生物讨论专区

purple_pig_33

到我有问题了
头要爆了
我分不清reduce和oxidised

在light reaction,
splitting of water can produce hydrogen ion by photolysis
这个hydrogen ion then combine with the electron of PS 1,
对不对？
然后produce NADPH^+ + H^+ 吗？
所以是reduce NADP to NADPH?????????????

四月一日的小皮

During photolysis,water split into Oxygen and Proton with electron.
Electron is used to oxidise PS II system,since PS II system had loss electron due to photoactivation. Proton are used either in production of ATP or Reduction of NADH.
i)Reduction of NADP is occur at last stage of non-cyclic photophosporylation in which NADP is reduced into NADPH + H WHICH is catalysed by NADP reductase.
ii)Proton is flow into thalakoid space along the concentration through cytochrome b6f complex,which is essential process for ATP production in chemiosmosis process.It can occur either in cyclic or non-cyclic phosphorylation process.

生物难题

原帖由 purple_pig_33 于 12-11-2009 11:44 PM 发表
到我有问题了
头要爆了
我分不清reduce和oxidised

在light reaction,
splitting of water can produce hydrogen ion by photolysis
这个hydrogen ion then combine with the electron of PS 1,
对不对？
然 ...

对呀，NADP+接收electron，所以是被reduced去NADPH。

Photolysis produces electrons 和 protons (H+) 和 oxygen。
那个electrons会去“填”掉PSII的electron hole，因为PSII之前lose了electron给它的primary electron acceptor。

但是，photolysis过后produce的hydrogen ion (proton)并没有combine with electron from PSI。
那些H+反而会逗留在thylakoid space / lumen里面，导致thylakoid space accumulate很多H+。
这样就会有proton gradient across thylakoid membrane (thylakoid space很多H+，stroma很少)。
有了proton gradient，就可以用chemiosmosis来制造ATP了。

希望帮到你。

[ 本帖最后由 生物难题 于 13-11-2009 01:17 AM 编辑 ]

purple_pig_33

formation of ATP by chemiosmosis 不是respiration那课吗？？

then Photolysis produces electrons 和 protons (H+) 和 oxygen。
这个H+不 combine NADP+ ，then NADPH怎样formed??
那calvin cycle 不能发生了

谢谢你们=）

生物难题

原帖由 purple_pig_33 于 13-11-2009 02:49 PM 发表
formation of ATP by chemiosmosis 不是respiration那课吗？？

then Photolysis produces electrons 和 protons (H+) 和 oxygen。
这个H+不 combine NADP+ ，then NADPH怎样formed??
那calvin cycle 不能发生了 ...

chemiosmosis是指使用proton gradient来制造ATP。
所以both mitochondria和chloroplast都是用chemiosmosis来制造ATP。
只不过一个是oxidative phosphorylation，另一个是photophosphorylation。

必须知道，photolysis是发生在the side facing thylakoid membrane，
所以H+会释放在tyhlakoid space。

NADPH formation发生在the side facing stroma，所以NADP+是使用stroma的H+来变成NADPH。
所以calvin cycle没有受到影响。

purple_pig_33

但是calvin cycle不是要用NADPH of light reaction的吗？

formation of ATP 不是当electron pass thro a series of electron carrier 才produce的瓦

生物难题

原帖由 purple_pig_33 于 13-11-2009 03:23 PM 发表
但是calvin cycle不是要用NADPH of light reaction的吗？

formation of ATP 不是当electron pass thro a series of electron carrier 才produce的瓦

对，calvin cycle是要用NADPH from light reaction.
所以我说了，photolysis的H+并没有combine with PSI，
但不代表NADPH不可以被formed。

NADP+是因为接受了electrons from PSI和H+ from stroma，才变成NADPH。
所以一样有form NADPH。有NADPH，就有Calvin cycle 咯。

对，formation of ATP是当electron pass through a series of electron carrier 才produce的。没有错。
但是，我们也必须要会解释为什么会这样。

原因是因为当electron pass through a series of electron carrier时，energy is released，
那些energy被b6f complex用来将stroma的H+ pumps去thylakoid space 里面，
以便制造proton gradient。有了proton gradient，就可以有chemiosmosis。

那些thylakois space的H+如果要出回来stroma，就一定要经过ATP synthase located in the thylakoid membrane。当H+ pass through ATP synthase，ATP就会被制造。

这就是chemiosmosis的photophosphorylation。

purple_pig_33

好复杂
今天读到我头痛死了
不过还是谢谢你

darksider

原帖由 purple_pig_33 于 2009/11/12 03:39 PM 发表
irreversible的应该没有competitive inhibitor
对吧？

所以说
inhibitor can be reversible and irreversible.
reversible 可以再分成 competitive and non-competitive
competitive compete with the subtra ...

改正一下，example of competitive inhibitor is malonate which competes with succinate for the active site in succinate dehydrogenase .

Example of irreversible incompetitive inhibitor is cyanide ions which inhibits the cytochrome oxidase in Electron Transport System. [muscle contraction 的是curare which competes with acetylcholine for active site of the protein receptor in post synaptic membrane causes paralysis]

Reversible incompetitive inhibitors are usually those that take part in end-product inhibition.
For example, threonine ---------- > isoleucine ; catalysed by enzyme threonine deaminase; when the concentration of isoleucine is high, it will bind to the allosteric site of threonine deaminase, making it unsuitable for theonine. So the reaction is inhibited.
*这个其实是negative feedback mechanism.Increase in concentration of isoleucine will inhibit the activity of enzyme threonine deaminase.



我觉得当一个人觉得ｂｉｏ很难读的话，他肯定有以下问题
i)没有好的参考书
ii)没有优质的老师
iii)他不喜欢biology

这个问题很容易解决
ｉ）http://intranet.col-westanglia.ac.uk/storage/resources_net/curriculum-press/　；　去下载那biology fact sheets
ii) 去买或下载好的参考书（campbell and reece, biochemistry for dummies, www.biologyguide.net , www.johnyrk.com
iii)用对的方法读书。
iv)用心去读

[ 本帖最后由 darksider 于 14-11-2009 11:29 AM 编辑 ]

darksider

原帖由 生物难题 于 2009/11/13 03:19 PM 发表


chemiosmosis是指使用proton gradient来制造ATP。
所以both mitochondria和chloroplast都是用chemiosmosis来制造ATP。
只不过一个是oxidative phosphorylation，另一个是photophosphorylation。

必须知道 ...

我学到的是photolysis occurs in the lumen of the thylakoid.photolysis所产生的H+ ions are used in the formation of NADPH...

the only molecule that can oxidise water is P680, a reacion centre Photosystem II. It contains the water-splitting complex which catalyses the oxidation of water in the presence of sun light.

Extract from Photosynthesis fact sheets:
6. The electrons emitted from PSI may:
a) Pass down through the same carrier molecules as the electrons from PSII, again generating ATP. Before returning to PSI.Thus electrons are cycled (PSI i carriers i PSI i carriers etc. The energy to begin this cycle came from light (photon) and is used to convert ADP to ATP i.e. to phosphorylate ADP (add a phosphate).
Hence this process is called cyclic photophosphorylation (CPP).

or

b) Combine with the hydrogen ions (protons) released from the photolysis of water to reduce nicotinamide adenine dinucleotide phosphate (NADP), forming NADPH


*刚刚看了这个ｖｉｄｅｏ，所用的Ｈ＋　ions come from stroma,catalysed by ferrodoxin reductase...
差不多每本书都说ＮＡＤＰＨ里的Ｈ都是从photolysis of water(through non-cyclic photophosphorylation)里拿到的，但这个video说的不一样。http://vcell.ndsu.edu/animations/photosynthesis/index.htm

http://faculty.spokanefalls.edu/InetShare/AutoWebs/johng/Chapter_7_Notes.pdf
A. Energy and materials for the reaction
1. The light-dependent reaction (Rxn) converts light energy to chemical energy
(which is then stored in ATP)
a. Liberated electrons and protons (H+) from water are picked up by NADP+

http://wiki.answers.com/Q/How_does_the_light_reaction_of_photosynthesis_takes_place
NADP+ + 2H+ + 2e- = NADPH + H+ The hydrogen ions needed for this come from the water which was split by PSII.



看了此图后，我觉得Ｈ＋ ions from stroma is used in the reduction of NADP 是对的。

*这就是说，很多人都assume that the H+ ions produced in photolysis of water is used up in the reduction of NADP because both are involved in the non-cyclic photophosphorylation. (为了方便写overall equation)

*大学教授, plant biologists 都说H+ ions are from stroma...因为那个ferrodoxin (terminal electron acceptor) are facing the stroma, not the lumen of thylakoid.

谢谢你，要不然我也不会深入学习光合作用。

[ 本帖最后由 darksider 于 13-11-2009 07:55 PM 编辑 ]

carly_yen

原帖由 darksider 于 11-11-2009 02:30 PM 发表
Anaerobic respiration
If oxygen is unavailable the Kreb’s cycle and electron transfer chain
cannot operate. This is because without oxygen there would be no
way of disposing of the hydrogen at, fo ...

我也来个补充...
SUPPOSE 有4 ATP FORMED.... 不过GLYCOLYSIS 前面的STEPS 有用到2 ATP 所以NETT 是 2 ATP~

CARI 有好多BIO 高人哦~~

darksider

原帖由 carly_yen 于 2009/11/11 07:32 PM 发表
我觉得好象是INELASTIC....
因为是TOUGH MEMBRANE, SUPPOSE TO BE INELASTIC....
IF IT'S FUNCTION IS TO PREVENT THE HEART FROM THE OVERFILLED WITH BLOOD, 那么如果是ELASTIC的话,不就根本就不能CARRY OUT THI ...

那pericardium sarc是一个inelastic的membrane.它的主要功能是把fix住心脏的位置和prevent the heart from overstretching (which is resulted from being overfilled with blood).

carly_yen

老实说... 这时哪一课的啊~~?? 哈哈哈~~
我好象没有读过......
我用COMMON SENSE回答罢了........

谢谢解答!

darksider

原帖由 carly_yen 于 2009/11/13 07:08 PM 发表
老实说... 这时哪一课的啊~~?? 哈哈哈~~
我好象没有读过......
我用COMMON SENSE回答罢了........

谢谢解答!

Transport那课...新的oxford fajar课本有提到。

carly_yen

请问BIO PAST YEAR 出过的题目还会再出吗????

carly_yen

原帖由 darksider 于 13-11-2009 07:10 PM 发表


Transport那课...新的oxford fajar课本有提到。

难怪.... 我用PELANGI 的~~~~~ 哈哈哈!

大家一起加油!

darksider

原帖由 carly_yen 于 2009/11/13 07:12 PM 发表
请问BIO PAST YEAR 出过的题目还会再出吗????

我想应该不会出同样的问题，但同样的ｔｏｐｉｃ就会。
上次听一位chemistry marker说，有些比较懒惰的examiners会用bank questions里面的考题来出（比如那些questions出现在2002 trial,他们4-5年后会出在STPM...可能只限于ＳＴＰＭ chemistry.

好的，一起加油，那个Ａ回来　

也要注意 Chordae tendinae and papillary muscle
Chordae tendinae is a cord-like tendon that connects the papillary muscle to the tricuspid/bicuspid valves to prevent them from inverting into their respective atrium.

During ventricle systole, the papillary muscle will contract so as to prevent the tricuspid and bicuspid valves from inverting into the atria. (pressure is being exerted to the valves during ventricle systole)...

关于它们的问题通常在objective q会出。

[ 本帖最后由 darksider 于 13-11-2009 08:04 PM 编辑 ]

purple_pig_33

原帖由 darksider 于 13-11-2009 06:38 PM 发表


改正一下，example of competitive inhibitor is malonate which competes with succinate for the active site in succinate dehydrogenase .

Example of irreversible incompetitive inhibitor is cyanide  ...

謝謝你的改正

生物难题

原帖由 darksider 于 13-11-2009 06:52 PM 发表


我学到的是photolysis occurs in the lumen of the thylakoid.photolysis所产生的H+ ions are used in the formation of NADPH...

the only molecule that can oxidise water is P680, a reacion centre Phot ...

哇！你讲解的很详细。
对啊，NADP+是因为接受了stroma的H+，才被reduced成为NADPH。
很多图片都是这样画的。

生物难题

原帖由 darksider 于 13-11-2009 07:58 PM 发表


我想应该不会出同样的问题，但同样的ｔｏｐｉｃ就会。
上次听一位chemistry marker说，有些比较懒惰的examiners会用bank questions里面的考题来出（比如那些questions出现在2002 trial,他们4-5年后会出在STPM.. ...

但是看了那么多年的past year objective都好像没有问过chordae tendinae and papillary muscle。
这个会不会detail了一点？