Parts of cell & How can the cell perform its functions ?
It the smallest functional and building unit in all living organisms , The cell is characterized by the ability to grow , It can reproduce , It can respond to the external stimuli and perform the different metabolic processes .
Parts of cell
The cell is made up of a protoplasmic mass surrounded by the cell membrane , The protoplasm is differentiated into parts which are nucleus and cytoplasm , Cytoplasm contains a group of cellular structures called cell organelles .
The cell wall and cell membrane ( plasma membrane ) .
The nucleus consists of nuclear envelope , Nucleolus , Nucleoplasm and Chromatin .
Cytoplasm contains membranous organelles and non-membranous organelles , membranous organelles ( contains Endoplasmic reticulum , Golgi body , Lysosomes , Mitochondria , Vacuoles and Plastids ) , non-membranous organelles ( includes Ribosomes and Centrosome ) .
Cell walls and plasma membranes
The cell wall surrounds the plant cell , algae , fungi and some types of bacteria , It is mainly composed of cellulose fibres .
Cell wall functions
- It supports and protects the cell .
- It allows the passage of water and dissolved substances through it easily because it is pitted .
The perennial trees such as palm trees are characterized by containing cell wall that play an important role in protecting the cells , making them withstand to wind and other weather factors , these walls provide the cells with strong support .
The small herbal plants are characterized by containing cell walls with little elasticity that makes them able to maintain their shapes as they are exposed to strong wind .
Cell membrane ( plasma membrane )
It surrounds the cytoplasm of plant and animal cells , Cell membrane is a fluid structure similar to a layer of oil because the phospholipids forming it are a fluid substance , It is a thin membrane consisting of :
- Two layers of the fluid phospholipid molecules , each of them consisting of Hydrophilic heads and Hydrophobic tails , Hydrophilic heads ( soluble easily in water ) meet the water medium in and out the cell , Hydrophobic tails ( insoluble in water ) and present inside the membrane .
- Molecules of protein are embedded between the molecules of phospholipids , where some of them work as cell identification sites for different substances such as nutrients , hormones and others , Some others work as gates to pass the substances into and from the cell .
- Cholesterol molecules linked with phospholipid molecules for maintaining the cell membrane cohesive and intact .
Cell membrane Functions
It covers the cell and separates its components from the surrounding medium , So , it prevents the spreading out of cytoplasm outside the cell .
It performs a basic role in organizing the passage of the substance to and from the cell .
Nucleus is the most obvious organelle in the cell that can be seen under the microscope , It has a spherical or oval shape and it is located at the middle of the cell .
The nucleus is composed of :
Nuclear envelope is a double membrane separates the contents of the nucleus from cytoplasm , There are several tiny pores in it through which substances pass between the nucleus and cytoplasm .
Nucleolus is responsible for synthesis of ribosomes which play an important role in protein synthesis , So , more than one nucleolus may be found in the nucleus especially in the cells forming and secreting proteins as enzymes and hormones .
Nucleoplasm is a transparent gelatinous fluid contains the chromatin .
Chromatin is minute tangled filaments coiled around themselves , during cell division and it changes into rod-like structures called chromosomes .
Chromosomes were called with this name because they stain by basic dyes , So , they appear coloured making them more clearly seen during cell division .
During metaphase of cell division , The chromosome appears consisting of two filaments , each filament of those is called chromatid , They are joined together by a central part called centromere .
Each chromatid is composed of the nucleic acid DNA coiled around protein molecules called histones .
DNA carries the genetic information ( genes ) that control the shape and structure of the cell and organize its vital activities , Genetic traits are transferred through them from a generation to another by reproduction .
Chromosome form the chromatin reticulum in cell nucleus , Chromosome is not consisted of two chromatids in all phases of mitosis where chromosome is consisted of two chromatids at the beginning of mitosis till its metaphase .
Chromosome becomes consisting of one chromatid in anaphase , telophase and called daughter chromosome , At the beginning of each new cellular division , its genetic material is duplicated to become consisted of two chromatids .
You can read this article about the cytoplasm