Chapter 5 - The Structure and Function of Large Biological Molecules

Question 1

macromolecule

Answer 1

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

Question 2

polymer

Answer 2

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

Question 3

monomer

Answer 3

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

Question 4

enzyme

Answer 4

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 5

dehydration reaction

Answer 5

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

Question 6

hydrolysis

Answer 6

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

Question 7

carbohydrate

Answer 7

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

Question 8

monosaccharide

Answer 8

The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, monosaccharides have molecular formulas that are generally some multiple of CH2O.

Question 9

disaccharide

Answer 9

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

Question 10

glycosidic linkage

Answer 10

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

Question 11

polysaccharide

Answer 11

A polymer of many monosaccharides, formed by dehydration reactions.

Question 12

starch

Answer 12

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

Question 13

glycogen

Answer 13

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

Question 14

cellulose

Answer 14

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

Question 15

chitin

Answer 15

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

Question 16

lipid

Answer 16

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

Question 17

fat

Answer 17

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

Question 18

fatty acid

Answer 18

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 known as a triacylglycerol or triglyceride.

Question 19

triacylglycerol

Answer 19

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

Question 20

saturated fatty acid

Answer 20

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 21

unsaturated fatty acid

Answer 21

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 22

trans fat

Answer 22

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

Question 23

phospholipid

Answer 23

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 24

steroid

Answer 24

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

Question 25

cholesterol

Answer 25

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 26

catalyst

Answer 26

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

Question 27

polypeptide

Answer 27

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

Question 28

protein

Answer 28

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

Question 29

amino acid

Answer 29

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

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

primary structure

Answer 31

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

Question 32

secondary structure

Answer 32

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 33

alpha (α) helix

Answer 33

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 34

beta (β) pleated sheet

Answer 34

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 35

tertiary structure

Answer 35

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 36

hydrophobic interaction

Answer 36

A type of weak chemical interaction caused when molecules that do not mix with water coalesce to exclude water.

Question 37

disulfide bridge

Answer 37

A strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer.

Question 38

quaternary structure

Answer 38

The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.

Question 39

sickle-cell disease

Answer 39

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

Question 40

denaturation

Answer 40

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 41

chaperonin

Answer 41

A protein complex that assists in the proper folding of other proteins.

Question 42

X-ray crystallography

Answer 42

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 43

gene

Answer 43

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

Question 44

nucleic acid

Answer 44

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 45

deoxyribonucleic acid (DNA)

Answer 45

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 46

ribonucleic acid (RNA)

Answer 46

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, gene regulation, and as the genome of some viruses.

Question 47

polynucleotide

Answer 47

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

Question 48

nucleotide

Answer 48

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

Question 49

pyrimidine

Answer 49

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 50

purine

Answer 50

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 51

deoxyribose

Answer 51

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

Question 52

ribose

Answer 52

The sugar component of RNA nucleotides.

Question 53

double helix

Answer 53

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

Question 54

antiparallel

Answer 54

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