Molecules in Biology, Molecular Biology

Molecules in biology refer to any tiny particles, such as charged organic molecules or substances (called biomolecules) that are naturally produced and occurring in organisms, such as proteins, carbohydrates and DNA.

In physics and chemistry, the smallest unit of an element or compound is connected together by two or more atoms through reinforced chemical bonds. A molecule is an electrically neutral group of atoms that can exist alone in a free state while retaining its characteristic properties.

The atoms containing the molecule may be of the same kind (such as an oxygen molecule composed of two oxygen atoms) or of different kinds (such as a water molecule composed of oxygen and hydrogen).

Molecules in Biology are also called Biomolecules or Biological molecules

Macromolecules necessary for life built from smaller organic molecules are called biological macromolecules. There are four major categories of biological macromolecules (carbohydrates, lipids, proteins and nucleic acids), each of which is an important part of the cell and has a wide range of functions. Combined, these molecules make up most of the cell mass.

Molecules in Biology are organic, meaning that they contain carbon. In addition, they may contain hydrogen, oxygen, nitrogen, phosphorus, sulfur and other minor elements. Biomolecules have a wide range of sizes and structures, and perform a large number of functions. In biomolecules, nucleic acids, namely DNA and RNA, have a unique function of storing the genetic code of organisms—the nucleotide sequence that determines the amino acid sequence of proteins, which is essential for life on Earth.

All molecules in biology share a common basic relationship between structure and function, which is affected by factors such as the environment in which a given biomolecule occurs. For example, lipids are hydrophobic (“water worries”); in water, many people spontaneously arrange themselves in such a way that the hydrophobic end of the molecule is protected, while the hydrophilic end is exposed to water. This arrangement produces lipid bilayer or two-layer phospholipid molecules, forming the membrane of cells and organelles. In another example, DNA, which is a very long molecule-in humans, the combined length of all DNA molecules stretched end to end in a single cell will be about 1.8 meters (6 feet)with a high degree of flexibility This structural feature plays a key role in making DNA suitable for the nucleus of the cell, where it plays its function of encoding genetic characteristics.


Carbohydrates are mainly composed of molecules in biology containing carbon, hydrogen and oxygen atoms. They are the basic energy and structural components of all life. They are one of the richest biomolecules on earth. They are constructed from four types of sugar units—monosaccharides, disaccharides, oligosaccharides, and polysaccharides.


Carbohydrates are macromolecules that most consumers are a little familiar with. In order to lose weight, some people adhere to a “low-carbohydrate” diet. In contrast, athletes usually “carbohydrate load” before important competitions to ensure that they have enough energy to compete at a high level. In fact, carbohydrates are an important part of our diet; grains, fruits and vegetables are all natural sources of carbohydrates.

Carbohydrates provide energy to the body, especially through glucose, a simple sugar. They also have other important functions in humans, animals, and plants. Represented by the formula(CH2O)n, where n is the number of carbon atoms in the molecule. In other words, the ratio of carbon to hydrogen to oxygen is 1: 2: 1 in carbohydrate molecules. Carbohydrates are divided into three subtypes: monosaccharides, disaccharides and polysaccharides.

Monosaccharides: (mono- = “one”; sacchar- = “sweet”) are simple sugars, the most common of which is glucose. Examples are Galactose ( Sugar in milk) and Fructose ( Sugar found in fruits)

Disaccharides: (di- = “two”) form when two monosaccharides undergo a dehydration reaction (a reaction in which the removal of a water molecule occurs). Common disaccharides include lactose, maltose, and sucrose.

Polysaccharides: (poly- = “many”) Are long chains of monosaccharides linked by covalent bonds. The chain may be branched or unbranched, and it may contain different types of monosaccharides. Polysaccharides may be very large molecules. Starch (found in Plants), glycogen ( storage forn in humans), cellulose (makes up the cell walls of plants), and chitin are examples of polysaccharides.



Lipids consist of a different set of compounds, which are combined by a common feature. Lipids are hydrophobic (“non-aqueous”), or insoluble in water, because they are non-polar molecules. This is because they are hydrocarbons that include only nonpolar carbon-carbon or carbon-hydrogen bonds. Lipids perform many different functions in cells.

Cells store energy in the form of lipids called fats for long-term use. Lipids also provide insulation from the environment for plants and animals.

Lipid Structure

For example, due to water repulsive, they help keep aquatic birds and mammals dry. Lipids are also an integral part of many hormones and are an important part of the plasma membrane. Lipids include fats, oils, waxes, phospholipids and steroids.

Fats: Molecules, such as triglycerides, consist of two main components: glycerol and fatty acids. Glycerol is an organic compound with three carbon atoms, five hydrogen atoms and three hydroxyl (–OH) groups. Fatty acids have a long chain of hydrocarbons, which are connected to an acidic carboxyl group, hence the name ” fatty acids.” ” During this covalent bond formation, three water molecules are released. The three fatty acids in the fat can be similar or not similar. These fats are also called triglycerides because they have three fatty acids.

Phospholipids: They are the main components of the plasma membrane. Like fats, they consist of fatty acid chains attached to glycerol or similar backbone chains. However, instead of the three fatty acids connected, there are two fatty acids and the third carbon of the glycerol backbone binds to the phosphoric acid group. Phosphate groups are modified by adding alcohols. Phospholipids have hydrophobic and hydrophilic regions.

Fatty acid chains are hydrophobic and excluded from water, while phosphates are hydrophilic and interact with water. The cells are surrounded by a membrane, which has a bilayer of phospholipids. The fatty acids of phospholipids face the inside, away from water, while the phosphoric acid groups can face the external environment or the inside of the cell, both of which are aqueous.

Steroids and Waxes: Unlike the phospholipids and fats discussed earlier, steroids have a ring structure. Although they are not like other lipids, they are grouped with them because they are also hydrophobic. All steroids have four connected carbocyclic rings, some of which, like cholesterol, have a short tail.


Protein is one of the most abundant organic molecules in the living system and has the most diverse functions among all macromolecules. Proteins can be structural, regulatory, contractile, or protective; they can function in transport, storage, or membranes; or they can be toxins or enzymes. Each cell in a living system may contain thousands of different proteins, each of which has a unique function. Their structure, just like their function, is very different.


However, they are all polymers of amino acids, arranged in a linear sequence. The functions of proteins are very diverse, because there are 20 different chemically different amino acids to form long chains, and amino acids can be in any order. For example, proteins can act as enzymes or hormones.

Enzymes: produced by living cells are catalysts for biochemical reactions (such as digestion), usually proteins. Each enzyme is specific to the substrate it acts on (the reactant that binds to the enzyme). The function of enzymes can break molecular bonds, rearrange bonds, or form new bonds. An example of an enzyme is salivary amylase, which breaks down amylose, a component of starch.

Hormones: are chemical signaling molecules, usually proteins or steroids, secreted by endocrine glands or a group of endocrine cells to control or regulate specific physiological processes, including growth, development, metabolism and reproduction. For example, insulin is a protein hormone that maintains blood sugar levels.

Types of Protein

Amino acids: are the monomers that make up proteins. Each amino acid has the same basic structure, which consists of a central carbon atom bonded to an amino group (–NH2), a carboxyl group (–COOH) and a hydrogen atom. Each amino acid also has another variable atom or group of atoms bonded to a central carbon atom called an R group. Group R is the only structural difference between the 20 amino acids; otherwise, the amino acids are the same.


Nucleic acids: are the key macromolecules for the continuation of life. They carry the genetic blueprint of the cell and carry instructions for cell function. The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is genetic material found in all living organisms, from single-celled organisms to multicellular mammals while RNA, is mainly involved in protein synthesis. DNA molecules never leave the nucleus, but use RNA mediators to communicate with the rest of the cell. Other types of RNA are also involved in protein synthesis and its regulation.


Nucleic Acid

DNA and RNA are composed of monomers called nucleotides. Nucleotides combine with each other to form polynucleotides, DNA or RNA. Each nucleotide consists of three components: a nitrogen-containing base, a pentose (five-carbon) sugar, and a phosphoric acid group. Each nitrogen base in the nucleotide is connected to the sugar molecule, and the sugar molecule is connected to the phosphoric acid group.

Molecular Biology as the Study of Molecules in Biology

Molecular biology is a branch of biology that deals with the molecular basis of biological activity within and between cells, including molecular synthesis, modification, mechanism and interaction. [1][2]The central dogma of molecular biology describes the process of transcribing DNA into RNA and then translating it into proteins.

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