Question

13. Explain the pros and cons of regulating an enzyme's activity at the post-translational level (i.e. feedback inhibition) versus the transcriptional level. 14. How does lactose induce the expression of the lac operon?

Answer 1

Pros and cons of Enzyme's activity regulation at the post translational level

Regulation of the enzyme activity by post translational modification is a short term mechanism which helps in modulating the enzyme activity. Phosphorylation, which is a Post Translational Modification mechanism involves in majority of cellular processes of the enzyme including metabolism. Regulation by PTMs also provides the enzymes a faster way to adjust to environmental conditions and internal stimulus. Moreover, regulation of enzyme's activity at post translational level means a modification of the translated protein only, therefore if regulations related to genetic makeup of the enzyme are to be made; it cannot be done at this level.

Pros and cons of Enzyme's activity regulation at transcriptional level

At transcriptional level the activity of the transcriptional regulation of mRNA of the enzymes can be made. Regulation at transcriptional level is done by a set of genes known as operons, which collectively controls the expression of an enzymatic gene.

14. When lactose is present, the lac genes in a lac operon are expressed as the lac repressor loses its activity. When lactose is absent lac repressor binds tightly to the operator region of the operon which prevents transcription of the operon.