Ribosomes

Introduction

A ribosome is a biological unit composed of RNA and protein and its primary function is to form proteins in the cell which are utilised in a number of biochemical and physiological processes The ribosome reads the messenger RNA sequence and, using the genetic code, transforms the RNA base sequence into an amino acid sequence. These are a component of the cell’s protein-making machinery. The ribosome, which attaches to messenger RNA, has a two-subunit structure. This structure also serves as a docking station for transfer RNA, which holds the amino acid that will eventually become a part of the developing polypeptide chain, which will finally form the protein.

Let us know more about ribosomes structure and functions In detail:

Using a microscope, Romanian-American cell researcher George Emil Palade discovered ribosomes as compact particles or granules in the mid-1950s.

Structure of Ribosomes

These are made about the same numbers of protein and ribonucleic acid. It is divided into two pieces, which are referred to as components. The mRNA attaches to and decodes in the smaller subunit, whereas the amino acids are contained in the larger subunit.

The large and small subunits each contain a pair of ribosomal RNA molecules as well as an uneven amount of ribosomal proteins. A variety of protein factors accelerate different aspects of protein synthesis. The translation of the genetic code is critical for the production of functional proteins as well as the growth of the cell.

Both subunits are made up of ribonucleic acid and protein components, and they are linked by interactions between proteins in one subunit and rRNAs in the other. The nucleolus, which is where these are grouped in a cell where ribonucleic acid is obtained.

When ribosomes are seen underneath an electron microscope, they seem flat and spherical, with a diameter of  20-30 nm.

Ribosomes are located in two different parts of the cytoplasm. A handful are attached on the rough endoplasmic reticulum and some are scattered throughout the cytoplasm.

The structure of free and bound ribosomes is remarkably similar, and they are both involved in protein synthesis . RNA makes up 37 to 62 percent of rRNA whereas  ribosomal proteins make up the balance.

Types of Ribosomes 

There are two types of ribosomes, namely, the 70S and 80S. Ribosomes are made up of rRNA and ribo-proteins which sediment to form an intact ribosome. Here ‘S’ is svedbergs and one svedberg is 10−13  s , it is the sedimentation coefficient that has a unit of time, expressed in svedbergs.

Let us discuss these organelles in detail:

There are two types of ribosomes, free and fixed (also known as membrane bound). They 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, whereas fixed ribosomes are attached to the rER.

1)    The 70S- 

•     Prokaryotes and eukaryotes both have 70S ribosomes
•     Ribosomes can be found freely in the cytoplasm of prokaryotes, plastid matrix and mitochondria of eukaryotes
•     With a size of (200—290 A) and a radius of (170—210 A), they are comparatively smaller
•     Prokaryotes and eukaryotes both have 70S ribosomes
•     Ribosomes can be found freely in the cytoplasm of prokaryotes, plastid matrix, and mitochondria of eukaryotes
•     With a size of (200—290 A) and a radius of (170—210 A), they are comparatively smaller

2)    The 80S-

•     They can only be found in eukaryotic cells
•     They can be found free or linked to ER in the cytoplasm of eukaryotes
•     Ribosomes are larger, measuring 300—340 A in length and 200—240 A in width
•     The coefficient of sedimentation is 80
•     They’re a lot heavier, weighing in at 4.0—4.5 million Daltons
•     The 40S and 60S are the two subunits

Functions of Ribosomes

Given below are various functions of ribosomes-

1. They function by bringing amino acids together to produce specific proteins necessary for the cell’s tasks to be completed.
2. By DNA transcription, deoxyribonucleic acid creates mRNA, which is then used to generate proteins.
3. During DNA translation, hereditary information from mRNA is translated into proteins.
4. In the mRNA, the configurations of protein assembly during protein synthesis are indicated.
5. The mRNA is organised in the nucleus and then transported to the cytoplasm for further protein production.
6. Proteins found in the cytoplasm are synthesised by ribosomes and are used within the cytoplasm.The bound ribosomes’ proteins are transported outside the cell.
7. The ribosome is a complicated molecular machine found in all living cells and is responsible for producing biological proteins.
8. Peptidyl transfers and peptidyl hydrolysis are two critically important biological processes in which ribosomes act as catalysts.

Ribosomes and Diseases

These are  necessary for life because they produce all of the protein needed for cells to thrive. Early-life bone marrow failure and anaemia are caused by mutations in several of the proteins that form ribosomes, followed by an increased cancer risk in middle age. The term used for this is “Ribosomopathies”.

The researchers discovered that faulty ribosomes generate a particular type of error when transcribing genetic information. This error causes patterns of gene expression to shift in cells, which can lead to cancer. The errors exacerbated the instability of a group of molecules that was already unstable. One class of chemicals is critical for maintaining telomeres—the DNA at the ends of chromosomes—in cells. The mutated cells had shortened telomeres, which has been related to cancer and ageing. The researchers hypothesised two separate, although not necessarily incompatible, explanations for the gene expression changes: the mutant ribosomes might be directly modifying gene expression patterns, and/or the second suppressor mutation could be causing the alterations.

Conclusion 

According to Ohio State University, ribosomes are found in more human cells than any other form of the cellular organelle. Ribosomes’ primary job is to create proteins that are used both inside and outside the cell. The human body would be unable to make the proteins it requires to exist if ribosomes were absent, and metabolism would come to a standstill.

Cells would be unable to operate correctly if ribosomes were not there to generate proteins. They would be unable to repair cellular damage, produce hormones, sustain the cellular structure, carry out cell division, or reproduce genetic information.