DrHeydari - The facts in biology are only as good as the...

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Unformatted text preview: The facts in biology are only as good as the tools available for investigation-- Lodish et al (1995) Molecular Cell Biology. Sci Am Books. The Central Dogma of Molecular Biology Transcription RNA Synthesis Translation Protein Synthesis Replication DNA duplicates Information Information mRNA DNA DNA RNA Protein Nucleus Cytoplasm Cytoplasm Nuclear Envelope Protein Ribosome Information Exon 1 Exon 2 Exon 3 Exon 4 mRNA Transcription Translation Protein DNA and a Diagram of a Typical Structural Gene Gene 5 3 Exon 1 Exon 2 Exon 3 Exon 4 Start site (Initiation codon) Stop site or Termination codon Regulatory Elements Introns Transcription Machinery ATP ADP Phosphorylation Transcription Machinery Inactivated Factor Protein A mRNA Element Translocation Transcription Machinery TATA Regulation of Genes via Interaction of Trans- Acting Factors and Cis-Acting Elements Trimerization Activated Factor Environmental Factors (e.g., diet) Protein A Proteins , the working molecules of a cell, carry out the program of activities encoded by genes.- Some build the structure of the cell- Others process materials by catalyzing intracellular or extracellular chemical reactions * It is difficult to think of any cell activity that does not involve proteins; perhaps there are none Proteins , are built from single chains of amino acids (20 common amino acids are found in natural proteins, thus a - Catalyze an extraordinary range of chemical reactions- Provide structural rigidity to the cell- Control flow of material through membrane- Regulate the concentrations of metabolites- Act as sensors and switches- Cause motion- And control gene function * A repeating theme in molecular biology is that large, complex structures are built from small, simple components. How proteins do all these functions? The three-dimensional structure of proteins has evolved to carry out these functions efficiently and under precise control. The spatial organization of proteins is a key to understanding how they work How a protein folds into a globular conformation. The polar amino acid side chains tend to gather on the outside of the protein, where they can interact with water. The nonpolar amino acid side chains are buried on the inside to form a hydrophobic core that is "hidden" from water. Amino acids, the monomeric units that link together to form proteins, have a common structure. The carbon atom (green) of each amino acid is bonded to four different chemical groups and thus is asymmetric. The side chain, or R group (red), is unique to each amino acid. The diversity of natural proteins reflects different linear combinations of the 20 naturally occurring amino acids. The short peptide shown here, containing only four amino acids, has 20 4 , or 160,000, possible sequences. An essential amino acid for an organism is an amino acid that cannot be synthesized by the organism from other available resources, and therefore must be supplied as part of its diet....
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DrHeydari - The facts in biology are only as good as the...

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