Do Animal Cells Have Endoplasmic Reticulum? 7 Complete Facts

An animal cell contains approximately 50% of the membrane. Let us discuss if animal cells have endoplasmic reticulum or not.

All animal cells consist of an endoplasmic reticulum. Every cell that falls under the category of eukaryotic domain including all the four kingdoms do contain endoplasmic reticulum. These cells’ endoplasmic reticulum, also denoted as ER have mesh of tubules and sacs that are flattened.

Endoplasmic reticulum is responsible for producing lipids and transmembrane proteins that is required by the membrane and various other cell organelles such as Golgi apparatus, lysosomes, secretory vesicles and also plant cell vacuoles.

Let us discuss where ER is located in animal cell, which animal cells lack ER, if animal cells have smooth and rough ER along with its major functions.

Where is endoplasmic reticulum located in animal cell?

Endoplasmic reticulum is a system of continuous membrane that makes up a series of flat sacs inside the cytoplasm. Let us discuss its location in animal cell.

Endoplasmic reticulum is found inside the cytoplasm of the cells of eukaryotes. They are a complex of mesh work of different tubular membranes that are located within the cytoplasm of the cell.

Why do animal cells have endoplasmic reticulum?

All cells of eukaryotes consist of an endoplasmic reticulum. Let us discuss why animal cells have endoplasmic reticulum.

Animal cells have endoplasmic reticulum as it is a necessary site where lipids or fats and proteins are being processed. Maximum of these products that are produced are either made for the organelles themselves or maybe exported outside.

How many endoplasmic reticula are in an animal cell?

In general, endoplasmic reticulum is considered as the transport system of the cells of eukaryotes. Let us explore how many of them are present in total in a cell.

In an animal cell, two types of endoplasmic reticula are present. They are smooth endoplasmic reticulum (SER) and rough endoplasmic reticulum (RER). They are present to perform functions like protein folding.

Blausen 0350 EndoplasmicReticulum
Smooth and rough endoplasmic reticulum- Image Credit: Wikipedia

Functions of endoplasmic reticulum

The presence of ER in both the animal and plant cells is because it has several functions to perform. Let us discuss it in detail.

Major functions of endoplasmic reticulum include:

  • Transport proteins and carbohydrates from one organ to another that also includes plasma membrane, lysosomes, Golgi bodies, etc.
  • As it is located on the surface of cytoplasm, they help in providing greater surface area for the cellular reactions to be performed.
  • They help in the formation of membrane of the nucleus during the cell division.
  • They also help in the formation of structure of the skeleton.
  • They act as an important cell organelle that produces protein, essential lipid like phospholipids, glycogen and also helps in the synthesis of cholesterol, progesterone, testosterone, etc.      
  • Helps in producing and secreting steroid hormones.
  • Helps in carbohydrate metabolism.
  • Endoplasmic reticulum releases calcium ions, that are important for the muscular and nervous systems.

Do animal cells have smooth endoplasmic reticulum?

Smooth endoplasmic reticulum is made of 3D polygonal mesh of tubules known as cristae. Let us explore if animal cells have smooth endoplasmic reticulum.

Smooth endoplasmic reticulum is present in almost all eukaryotic cells. It is a part of the endomembrane system of endoplasmic reticulum. They are differentiated from other components of ER by the lack of ribosomes that are membrane-bound.

Why do animal cells have smooth endoplasmic reticulum?

Smooth endoplasmic reticulum is present in the cytoplasm of the animal cells because it works for the synthesis of important lipids, for example phospholipids and cholesterol. Steroids hormones are produced and secreted here; metabolism of carbohydrates is also done by them. Calcium ions are stored and released by smooth endoplasmic reticulum.

Do animal cells have rough endoplasmic reticulum?

Rough endoplasmic reticulum has structure which is surrounded by ribosomes that gives them a “rough” texture. Let us see if animal cells have rough endoplasmic reticulum.

Animal and plant cells with a focus on protein synthesis will always have a rough ER than cells that just contain lipids (fats). When mRNA travels from nucleus to a ribosome on the membrane of the RER, protein synthesis begins.

Why do animal cells have rough endoplasmic reticulum?

Rough endoplasmic reticulum is present in the cytoplasm of the animal cells because its primary function is to synthesize different proteins. The second very significant function is protein sorting. They are a vital part as they also help in the process of protein folding. Provides quality control as well (regarding the correct procedure for protein folding).

Which animal cells are without endoplasmic reticulum?

The survival of a cell without endoplasmic reticulum is difficult. But still there are some animal cells that do not contain any ER in their cytoplasm. Let us discuss.

Red blood cells or spermatozoa are deprived of having endoplasmic reticulum in them. Most significantly, the nucleus is not present at the mature stage of red blood cells. Depending on the activity of the cell, various types of cells have varied ratios of the two types (smooth and rough) of ER.

Redbloodcells
Red blood cells- Image credit: Wikipedia

Why do red blood cells do not have any endoplasmic reticulum in them?

Endoplasmic reticulum is absent in RBCs because mature red blood cells need to have more space and higher amount of hemoglobin content in them as compared to other cells. As ER is absent, it has a lower surface-to-volume ratio, allowing for the storage of more red blood cells in a given space. This is why they do not contain cell components like ER, Golgi apparatus, mitochondria, etc.

Why do spermatozoa do not have endoplasmic reticulum in them?

Endoplasmic reticulum is not present in spermatozoa because its mainly responsible for protein synthesis. But proteins are not required for the sperms as they metabolize glucose. Thus, ER is not required by them. The main function of a sperm is to transport DNA to the egg. Now having an endoplasmic reticulum, sperms are unmanageable and also make the sperm quite bulky.

Human spermatozoa
Human spermatozoa- Image credit: Wikipedia

Conclusion

The endoplasmic reticulum or ER are continuous membrane systems forming a layer of flattened sacs in the eukaryotic cells (cytoplasm). They participate in modification, folding, synthesis and transportation of proteins.

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