Form6 Biology

creme

BluStAr 于 20-3-2005 01:21 AM  说 :
可以大概酱解释 electron transport system mah??
这个最难背了！

还没得到回答??

1. Electron transport system is a collection of molecules embedded in the inner membrane of the mitochondrion.

2. Each component of the chain oscillates between a reduced state and an oxidized state.

3. A component of he chain becomes reduced when it accepts electrons from its "uphill" neighbor.

4. Each member returns to its oxidized form as it passes electron to its "downhill" neighbor.

5. Electrons removed from food are transferred by NADH to the first molecule of the chain, a flavoprotein ( flavin mononucleotide, FMN)

6.Another source of electrons is FADH2 which adds its electrons to the chain at a lower energy level than NADH does, that is after the first ATP synthesis site.

7. Each hydrogen atom pasing fron coenzyme Q dissociates into a hydrogenion and an electron. The electron is then accepted by cytochrome b. The hydrogen ions are temporarily deposited in the surrounding medium until they are required at the end of the chain.

8. Each time the electron passes from one intermediate to another, a small amount of energy is liberated and incorporated into ATP.

9.Each NADH contributes enough energy to generate 3 ATP, while each FADH2 can oly generate 2 ATP.

10. Oxygen is the final acceptor of the reducing power released during the oxidation of the organic food molecules.

[ Last edited by creme on 14-4-2005 at 08:35 PM ]

creme

CYTOPLASMIC STREAMING

1. The living cytoplasm of many cells is constantly on the move, sweeping cell organelles about the cell.

2.The streaming of cytoplasm in individual sieve tube elements could be responsible for bi-directional movements along individual sieve tubes.

3.Movement of solutes across the sieve plate is either by acyive transport or by moving cytoplasm passing through the pores.

4. Cytoplasmic streaming carries protein, amino acids, sugars and mineral ions together at the same speed.

5. Evidence against this hypothesis includes :
  (a) Streaming has been obserbed in immature sieve tube tissue only.
  (b) Streaming movements are not fast enough to account for the observed rates of translocation.
  (c) This hypothesis cannot explain the different rates of translocation of different substances at the same time within the same sieve tube.

creme

PERISTALTIC WAVES

1. According to this hypothesis, within the sieve tube, there are fine cytoplasmic filaments known as phloem proteins.

2. These filaments pass through the pores of the sieve plates and enter the neighboring sieve tube elements. They are therefore known as transcellular strands.

3. The protein filaments seem to contract and relax, creating waves of peristalsis like that of the intestines In this case however, it forms a cytoplasmic wave of movement along the protein filaments.

4.These wave help to push and move solutes along the cytoplasmic filaments.

5.Such peristaltic waves can occur upwards and downwards --- two-way flow of solutes.

6.This process required energy (from companion cell).

蝎杰

什么是absolute refractory period?

蝎杰

hydrostatic pressure 是什么？？？当水由某个地方进入另一个地区所产生的压力吗？

lezheng

请问大家已经学到哪里了？
我目前正要进入Growth的部份。
因为考试快到，所以我决定从hormone那一课开始温习到第一课，然后同时学习volume 2的课。

秋月春风 于 3-4-2005 01:35 AM  说 :


勤

每个人都知道的道理，却不是人人做得到。求知识宜脚踏实地：用心理解，背，练习，做足了就凭运气了。

那除了这些还有什么吗?Math T 的 Trigonometry, Vector & Deduction geometry要怎样才会掌握呢?

雨天之魂

Mass Flow Hypothesis.

早上有阳光， 在叶子有光和作用生产出 sucrose －lower the water potential －附近细胞的水流入化淡 －产生出水压， 把食物推向根部。这个部分是 source region.

到了根部， sucrose 被转换成 starch 收藏起来, 恢复 water potential -水流回附近细胞， 透过 xylem 回到植物上部。
这个部分是 sink region.

晚上， 过程倒转。根部的 starch 被转换回去 sucrose 来使用。
根部变成 soucre region, 叶子变成 sink region.

雨天之魂

Cytoplasmic Streaming.

Phloem 内部细胞连贯， 食物在细胞的 cytoplasm 里面运行，
透过 plasmodesmata. 需要能量（ATP）。

Peristaltic wave movement.

指 phloem 管像人的食道一样会收缩抽动来推动里面的食物。

Electro-osmosis

K+ 会被 actively transported 进入 companion cells,
然后附近的K+会自动 diffuse 回来替补， 会不断旋转（propel),
推动食物移动向前。


只需要知道 mass-flow 的 details, 其他的大概知道就好。
自己参考课本看有什么证据证明／推翻上述四个说法。

坛主什么时候才会把notes post上来呢？我已经等到快变成长颈鹿了，在考试时东张西望（开玩笑而已）。

creme

其实大家可以参考biological science或者campbell会有很大的帮助啊...

请问各位这题怎么解答：
A hormone molecule M is made up of two polypeptide chains; one chain contains 20 amino acids and the other chain contains 31 amino acids. What is the minimum number of nitrogenous bases in DNA required to code this molecule?
A   51                       B 102
C   153                     D  306
书上给的答案是C。解释如下
Total number of amino acids
=20+31
=51
Total number of bases (nucleotides)
=51 x 3
=153
我想问为何要乘三？

雨天之魂

lmenwe 于 4-5-2005 16:05  说 :
请问各位这题怎么解答：
A hormone molecule M is made up of two polypeptide chains; one chain contains 20 amino acids and the other chain contains 31 amino acids. What is the minimum number of nitro ...

each amino acid is coded by 1 coden.
each coden is made up of 3 bases.

AUG AUC ACC AUU  etc. for example.

Thank you.

坛主啊，什么时候才会把你的notes post上来呢？半年考快到了，如果有空请帮帮忙。谢谢。

坛主Upper Six 到底要注意什么呢？我的老师已经放产假了麻烦你告诉我好吗？

babycow_1

大家好，我也是那生物的。。。有人能帮我 protien systhesis 吗？？这课好难唷！！你们在那里朴习啊？？ 我给 KHOR 的怡保的老师，他来北海教的。。。
还有 DNA systhesis。。。。

lezheng

关于这一课我前两天才明白，现在我把自己所理解的整理出来，希望大家多多指教。
Protein Synthesis分两个步骤： Transcription和Translation。

Transcription
-Helicase splits the DNA
-RNA polymerase attaches to promoter site next to the cistron
-This enzyme moves along the transcribing strand in the 5'->3' direction to build up mRNA
-It add complementary nucleotide from nucleoplasm by phosphodiester bond
-Therefore, complementary base pairing occurs to elongate the strand
-Ribose and phosphate group form the backbone
-When reachs terminator, the enzyme detachs then mRNA peels away the DNA then go into cytoplasm
-The DNA backs to normal

Translation
-mRNA carries codons, the 5' end binds to the binding site on small ribosomal subunit
-On the other hand, aminoacyl-tRNA synthatase actives an amino acid
-The amino acid attaches to a specific tRNA, produce aminoacyl-tRNA
-The anticodon (UAC) of the aminoacyl-tRNA binds to the start codon (AUG) on the mRNA
-Large ribosomal subunit is added to the small subunit to form ribosome
-Second aminoacyl-tRNA with complementary anticodon enters the A-site of ribosome, binds to second mRNA codon
-Peptide bond is formed to link the two adjacent amino acids to produce dipeptide
-The covalent bond between the amino acid and it's tRNA in P-site is broken
-The tRNA in P-site is lereased back into cytoplasm via E-site
-The ribosome moves along the mRNA by one codon
-Second tRNA translocated to P-site, A-site vacant for an incoming aminoacyl-tRNA
-Third aminoacyl-tRNA enters to A-site
-Peptide bond formed between two adjacent amino acid, tripeptide formed
-Second tRNA is released via E-site
-These processes repeat, a polypeptide chain is formed
-When the ribosome reachs terminator codon, releasing factor binds to the stop codon
-Hydrolysis of the bond between tRNA and last amino acid in the polypeptide chain occurs
-Complete polypeptide chain relaesed. It may then coil and fold to form functional protein
-The large and small ribosomal subunits are released

雨天之魂

babycow_1 于 13-5-2005 03:07  说 :
大家好，我也是那生物的。。。有人能帮我 protien systhesis 吗？？这课好难唷！！你们在那里朴习啊？？ 我给 KHOR 的怡保的老师，他来北海教的。。。
还有 DNA systhesis。。。。

Refer back to page 6 in this thread.

asapolh

请问有谁能提供taxonomy的notes吗？
背到头痛，老师给的notes太乱了。。。