Question

Describe the different levels at which metabolism can be regulated (transcriptional, translational, post translational).

Answer 1

Answer: Metabolism is defined as set of chemical reactions (anabolic + catabolic reaction) that occur in the cells. These anabolic and catabolic reactions are catalyzed by enzymes that are regulated at various levels such as transcription, translation and post-translational. Metabolic reactions are high regulated at various levels for proper functioning of the cell.

Regulation at transcriptional level: DNA consists of genes that encode various enzymes involved in the metabolic process. During transcription, DNA is converted to mRNA that is used as template for protein synthesis. The synthesis of the enzymes depends on the expression of corresponding gene (mRNA) that is regulated tightly. Various signal molecules such as neurotransmitters and hormones binds to the cell and passes the signal via signal transduction pathways, leading to activation or inhibition of gene expression. Transcription factors binds to the promoter of the genes and regulate their expression, leading activation or inhibition of gene expression.

Regulation at translational level: During translation, protein are synthesized using mRNA template and ribosome. Protein synthesis is highly regulated process that control the production of enzymes. Translational initiation is the first regulatory step. During Initiation, ribosomes must assemble on the mRNA molecule correctly to initiate the process. Proteins such as initiation factors regulate the ribosome assembly on mRNA. The availability and activity of initiation factors affects transcription initiation. Later, the translation is regulated at peptide elongation and peptide termination steps by various elongation and termination factors respectively.

Regulation at post-translational level: Once, the protein is formed, it undergoes various post-translational modification such as removal of a part of protein and chemical modification. Most of the enzymes are produced in pre-mature form that needs to be cleaved by proteases to form a mature enzyme. Example: pepsin and insulin. Chemical modification such as phosphorylation and ubiquitination regulate the activity of the enzyme. Phosphorylation changes the conformation of the enzyme and affects its activity. ubiquitination of proteins leads to their degradation.