Biochemistry and Molecular Biology - Belyasova N.A. 2002

Introduction
Subjects of Study in Biochemistry and Molecular Biology

Since both sciences often investigate the same objects, it is logical to characterize them together as a single whole.

1. Atoms. Average diameter — less than 0,4 нм. The most widespread atoms in living matter are carbon, oxygen, nitrogen, and hydrogen. The behavior of small molecules is determined by The properties of the atoms that form them.

2. Small molecules. Size — 0,5—1,0 нм. Small molecules of the following classes are of particular importance to living systems: Amino Acids, Monosaccharides, nitrogenous bases, inorganic phosphate, and glycerol. These molecules serve as the building blocks for macromolecules.

3. Genes. These are regions of Nucleic Acids that determine The Structure of Polypeptides, tRNA, and rRNA, and also play a role in the REGULATION OF METABOLISM. A single DNA (RNA) molecule can contain anywhere from a few to several thousand genes. The size of a Gene is determined by the number of nucleotide pairs and can range from several dozen to tens of thousands.

4. Macromolecules. Their size ranges from 3 to 300 нм. Proteins, nucleic acids, Polysaccharides, and Lipids are the most widespread and crucial for living organisms. They participate in The formation of Viral Particles and cellular Organelles.

5. Organelles are cellular structures that perform specific Functions. They range in size from 20 нм to 10 мкм. The largest and most highly organized organelles (found exclusively in Eukaryotic Cells) are nuclei, Cell/35.html">Mitochondria, and Chloroplasts.

6. Viruses are non-cellular entities. The diameter of viral particles ranges from 20 to 300 нм. Lacking their own metabolism, they are obligate ultraparasites incapable of self-Replication without the assistance of appropriate host cell systems.

7. Cells are the fundamental units of life capable of self-replication. They exist in two types: prokaryotic and eukaryotic. Their size ranges from 0,1 to 100 мкм.

8. Organisms: unicellular and multicellular; prokaryotic and eukaryotic. Ranging in scale from a single cell to giant forms.