Lecture 2- Friday, January 24, 2003 R. Jones Chapters 2,3 and 16
More on Origins of Life and the Cellular Basis of Life
1. Primitive earth atmosphere contained all essential ingredients for construction of cellular components.
2. All cells contain C (carbon), H (hydrogen), O (oxygen), N (nitrogen), P (phosphorus), S (sulphur) as major ingredients.
3. All cells contain carbohydrates, lipids, proteins and nucleic acids.
4. Composition of major cellular polymers.Carbohydrates (C,H,O) are made up of monosaccharides that are polymeriaed into oligosaccharides (only a few monosaccharides e.g. sucrose, a disaccharide) and polysaccharieds as in starch and cellulose. Insects have a ppolysaccharide polymer called chitin. Chitrin contains some N as well as C, H and O. Lipips are composed of two groups the fatty acid-containing oils and fats and steol containing lipids comon in membranes of cells. Proteins are polymers of amino acids.They contain C,H,O and N and in some case small amount sof S. These are 20 types of amino acids normally found in poteins, and proteins differ becuase of the order in which the individual amino acidsd are orgnaized. Nucleotides are polymerized into nucleic acids (C,H,O,N,P). These molecules are important in energy transformation in cells and in the genetic material RNA and DNA.
5. The leap from chemical evolution to the first living organism was a huge step that has no clear explanation other than the idea that aggregation of organic matter could eventually give rise to something that resembled an early cell.
6. A living organism is characterized as being: cellular, able to reproduce, grow, divide, develop, respond and metabolize
7. First cells to evolve 3-5 billion years ago (bya) were very simple and similar to today's bacteria (prokaryotic cell). These were Archaebacteria and eubacteria evolved from Archaea. Cyanobacteria that produce oxygen by photosynthesis are members of the Eubacteria and evolved around 2.8 bya.
8. Archaebacteria and eubacteria belong to the Kingdom Prkaryota. All organisms in this kingdom have a very simple cellular organization. A plasma membrane encloses the cytoplasm containing a circular strand of DNA and some ribisomes. The bacterial plasma membrnae is encirled by a cell wall and a covering referred to as a pellicle is often deposited on the outside of the cell wall. Flagella (sing. flagellum) are used for locomotion in motile bacteria.
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