Cellular organelles Structure and Function

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Eukaryotic Cellular Organelles: Structure and Function


Cells take many different forms in living organism’s but there are a certain common features in which eukaryotic cells share. Individual cells consist of minute membrane bound vesicles found in the cytoplasm called organelles. These organelles play a crucial role in undertaking the processes that go in inside the cell in order for it to function. The following text aims to explain the structure and function of the major organelles.


The nucleus is commonly referred to as the control centre or brain of the cell; it directs instructions to other organelle to carry out specific tasks and contains the genetic material of the cell. The long strands of DNA found in the nucleus combine with proteins to form chromatin; the chromatin is then used to create chromosomes.


A: Chromatin

B: Nuclear Pores

C: Nuclear Envelope

D: Nucleolus

E: Chromosomes

Above: A Nucleus.

The Nucleus is enclosed entirely by an inner and outer nuclear membrane which protects the fragile DNA and genetic material within. Throughout the surface of the nucleus the two membranes fuse together to create pores that allow the exit of RNA, and the entrance of nucleotides for DNA replication.

Endoplasmic reticulum (ER)

The endoplasmic reticulum is a network of folded tubules and vesicles found on the outside of the nucleus. Part of the membrane of the ER is merged with the outer membrane of the Nucleus which causes the close proximity between the organelles. The ER serves many general functions, including the facilitation of protein folding and the transport of synthesized proteins in sacs called cisternae. Many of these products are made for and exported to other organelles. The two types of endoplasmic reticulum found in eukaryotic cells, rough and smooth. These varieties are separate entities and are not joined together.

Rough endoplasmic reticulum (RER)

Rough endoplasmic reticulum is involved with the production, folding, and despatch of proteins. The organelle is considered rough as it is covered in ribosomes which are responsible for the assembly of many proteins. Message RNA instructions from the nucleus are sent to the ribosomes on the RER, which then pump their proteins in which they are producing into the lumen which are then despatched in vesicles to the Golgi body.

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A: Ribosomes

B: Lumen

Above: RER.

Smooth endoplasmic reticulum (SER)

The smooth endoplasmic reticulum has detoxifying qualities and breaks down drugs and poisons. It is described as smooth because it is associated with smooth oily fats, and it lacks the covering of ribosomes as found on the RER.

A: Lumen

Above: SER.

The SER produces lipids and steroid molecules such as cholesterol and testosterone which are then sent in vesicles to the Golgi body ...

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**** All of the main organelles are described. Sometimes the terminology used could be a little more scientific.