环境微生物学课件.ppt

Structure and Function of Genetic Materials DNA RNA DNA=deoxyribonucleic acid RNA=ribonucleic acid Basic building blocks: Nucleotides Phosphate group Pentose sugar Nitrogenous base * Structure of DNA Double stranded (double helix) Chains of nucleotides 5’ to 3’ (strands are anti-parallel) Complimentary base pairing A-T G-C * DNA Structure Phosphate-P Sugar-blue Bases-ATGC * DNA Replication Bacteria have closed, circular DNA Genome: genetic material in an organism E. coli 4 million base pairs 1 mm long (over 1000 times larger that actual bacterial cell. How it can be put into a cell? DNA takes up around 10% of cell volume * DNA Replication occurs at the replication fork 5’ to 3 ‘ DNA helicase-unzips + parental DNA strand that is used as a template Leading stand (5’ to 3’-continuous) DNA polymerase-joins growing DNA strand after nucleotides are aligned (complimentary) Lagging strand (5’ to 3’-not continuous) RNA polymerase (makes short RNA primer) DNA polymerase (extends RNA primer then digests RNA primer and replaces it with DNA) DNA ligase (seals Okazaki fragments-the newly formed DNA fragments) * Replication Fork 1 解旋酶打開DNA雙螺旋 * Protein Synthesis DNA-------? mRNA------? protein transcription translation Central Dogma(中心法則) of Molecular Genetics * Diffusion aided by a carrier protein - permease - in cell membrane Carrier provides specificity and increases rate to equilibrium is powered by the potential energy of a concentration gradient and does not require the expenditure of metabolic energy. Not highly important in prokaryotes What is facilitated diffusion? Passive 3. facilitated diffusion * Passive 3 Facilitated diffusion Diffusion facilitator protein Nutrient molec in high conc Specific binding of nutrient to facilitator protein Protein conformation (change shape) Release of nutrients into the cytoplasm of the cell * Important points about facilitated diffusion Most transport proteins are specific for a single nutrient. Over time facilitated dif