Regulation of gene expression in prokaryotic cells

Regulation of gene expression at the transcription level: 

In prokaryotic cells:

• Enzymes catalysing metabolic reactions involved in cellular functioons can synthesised at constant rate
• Enzymes only need under specific conditions are synthesised at various rates depending on what the cell needs 

The lac operon: 

• Bacterium E.coli normally metabolises glucose as respiratory substrate and use this as a source of energy
•  If glucose is not present, E.coli uses lactose as a source of its energy 
• E.coli breaks down this lactose but in order for this E.coli has to express the lac operon gene  
• The levels of glucose and dissachride lactose are detected by the proteins:
  • lac repressor- acts as a lactose sensor 
  • catabolite activator protein (CAP)- acts a glucose sensor 
• An operon : group of genes that function as a single transcription unit; first identified in prokaryotic cells 
• The lac operon is the group of genes that are involved in the transport of lactose but is only expressed when glucose is absent
• The lac operon consists of a length of DNA with an operator region lacO next to the structural genes lacZ and lacY, that code for the enzymes induced…