Cell Organelles and their function

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Cell Organelle

Ultra structure of plant cell

plant cell


Cell Organella

A small organ-like structure present inside the cell is called a cell organelle. It has a particular structural makeup and performs a specific function. Depending upon the presence or absence of membrane, cell organelles can be classified into three categories, namely:

  • Without membrane: Some cell organelles like ribosomes are not bounded by any membrane. They are present in prokaryotic as well as eukaryotic organisms.
  • Single membrane-bound: Some organelles are bounded by a single membrane. For example, vacuole, lysosome, Golgi Apparatus, Endoplasmic Reticulum etc. They are present only in a eukaryotic cell.
  • Double membrane-bound: Cell organelles like mitochondria and chloroplast are double membrane-bound organelles. They are present only in a eukaryotic cell.

Structure and Functions of Cells

Structure and functions of different cell inclusions are as follows-


Cell Organelle

A bilipid membraneous layer composed of proteins and carbohydrates.  It is fluid like.the cell membrane separates the cell from its external environment, and is selectively permeable (controls what gets in and out).  It protects the cell and provides stability. Proteins are found embedded within the plasma membrane, with some extending all the way through in order to transport materials. Carbohydrates are attached to proteins and lipids on the outer lipid layer.


The jelly-like substance composed of mainly water and found between the cell membrane and nucleus.  The cytoplasm makes up most of the “body” of a cell and is constantly streaming.Organelles are found here and substances like salts may be dissolved in the cytoplasm.


Cell Organelle

All plant and animal cells, which are eukaryote organisms, contain a true nucleus bounded by a nuclear membrane. (Prokaryotes such as bacteria and archaea don’t have a nucleus.) This structure contains a eukaryotic cell’s DNA and directs cell activities.

Endoplasmic reticulum

The cell membrane is double-layered in animals, and forms the outer cell boundary that protects the cell contents and regulates what goes in and out of cells. In plants, a plasma membrane lies just underneath the tough cell wall that supports plant tissue. The endoplasmic reticulum is an extensive membrane complex extending throughout the cytoplasm from the outer membrane of the nuclear envelope. It contains about half of the cell’s membranous tissue. Rough endoplasmic reticulum contains ribosomes that produce proteins. Smooth endoplasmic reticulum manufactures lipids.

Golgi Apparatus

Cell Organelle

Also called the Golgi complex or Golgi body, this organelle looks like a stack of flattened water balloons. It processes the proteins produced by the endoplasmic reticulum and ribosomes, modifying and storing them until it packages them in vesicles. Lysosomes also come from the Golgi apparatus. These are sacs containing enzymes capable of breaking down cell macromolecules.


Ribosomes are the protein factories of the cell. Composed of two subunits, they can be found floating freely in the cell’s cytoplasm or embedded within the endoplasmic reticulum. Using the templates and instructions provided by two different types of RNA, ribosomes synthesize a variety of proteins that are essential to the survival of the cell.


In plants and some algae, organelles known as chloroplasts serve as the site of photosynthesis. Chloroplasts contain a pigment known as chlorophyll, which captures the sun’s energy to transform water and carbon dioxide into glucose for food. Chloroplasts allow autotrophic organisms to meet their energy needs without consuming other organisms.


The “powerhouses” of the cell, mitochondria are oval-shaped organelles found in most eukaryotic cells. As the site of cellular respiration, mitochondria serve to transform molecules such as glucose into an energy molecule known as ATP (adenosine triphosphate). ATP fuels cellular processes by breaking its high-energy chemical bonds. Mitochondria are most plentiful in cells that require significant amounts of energy to function, such as liver and muscle cells.

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