If we put a cell under a microscope , there are three features that you could observe clearly in nearly every cell .
- These are : Plasma Membrane , a Nucleus , and Cytoplasm
- Cell organelles are also present in nearly every cell ( except prokaryotes ).
- These vary from cell to cell .
- In plant cells you can also observe an extra covering called the Cell wall .
Let us learn about the basic parts of a cell first:
Cell Membrane / Plasma Membrane
Every cell has a membrane around it to keep its contents separate from the external environment .
- The cell membrane is the outermost covering of an animal cell.
- It encloses the other components of the cell , such as the nucleus and the organelles.
- It is also known as the Plasma membrane .
- The cell membrane is flexible and its shape can be changed as needed.
- The plasma membrane is made of substances called lipids and proteins which lend it flexibility .
The functions of the Cell membrane are as follows:
- Protecting the integrity of the interior cell.
- Providing support and maintaining the shape of the cell.
- It acts as a semi - permeable membrane that allows the entry of only selected substances into the cell.
- Helps cells to catch/absorb food by changing its shape .
For Example - An amoeba catches its food by changing its shape and using pseudopodia to capture food.
Nucleus
- The Nucleus can be described as the brain of the cell .
- It is a membrane-bound (covered by a sheath ) structure.
- It contains the cell’s hereditary information (characteristics/genes obtained from parents) and controls the cell’s growth, reproduction and other essential functions.
- The membrane covering the nucleus is called the Nuclear membrane .
- The nuclear membrane separates the cytoplasm from the contents of the nucleus .
Cytoplasm
The cytoplasm is the fluid content inside the plasma membrane .
- It is a semi-liquid jelly-like material , between the nucleus and the cell membrane.
- All cell organelles such as endoplasmic reticulum, mitochondria, ribosomes, vacuoles, etc. float within the cytoplasm .
Cell Wall
It is the outermost covering of a plant cell .
- It separates the interior contents of the cell from the exterior environment .
- The cell wall is permeable in nature which means it allows the passage of most materials through it .
- The cell wall is made up of a substance called Cellulose .
- Cellulose gives it strength and rigidity .
Here are a few functions of the cell wall:
- It provides shape, strength and rigidity to the cell.
(The absence of the cell wall is the reason why animal cells are irregularly shaped . They have no support ).
- It provides protection from any physical stress as well as from the external environment .
- Controls the swelling of the cell during water intake . Without it, the cell would burst .
- Prevents water loss from cell by trapping in the water.
- It transports substances across different cells.
Apart from these 4 parts that are present in every cell, a cell may also contain cell organelles .
Each organelle has a separate function that it performs for the cell.
