Chapter 5: The Structure and Function of Large Biological Molecules

Question 1

Monomers

Answer 1

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

Question 2

Cellulose

Answer 2

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

Question 3

Denaturation

Answer 3

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 4

Tertiary structure

Answer 4

The overall shape of a protein molecule due to interactions of amino acid side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

Question 5

Macromolecules

Answer 5

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

Question 6

Carbohydrates

Answer 6

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

Question 7

Fat

Answer 7

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

Question 8

Glycosidic linkage

Answer 8

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

Question 9

Nucleotides

Answer 9

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 10

Lipids

Answer 10

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

Question 11

Fatty acid

Answer 11

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 12

Protein

Answer 12

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

Question 13

Hydrolysis

Answer 13

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

Question 14

Polymer

Answer 14

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

Question 15

Pyrimidine

Answer 15

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 16

Disaccharide

Answer 16

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

Question 17

Deoxyribose

Answer 17

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

Question 18

X-ray crystallography

Answer 18

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.

Question 19

Cholesterol

Answer 19

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 20

Triacylglycerol

Answer 20

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

Question 21

Ribose

Answer 21

The sugar component of RNA nucleotides.

Question 22

Purines

Answer 22

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 23

Beta pleated sheets

Answer 23

One form of the secondary structure of proteins in which the polypeptide chain folds back and forth. Two regions of the chain lie parallel to each other and are held together by hydrogen bonds between atoms of the polypeptide backbone (not the side chains).

Question 24

Sickle-cell disease

Answer 24

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

Question 25

Monosaccharides

Answer 25

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 C-H-subscript-2-O.

Question 26

Alpha helix

Answer 26

A coiled region constituting one form of the secondary structure of proteins, arising from a specific pattern of hydrogen bonding between atoms of the polypeptide backbone (not the side chains).

Question 27

Ribonucleic acid

Answer 27

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 28

Steroids

Answer 28

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

Question 29

Deoxyribonucleic acid

Answer 29

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 30

Secondary structure

Answer 30

Regions of repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains).

Question 31

Dehydration reaction

Answer 31

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

Question 32

Catalysts

Answer 32

A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.

Question 33

Trans fats

Answer 33

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

Question 34

Glycogen

Answer 34

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

Question 35

Primary structure

Answer 35

The level of protein structure referring to the specific linear sequence of amino acids.

Question 36

Phospholipid

Answer 36

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 37

Polysaccharides

Answer 37

A polymer of many monosaccharides, formed by dehydration reactions.

Question 38

Peptide bond

Answer 38

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

Question 39

Nucleic acids

Answer 39

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 40

Double helix

Answer 40

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

Question 41

Antiparallel

Answer 41

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

Question 42

Enzymes

Answer 42

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 43

Chitin

Answer 43

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

Question 44

Amino acid

Answer 44

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

Question 45

Polypeptide

Answer 45

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

Question 46

Polynucleotides

Answer 46

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

Question 47

Starch

Answer 47

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

Question 48

Saturated fatty acid

Answer 48

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 49

Unsaturated fatty acid

Answer 49

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.