Vocabulary Biology 1 – Chapter 2

Posted on August 11, 2010 by

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Bold-faced Words for Chapter 2

Mass – A property of all matter that measures the quantity of matter present; the greater the mass, the greater the quantity of matter.

Element – A substance composed of only one type of atom.

Atomic Number – The number of protons in the nucleus of an atom, also equal to the number of electrons around the neutral atom.  Determines the chemical properties of the atom.

Mass Number – The sum of the number of protons and neutrons in an atom’s nucleus.

Isotope – [Gr. isos: equal + topos: place] • Two isotopes of the same chemical element have the same number of protons in their nuclei, but differ in the number of neutrons.

Atomic Mass – (also called atomic weight) • The average mass of an atom of an element on the amu scale. (The average depends upon the relative amounts of different isotopes of an element on Earth.)

Radioisotopes – A radioactive isotope of an element. Examples are carbon-14 (14C) and hydrogen-3, or tritium (3H).

Chemical Reactions – A proces in which atoms combine or change bonding partners.

Orbital – The region of space where an electron is found at least 90% of the time.

Electron Shells – Energy levels around the nucleus.

Molecule– A particle made up of two or more atoms joined by covalent bonds or ionic attractions.

Chemical Bond – An attractive force stably linking two atoms.

Covalent Bond – A chemical bond that arises from the sharing of electrons between two atoms. Usually a strong bond.

Electronegativity – The tendency of an atom to attract electrons when it occurs as part of a compound.

Hydrogen Bond – A chemical bond which arises from the attraction between the slight positive charge on a hydrogen atom and a slight negative charge on a nearby fluorine, oxygen, or nitrogen atom. Weak bonds, but found in great quantities in proteins, nucleic acids, and other biological macromolecules.

Ion – [Gr.: wanderer] • An atom or group of atoms with electrons added or removed, giving it a negative or positive electrical charge.

Cation – An ion with one or more positive charges. (Contrast with anion.)

Anion – An ion with one or more negative charges. (Contrast with cation.)

Complex Ions – Groups of covalently bonded atoms that carry an electric charge.

Ionic Bonds – A chemical bond which arises from the electrostatic attraction between positively and negatively charged ions. Usually a strong bond.

Van der Waals Forces – A weak attraction between atoms resulting from the interaction of the electrons of one atom with the nucleus of the other atom. This attraction is about one-fourth as strong as a hydrogen bond.

Reactant – A chemical substance that enters into a chemical reaction with another substance.

Product – A chemical substance formed from a chemical reaction.

Energy – The capacity to do work; on a more intuitive level, it can be thought of as the capacity for change.

calorie – [L. calor: heat] • The amount of heat required to raise the temperature of one gram of water by one degree Celsius (1°C) from 14.5°C to 15.5°C. In nutrition studies, “Calorie” (spelled with a capital C) refers to the kilocalorie (1 kcal = 1,000 cal).

Joule – A unit of energy, equal to 0.24 calories.

Specific Heat – The amount of energy that must be absorbed by a gram of a substance to raise its temperature by one degree centigrade. By convention, water is assigned a specific heat of one.

Heat of Vaporization – The amount of heat required to change a substance from a liquid state to a gas.

Cohesive Strength – Explained by hydrogen bonding; allows amounts of water to “stick” together and remain a cohesive unit.

Surface Tension – The surface of liquid water exposed to the air is difficult to puncture due to the hydrogen bonding between the surface layer and the molecules beneath it.

Molecular Weight (or mass) – The sum of the atomic weights of the atoms in a molecule.

Mole – A quantity of a compound whose weight in grams is numerically equal to its molecular weight expressed in atomic mass units.  Avogadro’s number of molecules: 6.023 x 1023 molecules.

Acid – [L. acidus: sharp, sour] • A substance that can release a proton in solution. (Contrast with base.)

Base – A substance which can accept a proton (hydrogen ion; H+) in solution. (Contrast with acid.)

Reversible Reaction – A reaction that can proceed in either direction depending on the relative starting concentrations of the reactants and products.

pH Value – The negative logarithm of the hydrogen ion concentration; a measure of the acidity of a solution. A solution with pH = 7 is said to be neutral; pH values higher than 7 characterize basic solutions, while acidic solutions have pH values less than 7.

Buffer – A mixture of a weak acid and its conjugate base used in buffering, a  process by which a system resists change–particularly in pH, in which case added acid or base is partially converted to another form.

Organic Molecules – Any chemical compound that contains carbon and came from a source that is eaither currently alive or was at one time alive.

Functional Groups – Groups of atoms that make up part of a larger molecule and have particular chemical properties.

Isomers – Molecules consisting of the same numbers and kinds of atoms, but differing in the way in which the atoms are combined.

Structural Isomers – Isomers that differ in how their atoms are joined to each other.

Optical Isomers – Isomers that differ in the configuration of the four different groups attached to a single carbon atom; so named because solutions of the two isomers rotate the plane of polarized light in opposite directions. The two isomers are mirror images of one another.

Other Vocabulary Words

Acidic Having a pH of less than 7.0 (a hydrogen ion concentration greater than 10-7 molar).

Aldehyde A compound with a -CHO functional group. Many sugars are aldehydes. (Contrast with ketone.)

Amine An organic compound with an amino group (see Amino acid).

Basic having a pH greater than 7.0 (having a hydrogen ion concentration lower than 10-7 molar).

Carboxylic Acid An organic acid containing the carboxyl group, -COOH, which dissociates to the carboxylate ion, -COO.

Compound – A substance made up of atoms of more than one element.

Denaturation – Loss of activity of an enzyme or nucleic acid molecule as a result of structural changes induced by heat or other means.

Electron [L. electrum: amber (associated with static electricity), from Gr. slektor: bright sun (color of amber)] • One of the three most important fundamental particles of matter, with mass approximately 0.00055 amu and charge -1.

Hydrocarbon – A compound containing only carbon and hydrogen atoms.

Hydrophilic –  [Gr. hydro: water + philia: love] • Having an affinity for water. (Contrast with hydrophobic.)

Hydrophobic –  [Gr. hydro: water + phobia: fear] • Molecules and amino acid side chains, which are mainly hydrocarbons (compounds of C and H with no charged groups or polar groups), have a lower energy when they are clustered together than when they are distributed through an aqueous solution. Because of their attraction for one another and their reluctance to mix with water they are called “hydrophobic.” Oil is a hydrophobic substance; phenylalanine is a hydrophobic animo acid in a protein. (Contrast with hydrophilic.)

Hydroxyl Group The –OH group, characteristic of alcohols.

Iso- – [Gr.: equal] • Prefix used to denote two separate but similar or identical states of a characteristic. (See isomers, isomorphic, isotope.)

Ketone A compound with a C=O group attached to two other groups, neither of which is an H atom. Many sugars are
ketones. (Contrast with aldehyde.)

Neutron – [E.: neutral] • One of the three most fundamental particles of matter, with mass approximately 1 amu and no electrical charge.

Nonpolar Molecule A molecule whose electric charge is evenly balanced from one end of the molecule to the other.

Phosphate Group – The functional group -OPO3H2; the transfer of energy from one compound to another is often accomplished by the transfer of a phosphate group.

Polar Molecule A molecule in which the electric charge is not distributed evenly in the covalent bonds.

Proton [Gr. protos: first] • One of the three most fundamental particles of matter, with mass approximately 1 amu and an electrical charge of +1.

Solute – A substance that is dissolved in a liquid (solvent).

Solution – A liquid (solvent) and its dissolved solutes.

Solvent – A liquid that has dissolved or can dissolve one or more solutes.

Structural Formula – A representation of the positions of atoms and bonds in a molecule.

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