The Fundamental Unit of Life

Nucleus

Nucleus or Cell Nucleus is a double membrane bound cell organelles present in a eukaryotic cell. This double layered membrane of the cell nucleus is made up of lipids and proteins. Nucleus is not found in red blood cells, bacteria, and blue-green algae.

This double layer of the nucleus is called Nuclear Envelope or Nuclear Membrane.

The nucleus of a cell contains chromosomes which contain genetic information in the form of genes. And hence the cell nucleus plays important role in the gene transfer from the parent to the next generation and structural and constructing and organising information of cells.

The liquid content found in the nucleus is called Nucleoplasm.

Chromosomes

The DNA is packed into thread like structures in the nucleus of animal and plant cells known as Chromosomes. Chromosomes are composed of DNA and proteins.

The DNA stands for "Deoxyribo Nucleic Acid". The protein in the DNA is called Histones.

The DNA molecules contain the necessary information for constructing and organising cells.

Chromosomes are visible in the cell nucleus only during cell division or when a cell is about to divide. During cell division, the chromosomes are visible as rod-shaped structures. When a cell Is not dividing, the chromosomes are present as chromatin. Chromatin material has an entangled mass of thread like structure. While dividing the cell, the chromatin materials get organised into chromosomes.

Function of the Nucleus

The Nuclear Membrane keeps the cell nuclear separate from its external environment. This membrane has pores that allow the passing of substances within a cell.

The Nucleus keeps genetic information in it. The nucleus controls and regulates the activities of the cell. The nucleus is the command center of a cell.

Eukaryotes

Organisms that have a membrane bound nucleus in their cells are known as Eukaryotes. And such cells are known as Eukaryotic Cells. They belong to a group of organisms known as Eukaryota or Eukarya.

Prokaryotes

Unicellular organisms having lack nuclei and other membrane bound organelles are known as Prokaryotes, for example, bacteria and archaea.

Cytoplasm

Cytoplasm is the fluid content inside the plasma membrane of a cell. The cytoplasm is a dense liquid content and helps cell organelles to perform their work.

Endoplasmic Reticulum

The endoplasmic Reticulum is found in eukaryotic cells. The endoplasmic reticulum forms an interconnected large network of flattened membrane enclosed sacs and tubular structures. The endoplasmic reticulum is made up of proteins and lipids similar to the plasma membrane. The Endoplasmic Reticulum is the transport system of the eukaryotic cells.

Types of Endoplasmic Reticulum

Rough Endoplasmic Reticulum (RER)

Rough Endoplasmic Reticulum has ribosome particles attached to its surface. Because of the attached ribosomes particles, it looks rough and hence named Rough Endoplasmic Reticulum and abbreviated as RER.

Rough Endoplasmic Reticulum lies immediately after the outer nuclear membrane i.e. nuclear envelope.

Ribosomes attached to the Endoplasmic Reticulum are the sites of protein synthesis (manufacturing). After the synthesis, proteins are sent through Endoplasmic Reticulum to various places in the cell depending on the needs. The rough Endoplasmic Reticulum is the transport system of the cell.

Smooth Endoplasmic Reticulum (SER)

The Smooth Endoplasmic Reticulum (SER) is found towards the cell membrane. The Smooth Endoplasmic Reticulum does not associate with ribosomes. The Smooth Endoplasmic Reticulum (SER) has a tubular type structure.

The Smooth Endoplasmic Reticulum (SER) synthesises fats or lipids including cholesterol which are important for cell function. In certain cells, such as the liver cells the Smooth Endoplasmic Reticulum (SER) plays an important role in the detoxification of drugs and harmful chemicals.

Smooth Endoplasmic Reticulum (SER) are in abundance in some cells like testes, and ovaries. In muscles cells, Smooth Endoplasmic Reticulum (SER) regulates calcium ion concentration.

Membrane Biogenesis

Some of the proteins and fats or lipids synthesised by the Smooth Endoplasmic Reticulum (SER) help in building the cell membrane. This process is known as Membrane Biogenesis.

Golgi Apparatus or Golgi Body or Golgi Complex

Golgi Complex is an organelle found in most of the eukaryotic cells adjacent to the Endoplasmic Reticulum (ER). The Golgi Complex is known as Golgi Body or Golgi Apparatus or simply Golgi also.

It got its name as Golgi in 1898 in honour of Camillio Golgi who discovered it in 1897.

Golgi Complex has the structure of a series of flattened fused pouches called cisternae. Golgi Complex is also a membrane bound vesicle like other cell organelles.

The main function of the Golgi Complex is modifying and packaging of proteins and lipids into vesicles before transporting them to the targeted destination.

The Golgi Complex makes complex sugars from simple sugars in some cases. The Golgi Complex is also involved in the formation of lysosomes.

Lysosomes

Lysosome is a cell organelle found in most of eukaryotic cells. The lysosome is a membrane bound similar to other cell organelles. Lysosome has sac like structure filled with acidic digestive enzymes. The digestive enzyme of the lysosome is synthesised by the Rough Endoplasmic Reticulum (RER) and after the synthesis transported to the lysosome packed in vesicles. The membrane covering keeps the digestive enzyme present in the lysosome separated from mixing with the outer environment of the cell.

Lysosome acts like a scavenger. Lysosomes are a waste disposal system of the cell. Lysosome keeps the cell clean by engulfing and digesting the damaged parts of the cell. Lysosome also acts on unwanted foreign organisms like bacteria and kills them by engulfing and digesting them. In the case of damage or even whole cell, lysosome bursts and the enzyme digests its own cell.

Since lysosome keeps the cell cleaned and even digests the whole cell if damaged, hence lysosomes are called "SUICIDE BAGS" or "SUICIDE SACS" of the cell also.

A Belgian scientist Christian Rene de Duve discovered the lysosomes in the 1950s. For this discovery of the lysosomes, Christian Rene de Duve got the Noble Prize in the year of 1974.