What is Ribosome?
Ribosomes are dumbbell-shaped and minute particles, they are
made up of ribonucleic acid and protein called ribonucleoprotein (RNP) particle. Ribonucleoprotein is a
complex of ribonucleic acid and RNA-binding protein.
Ribosomes are the cell organelles that help in protein
synthesis (manufacturing of protein from an amino acid). These are sites of
protein synthesis, also called the protein factory of the cell.
Types of Ribosomes
There are two types of ribosomes; free and fixed (membrane-bound).
Both are identical in structure but differ in locations within the cell.
Free ribosomes are located in the cytosol and are able to
move throughout the cell. Free ribosomes synthesize protein used in the cytosol.
Fixed ribosomes are attached to the Rough Endoplasmic
reticulum (rER). The proteins produced by the attached ribosomes are
transported outside the cell.
Some ribosomes are bound to the Endoplasmic
reticulum and some float freely within the cytoplasm. Some ribosomes are also
located in mitochondria
cell organelle, where they synthesize mitochondrial protein.
Ribosome Structure
The ribosome consists of ribonucleic acid and ribonucleoprotein.
In eukaryotic cells ribosomes are found is of 80s.
It has two subunits, the larger subunit of 60s and the small subunit
of 40s. Polyribosomes (associated with mRNA) are found either free in the cytoplasm
(cytosol) or attached to the endoplasmic reticulum.
Functions of Ribosome
Key functions include-
1. Act as a site
for protein synthesis or translation.
2. Ribosome
contain rRNA (Ribosomal RNA), for
providing attaching point to mRNA (Messenger
ribonucleic acid), and tRNA (Transfer
ribonucleic acid). Proteins are synthesized with the help of
transfer RNA.
3. Ribosome
produce protein via a process called translation (process of translating mRNA
into protein). Protein is needed for many cell functions such as repairing
damage or directing chemical process.
The process of protein synthesis is a primary
function of Ribosome.
4. Proteins that
are synthesized by the ribosomes present in the cytoplasm are used by the
cytoplasm for the cell itself. The proteins produced by the bound ribosomes
(rER) are transported outside the cell.
What is rRNA, mRNA, tRNA?
Ribosomal ribonucleic acid (rRNA) is a ribonucleic acid
that, together with the ribosomal proteins, forms the ribosome.
Messenger RNA (mRNA) carries the genetic information that
transfers the genetic information from DNA in the nucleus to the cytoplasm.
mRNA is synthesized within the nucleus and exported to the cytoplasm for the
process of protein synthesis.
Transfer ribonucleic acid (tRNA) carries the amino acid to
the ribosome that helps decode a messenger RNA (mRNA) sequence into a protein.
tRNAs function at specific sites in the ribosome during translation (a process
of synthesizing a protein from an mRNA molecule).
How does Ribosome Makes Protein?
Protein Synthesis takes place in the cytoplasm. Ribosomes
are made up of ribosomal proteins and ribosomal ribonucleic acid (rRNA).
Step 1
DNA produces mRNA by the process of DNA transcription means
DNA to RNA (mRNA). From DNA to RNA transcription within the nucleus. Synthesis
of mRNA by an enzyme RNA Polymerase using DNA as a template.
All the RNA in a cell is made by DNA transcription.
Step 2
mRNA, molecule moved out from the nucleus into the cytoplasm. The ribosome binds to mRNA and reads the
code in mRNA. The protein factory in the cytoplasm is called a ribosome.
Step 3
tRNA carry the amino acid to the ribosome. mRNA read the tRNA delivered cross ponding amino acid. A growing chain of amino acid formed means translation occurs (mRNA to
protein).
Once the last amino acids are added the chain folds into a
complex 3d shape to form protein.
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