Ribosome structure & function - Week 5 Flashcards
what is translation
Translation is the mechanism by which a protein is formed using the information stored in mRNA.
what components play a role in translation
Translation is a complex process as it involves the function of many different components, which are:
- mRNA
- Ribosomal RNA (rRNA)
- transfer RNA (tRNA)
- ribosomes
- proteins
- enzymes
All these components play a distinct role during the process
what is the outcome of translation
The outcome of translation is the formation of a polypeptide, which is made up of a chain of amino acids, and each amino acid is covalently linked to each other via a peptide bond.
what happens after polypeptide is formed
After the polypeptide is formed in the cytosol, it is also subject to further modifications, such as phosphorylation, cleavage, and folding, to form a functional protein.
what is an amino acid made up of
The components of a single amino acid is a:
- amine group
- carboxylic group
- side-chain, which is specific to each amino acid (it is indicated as R)
why is the R group specific to each amino acid
The side chain (R group) is specific to each amino acid because the R group gives the amino acid a particular chemical property.
what groups are the 20 amino acids divided up into
There are 20 different amino acids that are found in different polypeptides.
These 20 amino acids are divided into groups according to the chemical property of the R group.
The different groups that the amino acids are divided into are the:
- non-polar group
- polar group
- electrically charged group
what is the chemical property of non-polar and polar amino acids
The non-polar group consists of amino acids like glycine, alanine, etc. They do not associate with water. Thus they are ‘water-fearing’.
The polar group consists of amino acids like serine, threonine, etc. They are able to associate with water. Thus they are ‘water-loving’.
where are the polar and non-polar amino acids usually located
Usually, the non-polar amino acids are present in the interior of a folded protein, and the polar amino acids are present on the surface of a protein.
what is the function of the R-group
the R group is the side chain of an amino acid which gives a unique chemical property to an amino acid and determines the function of the polypeptide.
how is a peptide bond formed
The formation of a peptide bond is an example of a condensation reaction. So 2 different amino acids are linked together with the release of water.
The peptide bond formation is by a link of the carboxyl group of a 1 amino acid and the amino group of another amino acid.
which direction is the formation of a polypeptide
The formation of the polypeptide has directionality. The polypeptide chain is formed in the amino-carboxyl direction, which corresponds to the 5’-3’ orientation of the codons in mRNA.
where does translation take place
The process of translation occurs at the ribosome.
where are ribosomes found
Ribosomes are small organelles:
they are found in the endoplasmic reticulum
- ‘Rough’ part of the rough endoplasmic reticulum is the ribosomes.
or ribosomes exist freely in the cytoplasm
what is a ribosome composed of
A ribosome is approximatively composed of 60% of ribosomal RNA (rRNA) and 40% of protein.
how many ribosomes are there in a cell
there are millions of ribosomes in each cell
what are the 2 subunits in a ribosome and what is their function in translation
A ribosome consists of 2 subunits:
- 1 large subunit
- 1 small subunit
These 2 subunits have different functions during translation. The smaller ribosome subunit reads the mRNA, the larger ribosome subunit is involved in the formation of the peptide bond thus the larger subunit is involved in joining the amino acids together to form a polypeptide chain.
what is the difference between eukaryotic and bacterial ribosome
In bacteria, such as E.coli, ribosomes are smaller in comparison to eukaryotic ribosomes.
what type of ribosome do the ribosomes in mitochondria and chloroplast resemble
Ribosomes of mitochondria and chloroplasts resemble prokaryotic ribosomes
what Sverdberg value is the smaller and larger subunit of bacteria and what does the Svergberg value indicate
In bacteria, the smaller subunit of the ribosome is called the 30S and the larger subunit is called 50S, S stands for Sverdberg value.
what is the Sverdberg value of the ribosome in eukaryotes
In eukaryotes, the 2 subunits of ribosomes form an 80S ribosome. The smaller one is a 40S subunit and the larger one is a 60S subunit. S stands for Sverdberg value.
what does the Sverdberg value refer to
the Sverdberg value refers to the rate of sedimentation in a centrifuge.
the S value doesn’t indicate the molecular weight of the ribosome but a coefficient of sedimentation, thus the Sverdberg value depends on the size and shape of a ribosome and not on the molecular weight of the ribosome.
What S value ribosome is formed in bacteria and eukaryotes
In bacteria, the 2 subunits of ribosomes form a 70S ribosome.
in eukaryotes, the larger subunit consists of 50 ribosomal proteins that associate with 2 different types of ribosomal RNA. Whereas the smaller subunit in eukaryotes consists of 33 ribosomal proteins that associate with 1 type of ribosomal RNA. Together both subunits form an 80S ribosome.
what are the 3 important sites in a ribosome
The ribosome contains 3 important sites, which are:
- A-site
- P-site
- E-site
