Bio 110 chapter 2 notes
Bio 110 chapter 2 notes BIOL 110 004
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This 7 page Class Notes was uploaded by Megan Ruth Simpson on Thursday September 8, 2016. The Class Notes belongs to BIOL 110 004 at University of South Carolina taught by Milan K. Dhameja in Fall 2016. Since its upload, it has received 4 views. For similar materials see General Biology in Biology at University of South Carolina.
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Date Created: 09/08/16
Biology 110 Chapter Two Matter consists of chemical elements in pure form and in combinations called compounds: -Element- a substance that can not be broken down to other substances by chemical reactions; purest form of matter - Compound- a substance consisting of two or more elements is a fixed ratio; has characteristics different from those of its element. Essential Elements of Life -about 25 of the 92 elements are essential to life -Carbon, Hydrogen, Oxygen, and Nitrogen make up 96% of living matter. The remaining 4% consists of Calcium, Phosphorous, Potassium, and Sulfur. -Trace Elements are those required by an organism in minute quantities Example: Iodine(I) and Iron(Fe) An Element’s properties depend on the structure of its atoms -Atom -An atom is the smallest unit of matter that still retains the properties of an element.; atoms are composed of subatomic particles Neutrons- No electrical charge; found in nucleus Protons- Positive charge; found in nucleus Electrons- Negative charge; found in the orbital 90% of the time -Protons and Neutrons form the Atomic Nucleus Neutron mass and Proton mass are almost identical and are measured in daltons -Atomic Number- is the number of protons in the nucleus -Mass Number- the sum of protons plus neutrons in the nucleus -Atomic Mass- The atom’s total mass, can be approximated by the mass number Isotopes All atoms of an element have the same number of protons but may differ in number of neutrons -Isotopes are two atoms of an element that differ in number of neutrons -Radioactive Isotopes- decay spontaneously, giving off particles and energy some applications of radioactive isotopes in biological research are: -Dating Fossils -Tracing atoms through metabolic processes -Diagnosing medical disorders Biology 110 Chapter Two The formation and function of molecules depend on chemical bonding between atoms -atoms with incomplete valence shells can share or transfer valance electrons with certain other atoms. The interactions usually result is atoms staying close together, held by attractions called Chemical Bonds Types of Chemical Bonds: 1. Covalent Bonds- sharing of electrons 2. Ionic or electrovalent bonds- transfer of electrons 3. Hydrogen Bonds- results between Hydrogen atom of one molecule and an electronegative atom in another molecule Covalent Bonds: A Covalent Bond is the sharing of a pair of valence electrons by two atoms; in a covalent bond, the shared electrons count as part of each atom’s valence shell -Molecule- consist of two or more atoms held together by covalent bonds -Single Bond- is the sharing of one pair of valence electrons (Example: Hydrogen) -Double Bond- Is the sharing of two pairs of valence electrons Bonding capacity is called the atom’s Valence Electronegativity- is an atom’s attraction for the electron in a covalent bond There are two types of covalent bonds: 1. Nonpolar covalent Bond- the atoms share the electron equally Example: Oxygen 2. Polar covalent Bond- one atom is more electronegative, and the atoms do not share the electron equally Example: H2O Ionic Bonds: A charged atom (or molecule) is called an Ion -Cation- is a positively charged ion -Anion- is a negatively charged ion -Ionic Bond- is an attraction between an anion and a cation Compounds formed by ionic bonds are called Ionic Compounds or Salts Hydrogen Bond: A Hydrogen Bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. Chemical Reactions make and break chemical Bonds Chemical Reactions are the making and breaking of chemical bonds. -The starting molecules of a chemical reaction is a Reactant. The final molecule of a chemical reaction is called a Product. -In the formula 6 CO2 + 6 H2O = C6H12O6 + 6 O2 6 CO2 + 6 H2O is the reactant and C6H12O6 + 6 O2 is the product. Biology 110 Chapter Two The polarity of water molecules results in hydrogen bonding Water is the biological medium on Earth Cells are about 70-95% water Polarity allows water molecules to form hydrogen bonds with each other. -The water molecule is a Polar Molecule: the opposite ends have opposite charges Four emergent properties of water contribute to Earth’s fitness for life four of water’s properties that facilitate an environment for life are: -Cohesive Behavior -Ability to moderate temperature -Expansive upon feeding -Versatility as a solvent Cohesion: Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion -Adhesion- is an attraction between different substances, for example, between water and plant cell walls -Surface Tension- is a measure of how hard it is to break the surface of a liquid. Surface tension is related to cohesion. Moderation on Temperature: Water absorbs heat from warmer air and releases stored heat to cooler air. -The Specific Heat- the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1-degree c. Water’s high specific heat can be traced to hydrogen bonding: -Heat is absorbed when hydrogen bonds break -Heat is released when hydrogen bonds form As a liquid evaporates, its remaining surface cools, a process called Evaporative Cooling; helps stabilize temperatures in organisms and bodies of water. Biology 110 Chapter Two The Solvent of Life: A Solution is a liquid that is a homogeneous mixture of substances. -a Solvent- is the dissolving agent of a solution -The Solute- is the substance that is dissolved -an aqueous solution is one in which water is the solvent water is a versatile solvent due to its polarity, which allows it to form hydrogen bonds easily. When an Ionic compound is dissolves in water, each ion is surrounded by a sphere of water molecules called a hydration shell Water reaches its greatest density at 4-degree C Effects of changing in PH Biologists use something called the PH Scale to describe whether a solution is acidic or basic Adding certain solutes, called acids and bases, modifies the concentration of H+ and OH- -Acid- is any substance that increases the H+ concentration of a solution -Base- is any substance that reduces the H+ concentration of a solution Buffers: The internal PH of most living cells must remain close to PH7 -Buffers- are substances that minimize changes in concentrations of H+ and OH- in a solution examples: Carbonic acid, Sodium Hydroxide, and Ammonia