structure and compositon 2012课件.ppt

mycoplasma(支原体) a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics such as penicillin. The cells often present a certain shape, with a characteristic small size, with typically about 10% of the volume of an E. coli cell. Archaebacteria 古细菌 A type of prokaryote, that is, a unicellular organism without a cell nucleus. Many species of archaebacteria live in extreme conditions similar to those prevalent on primitive Earth. They have similarities to both normal bacteria and the larger eukaryotes. In structure, they are like unicellular prokaryotes, but the genetic transcription and translation underlying their creation is similar to that of the more complex eukaryotes. Archaebacteria Archaea survive today in evaporative salt ponds on the edge of Great Salt Lake (above) and the boiling hot springs of Yellowstone National Park (right). Plasmid (质粒) Small circular DNA molecule that replicates independently of the genome. Plasmids enable additional functions, such as antibiotic resistance. Application: plasmid vectors for DNA cloning Key point comparison of procaryotes and eucaryotes Particle consisting of nucleic acid (RNA or DNA) enclosed in a protein coat and capable of replicating within a living cell and spreading from cell to cell. Viroids are molecules of RNA that are not classified as viruses because they lack a protein coat. Prions are infectious protein molecules that do not contain DNA or RNA. A bacteriophage is any one of a number of viruses that infect bacteria. * base purine pyrimidine cytosine uracil thymine adenine guanine B. function * The subunite of nucleic acid * Carrier of energy （ATP） * Coenzyme（CoA） * Signaling molecules （cAMP） IV. Macromolecules Molecule such as a protein, nucleic acid, or polysaccharide with a molecular mass greater than a few thousand daltons. Nucleic acid: RNA or DNA, a macromolecule consisting of a chain of nucleotides joined tog