a healthy body weight, the extremity of how it is currently presented negatively impacts millions of lives. In a study done in 2011, it was reported that â€Å"20 million women and 10 million men suffer from a clinically significant eating disorder at some time in theirShow MoreRelatedStress is in the Eyes of the Beholders2257 Words   |  10 PagesINSPIRATIONAL STORY 5 5.0 HOW TO MANAGE STRESS. 7 REFERENCES. 9 Stress is in the Eyes of the Beholders. 1.0 INTRODUCTION What is stress? According to a journal, Stress is a state of mental tension and worry caused by problems in your life, works, family and many more. It is also something that causes strong feelings of worry or anxiety and physical force or pressure. 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