Fundamentals of Molecular Biology. Part 1: Molecular Biology of the Cell - A. N. Ogurtsov 2011

Fundamentals of Cell Theory
Cell Theory

The Cell is the fundamental living system capable of self-renewal, self-regulation, and self-Replication; it serves as the basic Structural and functional unit of All living organisms.

For vital activities—such as growth, self-repair, and reproduction—Cells require energy, which they derive from their external environment.

METABOLISM (from the Greek metabole, meaning change or conversion) encompasses all chemical and physical reactions that sustain the vital processes of the cell.

Metabolic reactions are catalyzed by Enzymes.

Enzymes are protein molecules that accelerate biochemical reactions without being consumed in the process.

The molecular Structure of every enzyme (just like any other protein) is determined by a Gene.

A gene is a segment of a deoxyribonucleic acid (DNA) molecule that encodes a single polypeptide chain or RNA molecule.

Cellular molecular biology is the science that studies cellular life processes at THE MOLECULAR LEVEL, drawing upon disciplines such as biochemistry, biophysics, genetics, microbiology, Embryology, and evolutionary biology.

The cell was discovered by Robert Hooke in 1665, who also introduced the term "cell" ("cellula"). However, the generalization of the fundamental concepts regarding the cellular structure of living organisms, known as cell theory, was not formulated until the mid-19th century by botanist Matthias Schleiden and zoologist Theodor Schwann.

Modern cell theory is based on six core tenets:

1. The cell is the fundamental unit of structure for all living organisms.

2. The cell Functions as a unified system comprising numerous regularly interrelated elements—Organelles or organoids—which are distinct, integrated structures and cellular components that ensure the performance of specific functions throughout the cell's life cycle.

3. The cells of various organisms are similar (homologous) in their structure, chemical composition, basic physiological manifestations, and metabolism.

4. Cells reproduce exclusively through division, meaning every cell originates from a pre-existing cell.

5. A multicellular Organism represents a novel system—a complex ensemble of numerous cells integrated into Tissue and organ systems, interconnected through chemical, humoral, and neural factors.

6. The cells of Multicellular Organisms are totipotent, meaning they possess the genetic potential of all cells within that organism, contain identical Genetic information, but differ due to the differential expression (activity) of various genes, resulting in morphological and functional diversity—known as differentiation.