ENDOPLASMIC RETICULUM (ER)

• The endoplasmic reticulum (ER) is a large network of membrane-bound tubes and sheets. It looks like long tubules or round or long bags (vesicles).
• The ER membrane is similar in structure to the plasma membrane.
• There are two types of ER –– rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

FUNCTIONS OF ENDOPLASMIC RETICULUM (ER)

• Some of these proteins and lipids help in building the cell membrane. This process is known as membrane biogenesis.
• Some other proteins and lipids function as enzymes and hormones.
• Although the ER varies greatly in appearance in different cells, it always forms a network system.
• Thus, one function of the ER is to serve as channels for the transport of materials (especially proteins) between various regions of the cytoplasm or between the cytoplasm and the nucleus.
• The ER also functions as a cytoplasmic framework providing a surface for some of the biochemical activities of the cell.
• In the liver cells of the group of animals called vertebrates, SER plays a crucial role in detoxifying many poisons and drugs.

Golgi Apparatus or Golgi Complex

• The Golgi apparatus consists of a system of membrane-bound vesicles arranged approximately parallel to each other in stacks called cisterns.
• These membranes often have connections with the membranes of ER and therefore constitute another portion of a complex cellular membrane system.
• The material synthesized near the ER is packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus.
• Its functions include the storage, modification and packaging of products in vesicles.
• In some cases, complex sugars may be made from simple sugars in the Golgi apparatus.
• The Golgi apparatus is also involved in the formation of lysosomes.

Lysosomes

• Lysosomes are a kind of waste disposal system of the cell.
• Lysosomes help to keep the cell clean by digesting any foreign material as well as worn-out cell organelles.
• Foreign materials entering the cell, such as bacteria or food, as well as old organelles end up in the lysosomes, which break them up into small pieces. Lysosomes are able to do this because they contain powerful digestive enzymes capable of breaking down all organic material.

SUICIDE BAGS OF A CELL.

• During the disturbance in cellular metabolism, for example, when the cell gets damaged, lysosomes may burst, and the enzymes digest their own cell. Therefore, lysosomes are also known as the ‘suicide bags’ of a cell.
• Structurally, lysosomes are membrane-bound sacs filled with digestive enzymes. These enzymes are made by RER.

MITOCHONDRIA

• Mitochondria are known as the powerhouse of the cell.
• The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine Triphosphate) molecules.

                     [If Mitochondria is the Power Plant. ATP is the Electricity].

• ATP is known as the energy currency of the cell.
• The body uses energy stored in ATP for making new chemical compounds and for mechanical work.
• Mitochondria have two membrane coverings instead of just one.
• The outer membrane is very porous while the inner membrane is deeply folded. These folds create a large surface area for ATP-generating chemical reactions.
• Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes. Therefore, mitochondria are able to make some of their own proteins [ribosomes prepare proteins].