Cell Organelles - Structure, Types and their Functions

Cell organelles are specialized structures found within eukaryotic and prokaryotic cells that perform specific functions necessary for the survival and proper functioning of the cell. Cell organelles are membrane-bound structures that are responsible for carrying out various cellular processes such as energy production, protein synthesis, and waste disposal. Each cell organelle is unique in structure, function, and composition. In this article, we will discuss different types of cell organelles.

What are Cell Organelles?

The components of the cell are known as cell organelles. These cell organelles incorporate either membrane or non-membrane certain organelles, present within the cells, but their structure and function are different. There are some cell organelles in animal cells which are absent in plant cell and vice versa.

All cell organelles work together so that a cell will work properly. Few organelles help the cell to maintain its shape. Some organelles help in the motility of the cell or reproduction. Several types of organelles are present which are differentiated between 3 types based on the membrane. 

• Organelles Without membrane: The Cell wall, Ribosomes, and Cytoskeleton are non-membrane cell organelles. They're present in both prokaryotic and eukaryotic cells.
• Single-layer membrane organelles: All those membranes that are covered via one layer are included in this present in eukaryotic cells. Include organelles included are Vacoules, Golgi-apparatus, vacuoles, lysosome, and endoplasmic reticulum.
• Twofold layer membrane organelles: These organelles are covered via 2 layers, include-nucleus, mitochondria, and chloroplast. 

Cell Organelle Diagram

The different cell organelles labelled diagram is given below:

Cell Organelles and Their Functions

Different types of cell organelles and their functions are present in the cell which are:

Plasma Membrane

The plasma membrane is also known as the cell membrane or cytoplasmic membrane. It's a selectively porous membrane of the cell, that is created out of a lipid bilayer and proteins, present in both plant and animal cells

It allows only certain molecules to pass through the cell membrane which makes it selectively permeable. In animal cells, they also perform one function i.e., provide shape to the cell in plant cells it is done via the cell wall. 

Cytoplasm

Cytoplasm is a jelly-like substance present in both plant and animal cells. It is present between the nucleus and plasma membrane. Cytoplasm is composed of water, organic, and inorganic compounds. It is the site for many metabolic chemical reactions as it contains many cell enzymes. All the cell organelles are embedded in the cytoplasm.

Nucleus 

The nucleus is a double membrane structure present in all eukaryotic cells. It contains the maximum molecular weight of the cell.

The nucleus contains all the genetic material of the cell. It is circular in shape and dark in color having a double membrane. Nuclear membranes are also selectively permeable. They help in cellular transport. Nuclear pores are present over the nuclear membrane which help in the transport of proteins and transcription factors. The nuclear membrane differentiates the nucleoplasm from the cytoplasm.

Within the nucleus, a small spherical body is presently known as the nucleolus, which contains the chromosomes. They are the thin thread-like structure that contains the gene. Gene is the hereditary unit i.e., all the information from the parent to the offspring is transferred via gene. The key function of the nucleus is to maintain the cell and its metabolic activities. 

Endoplasmic Reticulum

The Endoplasmic Reticulum is the membranous structure containing cristae which are attached to the tubules filled with some fluid. Endoplasmic Reticulum is the cell transport system i.e., they help to transport various proteins and enzymes in the cell or outside the cell. There are unit 2 distinctive types of Endoplasmic Reticulum:

• Rough Endoplasmic Reticulum: they're created out of cisternae, tubules, and vesicles, that area unit half-track down at some stage in the cell and area which synthesis the protein.
• Smooth Endoplasmic Reticulum: They primarily work as a storage organelle. They also synthesize steroids and lipids. It also helps in detoxification.

Mitochondria

Mitochondria is a semiautonomous organelle i.e., they have some genes which form their proteins but not all. For some proteins, mitochondria are still dependent on the nucleus.

Mitochondria are known as the powerhouse of the cell. It is a double membrane structure present in all eukaryotic cells. Mitochondria carry in size and can of either circular or oval. It is the site for aerobic respiration.

Plastids

The large membrane-bound organelles containing pigments is known as a plastid. Depending on the type of pigments plastids are differentiated into 3 types:

• Chloroplasts: These are double membrane organelle. Chlropoplast is present in the leaf mesophyll cell. Chloroplast is the main pigment that helps in storing light energy and which helps in photosynthesis. 
• Chromoplasts: The chromoplasts incorporate fat-solvent, antioxidant shades like xanthophylls, and carotene, which provide the plants with their color - yellow, orange, red, and so on.
• Leucoplasts: Leucoplasts are colorless plastids that store nutrients in them.  Amyloplasts store carbs (like starch in potatoes), aleuroplasts store proteins, and elaioplasts store oils and fats.

Ribosomes

Ribosomes are single membrane-bound organelles that are mainly attached to the endoplasmic reticulum. They are composed of RNA and ribosomal proteins. Ribosomes can be of 2 types i.e. 70s present in prokaryotic cells and 80s in a eukaryotic cell. Where s stands for Svedbergs Unit. Both ribosomes are composed of 2 subunits large and small subunit. Ribosomes can be present in both forms either they are attached to the ER or present freely in the cytoplasm.

Golgi Complex

Golgi complex is also known as Golgi Apparatus. The diagram of Golgi complex is given below:

Golgi complex is a membrane-bound organelle form of flattened stacked pouches known as cisternae present in both plant and animal cells. Golgi apparatus helps in transporting the cargo, modifications, targeting, and packaging of proteins and lipids to the target site.

Microbodies

Microbodies are single membrane structures, minute, sac organelles, present in both plant and animal cells. Microbodies contain various enzymes which can be seen via electron microscope.

Cytoskeleton

Cytoskeleton is a proteinaceous structure that is present from the cell membrane to the nucleus. It is present everywhere in the cell. Cytoskeleton is present in all cells it provides shape to the cell and helps in the movement of the cargo. Cell matrix is a form of different types of proteins that assemble in a few minutes and disassemble depending on the cell requirement. They provide mechanical resistance to the cell and their contractile nature of filament helps the cell in movement.

Cilia and Flagella

Cilia and flagella are present in the outer part of the cell wall. They both help in the movement of the cell.

Cilia are hair-like projections present on the cell wall that help in the movement of cells or extracellular fluid. Flagella are a bit bigger than the cilia. Anoxene is the core of both cilia and flagella, which contain 9 microtubules and a set of central microtubules. Centriole is the basal body of both cilia and flagella.

Centrosomes and Centrioles

Centrosome is made when 2 perpendicular centrioles come together and form centrosomes.

Each centriole is composed of 9 microtubules, 3 such microtubules interlinked and form a centriole, it is also known as MTOC. Centrioles connect the peripheral fibril with the radial spoke. Cilia and flagella basal bodies are composed of centrioles.

Vacuoles

Vacuoles are the cell organelles with a single membrane. In plant cells, vacuoles have the maximum area of cells. Vacuoles help in storing various compounds. Normally they store nutrients and food which is required for the survival of a cell. Vacuoles also store waste products. The no. and shape of vacuoles vary depending on the cell.

Conclusion - Cell Organelles

Cell organelles are fundamental structures within cells, each designed to carry out specialized functions essential for the survival of the cell. There are various types of cell organelles in animal and plant cells. Understanding the various cell organelles and their function is important to learn about structure and function. of the cell.

Also Read:

• Semi-Autonomous Organelles
• Facts about Animal Cell
• Diagram of Animal Cell
• Cell the Unit of Life Class 11 Notes CBSE Biology Chapter 8
• Endomembrane System – Overview, Structure, and Functions