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Introduction to the Biological System
Published in Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu, Interdisciplinary Engineering Sciences, 2020
Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu
Biochemically, a cell membrane is composed of lipids (40%), proteins (55%), and carbohydrates (5%). The lipid bilayer of the plasma membrane makes it semi-permeable which regulates the passage of molecules, ions, and water (Figure 8.2). The bilayer structure also prevents these substances to enter the cytosol to maintain internal conditions. The cell surface receptor proteins play an important role in cell–cell interactions or cell–material interactions. The biological membranes can be best described as a phospholipid bilayer with several transmembrane proteins and voltage-gated ion channels. Such membrane physically separates intracellular organelles from the cytoplasm and a cell from the extracellular matrix.
Biomolecules and Complex Biological Entities
Published in Simona Badilescu, Muthukumaran Packirisamy, BioMEMS, 2016
Simona Badilescu, Muthukumaran Packirisamy
Carbohydrates or saccharides are the most abundant biomolecule. They serve as a major source of metabolic energy (storage and transport), as structural material (cellulose), and are one of three essential components of nucleic acids (deoxyribose). Carbohydrates linked to lipid molecules (gly-colipids) and proteins covalently linked to carbohydrates (glycoproteins) are the common components of biological membranes. These two classes of biomolecules, called glycoconjugates, are important components of cell walls and extracellular structures in plants, animals, and bacteria. For example, muramic acid and neuraminic acid, derivatives of polysaccharides, are components of cell membranes of higher organisms and also of bacterial cell walls. In addition to the structural roles such molecules play, they also serve in a variety of processes involving recognition events. Recognition events are important in normal cell growth, transformation of cells, and other processes. Members of this large and highly varied family act as ligands for complementary binding proteins called lectins, present on nearby cells. Lectin-carbohydrate interactions mediate intercellular communication in cell-cell recognition systems in the brain and elsewhere. The study of cell surface complex carbohydrates, lectins, and their roles in cell physiology is part of the rapidly emerging discipline called glycobiology.
The Essential Role of Cell Surface Hydrophobicity in Aerobic Granulation
Published in Yu Liu, Wastewater Purification, 2007
The general structure of biological membranes is a phospholipids bilayer. Phospholipids contain both highly hydrophobic (fatty acid) and relatively hydrophilic (glycerol) moieties and can exist in many different chemical forms as a result of variation in the nature of the fatty acids or phosphate-containing groups attached to the glycerol backbone (Madigan, Martinko, and Parker 2003). As phospholipids aggregate in an aqueous solution, they tend to form a bilayer structure spontaneously with the fatty acids in a hydrophobic environment, and the hydrophilic portions remain exposed to the aqueous external environment. Saturated alkyl chains of phospholipids can attract each other strongly in water, with a hydrophobic energy of attraction of −102 mJ m−2 in all cases (van Oss 1994b). The major proteins of the cell membrane generally have very hydrophobic external surfaces in the regions of the protein that span the membrane and have hydrophilic surfaces exposed on both the inside and the outside of the cell. The overall structure of the cytoplasmic membrane is stabilized by hydrogen bonds and hydrophobic interactions (Madigan, Martinko, and Parker 2003).
Comprehensive radiological parameterizations of proton and alpha particle interactions for some selected biomolecules: theoretical computation
Published in Radiation Effects and Defects in Solids, 2023
Abayomi M. Olaosun, Denen E. Shian
Lipids, proteins, and carbohydrates make up the three main structural components of biological membranes. The primary elements of lipids, the most significant energy storage molecules in mammalian cells, are fatty acids. They are required to create and repair cell membranes, assisting cells in obtaining the best nutrients and eliminating toxic waste. In addition, as vital fuels for the mechanical and electrical functions of the heart, they play a significant role in the life and death of cardiac cells. Nucleotide bases are very important in cellular metabolism because they serve as the currency of energy during metabolic transactions. There are five nucleotide bases, adenine (A), guanine (G), cytosine (C), uracil (U), and thymine (T). A, G, C, and T are contained in the deoxyribonucleic acid (DNA) while A, G, C, and U are contained in the ribonucleic acid (RNA). The most abundant biomolecules present in living organisms are carbohydrates. Essentially, carbohydrates serve as a short-term source of energy while apparently, they serve as intermediate-term energy storage (1–4).
Polarizable atomic multipole-based force field for DOPC and POPE membrane lipids
Published in Molecular Physics, 2018
Huiying Chu, Xiangda Peng, Yan Li, Yuebin Zhang, Hanyi Min, Guohui Li
Cells are typically surrounded and protected by biological membranes which consist of different types of lipids, proteins and carbohydrates. Membranes are mostly made of phospholipids, while membrane proteins, cholesterols, ions and water, etc. are also integral parts of membranes [1].Moreover, membrane proteins have been found to comprise approximately one-third of the human genome [2], and over half of these are known as drug targets. Thus, understanding the functionalities of membrane proteins has become an important focus of fundamental research.