The universe is said to have formed about 13.8 billion years ago as a catastrophic explosion of energy-rich subatomic particles. Seconds following explosion, simplest atoms hydrogen and helium have been formed. Some stars became massive and then exploded into supernovae, giving the energy needed to generate more complex elements from simpler atomic structures.
About four billion years ago, simple microbes with the capable of extract energy from simple chemical compound arose. Later they were advanced to produce complex biomolecules from sunlight and energy extracted from simple chemical compounds.
Biochemistry explores how amazing properties of living organisms come from a wide range of biomolecules. When these molecules are isolated and observed separately, they are compatible with all physical and chemical laws that describe the behaviour of living things.
The study of biochemistry shows how the collection of living inanimate or lifeless molecules interacts with living things to sustain and perpetuate life animated only by physical and chemical laws leading the non-living universe.
Nevertheless living things have extraordinary features, which can be useful to distinguish them from matter. What are these salient features?. High chemical complexity and microscopic organisation, use of systems of methods to extract energy from environment, components in organisms and their interactions, mechanisms for sensing and responding to changes in their environment, ability to self-recreate, ability to self-replicate and self-assembly and the ability to experience gradual evolution. Despite these common features and the basic unity of life they reveal, it is problematic to generalize organisms.
In actual speaking biochemistry describes biochemistry describes molecularly shared structures, mechanisms, and chemical processes that provide living organisms and their various underlying organisational principles, the principles of which we collectively call molecular reasoning of life.
Although biochemistry has provided important insight and practicality, its applications in the fields of medicine, agriculture, nutrition, and industry are ultimately concerned with the miracle of life. The unity and diversity of organisms is evident even at the cellular level.
The smallest organisms possess single cells and they are microscopic. Multicellular organisms have many types of cells. Despite these differences, fundamental properties can be seen at biochemical level. Cells of all kinds share certain structural characteristics. The plasma membrane is marvellous biochemical creature. It’s the margin of a cell made up of lipid and protein molecules that form a thin, tough, pliable, hydrophobic barrier around the cell. The internal volume enclosed by the plasma membrane, the cytoplasm, is composed of an aqueous solution, the cytosol, and a range of suspended particles with different functions. Cells have, for at least some part of their life, either a nucleoid or a nucleus, in which the genome—the complete set of genes, composed of DNA—is replicated, with its associated proteins. Interestingly, cellular dimensions are limited by diffusion.
Oxygen
Oxygen is only one of many low molecular weight types that must diffuse from outside the cell to various regions in a cells. The organisms differ based on the energy and biosynthetic precursors (Phototrophs and chemotrophs). Eukaryotic cells have a range of membranous organelles (membrane bound), which can be isolated individually (mitochondria, endoplasmic reticulum and nucleus).
The 1974 Nobel Prize in Physiology or Medicine was awarded to Albert Claude, Christian de Dove and George E. Pallad for their “discoveries about the structural and functional organisation of the cell”. It is a major advance in biochemistry.
Using cell fractionation, they developed a method to separate organelles from the cytosol. Fluorescence microscopy observations show several types of protein filaments crisscrossing the eukaryotic cell, forming an interlocking three-dimensional meshwork or a web kind of structure known as the cytoskeleton.
Interestingly, cells can make supramolecular structures. For example cells can make oxygen carrying hemoglobin.
In cells, the subunits of proteins, nucleic acids and polysaccharides are joined by covalent bonds. In supramolecular complexes, however, macromolecules are held together by weak noncovalent interactions compared to covalent bonds.
Biochemistry aims to explain the biological form and function of chemicals. In the early twentieth century, parallel biochemical experiments on glucose breakdown revealed significant chemical similarities between these two distinct cell types in yeast and animal muscle cells.
Less than 30 of the more than 90 naturally occurring chemical elements are essential to organisms. Most of the elements in living matter show low atomic numbers. The oxygen-transporting capacity depends on four iron ions. In addition, biochemical compounds in cells are compounds of carbons with a wide range of functional groups. Cells contain various set of small molecules, while macromolecules are the major constitute of cells. Proteins, long polymers of amino acids, represent the largest portion (besides water) of a cell.
The collection of all the proteins functioning in a given cell is known as the cell’s proteome, and proteomics. The nucleic acids, DNA and RNA, are polymers of nucleotides. They store and transfer genetic information, and some RNA molecules have structural and catalytic roles. The polysaccharides have three main functions: structural components, extracellular recognition elements and energy-rich fuel stores.
The lipids, water insoluble hydrocarbon derivatives in cells serve as structural components of membranes, energy-rich fuel supplies, pigments, and intracellular signals. It is interesting to see that when biomolecules interact, the “fit” between them must be stereochemically correct in most cases.
Living organisms
Living organisms exist in a dynamic state and organisms transfer energy and matter from their surroundings. The flow of electrons provide energy (oxidation reduction reactions) for organisms. Many cellular reactions continue at useful rates only because enzymes are present to catalyse them. Metabolism in cells is considered as the sum of many interconnected chemical and biochemical reaction sequences that interconvert cellular metabolites.
Occasional or rare genetic mutations produce organisms more suitable for survival and reproduction in an ecosystem, where their offspring dominate the population. Occasional inheritable mutations produce organisms that are better suited for survival and reproduction in an ecological niche, and their progeny come to dominate the population in that niche. This mutation and selection process is the basis of the Darwinian evolution that carried on from the first cell to all modern life.
Finally, unlike the previous two decades, modern genomic techniques have transformed our understanding of biochemistry more in detail.