chem stories

Definition reducing sugar
If a sugar contains aldehyde groups that are oxidised to carboxylic acids, then that sugar is classified as a reducing sugar. It is called a reducing sugar because it reduces the number of chemicals present in its structure through oxidation.

Examples
Reducing sugars include glucose, fructose, glyceraldehyde, lactose, arabinose and maltose.

Reducing Capabilities
Reducing capability is defined by the presence of potential aldehyde or ketone group, anomeric carbons found in sugars, which determine a substance's ability to lose or gain electrons to form new or more stable solutions or its reaction to other substances.

Testing
Benedict and Fehling's reagent are two solutions used to determine the reducing capability of a sugar. These solutions are used to determine the presence of free aldehyde or ketone group in sugars.

Non-Reducing Sugar
The reason that sucrose is a non-reducing sugar is that it has no free aldehyde or keto group. Additionally, its anomeric carbon is not free and can't easily open up its structure to react with other molecules.


SUCROSE
The common name for sucrose is table sugar. Just as the name implies, sucrose is used throughout the world as a sweetener for cooking, baking and sweetening edibles. Sucrose is commonly made by refining plant matter, such as sugarcane or sugar beets. In its most commonly used form, it is a white, orderless powder that is sweet to the taste. Although sucrose is a disaccharide, it is not a reducing sugar.

Sucrose is the technical term for table sugar such as cane sugar or white sugar. It is composed of the combination of one glucose molecule and one fructose molecule.

Formation
The process starts with a condensation reaction, a process involving the release of water. This process is followed by the formation of a glycosidic bond between two available and appropriate monosaccharide molecules, creating disaccharides like sucrose.

Properties
Sucrose is soluble in water but its molecules are too big to pass through the cell membrane during diffusion. It can only be broken down through a hydrolysis reaction, a reverse condensation reaction.

Disaccharide
Sucrose is a complex carbohydrate known as a disaccharide, meaning made up of two simple carbohydrates or monosaccharides. The monosaccharides that form sucrose are glucose and fructose. Disaccharide is the most common form of sugar that is found in nature. It results from the combination or reaction of two simple sugars (monosaccharides). It has two types, the reducing and non-reducing sugar. Sucrose is a classic example of a non-reducing sugar.


Significance
Although both glucose and fructose are reducing sugars, sucrose is not because it does not contain anomeric hydroxyl groups, and does not reduce the chemicals present in its structure through oxidation.

Identification
It is possible to test a substance such as sucrose for the qualities that make it a reducing sugar using Fehling's solution, a mixture of copper sulfate, distilled water, Rochelle salt and sodium hydroxide. In the presence of reducing sugars, the copper sulfate in the solution will oxidize and turn red.






Read more: Why Is Sucrose a Non-Reducing Sugar? | eHow.com http://www.ehow.com/facts_5882980_sucrose-non_reducing-sugar_.html#ixzz15o22o2m6

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Buffer solution is able to retain almost constant pH when small amount of acid/base is added. Quantitative measure of this resistance to pH changes is called buffer capacity.

Buffer capacity can be defined in many ways. You may find it defined as "maximum amount of either strong acid or strong base that can be added before a significant change in the pH will occur". This definition - instead of explaining anything - raises a question "what is a significant change?" - sometimes even change of 1 unit doesn't matter too much, sometimes - especially in biological systems - 0.1 unit change is a lot. Buffer capacity can be also defined as quantity of strong acid or base that must be added to change the pH of one liter of solution by one pH unit. Such definition - although have its practical applications - gives different values of buffer capacity for acid addition and for base addition (unless buffer is equimolar and its pH=pKa). This contradicts intuition - for a given buffer solution its resistance should be identical regardless of whether acid or base is added.



http://www.chembuddy.com/?left=pH-calculation&right=pH-buffer-capacity

In the cell have the chemical components which maintain the pH. So it always in optimum pH. The chemical components of solution is mineral salts in the form of phosphate salt solution.
The phosphate buffer system operates in the internal fluid of all cells. This buffer system consists of dihydrogen phosphate ions (H2PO4-) as hydrogen-ion donor (acid) and hydrogen phosphate ions (HPO42-) as hydrogen-ion acceptor (base). These two ions are in equilibrium with each other as indicated by the chemical equation below.
H2PO4-(aq) -----> H+(aq) + HPO42-(aq)

Enzymes are structured protein compounds which function as a catalyst and is known as bio-catalyst. Enzymes act as catalysts that catalyze chemical reactions that occur in biological systems.

In performing its role as a bio-catalyst in the body, how the enzyme is influenced by several factors, one of which is the degree of acidity or better known as the pH, this is because the enzyme is only willing and able to work at certain pH conditions. A pH conditions where the enzyme can work with the highest activity as may be named with the optimum pH.

In contrast at a certain pH of the enzyme at all is no longer active or even damaged. This can be explained * for us to know that enzymes are molecules of protein, the protein molecule stability could be affected by the level of acidity of the environment, in conditions of extreme acidity of the protein molecules from the enzyme will be damaged.
Hence, in an effort to maintain the cells occur in order to keep the optimum pH.

Cells can maintain pH chemically by using buffers. Buffers are molecules that easily interconvert between acidic and basic forms, donating or accepting protons as conditions change.

Two important biological buffer systems are the dihydrogen phosphate system and the carbonic acid system.

The phosphate buffer system operates in the internal fluid of all cells. This buffer system consists of dihydrogen phosphate ions (H2PO4-) as hydrogen-ion donor (acid) and hydrogen phosphate ions (HPO42-) as hydrogen-ion acceptor (base). These two ions are in equilibrium with each other as indicated by the chemical equation below.
H2PO4(aq) + H (aq) ----> H(PO4)2(aq)

Cells must constantly maintain their pH in order to function properly. In animals, for example, the maintainence of blood pH is crucial for life. A slightly acidic pH (6.95) would result in coma and death. A slightly more basic pH (7.7) would result in convulsions and muscle spasms. As another example, the pH of cellular organelles such as lysosomes (around 5) is lower than the pH of the cytoplasm (around 7.2). Lysosomes contain enzymes that function optimally in an acidic environment. Such an acidic environment, however, would be detrimental to biological processes in the cytoplasm. Each must maintain the appropriate pH.

A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. It has the property that the pH of the solution changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. Many life forms thrive only in a relatively small pH range; an example of a buffer solution is blood.

The central dogma of molecular biology was first articulated by Francis Crick in 1958 and re-stated in a Nature paper published in 1970:
The central dogma of molecular biology deals with the detailed residue-by-residue transfer of sequential information.. It states that information cannot be transferred back from protein to either protein or nucleic acid.
In other words, 'once information gets into protein, it can't flow back to nucleic acid.'
The dogma is a framework for understanding the transfer of sequence information between sequential information-carrying biopolymers , in the most common or general case, in living organisms . There are 3 major classes of such biopolymers: DNA and RNA (both nucleic acids ), and protein . There are 3×3 = 9 conceivable direct transfers of information that can occur between these The dogma classes these into 3 groups of 3: 3 general transfers (believed to occur normally in most cells), 3 special transfers (known to occur, but only under specific conditions in case of some viruses or in a laboratory), and 3 unknown transfers (believed never to occur). The general transfers describe the normal flow of biological information: DNA can be copied to DNA ( DNA replication ), DNA information can be copied into mRNA , ( transcription ), and proteins can be synthesized using the information in mRNA as a template ( translation ).

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Crawling around me...
Sleepless eyes...
Your hands, they haunt me...
finger tipping down my spine.

Heaven forbid, well aware of your sins.
In the wake I'll be just like the rest.
Tell the sun don't fall, so we'll never forget.
Heaven forbid, well aware of your sins.
In the wake I'll be just like the rest.
Past praying for.

Always kept quiet...
Clenching my teeth.
Find me fighting the floor.
Raise me from my bones once more.
You're way past praying for.

I wouldn't want to wake you from yourself.
...doesn't sit in your stomach just quite right.
Toying with time...
Lascivious stares and a dangerous rhyme

Tulisan ini pendapat pribadi..
Facebook demikian marak dibeberapa negara. Perkembangannya cukup pesat. Bermula dari situs jaringan sosial di sebuah universitas dan berkembang pesat ke banyak negara. Mengomentari hal ini segala sesuatu memang semula bermula dari hal kecil dan berkembang menjadi besar. Tingkat kompleksitas sistem dan jaringanpun berkembang dari semula sederhana menjadi sangat kompleks. Ide yang dapat diambil adalah rencanakan dari hal yang sederhana dan realisasikan rencana tersebut. Semua tidak ada yang instan. Seiring dengan realisasi tersebut tentunya perubahan-perubahan bisa dilakukan sehingga rencana semula yang sederhana menjadi suatu karya yang bermanfaat.
Kali ini saya ingin berbagi pendapat saya tentang facebook. Bermula dari dampak baiknya dahulu. Tentunya dengan Facebook kita dapat kembali bertemu dengan teman-teman lama walaupun di dunia maya. Dengan facebook komunikasi antar teman menjadi lancar walaupun berjauhan. Featurenya cukup beragam membuat nyaman menggunakannya. Bagi yang sedang jauh dari komunitas aslinya karena tugas misalnya sedang studi di luar kota atau luar negeri manfaat facebook sangat terasa. Yang saya alami saya masih tetap bisa mengikuti perkembangan komunitas saya di indonesia walupun saya sedang studi lanjut di jerman. Ini sangat diperlukan karena saya tidak akan terasing sekembalinya dari jerman dan menjalankan tugas di kampus saya semula. Banyak pengalaman teman-teman yang studi waktu dulu terasing selama bertahun-tahun sehingga seperti orang aneh ketika kembali ke komunitas semula.
Dengan Facebook kita bisa bertukar pikiran dengan sangat mudah. Pertukaran informasi difasilitasi dengan sangat bagus. Sebagai contohnya ketika kita butuh sesuatu atau ingin tahu tentang sesuatu tinggal kita tuliskan dalam status maka akan banyak respon dari teman kita.
Facebook dapat juga dimanfaatkan untuk mengkampanyekan suatu ide seperti Say No to Drug atau ide-ide lainnya. Membangun komunitas melalui Group atau Pages dengan tujuan yang baik akan sangat bermanfaat. Pertumbuhan Group atau Pages di Facebook terbilang cukup cepat. Sesuatu hal akan berkembang dengan cepat kalau dibangun secara bersama.
Dengan pages, suatu perusahaan juga dapat mengiklankan produknya. Mengenai aturan lebih detail bisa ditanyakan ke Facebook Team. Seharusnya memang Facebook kita manfaatkan secara positif.
Dampak baiknya mungkin banyak yang tahu. Dampak buruk yang terkadang tidak kita sadari. Saya uraikan beberapa hal dampak buruk Facebook:
1. Mengurangi kinerja
Banyak karyawan perusahaan, dosen, mahasiswa yang bermain facebook pada saat sedang bekerja. Mau diakui atau tidak pasti mengurangi waktu kerja. Sebenarnya bisa dikurangi akibatnya jika kita bisa memanage waktu yaitu bermain facebook ketika istirahat. Saya sendiri mengharamkan facebook bagi diri saya ketika saya sedang di institut. Hari senin sampai jum’at dari jam 9 sampai jam 18 adalah waktu terlarang bagi saya untuk membuka facebook.
2. Berkurangnya perhatian terhadap keluarga
Mau diakui atau tidak ini terjadi jika kita membuka facebook saat sedang bersama keluarga. Sebuah riset di inggris menunjukan bahwa orang tua semakin sedikit waktunya dengan anak-anak mereka karena berbagai alasan. Salah satunya karena Facebook. Bisa terjadi sang suami sedang menulis wall, si istri sedang membuat koment di foto sementara anaknya diurusi pembantu. Saya termasuk orang kolot dalam hal ini. Saya akan membatasi diri saya dan keluarga saya untuk sekedar bermain facebook atau sms-an yang tidak penting saat bersama keluarga.
3.Tergantikanya kehidupan sosial
Facebook sangat nyaman sekali. Saking nyamannya sebagian orang merasa cukup dengan berinteraksi lewat facebook sehingga mengurangi frekuensi ketemu muka. Ada sebuah hal yang hilang dari interaksi seperti ini. Bertemu muka sangat lain dan tidak seharusnya digantikan dengan bertemu di dunia maya. Obrolan, tatapan mata, ekspresi muka, canda lewat ketawa tidak bisa tergantikan oleh rentetan kata2 bahkan video sekalipun.
4.Batasan ranah pribadi dan sosial yang menjadi kabur
Dalam Facebook kita bebas menuliskan apa saja, sering kali tanpa sadar kita menuliskan hal yang seharusnya tidak disampaikan ke lingkup sosial. Persoalan rumah tangga seseorang tanpa sadar bisa diketahui orang lain dengan hanya memperhatikan status dari orang tersebut.
5. Tersebarnya data penting yang tidak semestinya
Seringkali pengguna Facebook tidak menyadari beberapa data penting yang tidak semestinya ditampilkan secara terbuka. Seperti sudah dijelaskan dalam artikel tentang keamanan facebook, default dari info kita seharusnya tertutup dan tidak tertampil. Kalau memang ada yang perlu baru dibuka satu per satu sesuai kebutuhan.
6. Pornografi
Sebagaimana situs jejaring sosial lainnya tentu ada saja yang memanfaatkan situs semacam ini untuk kegiatan berbau pornografi.
7. Pemanfaatan untuk kegiatan negatif
Walupun telah diatur dalam peraturan penggunaan Facebook, tetap saja ada pihak yang memanfaatkan facebook untuk kegiatan negatif melalui group ataupun pages.
8. Kesalahpahaman
Facebook merupakan jaringan sosial yang sifatnya terbuka antara user dan teman-temannya. Seperti kehidupan nyata gosip atau informasi miring dengan cepat juga dapat berkembang di jaringan ini. Haruslah disadari menulis di status, di wall dan komentar diberbagai aplikasi adalah sama saja seperti obrolan pada kehidupan nyata bahkan efeknya mungkin lebih parah karena bahasa tulisan terkadang menimbulkan salah tafsir. Sudah ada kasus pemecatan seorang karyawan gara-gara menulis yg tidak semestinya di facebook, juga terjadi penuntutan ke meja pengadilan gara-gara kesalahpahaman di Facebook.
9. Mempengaruhi kesehatan (masih perdebatan)
Sebuah artikel di media inggris menyebutkan Facebook dapat meningkatkan stroke dan penyakit lainnya. Alasan yang dikemukakan menurut saya masih perlu dikaji lagi. Kalau menurut pendapat saya bukan karena facebooknya tetapi karena kebiasaan duduk berlama-lama di depan komputer.
10. Penipuan
Seperti media online lainnya, Facebook juga rentan dimanfaatkan untuk tujuan penipuan. Kita tidak akan tahu sebenarnya siapa dibalik account facebook. Orang dengan mudah membuat account baru untuk keperluan yang tidak baik. Ada yang menggunakan modus berkenalan dan akhirnya menjadi akrab di dunia maya yang ternyata ujung-ujungnya digunakan untuk melakukan penipuan atau tindakan kriminal lainnya.
Bagi saya pribadi yang sedang jauh dari keluarga merasa sangat beruntung karena bisa berhubungan dengan keluarga lewat dunia maya. Dengan facebook aktivitas keluarga dapat diikuti walaupun berjauhan. Facebook adalah sarana, dampak baik atau buruk tergantung dari kemampuan seseorang mengatur dirinya. Mari pergunakan sesuatu sesuai porsinya. Pahami dengan benar etika dalam kehidupun maya selayaknya etika di kehidupan nyata.

sumber:dhidik.wordpress.com