Re: How does a cell make protein?

Candy:

To understand how a cell makes protein, you'll need to know about (1) three 
very important molecules, and (2) three basic steps.

Three very important molecules:

1. DNA
2. RNA
3. Ribosome

Three basic steps:

1. Gene transcription
2. RNA export
3. RNA translation

How do these fit together? 

As you mentioned, protein synthesis starts in the cell's nucleus. 

(Some of my scientist friends would want me to mention that prokaryotes, 
such as bacteria, have no defined nucleus, but their protein-making process 
is similar to what we'll discuss here. To keep things simple, we'll stick 
with eukaryotic cells -- the ones that do have nuclei. But if you want to 
know the difference between prokaryotes and eukaryotes, you can find out at 
The 
Biology Project website.) 

The instructions for making a protein are found within the nucleus, in the 
cell's DNA -- in the form of genes. Through a process called gene 
transcription, the information contained in the DNA is transferred to a 
molecule called RNA, which shares a similar chemical makeup with DNA. RNA 
is exported from the nucleus to the cytoplasm with the help of specific 
protein machinery. Once in the cytoplasm, the RNA is decoded -- or 
translated -- by ribosomes, which use the decoded information to make a 
protein chain out of single amino acids.  

Can you think of a good reason why a cell might need RNA to carry 
information from DNA to the ribosome? Here's a 
hint.) 

For me, pictures help make things more clear. I found a good one on this page.

My scientist friends would also want me to tell you that while I've 
covered the basics here, DNA transcription and translation are far more 
complex than I've described. Follow the links from this page 
for a more detailed description of the transcription/translation process.

Best,

Jennifer

Jennifer Logan, Ph.D.
Genetic Science Learning Center
Eccles Insitute of Human Genetics
University of Utah