The second step of protein synthesis relies on transcription. Transcription is a process where information from a gene is copied onto a complementary strand of RNA. This process provides for two major functions.
First, the information from a gene is copied to another type of nucleic acid (RNA). This allows for the RNA copy to be used for protein synthesis later in the cell. However, if the cell does not need the information from this gene, it can be destroyed by enzymatic action.
Second, the DNA strand and its complement of RNA form a kind of template for the creation of protein.
Translation occurs on ribosomes.
Translation occurs on ribosomes. A ribosome is a complex of RNA and proteins that carries out protein synthesis by reading the genetic code and translating it into a protein chain. In eukaryotic cells, there are two types of ribosomes: large and small. Large ribosomes are associated with the rough endoplasmic reticulum, while small ones are associated with the smooth endoplasmic reticulum.
- The first step in protein synthesis is transcription (DNA → RNA). Transcription involves enzymes called RNA polymerases that recognize specific DNA sequences and transcribe them into messenger RNA (mRNA), which then travels to the rough endoplasmic reticulum (RER) where translation takes place.
- The second step of protein synthesis is translation, which takes place in the cytoplasm. The process begins with transcription and then continues with translation. Transcription begins at the DNA, while translation begins at the RNA.
Ribosomes are made of two subunits, one large and one small.
Ribosomes are made of two subunits, one large and one small. The large subunit is responsible for the chemical reactions that combine amino acids into proteins, while the small subunit serves as a scaffold for these reactions.
Aside from their roles in protein synthesis, ribosomes also play an important role in mRNA translation. The mRNA strand contains the code for all of the amino acids that will be used to build a protein chain, but it needs help converting this code into a chemical signal that can be read by the ribosomal machinery. This process involves tRNA molecules, which carry amino acids to their proper locations within the ribosome.
Ribosome subunits are made of rRNA and protein.
The ribosome is the site of protein synthesis. The site of protein synthesis is called the ribosome. It is made up of ribosomal RNA (rRNA) and proteins. There are two types of ribosome found in cells: large and small. The large ribosomes make proteins for cellular structures, such as membranes and organelles, while the small ones make proteins for use within the cell itself.
The three-dimensional structure of a ribosome has been determined using x-ray crystallography and electron microscopy, giving us a better understanding of how they work.
The structure consists of two subunits (or halves), each consisting of an alpha (α) or beta (β) subunit; these are referred to as 30S and 50S particles respectively depending on their size and shape. The 30S particle contains 18 different proteins while the 50S particle contains 28 proteins plus 5 tRNAs that carry amino acids to the enzyme during translation.
Amino acids joined together is called a peptide.
The second step in protein synthesis involves joining the amino acid chain to a tRNA molecule. This occurs in the ribosome. The tRNA molecule is a small, single-stranded RNA molecule that carries the growing protein chain to the ribosome during translation.
During this step, two nucleotides are added to each growing end of the amino acid chain by ribosomal RNA (rRNA). Each nucleotide has a base and a sugar molecule attached to it. The addition of these nucleotides causes an elongation of the growing protein chain by one amino acid each time they are added.
This process continues until all 20 amino acids have been added to form a complete protein chain with an amino group at both ends of its backbone (backbone is a term used to describe how long molecules are).
The ribosome joins amino acids together in the order specified by the mRNA.
The second step of protein synthesis, called translation, occurs when an mRNA molecule attaches to a ribosome at a particular point called an initiation codon. The ribosome then translates the mRNA into a polypeptide, which is a chain of amino acids linked together by peptide bonds. The sequence of amino acids determines the structure and function of the protein.
Translation is accomplished by three types of RNA molecules: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). The first two types are both single-stranded molecules; rRNA is double-stranded. Each type of RNA has specific functions in protein synthesis:
- Messenger RNA carries information from DNA to the site where proteins are synthesized, which is on ribosomes in the cytoplasm.
- Transfer RNA carries one or more amino acids to their locations on a growing polypeptide chain during protein synthesis.
- Ribosomal RNA provides structural support for ribosomes and helps translate mRNA into proteins.
A ribosome consists of two subunits, one large and one small, which come together during initiation to bind an mRNA molecule at its 5′ end (the end with a free phosphate).
A ribosome consists of two subunits, one large and one small, which come together during initiation to bind an mRNA molecule at its 5′ end (the end with a free phosphate). The ribosome moves down the mRNA molecule, adding each successive amino acid to the growing polypeptide chain.
A tRNA molecule enters the A site, carrying an amino acid identical to the codon in the A site on the mRNA strand.
The tRNA molecule passes through a tunnel at the center of the ribosome, where it binds to its complementary codon on the mRNA strand. The ribosome then shifts, bringing together two subunits: one with a free P site and another with an empty E site. This allows for hydrolysis of GTP by EF-G, which leads to formation of a new peptidyl-tRNA bond between the growing polypeptide chain and tRNA.
Last Words
The second step in the process of protein synthesis occurs when the second tRNA molecule joins the other end of the mRNA string to make a complete, uninterrupted strand of mRNA. However, many individual cells will not be diploid and they will not contain two nuclei. While they can still synthesize proteins, this is not considered eukaryotic protein synthesis because all of the instructions are in one nucleus, which doesn’t really have a second step. Thus, the central dogma says that gene expression only occurs once eukaryotic cell has completed meiosis and fertilization.