Molecular Biology


Molecular biology  concerns the molecular basis of biological activity between bio molecules in the various systems of a cell, including the interactions between DNA, RNA and proteins and their biosynthesis, as well as the regulation of these interactions.

What is a Cell?

Fundamental working units of every living system. • Every organism is composed of one of two radically different types of cells:

  •  prokaryotic cells
  •  eukaryotic cells

which have DNA inside a nucleus. • Prokaryotes and Eukaryotes are descended from primitive cells and the results of 3.5 billion years of evolution.

Eukaryotic  and  Prokaryotic Cell

The distinction between prokaryotes and eukaryotes is considered to be the most important distinction among groups of organisms. Eukaryotic cells contain membrane-bound organelles, such as the nucleus, while prokaryotic cells do not. Differences in cellular structure of prokaryotes and eukaryotes include the presence of mitochondria and chloroplasts, the cell wall, and the structure of chromosomal DNA.

Prokaryotes were the only form of life on Earth for millions of years until more complicated eukaryotic cells came into being through the process of evolution.
Difference between Eukaryotic  and  Prokaryotic Cell

  • The most fundamental difference is that eukaryotes do have “true” nuclei containing their DNA, whereas the genetic material in prokaryotes is not membrane-bound.
  • In eukaryotes, the mitochondria and chloroplasts perform various metabolic processes and are believed to have been derived from endosymbiotic bacteria. In prokaryotes similar processes occur across the cell membrane; endosymbionts are extremely rare.
  • The cell walls of prokaryotes are generally formed of a different molecule (peptidoglycan) to those of eukaryotes (many eukaryotes do not have a cell wall at all). Prokaryotes are usually much smaller than eukaryotic cells.
  • Prokaryotes also differ from eukaryotes in that they contain only a single loop of stable chromosomal DNA stored in an area named the nucleoid, while eukaryote DNA is found on tightly bound and organised chromosomes.
  • Although some eukaryotes have satellite DNA structures called plasmids, these are generally regarded as a prokaryote feature and many important genes in prokaryotes are stored on plasmids.
  • Prokaryotes have a larger surface area to volume ratio giving them a higher metabolic rate, a higher growth rate and consequently a shorter generation time compared to Eukaryotes.

 Life depends on 3 critical molecules

  • DNAs (Deoxyribonucleic acid) – Hold information on how cell works
  •  RNAs (Ribonucleic acid) – Act to transfer short pieces of information to different parts of cell – Provide templates to synthesize into protein
  •  Proteins – Form enzymes that send signals to other cells and regulate gene activity – Form body’s major components