Chapter 13, Problem 1RTC

Summary Introduction

(a)

To write:

The in vitro translation system that consists only of the ribosomes and mRNA. It results in the secretory proteins which were larger than the identical protein when translated in a cell.

Introduction:

A secretory protein refers to a protein released by a cell of the exocrine or endocrine system. These proteins are comprised of many enzymes, hormones, antimicrobial peptides, and toxins. These are produced in the endoplasmic reticulum.

Explanation of Solution

In vitro translation is a method that allows the researchers to quickly express and make small quantities of functional proteins for a diversity of applications. In the absence of endoplasmic reticulum membranes, the complete protein is being translated. Then the ER signal arrangement is left on the protein.

Conclusion

Hence, in the absence of endoplasmic reticulum membranes, the complete protein is being translated.

Summary Introduction

(b)

To write:

The system has the microsomes that make the secretory proteins are identical in size to those found in a cell.

Introduction:

A secretory protein refers to a protein released by a cell of the exocrine or endocrine system. These proteins are comprised of many enzymes, hormones, antimicrobial peptides, and toxins. These are produced in the endoplasmic reticulum.

Explanation of Solution

When the translation process takes place in the presence of ER-holding microsomes. Then the protein gets translated into the microsomes lumen. This process is followed by the signal sequence. That signal sequence is then cleaved to produce a smaller protein.

Conclusion

Hence, when the translation process takes place in the presence of ER-holding microsomes then the signal sequence is then cleaved to produce a smaller protein.

Summary Introduction

(c)

To write:

The microsomes were added after the in vitro translation process. The newly synthesized proteins were larger than the manufactured in a cell.

Introduction:

In vitro translation is a method which allows the researchers to quickly express and make small quantities of functional proteins for a diversity of applications.

Explanation of Solution

Translation and translocation through the ER membrane are an instantaneous phenomenon. If they do not take place in the same period, then the protein is not imported in a proper way, into the ER. Normally, this is the site for the cleavage of the signal sequence. But due to the improper import of protein, there is the formation of newly synthesized larger proteins. So, there is a change in the process of post-translational translocation.

Conclusion

Hence, due to the abnormal import of protein into the ER, there is the formation of newly synthesized larger proteins after the in vitro translation process.