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The chemical Level of Organization.docx

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Biological Sciences
Kenneth Welch

The Chemical Level of Organization Atoms, Molecules and Bonds Atoms are the smallest stable units of matter • Subatomic particles • Protons = positive charge; weight of approximately 1 Dalton • Neutrons = no charge; weight similar to protons • Electrons = negative charge; weigh 1/1836 Dalton • Protons and neutrons are found in the nucleus; electrons occupy electron cloud • Atomic number = proton number; atomic mass = protons and neutrons • Isotopes are elements with similar numbers of protons but different numbers of neutron Electrons occupy a series of energy levels or electron shells. • The outermost electron shell determines the reactivity of the element. Atoms combine through chemical reactions • Molecule = a chemical structure consisting of molecules held together by covalent bonds • Compound = a chemical substance composed of atoms of two or more elements • There are three types of bond: Ionic, covalent, and hydrogen Ionic Bonding • Exchange of electrons from one atom to another Ionic = attraction between positive cations and negative anions Covalent bonds exist between atoms that share electrons to form a molecule • Double covalent bond • Non-polar covalent bond • Polar covalent bond Hydrogen bonds are weak forces that affect the shape and properties of compounds • Polar covalent bonds that occur when hydrogen covalently bonds with another element Matter and chemical notation • Matter can exist as a solid, liquid or gas • Depends on the interaction of the component atoms or molecules • Molecular weight is the sum of the atomic weights of the component atoms • Chemical notation • Short-hand that describes chemical compounds and reactions Chemical Reactions A chemical reaction occurs when reactants combine to generate one or more products • All chemical reactions in the body constitutes metabolism • Metabolism provides for the capture, storage and release of energy Basic energy concepts • Work = movement of an object or change in its physical structure • Energy = the capacity to perform work • Kinetic energy is energy of motion • Potential energy is stored energy resulting from position or structure • Conversions are not 100% efficient, resulting in release of heat Metabolism • Types of reaction • Decomposition • Synthesis • Exchange • Metabolism is the sum of all reactions • Through catabolism cells gain energy (break down of complex molecules) • Anabolism uses energy (synthesis of new molecules) Reversible reactions • All reactions are theoretically reversible • At equilibrium the rates of two opposing reactions are in balance • Anabolism = catabolism Enzymes, energy and chemical reactions • Activation energy is the amount of energy needed to begin a reaction • Enzymes are catalysts • Reduce energy of activation without being permanently changed or used up Inorganic Compounds Nutrients and Metabolites • Nutrients are essential chemical compounds obtained from the diet • Metabolites are molecules synthesized or broken down inside the body • These can be classified as organic or inorganic compounds • Organic compounds have carbon and hydrogen as their primary structural component • Inorganic compounds are not primarily carbon and hydrogen Water and its properties • Water is the most important constituent of the body • Solution is a uniform mixture of two or more substances • Sol
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