Trivia - Fotosintesis

babyridz

Apakah nama langkah dalam proses fotosintesis untuk mengeluarkan molekul air?

Elle_mujigae

Condensation?

babyridz

Elle_mujigae posted on 5-4-2013 09:22 AM
Condensation?

Salah

Elle_mujigae

Oxidation....

babyridz

Elle_mujigae posted on 5-4-2013 09:38 AM
Oxidation....

salah jugak

babyridz

mana mod eva nehhh

Eva_yy_Ellin

babyridz posted on 5-4-2013 09:39 AM
mana mod eva nehhh

Kalau kita tak jawab maksudnya kita tak taulah tu...

Sat cari jap.

Elle_mujigae

Photophosphorylation.....

Elle_mujigae

Light dependant reaction.....

babyridz

Eva_yy_Ellin posted on 5-4-2013 09:42 AM
Kalau kita tak jawab maksudnya kita tak taulah tu...

Sat cari jap.

oh gitu

babyridz

Elle_mujigae posted on 5-4-2013 09:51 AM
Light dependant reaction.....

ya betul jua akhirnya

babyridz

The Light Reactions of Photosynthesis
Figure

Chloroplasts (left) convert light energy into chemical energy. High-energy electrons in chloroplasts are transported through two photosystems (right). During this transit, which culminates in the generation of reducing power, ATP is synthesized in a manner (more...)

Essentially all free energy utilized by biological systems arises from solar energy that is trapped by the process of photosynthesis. The basic equation of photosynthesis is deceptively simple. Water and carbon dioxide combine to form carbohydrates and molecular oxygen.

In this equation, (CH2O) represents carbohydrate, primarily sucrose and starch. The mechanism of photosynthesis is complex and requires the interplay of many proteins and small molecules. Photosynthesis in green plants takes place in chloroplasts (Figure 19.1). The energy of light captured by pigment molecules, called chlorophylls, in chloroplasts is used to generate high-energy electrons with great reducing potential. These electrons are used to produce NADPH as well as ATP in a series of reactions called the light reactions because they require light. NADPH and ATP formed by the action of light then reduce carbon dioxide and convert it into 3-phosphoglycerate by a series of reactions called the Calvin cycle or the dark reactions. The Calvin cycle will be discussed in Chapter 20. The amount of energy stored by photosynthesis is enormous. More than 1017 kcal (4.2 × 1017 kJ) of free energy is stored annually by photosynthesis on Earth, which corresponds to the assimilation of more than 1010 tons of carbon into carbohydrate and other forms of organic matter.

Figure 19.1

Electron Micrograph of a Chloroplast from a Spinach Leaf. The thylakoid membranes pack together to form grana. [Courtesy of Dr. Kenneth Miller.]

As animals ourselves, we perhaps easily overlook the ultimate primacy of photosynthesis for our biosphere. Photosynthesis is the source of essentially all the carbon compounds and all the oxygen that makes aerobic metabolism possible. Moreover, as we shall see, there are considerable mechanistic and evolutionary parallels between the light reactions of photosynthesis and steps in oxidative phosphorylation.

19.0.1 Photosynthesis: An Overview:

We can use our understanding of the citric acid cycle and oxidative phosphorylation to anticipate the processes required of photosynthesis. The citric acid cycle oxidizes carbon fuels to CO2 to generate high-energy electrons, notably in the form of NADH. The flow of these high-energy electrons generates a proton-motive force through the action of the electron-transport chain. This proton-motive force is then transduced by ATP synthase to form ATP. A principal difference between oxidative phosphorylation and photosynthesis is the source of the high-energy electrons. The light reactions of photosynthesis use energy from photons to generate high-energy electrons (Figure 19.2). These electrons are used directly to reduceNADP+ to NADPH and are used indirectly through an electron-transport chain to generate a proton-motive force across a membrane. A side product of these reactions is O2. The proton-motive force drives ATP synthesis through the action of an ATP synthase, homologous to that in oxidative phosphorylation. In the dark reactions, the NADPH and ATP formed by the action of light drive the reduction of CO2 to more-useful organic compounds.

Photosynthetic yield-

“If a year's yield of photosynthesis were amassed in the form of sugar cane, it would form a heap over two miles high and with a base 43 square miles.”

-G. E. Fogge

If all of this sugar cane were converted into sugar cubes (0.5 inch on a side) and stacked end to end, the sugar cubes would extend 1.6 × 1010 miles, or to the planet Pluto.

Figure 19.2

The Light Reactions of Photosynthesis. Light is absorbed and the energy is used to drive electrons from water to generate NADPH and to drive protons across a membrane. These protons return through ATP synthase to make ATP.

Eva_yy_Ellin

Huhu...tak sempat. Mencari dari tadi... Kalau dalam bmnya reaksi terang, kan...?

babyridz

yang dalam BM



Pengertian dan Proses Reaksi Terang Fotosintesis - Pengertian reaksi terang adalah reaksi penangkapan energi cahaya. Energi cahaya yang diserap oleh membran tilakoid akan menaikkan elektron berenergi rendah yang berasal dari H2O. Elektron-elektron bergerak dari klorofil a menuju sistem transpor elektron yang menghasilkan ATP (dari ADP + P). Elektron-elektron berenergi ini juga ditangkap oleh NADP+. Setelah menerima elektron, NADP+ segera berubah menjadi NADPH. Molekul-molekul ini (ATP dan NADPH) menyimpan energi untuk sementara waktu dalam bentuk elektron berenergi yang akan digunakan untuk mereduksi CO2. Reaksi terang (Light-Dependent Reaction) terjadi dalam membran tilakoid yang di dalamnya terdapat pigmen klorofil a, klorofil b, dan pigmen tambahan yaitu karoten. Pigmen-pigmen ini menyerap cahaya ungu, biru, dan merah lebih baik daripada warna cahaya lain. Reaksi terang melibatkan dua jenis fotosistem, yaitu fotosistem I dan fotosistem II. Apakah sebenarnya fotosistem itu?Telah dijelaskan di depan bahwa dalam tilakoid terdapat beberapa pigmen yang berfungsi menyerap energi cahaya. Pigmen-pigmen itu antara lain klorofil a, klorofil b, dan pigmen tambahan karotenoid. Setiap jenis pigmen menyerap cahaya dengan panjang gelombang tertentu. Molekul klorofil dan pigmen asesori (tambahan) membentuk satu kesatuan unit sistem yang dinamakan fotosistem. Setiap fotosistem menangkap cahaya dan memindahkan energi yang dihasilkan ke pusat reaksi, yaitu suatu kompleks klorofil dan protein-protein yang berperan langsung dalam fotosintesis.

Fotosistem I terdiri atas klorofil a dan pigmen tambahan yang menyerap kuat energi cahaya dengan panjang gelombang 700 nm sehingga sering disebut P700. Sementara itu, fotosistem II tersusun atas klorofil a yang menyerap kuat energi cahaya dengan panjang gelombang 680 nm sehingga sering disebut P680. Ketika suatu molekul pigmen menyerap energi cahaya, energi itu dilewatkan dari suatu molekul pigmen ke molekul pigmen lainnya hingga mencapai pusat reaksi. Setelah energi sampai di P700 atau di P680 pada pusat reaksi, sebuah elektron kemudian dilepaskan menuju tingkat energi lebih tinggi. Elektron berenergi ini akan disumbangkan ke akseptor elektron. Dalam reaksi terang, terdapat 2 jalur perjalanan elektron, yaitu jalur elektron siklik dan jalur elektron nonsiklik.

babyridz

Eva_yy_Ellin posted on 5-4-2013 09:57 AM
Huhu...tak sempat. Mencari dari tadi... Kalau dalam bmnya reaksi terang, kan...?

yezza dh tepek info di atas

alisyadania

respiration/respiracion???

Elle_mujigae

terma "mengeluarkan" molekul air tu agak mengelirukan sbb i terus terbayang air as"by-product" ...
rupanya "splitting" of water molecule....

babyridz

Elle_mujigae posted on 5-4-2013 11:51 AM
terma "mengeluarkan" molekul air tu agak mengelirukan sbb i terus terbayang air as"by-product" ...
...

bod trivia dh jadi bod sains dah

Elle_mujigae

babyridz posted on 5-4-2013 11:56 AM
bod trivia dh jadi bod sains dah

matematik pun ada kadang2 so jadi Bod all-in-one....

Elle_mujigae

Elektron berenergi ini akan disumbangkan ke akseptor elektron.

Dalam reaksi terang, terdapat 2 jalur perjalanan elektron, yaitu jalur elektron siklik dan jalur elektron nonsiklik.

Susahnya belajar bio dlm bahasa Melayu....
Jalur elektron siklik?