原始地球에 있어서 化學進化와 原始生命體 誕生

• 영문명: Chemical evolution and first life forms on the primitive earth
• 발행기관: 한국육종학회
• 저자명: C. Harn(韓昶烈) M.Z. Kim(金文子) Chee Harn(韓智學)
• 간행물 정보: 『한국육종학회지』Vol.26 No.2, 205~224쪽, 전체 20쪽
• 주제분류: 농수해양 > 기타농수해양
• 파일형태: PDF
• 발행일자: 1994.06.30

영문 초록

The Earth has existed in solid form for 4.6 billion years. Abiotic synthesis of organic molecules had occurred on the primeval Earth in the absence of life : first, simple primitive molecules such as hydrogen cyanide(HCN) and aldehyde(R-CHO) from the primitive atmospheric gas, then such monomers as amino acids or ribose sugar, and eventually polymers such as polypeptides and nucleic acids. The first on billion years after the formation of the Earch are said to be the era of chemical evolution. Fossil evidences discovered in Australia and South Africa suggest that true life forms apperaed on the Earth around 3.6 billion years ago. Cellular life has three basic components of (1) a membrance boundry separating the living system from its environment, (2) metabolism catalized by enzymes, and (3) information-storing genetic system capable of self-replication and transmission to descendants. Three major models of protobionts are proposed : Opariri’s coacervate model, Fox’s proteinoid microsphere, and Goldacre’s lipid bilayer model, which have in common a selectively permeable boundary. These three protobionts are not true life forms but precursors, being simply membrane-bound metabolizing systems lacking a genetic component. With the incorporation of a genetic system, protobionts would have evoled into true life forms, the eubionts. All cellular life today stores its genetic information in the form of triplet codon in the DNA molecules. It has been suggested, however, that earlier life forms had RNA as their information storage system, and the RNA had been replaced later by DNA. RNA is considered fit as genetic system for the primeval life as it has dual function of information storage and catalytic activities. Primordial anaerobic heterotrophs relied on abundant pre-existing organic nutrients. Scarcity of a nutrient favored selection of those that could produced the nutrient from a precursor. By this process, progressively longer and more complex metabolic pathways evoleved. With the appearance of such photosynthetic autotrophs as cyanobacteria(blue green algae) which used CO₂ and hydrogen from water and released oxygen, the originally reducing atmosphere turned to oxidizing atmosphere. After the long, era of prokayotes which lasted nearly two billion years, eukaryotes had arisen from cell wall-less prokaryote with motile plasma membrance around 1.5 billion years ago. DNA was relocated to the cell interior from its attachment site on the plasma membrance and a nuclear envelope developed, forming nucleus and establishing mitotic system. Multicellularity gave organism possibilities for structural and functional spcialization that increased their life expectancy, stability, and efficiency.

목차

ABSTRACT

1. 緖言

2. 地球의 形成

3. 有機物의 無生物的 合成(abiotic synthesis)

4. Miller-Urey의 實驗

5. 隕石안의 有機物

6. Monomer

7. Polymer

8. 生命體의 誕生

9. 最初의 生命體의 證據

10. 生命前驅體 形成에 관한 假說

11. 生命體로서의 要件

12. 原始地球에 처음 생긴 遺傳物質

13. RNA의 構成

14. RNA의 酵素 機能

15. Intron, reverse transcriptase의 起源

16. DNA의 有利한 點

17. RNA의 進化

18. 原始 生命體의 에너지源과 大氣 酵素量의 變化

19. Evolution backward

20. 眞核生物의 出現

21. 多細胞體로의 分化

引用文獻

키워드

Abiotic synthesis Eubionts Primeval life Protobionts