Molecules of Life - Fall 2024 PDF

Molecules of Life  Structure Dictates Function ▪ We define cells partly by their capacity to build complex carbohydrates and lipids, proteins, and nucleic acids ▪ All of these organic compounds have functional groups attached to a backbone of carbon atoms  Carbon – The S...

Molecules of Life  Structure Dictates Function ▪ We define cells partly by their capacity to build complex carbohydrates and lipids, proteins, and nucleic acids ▪ All of these organic compounds have functional groups attached to a backbone of carbon atoms  Carbon – The Stuff of Life ▪ Organic molecules are complex molecules of life, built on a framework of carbon atoms Carbohydrates Lipids Proteins Nucleic acids  From Structure to Function ▪ The function of organic molecules in biological systems begins with their structure ▪ The building blocks of carbohydrates, lipids, proteins, and nucleic acids bond together in different arrangements to form different kinds of complex molecules ▪ Carbohydrates are the most plentiful biological molecules in the biosphere ▪ Cells use some carbohydrates as structural materials; others for stored or instant energy ▪ Carbohydrates Organic molecules that consist of carbon, hydrogen, and oxygen in a 1:2:1 ratio ▪ Three types of carbohydrates in living systems Monosaccharides Oligosaccharides Polysaccharides  Simple Sugars Monosaccharides (one sugar unit) are the simplest carbohydrates Backbones of 5 or 6 carbons Example: glucose  Short-Chain Carbohydrates ▪ Oligosaccharides Short chains of monosaccharides Example: sucrose, a disaccharide Cellulose, Starch, and Glycogen  Chitin ▪ Chitin A nitrogen-containing polysaccharide that strengthens hard parts of animals such as crabs, and cell walls of fungi What Cells Do to Organic Compounds A) Condensation. An —OH group B) Hydrolysis. A molecule splits, from one molecule combines then an —OH group and an H with an H atom from another. atom from a water molecule Water forms as the two become attached to sites molecules bond covalently. exposed by the reaction. What Cells Do to Organic Compounds ▪ Condensation Covalent bonding of two molecules to form a larger molecule Water forms as a product ▪ Hydrolysis The reverse of condensation Cleavage reactions split larger molecules into smaller ones Water is split What Cells Do to Organic Compounds ▪ Monomers Molecules used as subunits to build larger molecules (polymers) ▪ Polymers Larger molecules that are chains of monomers May be split and used for energy  Greasy, Oily – Must Be Lipids ▪ Lipids function as the body’s major energy reservoir, and as the structural foundation of cell membranes ▪ Lipids Fatty, oily, or waxy organic compounds that are insoluble in water  Fatty Acids ▪ Many lipids incorporate fatty acids Simple organic compounds with a carboxyl group joined to a backbone of 4 to 36 carbon atoms ▪ Essential fatty acids are not made by the body and must come from food Omega-3 and omega-6 fatty acids Triglycerides: Fats with 3 Fatty Acid Tails Phospholipids  Waxes ▪ Waxes Complex mixtures with long fatty-acid tails bonded to long-chain alcohols or carbon rings Protective, water-repellant covering Cholesterol: Lipid without a fatty acid tail  Proteins – Diversity in Structure and Function ▪ Proteins are the most diverse biological molecule (structural, nutritious, enzyme, transport, communication, and defense proteins) ▪ Cells build thousands of different proteins by stringing together amino acids in different orders Amino Acid Structure A DNA encodes the B In a condensation reaction, a peptide bond order of amino acids in a forms between the methionine and the next amino new polypeptide chain. acid, alanine (ala) in this example. Leucine (leu) Methionine (met) is will be next. typically the first amino acid. C A peptide bond forms between the D The sequence of amino acid alanine and leucine. Tryptophan (trp) subunits in this newly forming peptide will be next. The chain is starting to chain is now met–ala–leu–trp. twist and fold as atoms swivel around some bonds and attract or repel their The process may continue until there neighbors. are hundreds or thousands of amino acids in the chain. Fig. 3-16b, p. 45 Why Is Protein Structure So Important? ▪ When a protein’s structure goes awry, so does its function Just One Wrong Amino Acid… ▪ Hemoglobin contains four globin chains, each with an iron- containing heme group that binds oxygen and carries it to body cells ▪ In sickle cell anemia, a DNA mutation changes a single amino acid in a beta chain, which changes the shape of the hemoglobin molecule, causing it to clump and deform red blood cells  Globin Chains in Hemoglobin Hemoglobin contains four globin chains, each with an iron-containing heme group that binds oxygen and carries it to body cells In sickle cell anemia, a DNA mutation changes a single amino acid in a beta chain, which changes the shape of the hemoglobin molecule, causing it to clump and deform red blood cells Molecular Basis of Sickle Cell Anemia  Proteins Undone – Denaturation ▪ Proteins function only as long as they maintain their correct three- dimensional shape ▪ Heat, changes in pH, salts, and detergents can disrupt the hydrogen bonds that maintain a protein’s shape ▪ When a protein loses its shape and no longer functions, it is denatured Key Concepts: Proteins ▪ Structurally and functionally, proteins are the most diverse molecules of life ▪ They include enzymes, structural materials, and transporters ▪ A protein’s function arises directly from its structure  Nucleic Acids ▪ Some nucleotides are subunits of nucleic acids such as DNA and RNA ▪ Some nucleotides have roles in metabolism  Nucleotides ▪ Nucleotide A small organic molecule consisting of a sugar with a five-carbon ring, a nitrogen-containing base, and one or more phosphate groups ▪ ATP A nucleotide with three phosphate groups Important in phosphate-group (energy) transfer ATP RNA ▪ RNA (ribonucleic acid) Contains four kinds of nucleotide monomers, including ATP Important in protein synthesis DNA ▪ DNA (deoxyribonucleic acid) Two chains of nucleotides twisted together into a double helix and held by hydrogen bonds Contains all inherited information necessary to build an organism, coded in the order of nucleotide bases  adenine (A) thymine (T) base with a base with a 3 phosphate double ring single ring groups structure structure sugar guanine (G) cytosine (C) (deoxyribose) base with a base with a double ring single ring structure structure The DNA Molecule Key Concepts: Nucleotides and Nucleic Acids ▪ Nucleotides have major metabolic roles and are building blocks of nucleic acids ▪ Two kinds of nucleic acids, DNA and RNA, interact as the cell’s system of storing, retrieving, and translating information about building proteins ▪ https://youtu.be/1Dx7LDwINLU?si=gZ8Dg2CiV225N3OB Stay Safe , Healthy and Happy