Ribosome (Translation) — Role & Importance

(Video) What are Ribosomes? | Ribosome Function and Structure

by 2 Minute Classroom

This video quickly explains how ribosomes work to synthesize proteins as part of translation, the differences between different ribosomes, and what a ribosome is made of.

Ribosomes

Ribosomes are found in both prokaryotic and eukaryotic cells.

The job of the ribosome is to read the mRNA strand and form bonds between the amino acids.

The small ribosomal subunit reads the mRNA strand and finds the start codon. Then it recruits the large ribosomal subunit.

The large ribosomal subunit reads the mRNA codons and picks the appropriate tRNA molecules from the surrounding area.

It then bonds the amino acids that the tRNA carries into a chain.

How Do Ribosomes Help with Translation?

The mRNA is decoded in the ribosome and the tRNA and mRNA work together to make sure the correct amino acids are bonded together. As the single-stranded mRNA passes through the ribosome one codon at a time, the tRNA brings in the amino acids that match the instructions. You can think of the ribosome like a screwdriver that helps you build a complex structure and the mRNA is the instructions.

The ribosome then does its duty as a tool to link the amino acids together with peptide bonds. At the same time, it breaks the bond between the tRNA and the amino acid which allows the tRNA to go grab another amino acid.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Translation}}$ : The cell uses the information from RNA to make proteins

$\color{#8925AE}{\text{mRNA}}$ : Messenger RNA. mRNA nucleobases act as instructions for the cell to build polypeptides

$\color{#8925AE}{\text{tRNA}}$ : Transfer RNA. Carries a specific amino acid to the ribosomes to help build proteins

$\color{#8925AE}{\text{Codon}}$ : A group of three nucleobases that code for a specific amino acid

Structure and Function of Ribosomes

The ribosome plays a crucial role in protein synthesis. Ribosomes are responsible for reading a strand of mRNA and, with the help of tRNA, finding the corresponding amino acid for each codon in the mRNA code.

The structure of the ribosome is pretty unique. Ribosomes are composed of both proteins and RNA, in this case a class of RNA called ribosomal RNA (rRNA). The rRNA is very important in ribosome function because it is the RNA, not the protein, which makes the peptide bonds between amino acids.

Ribosomes can be split into two distinct subunits: the large subunit and the small subunit. The small subunit is the first subunit to attach to the mRNA strand. It then moves down the strand until it finds the start codon (AUG), at which point it recruits the large subunit. The large subunit then allows tRNA molecules to pass through and check if their anticodon matches the corresponding mRNA codon. This is basically like a game of guess and check; if there is not a match the large subunit will push the tRNA out, but if there is a match the large subunit will assist in adding the amino acid to the amino acid chain. This process will keep going until a stop codon is reached, signaling the end of translation.

Above is a good model of a ribosome in action. This ribosome is already in the second phase of translation: elongation. This means that the ribosome is moving in the 5' $\rightarrow$ 3' direction along the mRNA strand, adding amino acids when the right match is made between the codon on the mRNA strand and the anticodon on the tRNA.