Ch 2 - Chemical Components of Cells

Question 1

acid

Answer 1

a molecule that releases a proton when dissolved in water; this dissociation generates hydronium (H3O+) ions, thereby lowing the pH

Question 2

amino acid

Answer 2

small organic molecule containing both an amino group and a carboxyl group; it serves as the building block of proteins

Question 3

atom

Answer 3

the smallest particle of an element that still retains its distinctive chemical properties; consists of a positively charged nucleus surrounded by a cloud of negatively charged electrons

Question 4

atomic weight

Answer 4

the mass of an atom relative to the mass of a hydrogen atom; equal to the number of protons plus the number of neutrons that the atom contains

Question 5

ATP

Answer 5

activated carrier that serves as the principal carrier of energy in cells; a nucleoside triphosphate composed of adenine, ribose and three phosphate groups

Question 6

Avogadro’s number

Answer 6

the number of molecules in a mole, the quantity of a substance equal to its molecular weight in grams; approx. 6 x 10 power 23

Question 7

base

Answer 7

molecule that accepts a proton when dissolved in water; also used to refer to the nitrogen-containing purines or pyrimidines in DNA and RNA

Question 8

buffer

Answer 8

mixture of weak acids and bases that maintains the pH off a solution by releasing and taking up protons

Question 9

chemical bond

Answer 9

a sharing or transfer of electrons that holds two atoms together (covalent / non - covalent)

Question 10

chemical group

Answer 10

a combination of atoms, such as a hydroxyl group (-OH) or an amino group (-NH2) with distinct chemical and physical properties that influence the behaviour of the molecule in which it resides

Question 11

condensation reaction

Answer 11

chemical reaction in which a covalent bond is formed between two molecules as water is expelled; used to build polymers, such as proteins, polysaccharides and nucleic acids

Question 12

conformation

Answer 12

precise, three-dimensional shape of a protein or other macromolecule, based on the spatial location of its atoms in relation to one another

Question 13

covalent bond

Answer 13

stable chemical link between two atoms produced by sharing one or more pairs of electrons

Question 14

DNA (deoxyribonucleic acid)

Answer 14

Double stranded polynucleotide formed from two separate chains of covalently linked deoxyribonucleotide units. it serves as the cell’s store of genetic information that is transmitted from generation to generation.

Question 15

electron

Answer 15

negatively charged subatomic particle that occupies space around an atomic nucleus (e-)

Question 16

electronegativity

Answer 16

the tendency of an atom to attract electrons

Question 17

electrostatic attraction

Answer 17

force that draws together oppositely charged atoms. examples include ionic bonds and the attractions between molecules containing polar covalent bonds

Question 18

fatty acid

Answer 18

molecule that consists of a carboxylic acid attached to a long hydrocarbon chain. used as a major source of energy during metabolism and as a starting point for the synthesis of phospholipids

Question 19

hydrogen bond

Answer 19

a weak noncovalent interaction between a positively charged hydrogen atom in one molecule and a negatively charged atom, such as nitrogen or oxygen, in another; hydrogen bonds are key to the structure and properties of water

Question 20

hydrolysis

Answer 20

chemical reaction that involves cleavage of a covalent bond with the accompanying consumption of water (its -H being added to one product of the cleavage and its -OH to the other); the reverse of a condensation reaction

Question 21

hydronium ion

Answer 21

the form taken by a proton (H+) in aqueous solution

Question 22

hydrophobic

Answer 22

nonpolar, uncharged molecule or part of a molecule that forms no hydrogen bonds with water molecules and therefore does not dissolve; literally water fearing

Question 23

hydrophillic

Answer 23

molecule or part of a molecule that readily forms hydrogen bonds with water, allowing it to readily dissolve; literally water loving

Question 24

hydrophobic force

Answer 24

a noncovalent interaction that forces together the hydrophobic portions of dissolved molecules to minimize their disruption of the hydrogen-bonded network of water; causes membrane phospholipids to self-assemble into a bilayer and helps to fold proteins into a compact, globular space

Question 25

ionic bond

Answer 25

interactions formed when one atom donates electrons to another; this transfer of electrons causes both atoms to become electrically charged.

Question 26

inorganic

Answer 26

not composed of carbon atoms

Question 27

ion

Answer 27

an atom carrying an electrical charge, either positive or negative

Question 28

lipid bilayer

Answer 28

thin pair of closely juxtaposed sheets, composed mainly of phospholipid molecules, that forms the structural basis for all membranes

Question 29

macromolecule

Answer 29

polymer built from covalently linked subunits; includes proteins, nucleic acids and polysaccharides with a molecular mass great than a few thousand dalton

Question 30

lipid

Answer 30

an organic molecule that is insoluble in water but dissolves readily in nonpolar organic solvents; typically contains long hydrocarbon chains or multiple rings. One class, the phospholipids, forms the structural basis for biological membranes

Question 31

molecule

Answer 31

group of atoms joined together by covalent bonds

Question 32

molecular weight

Answer 32

sum of atomic weights of the atoms in a molecule; as a ratio of molecular masses, it’s a number without units

Question 33

monomer

Answer 33

small molecule that can be linked to other of a similar type to form a larger molecule (polymer)

Question 34

noncovalent bond

Answer 34

chemical association that does not involve the sharing of electrons; singly they are relatively weak, but they can sum together to produce strong, highly specific interactions between molecules. examples are hydrogen bonds and van der Waals attractions.

Question 35

nucleotide

Answer 35

basic building block of the nucleic acids, DNA and RNA; a nucleoside linked to a phosphate

Question 36

organic molecule

Answer 36

chemical compound that contains carbon and hydrogen

Question 37

pH scale

Answer 37

concentration of hydrogen ions in a solution, expressed as a logarithm. an acidic solution with ph3 will contain 10 power -3 M hydrogen ions.

Question 38

polar

Answer 38

in chemistry, describes a molecule or bond in which electrons are distributed unevenly

Question 39

polymer

Answer 39

long molecule made by covalently linking multiple identical or similar subunits (monomers)

Question 40

protein

Answer 40

macromolecule built from amino acids that provides cells with their shape and structure and performs most of their activities

Question 41

proton

Answer 41

positively charged particle found in the nucleus of every atom; also, another name for a hydrogen ion (H+)

Question 42

RNA

Answer 42

molecule produced by the transcription of DNA; usually single-stranded, it is a polynucleotide composed of covalently linked ribonucleotide subunits. Serves a variety of information, structural, catalytic and regulatory functions in cells.

Question 43

sequence

Answer 43

the linear order of monomers in a large molecule -for example, amino acids in a protein or nucleotides in DNA; encodes information that specifies a macromolecule’s precise biological function

Question 44

subunit

Answer 44

a monomer that forms part of a larger molecule, such as an amino acid residue in a protein or a nucleotide residue in a nucleic acid. can also refer to a complete molecule that forms part of a larger molecule. many proteins, for example, are composed of multiple polypeptide chains, each of which is called a protein subunit

Question 45

sugar

Answer 45

a substance made of carbon, hydrogen and oxygen with the general formula (CH2O)n. a carbohydrate or saccharide. the sugar of everyday use is sucrose, a sweet-tasting disaccharide made of glucose and fructose

Question 46

van der Waals attraction

Answer 46

weak noncovalent interaction, due to fluctuating electrical charges, that comes into play between two atoms within a short distance of each other