Chapter 2 - Chemistry for Biology
Chapter 2 - Chemistry for Biology Biology 110 002
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This 3 page Class Notes was uploaded by Kathleen Maris on Sunday October 11, 2015. The Class Notes belongs to Biology 110 002 at University of South Carolina - Columbia taught by Dr. Dhameja in Fall 2015. Since its upload, it has received 32 views. For similar materials see General Biology in Science at University of South Carolina - Columbia.
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Date Created: 10/11/15
Chapter 2 Chemistry for Biology 0 Matter consists of chemical elements in pure form and in compounds 0 O O Organisms are composed of matter I Subatomic particles to atoms to macromolecules to organelles to cells to tissues to organs to organism Matter is anything that takes up space and has mass Matter is made up of elements 0 An element is matter in its purest form 0 00000 An element cannot be broken down to other substances by chemical reactions About 25 of the 92 elements are essential to life 120 on Table Carbon hydrogen oxygen and nitrogen make up 96 of living matter Most of the remaining 4 consists of calcium phosphorus potassium and sulfur An organism requires trace elements Iodine Iron in minute quantities Each element consists of unique atoms and an element s properties depend on the structure of its atoms 0 Atoms are the smallest unit of matter that still retains the properties of an element 0 O O O Atoms are composed of subatomic particles I Neutrons no electrical charge I Protons positive charge I Electrons negative charge The atomic nucleus is made of neutrons and protons I Electrons form a shellcloud around the nucleus 0 The first shell has up to two electrons and the shells after that up to eight each 0 The valence shell is the outermost shell I An element s atomic number is the number of protons in its nucleus I An element s mass number is the sum of protons plus neutrons in the nucleus I Atomic mass the atom s total mass can be approximated by the mass number Daltons are the unit of measurement for neutron and proton mass A11 atoms of an element have the same number of protons but may differ in number of neutrons 0 Isotopes are two atoms of an element that differ in number of neutrons O Radioactive isotopes decay spontaneously giving off particles and energy I Useful for dating fossils tracing atoms through metabolic processes and diagnosing medical disorders 0 Chemical bonds are attractions between two or more atoms creating molecules 0 O Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms Molecules have to break bonds to make bonds O Covalent bonds result from the sharing of electrons by two atoms I They are usually the strongest form of bond I The shared electrons count as part of each atom s valence shell I A single bond is the sharing of one pair of valence electrons I A double bond is the sharing of two pairs of valence electrons I They can form between atoms of the same element or atoms of different elements I A compound is the combination of two or more different elements I Nonpolarity refers to the unequal sharing of bonds I Polarity refers to the equal sharing of bonds 0 Ionicelectrovalent bonds result from transfer of electrons I Ions are charged atoms I Cations are positive ions I Anions are negative ions 0 Hydrogen bonds result between the hydrogen atom of one molecule and an electronegative atom of another molecule I In living cells the partners are usually oxygen or nitrogen atoms Chemical reactions are the making and breaking of chemical bonds 0 Reactants are the molecules that start a chemical reaction 0 Products are the final molecules of a chemical reaction Water is the biological medium of Earth all living organisms require water more than any other substance 0 Most cells are surrounded by water and cells themselves are about 7095 water 0 Water molecules are polar molecules the opposite ends have opposite charges 0 Polarity allows water molecules to form hydrogen bonds with each other 0 Four properties of water I Cohesive behavior I Ability to moderate temperature I Expansion upon freezing I Versatility as a solvent Cohesion is when hydrogen bonds hold water molecules together Adhesion is an attraction between different substances Surface tension is a measure of how hard it is to break the surface of a liquid Ice oats in liquid water because hydrogen bonds in ice are more ordered making ice less dense Water reaches its greatest density at 4 C A solution is a liquid that is a homogeneous mixture of substances 0 A solvent is the dissolving agent of a solution 0 The solute is the substance that is dissolved 0 An aqueous solution is one in which water is the solvent 0 When an ionic compound is dissolved in water each ion is surrounded by a sphere of molecules called a hydration shell 0000 The pH scale describes whether a solution is acidic or basic Concentrations of H and OH are equal in pure water Adding certain solutes acids and bases modifies those concentrations I An acid is any substance that increases the H concentration of a solution I A base is any substance that reduces the H concentration of a solution The internal pH of most living cells must remain close to pH 7 Buffers are substances that minimize changes in concentrations of H and OH I Most buffers consist of an acidbase pair that combines With H I Some examples are carbonic acid sodium hydroxide and ammonia