IB BIOLOGY TOPIC 2 MOLECULAR BIOLOGY COMPLETE STUDY GUIDE 2023

IB BIOLOGY TOPIC 2 MOLECULAR BIOLOGY COMPLETE STUDY GUIDE 2023 Topic 2.1 – Molecules to Metabolism x Atom: It is a single uncharged particle of an element. E.g. H, O, N, S, Na, Fe, etc. x Molecule: A group of two or more atoms held together by covalent bonds. E.g. H2O, N2, CO2, etc. x Ion: Ions are atoms or groups of atoms that are charged E.g. H+ , Na+ , OH- , etc. Metabolism ¾ Metabolism is the web of all the enzyme-catalysed reactions in a cell or organism. Metabolism is mainly divided into 2 categories:- x Anabolism: Anabolism is the synthesis of complex molecules from simpler molecules including the formation of macromolecules (very large molecules) from monomers (smaller sub-units) by condensation reactions. E.g. 1) Photosynthesis (Synthesis of glucose from simpler molecules like CO2 and H2O) 2) Formation of a dipeptide from 2 amino acids (by condensation reaction) x Catabolism: Catabolism is the breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers. E.g. 1) Cellular respiration (Breaking down glucose into simpler components) 2) Hydrolysing a polypeptide into its corresponding amino acid residues lOMoARcPSD| Q: Why carbon is mostly occurring in living world? x Covalent bonds are relatively strong bonds, so molecules can be stable structures. x Each carbon atom forms four covalent bonds, allowing a great diversity of compounds to exist. x Therefore, the molecules used by living organisms are based on carbon. Q: State the most frequently occurring elements in living things: x The most frequently occurring chemical elements in living things are carbon, hydrogen oxygen and nitrogen (C, H, O, N). Q: State the main classes/types of molecules in the body and name the elements they contain. x The main types of molecules used by living organisms are carbohydrates, lipids, proteins and nucleic acids. x Types of elements that exist in different class of biological molecules; 1. Carbohydrates: C, H, O 2. Protein: C, H, O, N, (S) 3. Lipid: C, H, O 4. Nucleic acids: C, H, O, N, P Q: State that a variety of other elements are needed by living organisms, and explain their role/ function of each of these elements: x Apart from carbon (C), hydrogen (H), oxygen (O) and nitrogen (N), there are still a variety of other elements that living organisms require, including sulphur, calcium, phosphorus, iron and sodium. x Their functions are as follows: 1) Sulphur: Formation of proteins. Found in certain amino acids (methionine and cysteine), allowing proteins to form disulphide bonds. 2) Calcium: Found in bones and teeth. It is also involved in neurotransmitter release in synapses. 3) Phosphorous: Component of nucleic acids (DNA & RNA