Cell Organelles - Types, Structure and their Functions

What is Cell Organelles?

Cells are the basic unit of life that make up all living creatures starting from simple unicellular bacterias to complex structures like humans. It was first discovered by Robert Hook, mainly he saw the cell wall. Every living organism is made up of one or more cells that are responsible for carrying out vital metabolic activities that keeps an organism alive.

Inside each cell, there are several cell organelles that are specialised to perform a specific vital role- from making proteins, producing energy to getting rid of bodily wastes. All these functions performed by each cell organelles are needed for the systematic function of the body.

There are basically two kinds of cells:

Prokaryotic cells are non- membrane cells that are devoid of true nucleus and other membrane bound organelles. They are found in simple unicellular organisms like bacteria and archaebacteria. While Eukaryotic cells are true cells that consist of true nucleus and other membrane bound cell organelles and are basically found in multicellular organisms like protists, fungi, plants and animalia.

What are The Types of Cell Organelles?

Each cell contains numerous cell organelles, each with its own important job to keep the cell alive. Some key organelles include-

The Nucleus: The Control Center
Mitochondria: The Powerhouse of the Cell
Ribosomes: The Protein Factories
Endoplasmic Reticulum (ER): The Transportation Network
Golgi Apparatus: The Packaging Center
Other cell organelles

Each of these are responsible for performing their role that leads to the proper functioning of the cell.

The Nucleus: The Control Center

The nucleus is the largest and most important organelle in eukaryotic cells, often called the cell’s control centre. It is crucial for maintaining the life and proper function of the cell.

Nuclear envelope

Nucleus is a double membranous structure surrounded by nuclear envelope
The envelop helps in separating the nucleus and its interior from the cytoplasm
It has pores on its surface called the nuclear pores that regulate the entry and exit of substances in and out of the nucleus.

Nucleoplasm

Inside the nucleus, there is a gel-like substance called nucleoplasm.
Nucleoplasm contains chromatin and nucleolus.

Nucleolus

The nucleolus is a dense area within the nucleoplasm.
Site of formation of ribosomal RNA (rRNA).
Ribosome assembly also begins in the nucleolus.

Chromatin

Chromatin contains DNA, histones, non histones proteins and RNA
During cell division, chromatin forms chromosomes.

Function of the Nucleus

The main function of the nucleus is to store and protect the cell’s genetic material (DNA).
DNA contains instructions for all the cell’s activities.

Gene Regulation

The nucleus controls growth, metabolism, and protein production by regulating gene expression.
It determines which genes are turned on or off.

mRNA Synthesis and Export

In the nucleus, DNA is transcribed into messenger RNA (mRNA).
mRNA then exits the nucleus through the nuclear pores and goes to the cytoplasm, where it helps in making proteins

Mitochondria: The Powerhouse of the Cell

Mitochondria are known as the ‘powerhouse of the cell’ because they produce energy. This cell organelle is vital for maintaining the cell’s function and overall vitality.

Double Membrane Structure

Mitochondria is a double membranous structure having two membranes: an outer membrane and an inner membrane.
The outer membrane provides structural support
The inner membrane folds inward to form cristae. These cristae increases the surface area for energy production.

Matrix

Mitochondria has a fluid filled space inside the inner membrane called matrix that contains enzymes that are crucial for the citric acid cycle.

Cellular Respiration

Mitochondria generate energy through a process called cellular respiration.
This process converts nutrients into adenosine triphosphate (ATP).

ATP: Adenosine Triphosphate

ATP is the primary energy source for the cell.
The energy produced by mitochondria powers various cellular activities.

Ribosomes: The Protein Factories

Ribosomes are small, round organelles responsible for making proteins.

Location: Ribosomes can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum (ER).
Composition: Ribosomes are made up of ribosomal RNA (rRNA) and proteins.
Role in protein synthesis: Ribosomes play a key role in protein synthesis by translating messenger RNA (mRNA) into polypeptide chains.
Rough ER Ribosomes: Ribosomes attached to the Rough ER typically produce proteins that are secreted or used in the cell membrane.
Free Ribosomes: Free ribosomes synthesise proteins that are used within the cytoplasm.
Importance for Cell Growth and Repair: Ribosomes are essential for the growth and repair of cells, making them crucial for cell function.

Endoplasmic Reticulum (ER): The Transportation Network

The endoplasmic reticulum (ER) is an important organelle that functions as a transport network within the cell.

Types of ER

The ER exists in two forms: Rough ER and Smooth ER.

Rough ER: The Rough ER is covered with ribosomes on its surface. It is involved in the synthesis and processing of proteins, especially those meant for secretion or the cell membrane.
Smooth ER: The Smooth ER lacks ribosomes on its surface. It is responsible for lipid synthesis, detoxification of harmful substances, and calcium ion storage.
Role: Together, the Rough ER and Smooth ER form an interconnected network. This network supports the production of proteins and lipids, which are essential for cell function.

Golgi Apparatus: The Packaging Center

The Golgi apparatus is a stack of membrane-bound sacs that serves as the cell’s packaging and distribution centre.

Modification of Proteins and Lipids- It modifies proteins and lipids received from the endoplasmic reticulum (ER). Modifications may include adding sugar molecules or other changes as needed.
Sorting and Packaging- After processing, the Golgi apparatus sorts and packages these molecules into vesicles. These vesicles are prepared for transport to their final destinations.
Destinations of Packaged Molecules- The packaged molecules are sent to various locations, such as the cell membrane, lysosomes, or for secretion outside the cell.
Role- The Golgi apparatus is crucial for directing the flow of cellular products, ensuring proteins and lipids reach their correct locations within or outside the cell.

Other cell organelles

There are other cell organelles present inside the cell performing various other crucial activities.

Chloroplasts

Structure: Two membranes and a fluid called stroma
Function: Carry out photosynthesis
Key Components: Thylakoids, grana, and chlorophyll
Process: Capture sunlight to produce glucose and oxygen from carbon dioxide and water

Peroxisomes

Structure: Small, membrane-bound organelles
Function: Detoxify the cell and break down fats
Key Components: Enzymes like catalase
Process: Neutralise hydrogen peroxide and break down fatty acids for energy production

Vacuoles

Structure: Large storage compartments
Function: Store water, nutrients, and waste
Key Components: Help maintain cell pressure and remove waste products
Mainly Found: Plant cells

Cytoskeleton

Structure: Network of protein fibres
Function: Give the cell its shape and support
Key Components: Microtubules, actin filaments, and intermediate filaments
Process: Help move materials inside the cell and enable cell movement

FAQs on Cell Organelles

What is cell organelles?

Cell organelles are specialized structures within a cell that perform distinct functions necessary for cellular operation and survival.

What are the 7 main organelles of a cell?

The seven main organelles are the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, and vacuoles.

What are 4 important cell organelles?

Four important cell organelles are the nucleus (genetic material storage), mitochondria (energy production), endoplasmic reticulum (protein and lipid synthesis), and Golgi apparatus (modification and packaging of proteins).

What are the 9 types of cell organelles?

The nine types of cell organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, vacuoles, peroxisomes, and cytoskeleton.

What is the largest organelle in the cell?

The largest organelle in the cell is typically the nucleus, which houses the cell's genetic material.