Biology Tutorials > Cell Biology > Role of Golgi Apparatus & Endoplasmic Reticulum in Protein Synthesis

Role of Golgi Apparatus & Endoplasmic Reticulum in Protein Synthesis

Golgi apparatus (3-D illustration)

Golgi apparatus (3-D illustration)

Continued from the previous tutorial that introduces protein synthesis

mRNA and tRNA

mRNA leaves the nucleus and enters the cytoplasm where ribosomes can be found, the site of protein synthesis.

The mRNA strand is met in the ribosome by complementary tRNA anticodons, which have opposing bases to that of the mRNA strand (the codons).

For example,
if the mRNA sequence is A-A-U-C-A-U, (codon)
then the tRNA sequence is U-U-A-G-U-A (anticodon)

Each tRNA molecule consists of 3 bases, deemed an anticodon that complements the opposing bases on the mRNA strand. These, in turn, have the amino acid sequence to successfully code for a particular amino acid.

Each amino acid has a certain sequence of bases to make it unique. Therefore, as a summary:

  • The initial DNA contained a certain sequence of nucleotides
  • The mRNA has a pre-determined sequence (because it is transcribed from the DNA)
  • Again, as a consequence, the anticodons possess a pre-determined sequence due to the mRNA
  • As each amino acid corresponds to a particular anticodon, a unique amino acid sequence is created forming a protein

These amino acids (peptides) can combine to form a polypeptide chain (proteins), which are used in a variety of structures such as enzymes and hormones (explained in the protein variety tutorial)

Ribosomes and Rough Endoplasmic Reticulum (RER)

Ribosomes are the site of protein synthesis and can occur freely in the cytoplasm though more commonly on the outer surface of the rough endoplasmic reticulum. The endoplasmic reticulum presents a large surface area on which these ribosomes can be situated, therefore allowing protein synthesis to occur on a large scale.

The rough endoplasmic reticulum is particularly abundant in growing cells which demand a high turnover of materials in its growth. Rough ER is responsible for transporting the newly synthesized proteins to the Golgi apparatus.

The Golgi Apparatus

The Golgi apparatus is composed of flattened fluid-filled sacs that control the flow of molecules in a cell. This is also the case of protein. Carbohydrates are added to the protein to complete its production.

This finished product, glycoprotein, is ‘pinched off’ the Golgi apparatus, and is transported by a vesicle of the cell membrane. When this vesicle reaches the cell membrane, it binds to a receptor on the surface and excretes the protein, where it can then undergo its function.

These newly formed glycoproteins (proteins with added carbohydrates) are used in a variety of ways, and in light of this, there is a wide variety of proteins in relation to their function. This is investigated in the next tutorial

 

Quiz

Arrange the events in the proper chronological event starting from 1 to 5.

As each amino acid corresponds to a particular anticodon, an amino acid sequence is, thereby, created.
In the nucleus, mRNA is synthesized according to the sequence of nucleotides in the DNA.
tRNAs carrying specific anticodons pair up with the codons of the mRNA.
The resulting chain of amino acids undergoes post-translational modification to form a mature protein.
The mRNA moves to the cytoplasm towards the ribosomes.

Send Your Results (Optional)

Your Name
To Email
Biology Tutorials > Cell Biology > Role of Golgi Apparatus & Endoplasmic Reticulum in Protein Synthesis

You will also like...

An artist's depiction of the origin of amphibians
Amphibians & Early Reptiles

Obtaining air outside an aquatic environment required species to acquire suitable adaptations, and this was the case of ..

Types and Causes of Brain Damage
Types and Causes of Brain Damage

This tutorial describes the different types and causes of brain damage. Find out how genetics, physical injury, lack of ..

Endemic Flora of New Zealand
New Zealand’s Unique Flora

If New Zealand has lots of unique animals, it's also got a whole lot of unique plants. Find out more about some of them,..

Origins of Life on Earth
Origins of Life on Earth

Earth was created around 4.5 billion years ago and life began not long after. Primitive life likely possessed the elemen..

Still Water Animals
Still Water Animals

Animals living in aquatic habitats have diversified and evolved through time. They eventually occupy ecological niches a..

Population Growth and Survivorship
Population Growth and Survivorship

This lesson looks at population attributes, regulation, and growth. It also covers population genetics, particularly gen..