Chapter 5 The Structure and Function of Large Biological Molecules

Question 1

amino acid

Answer 1

An organic molecule possessing both a carboxyl and an amino group. Amino acids serve as the monomers of polypeptides.

Question 2

antiparallel

Answer 2

Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5′ S 3′ directions).

Question 3

bioinformatics

Answer 3

The use of computers, software, and mathematical models to process and integrate biological information from large data sets.

Question 4

carbohydrate

Answer 4

A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).

Question 5

catalyst

Answer 5

A chemical agent that increases the rate of a reaction without being deformed in the reaction.

Question 6

cellulose

Answer 6

A structural polysaccharide of plant cell walls, consisting of glucose monomers joined by b glycosidic linkages.

Question 7

chitin

Answer 7

A structural polysaccharide, consisting of amino sugar monomers, found in many fungal cell walls and in the exoskeletons of all arthropods.

Question 8

cholesterol

Answer 8

A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as many hormones.

Question 9

dehydration reaction

Answer 9

A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule.

Question 10

denaturation

Answer 10

In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive; in DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme (noncellular) conditions of pH, salt concentration, or temperature.

Question 11

deoxyribonucleic acid (DNA)

Answer 11

A nucleic acid molecule, usually a double-stranded helix, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of being replicated and determining the inherited structure of a cell’s proteins.

Question 12

deoxyribose

Answer 12

The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides.

Question 13

disaccharide

Answer 13

A double sugar, consisting of two monosaccharides joined by a glycosidic linkage formed by a dehydration reaction.

Question 14

double helix

Answer 14

The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.

Question 15

enzyme

Answer 15

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins.

Question 16

fat

Answer 16

A lipid consisting of three fatty acids linked to one glycerol molecule; also called a triacylglycerol or triglyceride.

Question 17

fatty acid

Answer 17

A carboxylic acid with a long carbon chain. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also called triacylglycerol or triglyceride.

Question 18

gene

Answer 18

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

Question 19

gene expression

Answer 19

The process by which information encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead function as RNAs.

Question 20

genomics

Answer 20

The systematic study of whole sets of genes (or other DNA) and their interactions within a species, as well as genome comparisons between species.

Question 21

glycogen

Answer 21

An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.

Question 22

glycosidic linkage

Answer 22

A covalent bond formed between two monosaccharides by a dehydration reaction.

Question 23

hydrolysis

Answer 23

A chemical reaction that breaks bonds between two molecules by the addition of water; functions in disassembly of polymers to monomers.

Question 24

lipid

Answer 24

Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water.

Question 25

macromolecule

Answer 25

A giant molecule formed by the joining of smaller molecules, usually by a dehydration reaction. Polysaccharides, proteins, and nucleic acids are macromolecules.

Question 26

monomer

Answer 26

The subunit that serves as the building block of a polymer.

Question 27

monosaccharide

Answer 27

The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also called simple sugars, monosaccharides have molecular formulas that are generally some multiple of CH 2 O .

Question 28

nucleic acid

Answer 28

A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.

Question 29

nucleotide

Answer 29

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one to three phosphate groups.

Question 30

peptide bond

Answer 30

The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction.

Question 31

phospholipid

Answer 31

A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. Phospholipids form bilayers that function as biological membranes.

Question 32

polymer

Answer 32

A long molecule consisting of many similar or identical monomers linked together by covalent bonds.

Question 33

polynucleotide

Answer 33

A polymer consisting of many nucleotide monomers in a chain. The nucleotides can be those of DNA or RNA.

Question 34

polypeptide

Answer 34

A polymer of many amino acids linked together by peptide bonds.

Question 35

polysaccharide

Answer 35

A polymer of many monosaccharides, formed by dehydration reactions.

Question 36

protein

Answer 36

A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.

Question 37

proteomics

Answer 37

The systematic study of sets of proteins and their properties, including their abundance, chemical modifications, and interactions.

Question 38

purine

Answer 38

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G) are purines.

Question 39

pyrimidine

Answer 39

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. Cytosine (C), thymine (T), and uracil (U) are pyrimidines.

Question 40

ribonucleic acid (RNA)

Answer 40

A type of nucleic acid consisting of a polynucleotide made up of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis, in gene regulation, and as the genome of some viruses.

Question 41

ribose

Answer 41

The sugar component of RNA nucleotides.

Question 42

saturated fatty acid

Answer 42

A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that are attached to the carbon skeleton.

Question 43

sickle-cell disease

Answer 43

A recessively inherited human blood disorder in which a single nucleotide change in the a-globin gene causes hemoglobin to aggregate, changing red blood cell shape and causing multiple symptoms in afflicted individuals.

Question 44

starch

Answer 44

A storage polysaccharide in plants, consisting entirely of glucose monomers joined by glycosidic linkages.

Question 45

steroid

Answer 45

A type of lipid characterized by a carbon skeleton consisting of four fused rings with various chemical groups attached.

Question 46

trans fat

Answer 46

An unsaturated fat, formed artificially during hydrogenation of oils, containing one or more trans double bonds.

Question 47

triacylglycerol

Answer 47

A lipid consisting of three fatty acids linked to one glycerol molecule; also called a fat or triglyceride.

Question 48

unsaturated fatty acid

Answer 48

A fatty acid that has one or more double bonds between carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.

Question 49

X-ray crystallography

Answer 49

A technique used to study the three-dimensional structure of molecules. It depends on the diffraction of an X-ray beam by the individual atoms of a crystallized molecule.