Describe how lac operon works

Question

Describe how lac operon works

What are CAPs and what are repressors and activators

 

Answer 1

The lac operon is a system used by bacteria (such as E. coli) to control whether genes involved in lactose metabolism are turned “on” or “off.”

When lactose is NOT present, the bacterium does not need the enzymes required to break it down. In this situation, a protein called the repressor binds to the operator region of the lac operon and blocks RNA polymerase from transcribing the genes. In simple terms, the genes stay OFF.

When lactose becomes available, a lactose-derived molecule binds to the repressor and changes its shape. This causes the repressor to detach from the DNA, allowing RNA polymerase to transcribe the genes needed to digest lactose. The genes are now turned ON.

Another important regulator is CAP (catabolite activator protein). CAP helps activate the lac operon when glucose levels are low. Since bacteria prefer glucose as an energy source, the lac operon works most strongly when:

1) lactose is present

2) glucose is low

One easy way to think about it:

The lac operon is like an energy-saving system. The bacteria only produce lactose-digesting enzymes when lactose is actually available and needed.