Genetics and metabolism (L4)

• ATP


  Energy carrier, Nucleotide, Contains phosphate connected by high energy bonds
• Anabolism


  1. Biosynthesis of amino acids and nucleotides

  2. Biosynthesis of sugars and polysaccharides

  3. Biosynthesis of fatty acids and lipids
• Amino group


  Usually derived from inorganic nitrogen source
• Purines


  Constructed from key compound, inosinic acid
• Pyrimidines


  Constructed from key compound, uridylate
• Polysaccharides


  Synthesized from either uridine diphosphoglucose or adenosine diphosphoglucose
• Fatty acid biosynthesis


  1. Fatty acids biosynthesize 2 C atoms at a time using acyl carrier protein (ACP)

  2. ACP holds fatty acids as its being synthesized

  3. Each 2 C unit derived from a 3 C compound (malonate)

  4. Most common fatty acids contain C12-C20 fatty acids

  5. Lipid formulation occurs when fatty acids are added to glycerol
• Respiration


  1. Anaerobic (includes glycolysis and fermentation)

  2. Aerobic/catabolism (includes glycolysis and Krebs cycle)
• Glycolysis


  Converts glucose to pyruvate, producing ATP and NADH
• Krebs cycle


  Series of biochemical reactions in which large amounts of potential chemical energy is released, through a series of oxidations and reductions that transfer the potential energy to electron carrier coenzymes

  
• Metabolism of fatty acids

  1. Fatty acids are broken down to acetic acid

  2. If fatty acids are the sole source of carbon, bacteria utilize a modified Krebs cycle (glyoxylate cycle) which is not generally found in animal cells
• Gene expression


  DNA is expressed by synthesis of specific RNAs and proteins (transcription and translation)

  
• Bacterial genomes vary in size
• Regulation of gene expression


  Induction and repression enable bacteria to regulate production of specific gene products
• Operon


  A group of contiguous genes that is transcribed as a single unit and translated to produce the corresponding gene products, can be induced or repressed
• Regulon


  Alters expression of a groups of genes and operons
• Inducible genes


  Genes whose expression is turned on by the presence of some substance, e.g. Lactose induces expression of the lac genes

  
• Catabolite repression


  Many inducible operons are controlled by inducers and regulatory genes, AND the level of glucose in the environment
• Repressible genes


  Genes whose expression is turned off by the presence of some substance (co-repressor), e.g. Tryptophan represses the trp genes
• Attenuation


  In many repressible operons, transcriptions initiated at the promoter can terminate prematurely, called premature termination
• Plasmids


  • DNA molecules that encode traits not essential for bacterial viability, such as resistance, production of toxins, and synthesis of cell surface structures
  • Two types: stringent (replicate only when the chromosome replicates) and relaxed (replicate on their own)

  
• Bacteriophages


  Viruses that infect bacteria.

  Either DNA or RNA, obligate intracellular parasites in bacteria, extracellular phage particles are metabolically inert
• Mutations


  Heritable changes in the genome
• Genetic interactions between microbes

  Enable genomes to evolve much more rapidly than by mutation alone
• Processes in bacteria involving transfer of genetic information

  1. Transformation

  2. Transduction

  3. Conjugation
• Transposons


  Segments of DNA that can move, can cause mutations, mediate genomic rearrangements, function as portable regions of genetic homology, and acquire new genes and contribute to their dissemination, but are not self-replicating genetic elements
• Polysaccharides:

  Synthesised from either uridine diphosphoglucose or adenosine diphosphoglucose
• Bacterial DNA is:

  • Double stranded
  • Free in the cytosol
  • Attached at mesosome to cell wall
• lac i: regulatory gene that codes for regulatory proteins
• lac o: operator and where the protein attaches to
• What happens when a protein attaches to a gene?

  steric interference occurs causing gene to not be readable
• lac p: promoter, aids in RNA polymerase binding
• lac z: β - galactosidase, enzyme that catalyses the hydrolysis of β - galactosidase
• lac y: permease, a protein present in cell wall that allows lactose to be brought into the cell
• lac a: transacetylase
• alolactose: isomer of lactose, attaches to regulatory gene and it falls off so gene can now be read
• Transformation: a donor bacterium lysis and the fragments of DNA released are taken up directly from the extracellular environment by recipient bacteria
• Transduction: bacteriophages act as vectors to introduce DNA from donor bacteria into recipient bacteria
• Conjugation: direct contact between donor bacterium and recipient bacterium via a conjugation pili, allowing genetic information to transfer fromndinor bacterium to recipient bacterium
• Breakage and joining of parental DNA molecules: forms hybrid, recombinant molecules