Composition Structure and Function of Biomolecules The molecules

Composition, Structure and Function of Biomolecules � � � The molecules found in the organisms are called biomolecules and they obey the same laws of physics and chemistry. Biomolecules are molecules that occur naturally in living organisms. Biomolecules include macromolecules like proteins, carbohydrates, lipids and nucleic acids. It also includes small molecules like primary and secondary metabolites and natural products. Biomolecules consists mainly of carbon and hydrogen with nitrogen, oxygen, sulphur, and phosphorus. Biomolecules are very large molecules of many atoms that are covalently bound together. Most, but not all, of the carbon-containing molecules in cells are built up from members of one of four different families of small organic molecules: sugars, amino acids, nucleotides, and fatty acids. Each of these families contains a group of molecules that resemble one another in both structure and function. In addition to other important functions, these molecules are used to build large macromolecules. For example, the sugars can be linked to form polysaccharides such as starch and glycogen, the amino acids can be linked to form proteins, the nucleotides can be linked to form the DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) of chromosomes, and the fatty acids can be linked to form the lipids of all cell membranes.

� All forms of life are composed of biomolecules only. Biomolecules are organic molecules especially macromolecules like carbohydrates, proteins in living organisms. All living forms bacteria, algae, plant and animals are made of similar macromolecules that are responsible for life. All the carbon compounds we get from living tissues can be called biomolecules. component percent of total cell weight water 70 Inorganic ions (sodium, potassium, magnesium, calcium, chloride, etc. ) 1 miscellaneous small metabolites 3 proteins 18 RNA 1. 1 DNA 0. 25 phospholipids and other lipids 5 polysaccharides 2 Approximate chemical composition of a typical mammalian cell

Cell membrane � The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasma lemma) is a biological membrane that separates the interior of all cells from the outside environment (the extracellular space). It consists of a lipid bilayer with embedded proteins. The basic function of the cell membrane is to protect the cell from its surroundings. The cell membrane controls the movement of substances in and out of cells and organelles. In this way, it is selectively permeable to ions and organic molecules. Figure (3): Comparison of Eukaryotes vs. Prokaryotes