The Fundamental unit of life - Part 2

The Fundamental unit of life

STRUCTURE OF A CELL

A typically cell consist of three major components:-

1. Plasma membrane 
2. Nucleus 
3. Cytoplasm 

CELL WALL

• It's the toughest outer membrane present only in plant cell.
• It was firstly discovered by Robert Hook.
• Cell wall in plants is mainly composed of green color cellulose.
• Cell wall is freely permeable i.e both solute and solvent can pass through it. 

FUNCTION:-

• It maintained the shape of the cell.
• In roots cell wall helps in the absorption of water and mineral.
• Cell wall helps to prevent the cell itself bursting.

PLASMA  MEMBRANE / CELL MEMBRANE

• The outermost covering that separate the content of the cell from surrounding. In animal cell it's the first membrane and in plant cell it's the second membrane after the cell wall.
• Plasma membrane is about 6 to 10 nm thick layer.
• It's composed of phospholipid layers and associated proteins.
•  The proteins and lipids are arranged in an irregular and uneven pattern and the protein are able to move within the  membrane.

FUNCTION:-

• They form cell boundary and maintain the individuality of the cell.
• It protect the cell from external injury and contaminant.
• Cell membrane is called as selectively permeable membrane.
• The intake of material by the cell is called as endocytosis. 
• The intake of solid form is called as phagocytosis and the intake of liquid form is called as pinocytosis.
• In the plasma membrane the diffusion of gases take place.

DIFFUSION :- The movement of a substance from higher concentration region to its lower concentration region is known as diffusion. Most of the gas like CO2 and O2 move in and out of the cell.

OSMOSIS :-  The movement of  water from higher concentration region to its lower concentration region is known as osmosis.

NUCLEUS

• It's the most important part of the cell it is basically located in the middle of the cell.
• Nucleus was discovered by Robert Brown in 1831.
• It is important because it control all the metabolic activity of the cell as well as it contain the genetic material of the cell which is DNA (De-oxy ribo nucleic acid) or RNA (Ribonucleic acid).
• Nucleus is surrounded by a double walled membrane called as Nuclear membrane.
• It the nucleus they contain a semi fluid structure called as Nucleoplasm.
• The nucleus also have chromatin thread which become Chromosome later on.

CHROMOSOME

• They have very thick rod like structure which can be visible at the time of cell division.
• The chromatin material consist of DNA and Protein.
• The genetic information in a chromosomes, is present in the form of smell segments of DNA are called as Genes.
• In human beings there are basically  23 pairs of chromosomes.

FUNCTIONS:-

• Nucleus is the center of genetic information so it has command and control on all activities inside a cell.
• Nucleus provide information for protein synthesis.
• Nucleus plays a crucial role in cell division.

CYTOPLASM 

• They have a jelly matrix like structure called as cytoplasm.
• The cytoplasm contain 70 t 80% water and the remaining part include sugar, minerals, vitamins, nucleotides, tRNA, many enzymes, proteins,
  
  amino acids and fats.
• In cytoplasm they have various cell organelle such as:-

1. Endoplasmic Reticulum (ER)
2. Golgi Body
3. Lysosomes
4. Mitochondria
5. Plastids
6. Ribosomes
7. Vacuoles

ENDOPLAMIC RETICULUMN (ER)

• It's found in all living cells. except prokaryotes and mature mammalian RBC 
• ER have a large network of membrane bound tubes and sheets.
• It transport various substance such as protein within the cell.
• The ER is of two types.

1. Smooth Endoplasmic Reticulum (SER)
2. Rough Endoplasmic Reticulum (RER)

1. Smooth Endoplasmic Reticulum (SER) :-

• It does not contain ribosomes, therefore the surface is smooth.
• SER is mainly involved in lipid and steroid synthesis.  

2. Rough Endoplasmic Reticulum (RER)

• In this there is the presence of Ribosomes on it's surface.
• Its basically actively engaged in protein synthesis.

FUNCTION :- 

• ER helps in the transparent of material within the cell.
• It also help in conversion of glycogen into glucose.
• RER helps in the formation of Protein.
• SER helps in the formation of lipid and fat. 

GOLGI APPARATUS OR GOLGI BODY

• The Golgi body is discovered by Camillo Golgi in 1898.
  
• They contain many membrane bound Vesicles and tubules.
• These tubules are connected to ER. They helps in the formation of cellular membrane network.
• They also help to give rise the lysosomes.

FUNCTION

• They helps in the packaging of proteins.
• they help in the formation of Lysosomes.

LYSOSOMES

• It is discovered by Christian de Duve.
• They are single membranous bound Vesicles which contains very strong digestive enzymes.

FUNCTION

• They helps in the digestion of materials that enters the cell. They are also called as 'Digestive bags'.
• They keep the cell clean by destroying old organelles and foreign particles.
•  Sometime, during some disturbance in cellular metabolism the lysosomes may burst. These bursting can damage all the cell parts. This may cause death of the cell, So, lysosomes are also known as "Suicidal bags".

MITOCHONDRIA

• They are the Powerhouse of the cell because they serves to produce
  
  energy for the cell.
• They are long rod or oval shaped like structure.
• They are double membrane i.e Outer and inner membrane.
• Inner membrane has many folding called as Cristae. They helps to increase the surface area of inner membrane for ATP ( Adenosine tri phosphate).
• They contains there own DNA and ribosomes.

FUNCTION

• The chief function of mitochondria is to manufacture ATP which is known as the energy currency of the cell. They give the energy to all type of biochemical and mechanical process.

PLASTIDS

• These organelles are found only in plant cell.

  

  Chloroplast

• They have there own DNA and 70S type of ribosomes.
• On the basis of their structure they are divided into three types:-

1. Leucoplasts :- 

• These are colorless or white plastids, due to the presence of various pigments.
• They do not participate in photosynthesis.
• They serve to store reserve food such as starch, fats and oil.

2. Chromoplasts :-

• These are colored plastid due to the presence of various pigments.
• They usually serve to manufacture food by photosynthesis.
• The provide various color in fruits and vegetables.

3. Chloroplasts :- 

• These are the most common types of plastids and found in almost all autotrophs.
• The plants are always green in colour, because in that there is the presence of chlorophyll.
• This is the main site for the process of photosynthesis.

RIBOSOMES

• They are the form of Protein synthesising machinery of the cell.
• They are found in all living cell since they are the site of protein synthesis.
• The ribosomes are of two main types i.e in 70S and 80S (S is called as sedimentation coefficient )

FUNCTION

• There main work in to synthesis the protein only in the cell.

VACUOLES

• They are the storage sac of the cell.
• They are single membrane bound organelle which is present in the cytoplasm  of the cell.
• In plant there size is big which cover almost all the space of the plant cell but in animal they have small size but large in number.

FUNCTIONS

• They provide turgidity and rigidity to the cell.
• Thee are many important things like minerals, salts and other soluble substance are stored within the vacuoles.
• It maintain the concentration of salts and water in the salts.
• They also store amino acid, protein, sugars, and some organic acids.