Bacteria caq

💊 Bacteria Created Tags Advantages of operon Allow bacteria to coordinately regulate the expression of a group of genes that encode proteins with a common functional goal Ensure that all proteins necessary to metabolise a particular compound are under a single promoter so that these genes are made turned off or turned on at the same time helping the bacteria to respond quickly to environmental changes (how operons allow for rapid response by bacteria to environmental change), providing a selective advantage Bacteria only produces enzymes when required, preventing waste of limited energy and resources which provides a selective advantage as they are able to respond quickly to changes in environment Different operant allow bacteria to utilise different types of carbon source/ a variety of sugars for their energy requirements For repressible systems only: When end product is abundant, synthesis would stop and operon can be repressed to minimise wastage and conserve resources and these resources can be redirected to other cellular processes important to bacterium How does lac operon works/ how the metabolism of lactose in bacterial cells is regulated Regulation of the metabolism of the lactose is done by lac operon With Lac ZYA under the control of one promote sequence which codes for enzymes/ August 7 , 2025 124 1 PM Bact er ia 1

proteins that hydrolyse lactose to allolactose(lac Z and transport lactose into the cell (lac Y Lac L gene codes for an active lac repressor which is complementary in shape and binds to the operator sequence, a repressor binding site When lactose is absent, there is basal transcription level as repressor is bound to the operator sequence, inhibiting RNA polymerase from binding to promoter When lactose is present and glucose is absent, lactose is transported into the cell by permease and is converted to allolactose by beta-galactosidase Allolactose acts as an inducer and binds to the allosteric site of lac repressor and changes the conformation of active lac repressor thereby inactivating it as it is no longer complementary to the operator sequence and thus dissociates from operator, no longer can bind to the operator This allows the binding of RNA polymerase to promoter and move downstream to transcribe the structural genes to form beta galactosidase, permease and transacetylase for metabolism of lactose ATP converted to cAMP by adenyl Cyclase and cAMP binds to Catabolite Activator Protein CAP to form cAMPCAP complex activating it which then binds to the CAP site upstream of promoter, increasing expression of Lac operon as it increases the affinity of RNA polymerase to promoter (relate to cell signalling where low glucose causes glucagon to bind to GPCR, eventually activating adenyl Cyclase) When glucose is present, it inhibits adenyl Cyclase which is responsible the conversion of ATP to cAMP, low levels of cAMP, lesser cAMP to bind to CAP, to form cAMPCAP complex amd activating it, lac expression at basal level Binary fission significance Results in the production of genetically identical daughter cells thus gene that codes for desirable traits are passed on to daughter cell favouring success colonisation It is a form of asexual reproduction in bacteria and hence it is a fast process allowing rapid reproduction of bacteria Bact er ia 2

Short generation span helps in the accumulation of mutations and evolution process benefits of conjugation they may receive genes that codes for antibiotic resistance They may receive fences that codes for enzymes not originally present, giving them the ability to use a new metabolite They may receive genes that codes for xenobiotic resistance ( substances that are foreign) How does prokaryotic genome have variation yet preserved Preserved ref to mechanism of proper separation Ref to semi-conservative DNA replication Ref to two genetically identical daughter cells Variation Conjugation: F cell forms a mating bridge with F cell One strand of DMA of F plasmid breaks, peeks off and enters F cells Unbroken strand of F plasmid in F cell serves as a template to synthesise the new strands , reforming the double stranded F plasmid The transferred plasmid strand that enters the F cell serves as as a template for synthesis of new strands, molecule circular itʼs to form New F plasmid Compare eukaryotic and prokaryotic genome Features Eukaryotes Prokaryotes Shape Linear molecule Circular molecule Amount Multiple Singular Bact er ia 3

Features Eukaryotes Prokaryotes Level of DNA packing Forms a nucleosomes Folds into chromosomal looped domains by protein-DNA association Protein associated with packing Histone association Loop around histone like proteins Location Nucleus surrounded by nuclear envelope Nucleoid region, not-membrane bound Origin of replication Many One both have promoters Double helix dna Role of F plasmid F factor on f plasmid codes for proteins necessary for the formation of the sex puli and subsequent cytoplasmic mating bridge allowing for conjugation to occur between bacteria Allows bacterial genes to be transferred between bacteria and hence increases genetic variation between bacteria Structural and regulatory genes Lac Z, lac Y and lac A are structural genes that codes for protein products that has an enzymatic function in a metabolic pathway Lac I gene is a regulatory genes that codes for a protein such as a repressor involved in regulating expression of structural gene How DNA is arranged in eukaryotes and prokaryotes Eukaryotic DNA coils around proteins called histone s to form nucleosomes followed by coiling around itself to form solenoid which will associate with scaffold proteins forming looped domains Bact er ia 4

Supercooling of loops to condense into the metaphase chromosome Prokaryotic DNA associated with relatively fewer proteins to form loops and there is supercooling to cause further compaction Describe a feature of operon/ prokaryotic transcription Genes coding for protein involved in the same biochemical pathway usually clustered together on one operon under a single promoter If repressor is active it binds to the operator which overlaps with the promoter and prevent the RNA polymerase from binding to the promoter thus preventing transcription Account for population growth of bacterium grown in limited concentrations of glucose and lactose Population size initially increases as bacterial cells are utilising glucose for cellular respiration in order to produce ATP during glycolysis and oxidative phosphorylation to provide energy for binary fission Population size levels off when glucose depletes and bacteria take time to activate lac operon to produce beta galactosidase Population size in eases again as bacterial cells are hydrolyse lactose into glucose and galactose to utilise the glucose Population size levels off again as lactose is depleted Bact er ia 5

Explain what is meant by an operon It is a functioning unit consisting of a promoter, operator, cluster of structural genes and a terminator The cluster of structural genes encodes gene products that function in a common pathway and the genes transcribed together give a polycistronic mRNA Describe the molecular basis of or the inhibition of lac operon controlled by negative gene regulation Lac I gene codes for lac repressor protein, synthesised in its active form in absence of lactose Active repressor binds to operator region of lac operon, preventing RNA polymerase from binding to the promoter Structural genes lac Z Y and A not transcribed Describing horizontal gene transfer ( gene transfer between different cells) Conjugation: Sex pilus of F bacterial cell makes contact with F bacterial cell amd retracts to bring the F cell closer so a mating bridge is formed between the 2 cells One of the 2 strands of the plasmid DNA in F cell is nicked and transferred from the F cell to F cell through a cytoplasmic ma