Nucleic Acids 和 Protein synthesis 一直是A Level的重點章節，也是經常被同學們提問的地方。下面幫大家整理了一份內部複習資料，在即將考試期間提供給同學們，希望能幫助到大家！
DNA is the genetic material, which carries the genetic information.
Chromosome is a DNA molecule associate with the histone proteins.
Gene is the small section of DNA, which can be used to make the proteins.
■ DNA
- Deoxyribonucleic acids
- Double helix structure with antiparallel strands。
- DNA is the polymer of DNA nucleotides (Polynucleotides)
■ RNA
- Ribonucleic Acids
- Made up by RNA nucleotides.
- Messenger RNA: Copy the genetic information from DNA in the nucleus and bring the information to the ribosome in cytoplasm.
- Transfer RNA: Carry the specific amino acid to the ribosome.
- Ribosomal RNA: Form the subunits of the ribosome.
l Nucleotide contains a pentose sugar, a phosphate group and a nitrogen-containing base:
■ Each nucleotide is linked to the next one by phosphodiester bonds between the phosphates of a nucleotide and pentose of another nucleotide to form the polynucleotide.
■ Commentary base pairing: purine bases pair with pyrimidine bases (A-T, G-C)
- Adenine always pairs with thymine (uracil in RNA) via 2 hydrogen bonds.
- Guanine always pairs with cytosine via 3 hydrogen bonds.
■ Two polynucleotide strands of the DNA is held by the hydrogen bonds between the complementary base pairing.
■ Occurs during interphase before the cell division to ensure each daughter cell get correct amount of genetic material.
■ DNA replicates by semi-conservative replication: Each daughter DNA molecule contains one strand from parent DNA and one newly formed strand.
■ Process:
1. The DNA double helix structure is unwound and unzipped by helicase.
2. Both separated DNA strands are used as the template strands.
3. Free nucleotides joined with templet strand and held by the hydrogen bonds between the complementary base pairs.
4. DNA polymerase catalyses the formation of the phosphodiester bonds between DNA nucleotides.
5. Due to the new DNA strands have to formed from 5』 end to 3』 end, and the DNA is antiparallel, one daughter DNA strand is formed discontinuously. The DNA segments are connected by the DNA ligase.
6. Two identical daughter DNA molecules are formed.
Part 3 ：Protein synthesis
■ Two strands of DNA: sense strand (coding strand) + antisense strand (template strand)
■ The genes are on the antisense strand
■ Transcription (occurs in the nucleus):
1. Double strands of DNA are unwound and unzipped and the antisense strand is used as the template.
2. RNA nucleotides pair up with their complementary bases on the template strand via hydrogen bonds.
3. RNA polymerase catalyse the formation of the phosphodiester bonds between the RNA nucleotides.
4. The mRNA molecules is formed, and then the hydrogen bonds between the mRNA and DNA template strand are broken.
5. The DNA rewind into the double helix structure and mRNA molecule leaves the nucleus via nuclear pore.
■ Translation: (occurs on the ribosome)：
1. The mRNA moves into the cytoplasm and attached by ribosomes to provide the binding site for tRNA.
2. tRNA will brings the specific amino acids and bind with the mRNA and ribosome via the complementary base pairing between the codon and anticodon.
3. Then, second tRNA bring another amino acids and bind with the mRNA.
4. The peptide bond form between the adjacent amino acids.
5. The first tRNA detached from the its amino acids and he ribosome moves along the mRNA molecule, and a new tRNA with the amino acids will bind with the next codon.
6. The polypeptide is formed gradually until the ribosome reach the stop codon, then the formation of the polypeptide is completely. It will fold in the secondary and tertiary structure immediately.
7. The mRNA can be read by several ribosomes at the same time to produce many polypeptide.
Alevel生物中最有效的實驗題答法——PEE答題法，專治各種疑難實驗題。我們就用這道AQA考試局的生物AS真題來舉例子。請看下圖：
這道題的背景不是非常複雜，涉及到的幾個關鍵詞，例如：inhibitor（抑制劑），mitosis（有絲分裂），trial（實驗組）。
在前一道小題中也解釋了kenisin 是一種控制細胞分裂涉及到的酶。kenisin的功能一旦被抑制劑抑制，就會形成那種單面的spindle fibre。這種畸形的spindle fibre越多，就越會降低細胞分裂的速率。
好了，我們再看一下問題是什麼：
Q：一個學生根據實驗數據得出結論：在接下來的實驗治療過程中，用濃度為100nmol dm-3 的抑制劑來抑制腫瘤生長是最合適的。實驗的數據支持這個結論嗎？為什麼？
這個問題我們要通過兩方面回答，先說是，為什麼。再說不是，為什麼。當然，你的觀點是不算分的，給出支持你觀點的數據和理由才是給分點。
我推薦用PEE的答題法：
P: point，觀點，對/錯，支持/不支持。
E: evidence, 證據，你提出的觀點依據究竟是什麼。
E: explain, 解釋，原因究竟是什麼。
具體解題思路如下：
正方觀點
Point: 該生的觀點正確。
Evidence:在濃度到達100nmol dm-3之後，形成的畸形spindle fibre的數量增長並不明顯。
Explain: 濃度過高的抑制劑可能對身體造成傷害。
Point: Yes
Evidence: When the concentration is above 100, the increase in % of cells not undergoing mitosis is very little.
Explain: High concentration of inhibitors may be harmful to human bodies.
Point: 該生的觀點不正確。
Evidence: 在濃度到達100nmol dm-3 之後，還有殘餘的少量癌變細胞。
Explain: 殘餘的少量細胞還會繼續繁殖，形成腫瘤。
Point: No.
Evidence: When the concentration is at 100, there are still 7% cancer cells undergoing mitosis.
Explain: The cancer cells that survived may continue to form tumors.
這種回答方式看起來條理更清晰，話術也不難說，都是一些很基礎的點，而且正好湊足4個打分點。
注意：寫的時候把PEE的題頭去掉。
www.bozemanscience.com/science-videos/
在這個網站上你能找到很多關於生物的YouTube視頻，而且也有生物網絡課程
www.cellsalive.com
這是一個交互式網站，上面有大量的圖片和動畫，
對AS生物中的細胞學、顯微鏡學、微生物學、免疫部分的學習都非常有幫助
www.biology.arizona.edu/default.html
美國亞利桑那大學生物項目，上面有非常好的動畫、教程和在線測試
www.dnaftb.org/dnaftb/
提供DNA、基因、基因組成等方面的在線教程
www.chemguideforcie.co.uk/index.html
這個是CIE AS與A Level化學網站，
但是裡面的部分化學內容對生物分子的Section 2學習非常有用
www.rsc.org/Education/Teachers/Resources/cfb/
英國皇家化學學會網站，對生物分子Section B的學習非常有幫助
www.beep.ac.uk/
布裡斯託生物倫理教育項目，上面有很多 A Level課程討論的倫理話題
www.who.ch
歸屬於WHO，在上面可以找到關於傳染性疾病和非傳染性疾病的最新信息
www.cdc.gov/
美國疾病控制中心網站，同樣能在這個網站上找到關於疾病的最新信息
www.mbgnet.net/bioplants/main.html
密蘇裡植物園官方網站，非常適合了解植物
images.botany.org/
同樣包含非常多有用的植物圖片，填補上一個網站的空缺部分
www.bu.edu/histology/m/index.htm
包含非常多電子顯微鏡下的動物細胞和組織的照片
library.med.utah.edu/WebPath/
這個網站上有很多人體解剖學和組織學的圖片
evolution.berkeley.edu/
美國加利福尼亞大學古生物博物館網站提供的很多生物進化的學習資源
www.nobelprize.org/
諾貝爾獎官方網站，上面有非常多的教育資源，而且還有諾獎得主的介紹
www.wellcometreeofl ife.org/
同樣屬於 Wellcome Trust基金會，可以幫助你A Level課程生物多樣性的學習
整理了這麼多，希望能夠在考試中幫到大家。方法有效也不如親身試驗，建議同學們多動手進行練習。
額外，還準備了19個Topic筆記和Alevel考試歷年真題供同學們參考學習，助大家Alevel輕鬆突破A*。
話不多說，送上福利
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9月29日(周二)晚20:45-21:30，Alevel生物名師Adam老師親自授課：45分鐘教你快速入門Alevel細胞學。回復 「A2」：獲取AS & A2 Notes 筆記戳 閱讀原文，開啟高效提分之旅！