1. Cell structure and Function
1.5.a. Cell organelles of both Plant and animals
Cell organelles of both plant and animal cell
Dr V Malathi and Mrs Sushumna Rao
The Nucleus
The nucleus (plural = nuclei) is the most prominent and largest organelle in a cell. It is the cell’s control center.
The DNA is present in the nucleus. The DNA is encoded with the genetic information.
Nucleus contains a thick liquid called nucleoplasm
The composition of nucleoplasm is similar to that of cytoplasm.
Most eukaryotic cells contain just a single nucleus.
Some types of cells like red blood cells contain no nucleus and a few other types of cells such as muscle cells contain multiple nuclei.
The nucleus is surrounded by a double membranous structure called the nuclear envelope.
The tiny holes are present in the nuclear envelope and these are called nuclear pores through which molecules move in and out of the nucleus.
The structure called nucleolus is housed inside the nucleus. It is mainly involved in the assembly of ribosomes.
The ribosomes after being produced in the nucleus are exported to the cytoplasm, where they are involved in the synthesis of proteins.
“Nucleus” by CNX OpenStax, is licensed under CC BY 4.0
Mitochondria
The mitochondrion ( plural mitochondria) are the “powerhouse of a cell” as they make energy required for a cell .
They use organic compounds such as glucose and through metabolic process called , and make ATP ( Adenosine Triphosphate molecules)
Mitochondria have a complex structure including an inner and outer membrane.
The inner membrane contains a version of cytoplasm, called matrix.
Can mitochondria be considered a cell? as they have there own DNA and ribosomes.
To explain this scientists have put forward a theory called Endosymbiotic theory.
According to this theory mitochondria were once considered to be free-living organism as they contain their own DNA and were considered as ancient prokaryotic cells.
These cells were then engulfed by larger prokaryotic cells.
The two cells then evolved a symbiotic relationship where the larger cells provided the smaller prokaryotes with a place to live. In return, the larger cells got extra energy from the smaller prokaryotes.
Eventually, the smaller prokaryotes became permanent guests of the larger cells and stayed as organelles inside them.
Endoplasmic Reticulum
The endoplasmic reticulum (ER) is a series of interconnected membranous tubules.
There are two separate areas of the endoplasmic reticulum: the rough endoplasmic reticulum and the smooth endoplasmic reticulum, respectively.
The hollow portion of the ER tubules is called the lumen or cisternal space.
The membrane of the ER is a phospholipid bilayer embedded with proteins and is continuous with the nuclear envelope.
The rough endoplasmic reticulum (RER) : This is so named because when viewed through the electron microscope ,the ribosomes attached to its cytoplasmic surface give it a studded appearance . The ribosomes synthesize proteins while att