‘LIFE’, this word refers to the all living organisms on the earth. Without life they won’t be viable at all. ”CELL” is the basic functional and structural unit of the living organisms. On the basis of the structure of the cell there are two types of living organisms, prokaryotes and eukaryote. Prokaryotes (e.g bacteria, yeast) are simple living organisms and eukaryotes (mammals, birds) are more advanced complex living organisms. The main difference is prokaryotes are not having nucleus, only having nuclear material to regulate functions compared to the eukaryotes. Usually eukaryotes made of more than one cell while prokaryotes are single cell organisms with cytoplasm lined by cell membrane.
Life of living organisms is determined particular primary functions of the cells which are regulated by the functional components inside the cell. It is applicable for both prokaryotes and eukaryotes. Those particular functions which are salient for maintain the life of living organisms are growth and development, reproduction, metabolism, synthesis of enzymes and proteins, excretion, responding to external and internal stimuli etc. So all of the functions are regulated and maintained by the functional components of the cells it self.
Major functional components that eukaryotic cell is having are cell membrane, cytoplasm, nucleus with nucleolus, mitochondria, ribosomes, rough endoplasmic reticulum(RER), smooth endoplasmic reticulum (SER) etc. Cell membrane keep the organelles inside the cell while keep the cells together and act as an outline which demarcates the cells from the outside environment. It is electively permeable and allowing the things to be moved inside and outside which assist in metabolism of the cell. Mitochondria are the energy producers of the cells which is a main component for the viability of the cells. The quantity of the mitochondria inside the cell is vary according to the type of cell and the energy demand. They generate energy as ATP which maintain most of vital primary functions of the cells. Synthesis of cellular proteins is the key component in maintaining life of living organisms. Enzymes are type of proteins which are functional workhorses of cells which account for 10000 types of different proteins. Ribosomes, RER, nucleus are functional organelles participating protein synthesis. The nucleus is the control centre of a cell which containing genetic material in the form of DNA and also having information for synthesis of proteins. Ribosomes locate in the cytosol and synthesise appropriate proteins when required by interpretation of the cellular information carried in the nucleus. RER produce lipids and proteins inside the cells and actively participate on cellular metabolism. Ribosomes are attached to the surface of them and therefore named as rough endoplasmic reticulum.
Major primary function of the cells which refers to the life of living organisms is reproduction. Reproduction is formation of daughter cells by parent cells. Reproduction is done by the means of cellular division. So ultimately cell division is more helpful in maintaining the life of a living organism. Ancient way of reproduction is seen in prokaryotes, which is named as binary division. In eukaryotes there are two types of cell division. They are meiosis andmitosis. Mitosis is a type of cell division allows multicellular organisms to grow and repair damaged cells and tissues. Here division of parent cell into two identical daughter cells duplicating all the cellular organelles. In sexual reproduction meiosis type of cell division seen ( e.g. sperms, eggs). Here one parent cell produces four daughter cells but they are having half the number of parent chromosomes and identical to each other.
In the nucleus genetic material and information for the protein synthesis carried by DNA. This information carried in chromosomes which are packages of DNA. Human cells having 23 distinct chromosomes. Except germ cells (e.g. sperms, eggs) each somatic cell is having 2 copies of each chromosomes. 23 pairs account for 46 chromosomes in total. One chromosome comes from female parent and other one comes from male parent in each chromosome pair. Chromosomes contain most protein and DNA. DNA is the main genetic information carrier inside the cells. It is double stranded long linear molecule with strong polymer of nucleotide. Basic unit of DNA molecule is nucleotide which is a complex molecule made up from three components, sugar, nitrogenous base and phosphoric acid. Double helix is formed with base pairing, the bases are adenine(A), Guanine(G), thymine(T) and cytosine(C). DNA molecule can be several or million nucleotides length. And there is no order in which nucleotide join together. Discrete segment of DNA molecules stands for genes. So the nucleotide sequence of the DNA molecule represents the biological information carried by the genes which helpful in maintaining life of living organisms. So that nucleotide sequence is the most important factor in the genetics. DNA of higher organisms is packed in the several chromosome in each cell. The total genetic material stored in the chromosomes of an organism is known as genome. Genes may lie on different polynucleotides of a DNA strand.the nucleotide sequence is the essential set of instructions for the synthesis of RNA molecule. RNA plays important role in transcribing genetic information DNA to proteins or enzymes. The process which translating genes into protein is called gene expression. This formed proteins or enzymes from the genetic material stored in the DNA molecule do the real work of the living organism maintaining it’s life. They make bones, cartilages, muscles, haemoglobin, hormones, antibodies stores, releases and convert energy inside cells. Proteins are sequences composed of amino acids. Nucleotide sequence of a m-RNA molecule translated into a particular amino acid sequence of corresponding protein. The sequence of nucleotide in m-RNA reading serial order in group of three nucleotide in DNA strand, which is named as codon. Each triplet of nucleotide or codon specifies one amino acid in polypeptide chain of protein molecule. Only 20 types of amino acids are found in proteins and there are 64 codons for coding synthesis of those amino acid and it is more than enough. So in protein synthesis pathway DNA and RNA play key roles.because protein is a sequence of amino acids and amino acid sequence is determined by the nucleotide sequence of m-RNA molecule while sequence of m-RNA complement to the nucleotide sequence of DNA strand which stored genetic material.
So life of an living organism depends on the functional components of the cells including nucleus, chromosomes, DNA, RNA, ribosomes as well as primary vital functions of the cells such as reproduction by cell division,protein or enzyme synthesis etc.
