Nucleus Flashcards
Function of the nucleus
1- Controls all the function of the cell
2- storing of the genetic material
3- determine the type and the function of the cell
4- formation if RNA
5- play an important role in heredity
Staining of the nucleus
Has basophilic structure it can be stained by hematoxylin its color is blue .
Nucleus position
Central , peripheral , basal , eccentric
Size of nucleus
Small , medium , large ,
“ its very in size “
Shape of nucleus
Rounded , oval , flattened , elongated , rod shaped , bilobed , kidney shaped , segmented
“ vary in shape “
Number of nucleus
- Usually there is one nucleus in each cell
- tow nucleus may be present in liver cells or transitional epithelium
- more then two nucleus are present in osteoblasts cells of bone or skeletal muscle cells
Location of nucleus
Present in all mammalian cells except red blood corpuscles
Structure of nucleus from outside to inside
- nuclear membrane / envelope
- nuclear sap / karyolymph
- nucleolus
- chromatin — euchromatin — heterochromatin
What is the nuclear membrane
- It is a membrane that surround the nucleus
- this membrane disappear during cell division
Nuclear membrane under L.M.
Appear as basophilic single line .
Nuclear membrane under E.M.
- Two thin membranes separated by a perinuclear space
- inner nuclear membrane
- outer nuclear membrane
- nuclear pores
Inner nuclear membrane contains ?
It has a chromatin granules on the inner space
Outer nuclear membrane contains ?
It has ribosomes on the outer surface
What is the nuclear pore ?
It is a canal between inner and outer membrane in order to form diaphragm
Function of diaphragm
- regulate the exchange process of metabolites and molecules between nucleus and cytoplasm
- regulate the passage of RNA from inside to outside the nucleus
Definition of chromatin
Are particles and thread which form the chromosomes during cell division
Structure of chromatin
It is composed of DNA and Histone
Chromatin under L.M.
Appear as coarse and fine basophilic granules
Types of chromatin
1- Euchromatin / extended chromatin / active chromatin
2- heterochromatin / condensed chromatin / inactive chromatin
Function of chromatin
1- guide the protein synthesis inside the cell
2- stores the genetic information
— which are transmitted through successive generation
— this done through duplication of DNA
— before the starting of cell division
3- m RNA , t RNA , r RNA , are synthesized from DNA which located in chromatin .
Structure of DNA “ deoxy ribonucleic acid “
- Has a double helix chain
- each chain is formed of phosphate and sugar ( deoxyribose ) groups
- the double helix chain are linked transversally by a base ( nitrogenous base )
- this base extend laterally from each sugar group
There is four types of nitrogenous bases in the DNA molecule which are ?
1- adenine (A)
2- thymine (T)
3- guanine (G)
4- cytosine (C)
Function of DNA
The main function of DNA is the transferring of “genes” ( genetic information ) by two processes .
1- replication of DNA , which form more DNA
2- transcription of DNA , which form three types of RNA , rRNA , tRNA , mRNA .
Location of DNA
Present in nucleus and mitochondria
Staining of DNA
DNA takes blue color with methyl-green pyronin stain
Structure of RNA
- each RNA is formed of single stand of helix , however some RNAs have double helix .
- each RNA stand contain ribose sugar instead of deoxyribose sugar
Location of RNA
Present in nucleus and cytoplasm
Staining of RNA
With methyl - green pyronin RNA takes red color .
Formation of ribosomal RNA
Formed in nucleus from a loop of DNA called nuclear organizer
The pathway of Ribosomal RNA
The newly formed ribosomal RNA molecules are transported to the cytoplasm
The Function of ribosomal RNA
They serve as essential sites for protein synthesis ( factories of protein formation )
Formation of messenger RNA
The information codes for protein synthesis are present on the DNA molecule as a series of units , from this DNA molecule , messenger RNA is formed carrying the information codes of protein synthesis .
The pathway of Messenger RNA
The newly formed messenger RNA is then transported to the cytoplasm carrying with it the information which controls the process of protein synthesis at the sites of cytoplasmic ribosomes
Formation of transfer RNA
The formation of t RNA occurs inside the nucleus from a special type of DNA molecule
The pathway of t RNA
To the cytoplasm
Function of t RNA
- they play an important role in the process of protein synthesis
- there are a different forms of t RNA which transfer specific amino acids from the cytoplasm to their specific position in polypeptide chains
- the amino acids in this process are have been activated by special enzymes
- the polypeptide chains are manufactured in the ribosomal RNA
Nucleolus under L.M
appears as a dark basophilic mass
Nucleolus under E.M
Formed of an irregular spongy mass not limited by a membrane , it shows light and dark areas .
Function of nucleolus
- It forms r RNA which pass through the nuclear pores to the cytoplasm ,
- the r RNA considered as factories for protein synthesis
Structure of nucleolus
It is formed mainly of protein , RNA and DNA , also contains certain enzymes as acid phosphatase and RNA methylase .
Appearance of nucleolus
Disappears during cell division , reappears in the new daughter cells
Nucleolus staining
It is basophilic because it is rich in RNA
Shape of nucleolus
It is rounded in shape surrounded by chromatin material .
