Ribosomes

Ribosomes are tiny, granular organelles found in both eukaryotic and prokaryotic cells. They are found inside the cytosol of the cell. Ribosomes are the site of protein synthesis. They translate the genetic information conveyed by messenger RNA (mRNA) into functional proteins.

Ribosomes are composed of two subunits, one larger and one smaller, each of which is made up of proteins and RNA molecules. In this article, we will cover the ribosome structure and function, diagram, and more.

Ribosome Definition

A ribosome is a cellular structure that assembles proteins by linking together amino acids based on genetic instructions from messenger RNA (mRNA).

What are Ribosomes?

Ribosomes were first observed by George Palade (1953) under the electron microscope. It is a kind of complex molecular machine that produce proteins from amino acids during a process of protein synthesis also called translation. Ribosome translates genetic information stored in messenger RNA into proteins.

The process occur in three stages: initiation, elongation and termination. Within ribosomes, ribosomal RNA (rRNA) catalyzes the peptidyl transferase reaction, to form peptide bonds between amino acids, enabling them to form proteins. After protein is formed in the ribosome, they move to different areas of the cell for various cellular functions.

Ribosomes Location in Cell

Ribosomes are present in the cytosol or attached to the endoplasmic reticulum in both plant and animal cells. They play an important role in translating DNA into proteins. While some ribosomes are permanently associated with the rough endoplasmic reticulum, their association depends on the specific proteins they help to produce. In animal or human cells, there can be as many as 10 million ribosomes. Multiple ribosomes can be linked to the same mRNA strand, a structure known as a Polysome.

Ribosomes Diagram

The labelled diagram of ribosomes is given below:

Ribosome Structure

The structure of the ribosome is described as follows:

• Ribosomes consist of both ribonucleic acid (RNA) and protein part. The RNA component is called ribosomal RNA (rRNA), and the protein component consists of various ribosomal proteins.
• Ribosomes consists of two subunits – a small subunit and a large subunit and these subunits work together for the process of protein synthesis.
• The small subunit reads the genetic information and binds to mRNA. The large subunit catalyzes peptide bond formation and binds to the aminoacylated tRNAs. 
• Ribosome has specific binding sites for different molecules involved in protein synthesis. These include: A (aminoacyl) site: The site where aminoacylated tRNA molecules are accepted. P (peptidyl) site: contains the tRNA which carries the growing peptide chain. E (exit) site: the site where deacylated tRNA molecules remains before leaving the ribosome.
• The ribosomes when attached to the endoplasmic reticulum, it is called the rough endoplasmic reticulum.
• Bound and free ribosomes are similar in structure, and they are involved in protein synthesis.

Characteristics of Ribosomes

Ribosomes is a cellular structures that take part in the protein synthesis in all living organisms. The characteristics of ribosomes is as follows:

• Ribosomes are found in both prokaryotic or eukaryotic organisms.
• Ribosomes are composed of ribonucleic acid (RNA) and proteins. The RNA component is called ribosomal RNA (rRNA).
• Ribosomes consist of two subunits, a small subunit and a large subunit. Both work together during protein synthesis.
• Ribosomes have specific binding sites for molecules carrying out protein synthesis.
• Ribosomes are found in two regions of the cell: scattered throughout the cytoplasm and attached to the endoplasmic reticulum in some cases, and form the rough endoplasmic reticulum.
• Prokaryotes possesses 70S ribosomes, consisting of a small subunit (30S) and a large subunit (50S). Eukaryotes possess 80S ribosomes, with a small subunit (40S) and a large subunit (60S).
• They read the genetic code carried by messenger RNA (mRNA) and use it to assemble amino acids into a specific sequence, ultimately forming proteins.

Ribosomes Functions

Ribosomes have two principal function, which involve decoding the messages and the formation of peptide bonds.

• Ribosomes participate in the creation of proteins, the DNA makes RNA by DNA transcription.
• The mRNA is converted into proteins by the process of translation.
• The mRNA is organized in the nucleus and is moved to the cytoplasm for the process of protein synthesis.
• The ribosomal subunits in the cytoplasm are bound around mRNA polymers. The tRNA then integrates proteins.
• The proteins organized in the cytoplasm are used in the actual cytoplasm, and the proteins synthesized by bound ribosomes are moved to external cells. 

Ribosome Related Diseases 

Disorders caused by the improper functioning of ribosomes are called ribosomopathies. Mutations that occur in some of the proteins made by ribosomes can cause disorders that are characterized by like bone marrow failure and anemia.

Many congenital syndromes are caused by defective ribosome biogenesis, which includes Diamond-Blackfan anemia (DBA), X-linked dyskeratosis congenita (DKC), cartilage hair hypoplasia (CHH), and Treacher Collins syndrome (TCS).

Diamond-Blackfan anemia (DBA)

It is a rare blood disorder that affects the bone marrow. The bone marrow can make fresh blood cells, including red blood cells, white blood cells, and platelets. In DBA, the bone marrow can’t make sufficient RBC to address the body’s issues. DBA is described as a deficiency of RBC that causes anaemia.

DBA causes abnormal pre-rRNA maturation and shows mutations in one of several ribosomal protein genes that encode structural components of the ribosome.

Conclusion – Ribosomes

In conclusion, ribosomes are responsible for protein synthesis, decoding genetic information, and forming peptide bonds. Ribosomes are found in both prokaryotic and eukaryotic organisms. Ribosomes are made up of ribonucleic acid (RNA) and proteins, with specific binding sites for molecules involved in protein synthesis. Dysfunctions in ribosomes can lead to ribosomopathies, such as Diamond-Blackfan anemia (DBA), characterized by impaired red blood cell production due to mutations affecting ribosomal protein genes. Understanding ribosome structure and function is crucial for understanding essential cellular processes and addressing related disorders.

FAQs on Ribosomes

What are Ribosomes?

Ribosomes are cellular structures responsible for protein synthesis in living organisms. They consist of ribonucleic acid (RNA) and proteins and are found in all types of cells. 

Where are Ribosomes Located in the Cell?

Ribosomes is found in two regions within the cell: scattered throughout the cytoplasm and attached to the endoplasmic reticulum (ER) in some cases, forming the rough endoplasmic reticulum.

What is the Function of Ribosomes?

The function of ribosomes is to read the genetic information carried by messenger RNA (mRNA). It uses that information to arrange amino acids into specific sequences, forming proteins.

What is the Structure of Ribosomes?

Ribosomes is made up of two subunits, a small subunit and a large subunit, each composed of ribosomal RNA (rRNA) and proteins. They are connected through bonding between proteins in one subunit and the rRNAs in the other.

How do Ribosomes Work?

Ribosomes read the genetic information in mRNA and it matches it with the specific transfer RNA (tRNA) molecules. The ribosome then links these amino acids together to form a protein.