Encyclopedia of Molecular Biology

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Encyclopedia of Molecular Biology

Molecular biology is a broad science that covers the study of the composition, structure and interaction of cellular molecules such as nucleic acids and proteins. These molecules carry out the biological processes essential for the functions and maintenance of the cells.

https://www.nature.com/subjects/molecular-biology
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Cells
The discovery of the cells has been attributed to Robert Hooke who was a microscopist who observed pieces of cork, where he noticed that it had a porous structure when observed under the microscope and called these pores "cells", however, what was really observed by Hooke, were the empty walls of plant tissue, which were produced by living cells. Then Anton van Leeuwenhoek who is said to have been the first to observe a drop of water and there to identify microscopic "little animals", in addition to describing different forms of bacteria found in the water. Subsequent observations and studies of cells made by Theodor Schwann (1839) and Matthias Schleiden of both plants and animals, two dogmas of the cell theory were postulated: (i) all organisms are composed of one or more cells and (ii) the cell is the structural unit of life.
Several years passed and several observations were carried out to prove that cells are not produced from non-cellular materials nor that organisms are produced by spontaneous generation, thus Rudolf Virchow (1855) proposed the third dogma of the cell theory: (iii) cells can only originate by division of a pre-existing cell.
Properties of cells
a) Cells are very complex and have a high degree of organization, so depending on the tissue they are configuring, they will have a certain shape and function. This organization and complexity transcends even its organelles, which also have a certain shape.

b) Cells contain a genetic program that is packed into chromosomes found in the nucleus of the cell (in eukaryotes).
c) Cells can reproduce themselves, through a process of division whereby information from a "mother cell" passes to two "daughter cells." For this to happen, the genetic material of the stem cell must have been duplicated, thus each daughter cell receives an exact copy of this information.
d) Cells also require energy to fulfill their functions, which ultimately provide solar radiation. In animal cells, this energy is already packed in sugar (glucose), so that ATP is obtained, used to carry out various reactions to maintain the correct functioning of the cell and organisms in general.
e) Several chemical reactions take place in cells that together form what is known as cellular metabolism and are carried out by enzymes.
f) Cells also respond to stimuli because they have receptors on their cell membranes that allow them to interact with particles of the extra and intracellular environment. Thus, this interaction generates specific responses that cause changes in metabolism, division process, displacement, and even cause its own death.
g) Cells have a surrounding membrane that separates the inner environment (cytoplasm) from the outer environment. The cell membrane, or cytoplasmic membrane, is made up of a double layer of phospholipids along with proteins.

However, life itself depends on the information contained in molecules such as nucleic acids and proteins

Karp's Cell and Molecular Biology: Concepts and Experiments (2006)
Clark, David P. (2019). Molecular Biology || Cells and Organisms.
https://archive.org/details/molecularbiology00clar_0

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Nucleic acids are macromolecules made up of smaller molecules called nucleotides. There are two types of nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleotides are linked together by means of links forming a chain. The nucleotides of DNA are called thymine (T), adenine (A), cytosine (C), and guanine (G). DNA differs from RNA in that it contains a T, while RNA includes a uracil (U) in its place.
Although each organism’s DNA is unique, all DNA is composed of the same nitrogen-based molecules. But then, how does DNA differ from one organism to another? it depends on how these molecules are arranged and this differs among individuals.

https://www.nature.com/scitable/topicpage/dna-is-a-structure-that-encodes-biological-6493050/
Clark, David P. (2019). Molecular Biology || Nucleic Acids and Proteins
https://archive.org/details/molecularbiology00clar_0