Biology Chapter 2 Terms

Front 1

a substance that releases hydrogen ions (H+) into solution; a solution with a pH of less than 7.

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acid

Front 2

with an H+ concentration exceeding that of OH-; releasing H+.

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acidic

Front 3

any molecule that reacts with free radicals, neutralizing their ability to damage biological molecules. Vitamins C and E are examples of dietary antioxidants.

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antioxidant

Front 4

the smallest particle of an element that retains the properties of the element.

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atom

Front 5

the central part of an atom that contains protons and neutrons.

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atomic nucleus

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the number of protons in the nuclei of all atoms of a particular element.

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atomic number

Front 7

(1) a substance capable of combining with and neutralizing ions in a solution; a solution with a pH of more than 7; (2) in molecular genetics, one of the nitrogen-containing, single- or double-ringed structures that distinguish one nucleotide from another. In DNA, the bases are adenine, guanine, cytosine, and thymine.

Back 7

base

Front 8

with an concentration less than that of combining with

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basic

Front 9

a compound that minimizes changes in pH by reversibly taking up or releasing ions.

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buffer

Front 10

a unit of energy, in which the energy content of foods is measured; the amount of energy required to raise the temperature of 1 liter of water 1 degree Celsius; also called a kilocalorie , equal to 1000 calories.

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calorie

Front 11

the force of attraction between neighboring atoms that holds them together in a molecule.

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chemical bond

Front 12

the process that forms and breaks chemical bonds that hold atoms together.

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chemical reaction

Front 13

the tendency of the molecules of a substance to stick together.

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cohesion

Front 14

a substance whose molecules are formed by different types of atoms; can be broken into its constituent elements by chemical means.

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compound

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a chemical bond between atoms in which electrons are shared.

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covalent bond

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a subatomic particle, found in an electron shell outside the nucleus of an atom, that bears a unit of negative charge and very little mass.

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electron

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a region within which electrons orbit that corresponds to a fixed energy level at a given distance from the atomic nucleus of an atom.

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electron shell

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a substance that cannot be broken down, or converted, to a simpler substance by ordinary chemical means.

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element

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a molecule with an unpaired electron, which makes it highly unstable and reactive with nearby molecules. By stealing an electron from the molecule it attacks, it creates a new free radical and begins a chain reaction that can lead to the destruction of biological molecules crucial to life.

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free radical

Front 20

the weak attraction between a hydrogen atom that bears a partial positive charge (due to polar covalent bonding with another atom) and another atom, normally oxygen or nitrogen, that bears a partial negative charge; hydrogen bonds may form between atoms of a single molecule or of different molecules.

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hydrogen bond

Front 21

pertaining to a substance that issolves readily in water or to parts of a large molecule that form hydrogen bonds with water.

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hydrophilic

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pertaining to a substance that does not dissolve in water.

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hydrophobic

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the tendency for hydrophobic molecules to cluster together when immersed in water.

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hydrophobic interaction

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a charged atom or molecule; an atom or molecule that has either an excess of electrons (and hence is negatively charged) or has lost electrons (and is positively charged).

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ion

Front 25

a chemical bond formed by the electrical attraction between positively and negatively charged ions.

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ionic bond

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one of several forms of a single element, the nuclei of which contain the same number of protons but different numbers of neutrons.

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isotope

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a particle composed of one or more atoms held together by chemical bonds; the smallest particle of a compound that displays all the properties of that compound.

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molecule

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a subatomic particle that is found in the nuclei of atoms, bears no charge, and has a mass approximately equal to that of a proton.

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neutron

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a covalent bond with equal sharing of electrons.

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nonpolar covalent bond

Front 30

a scale, with values from 0 to 14, used for measuring the relative acidity of a solution; at pH 7 a solution is neutral, pH 0 to 7 is acidic, and pH 7 to 14 is basic; each unit on the scale represents a tenfold change in concentration.

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pH scale

Front 31

a covalent bond with unequal sharing of electrons, such that one atom is relatively negative and the other is relatively positive.

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polar covalent bond

Front 32

a subatomic particle that is found in the nuclei of atoms, bears a unit of positive charge, and has a relatively large mass, roughly equal to the mass of the neutron.

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proton

Front 33

pertaining to an atom with an unstable nucleus that spontaneously disintegrates, with the emission of radiation.

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radioactive

Front 34

a liquid capable of dissolving (uniformly dispersing) other substances in itself.

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solvent

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the property of a liquid to resist penetration by objects at its interface with the air, due to cohesion between molecules of the liquid.

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surface tension