2- Molecules of life_ 2023-2024 2.pdf

MOLECULES OF LIFE  Objectives The student will be able to : List the four major classes of organic macromolecules and recognize their composition , functions and providing examples of each.​  Organic Molecules A cell is mostly...

MOLECULES OF LIFE  Objectives The student will be able to : List the four major classes of organic macromolecules and recognize their composition , functions and providing examples of each.​  Organic Molecules A cell is mostly water and the rest of it consists mostly of carbon-based molecules. Compounds that contain carbon atom are called organic compounds. Simplest organic compounds are hydrocarbons which consist of only carbon and hydrogen. There are four classes of organic molecules: 1. Carbohydrates. 2. Lipids. 3. Proteins. 4. Nucleic acids.  Organic Molecules  They are often called macromolecules because of their large size.  They are also called polymers because they are made from identical building blocks strung together.  The building blocks are called monomers.  Monomers: are molecules used as subunits to build larger molecules (polymers).  Polymers: are Larger molecules that are chains of monomers.  Carbohydrates  They are the major source of energy for cells.  The building blocks for carbohydrates are simple sugars.  There are three classes of carbohydrates: 1. Monosaccharides. 2. Disaccharides. 3. Polysaccharides.  Carbohydrates 1. Monosaccharides: Monosaccharides are simple sugars (monomer of carbohydrates). Examples: glucose, fructose, galactose. 2. Disaccharides. Disaccharides are formed when a dehydration reaction joins two monosaccharides. Examples : 1. Sucrose: it is formed from glucose and fructose. 2. Maltose: it is formed from glucose and glucose. 3. Lactose: it is formed from glucose and galactose.  Carbohydrates 3. Polysaccharides. They are long chain polymers composed of simple sugars (monosaccharides). Examples: 1. Starch: is a storage polysaccharide composed of glucose monomers and found in plants. 2. Glycogen: is a storage polysaccharide composed of glucose monomers and found in animals. 3. Cellulose: is a polymer of glucose that forms the plant cell walls. Classification of carbohydrates  Lipids  Lipids are hydrophobic (water-fearing) compounds.  The most biologically important lipids are fats, phospholipids, and steroids.  Fats  Fats are lipids that are mostly energy-storage molecules.  Fats are constructed from glycerol and fatty acids.  Dietary fat consists largely of the molecule triglyceride.  Triglyceride is a combination of glycerol and three fatty acids.  Phospholipids  Phospholipids are structurally similar to fats and are an important component of all cells as they form a major part of cell membranes, in which they cluster into a bilayer of phospholipids.  In a phospholipid, there are two fatty acids and a phosphate group attached to glycerol , the two fatty acid tails are hydrophobic tails, but the phosphate group and its attachments Section of a phospholipid membrane form a hydrophilic head.  Steroids  Steroids are lipids composed of fused ring structures.  Cholesterol is an example of a steroid that plays a significant role in the structure of the cell membrane.  In addition, cholesterol is the compound from which we synthesize sex hormones.  Proteins  Protein is a polymer built from amino acids monomers.  All proteins are constructed from a common set of 20 different kinds of amino acids.  Amino acids are linked together by peptide bonds forming a long chain of proteins.  Amino acids , the building blocks of proteins, have an amino group and a carboxyl groups which are attached to a central carbon atom.  Amino acids differ in their properties due to differing side chains, called R groups. Peptide bond formation  Functions of proteins 1. Structural components of muscle (actin and myosin). 2. Defensive proteins include antibodies (immunoglobulins). 3. Transport molecules (haemoglobin). 4. Cell surface receptors and channels. 5. Enzymes which act as a catalysts that speed up the chemical reactions. 6. Hormones (e.g., insulin, growth hormone).  Nucleic Acids  Nucleic acids are polymers called polynucleotides.  There are two types of nucleic acids: Deoxyribonucleic acid (DNA). Ribonucleic acid (RNA).  A nucleic acid polymer , a polynucleotide , is made of monomers called nucleotides.  Each nucleotide consists of three parts: 1. Pentose sugar 2. Phosphate group 3. Nitrogenous base  Nucleic Acids​  Function of DNA : Storage of the genetic material.  Function of RNA : Transfer the genetic information from the Nucleus to cytoplasm for protein synthesis. Thank You