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ESSENTIAL CELL BIOLOGY, FOURTH EDITION CHAPTER 2: CHEMICAL COMPONENTS OF CELLS © 2014 G ARLAND SCIENCE PUBLISHING
Chemi!" B#$%& 2-1
elect the ans!er that best co"pletes co"pletes the follo!ing state"ent: Che"ical reactions in li#ing syste"s occur in an $$$$$$$$$$$$ en#iron"ent% !ithin a narro! range of te"peratures. &a' opti"al &b' organic &c' e(tracellular &d' a)ueous
2-2
*ndicate !hether the state"ents belo! are true or false. *f a state"ent is false% e(plain !hy it is false. A. Thee che"i Th che"ist stry ry of lif lifee is car carri ried ed out out and and coord coordin inat ated ed pri" pri"ar aril ily y by the the actio action n of s"all "olecules. B. Carb Carbon on-ba -base sed d co"p co"poun ounds ds "ak "akee up the the #as #astt "a+o "a+ori rity ty of of "ol "olec ecul ules es foun found d in cel cells ls.. C. Thee che"i Th che"ical cal rea react ctio ions ns in in li#i li#ing ng syst syste" e"ss are are loos loosel ely y regul regulat ated% ed% all allo! o!in ing g for for a !ide range of products and "ore rapid e#olution.
2-3
,hich subato"ic particles contribute to the ato"ic nu"ber for any gi#en ele"ent &a' protons &b' protons and neutrons &c' neutrons &d' protons an and el electrons
2-4
,hich subato"ic particles contribute to the ato"ic "ass for any gi#en ele"ent &a' protons &b' protons and neutrons &c' neutrons &d' protons an and el electrons
2-5
,hich subato"ic particles can #ary bet!een isotopes of the sa"e ele"ent% !ithout changing the obser#ed che"ical properties &a' electrons &b' protons and neutrons &c' neutrons &d' neutrons and electrons
2-6
Figure -0 depicts the structure of carbon. 1se the infor"ation in the diagra" to choose the correct ato"ic nu"ber and ato"ic !eight% respecti#ely% for an ato" of carbon.
2age 3 of
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Figure Q2-6
&a' &b' &c' &d'
0 % 3 3 % 3 0 % 3 3 % 0
2-7
Carbon 34 is an unstable isotope of carbon that decays #ery slo!ly. Co"pared to the co""on% stable carbon 3 isotope% carbon 34 has t!o additional $$$$$$$$$$$$$$. &a' electrons. &b' neutrons. &c' protons. &d' ions.
2-8
*f the isotope 5 has 30 protons and 30 neutrons% ho! "any protons% neutrons% and electrons !ill the isotope 56 ha#e% respecti#ely &a' 3 0% 7% 3 6 &b' 3 0% 38 % 3 6 &c' 3 0% 3 8% 3 0 &d' 3 0% 38 % 3 9
2-9
A. B. C.
*f 7.6 "o "ole le of of gluc glucos osee !eig !eighs hs 87 87 g% !hat !hat is is the the "ol "olec ecul ular ar "as "asss of gluc glucos ose e ,hat ,hat is is the the con conce cent ntra rati tion on%% in gra gra"s "s per lite literr &g/ &g/'% '% of of a 7. 7.6 6 ; sol solut utio ion n of glucose
2-10
,hich of the follo!ing ele"ents is least abundant abundant in li#ing organis"s &a' sulfur &b' carbon &c' o(ygen &d' nitrogen
2-11
=ou e(plain to a friend !hat you ha#e learned about A#ogadro>s nu"ber. =our friend thinks the nu"ber is so large that he doubts doub ts there is e#en a "ole of li#ing cells on the Earth. =ou =ou ha#e recently heard that there are about 67 trillion &6 ? 3735' hu"an cells in each adult hu"an body and that each hu"an contains "ore bacterial cells &in the 2age of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts digesti#e syste"' than hu"an cells% so you bet your friend @6 that there is "ore than a "ole of cells on Earth. The hu"an population is appro(i"ately 9 billion &9 ? 378'. ,hat calculation can you sho! your friend to con#ince hi" you are right 2-12
A#ogadro>s nu"ber% calculated fro" the ato"ic !eight of hydrogen% tells us ho! "any ato"s or "olecules are in a "ole. The resulting base for all calculations of "oles and "olarity &ho! "any "olecules are present !hen you !eigh out a substance or "easure fro" a stock solution' is the follo!ing: 3 g of hydrogen ato"s 0 ? 375 hydrogen ato"s 3 "ole of hydrogen ulfur has a "olecular !eight of 5.
2-13
The first task you are assigned in your su""er laboratory +ob is to prepare a concentrated a< stock solution. The "olecular !eight of a< is 47.
2-14
=ou ha#e a concentrated stock solution of 37 ; a< and !ant to use it to produce a 367 " solution of 5 ; a<. ,hat #olu"e of !ater and stock solutions !ill you "easure out to "ake this ne! solution &a' 356 " of !ater% 36 " of a< stock &b' 336 " of !ater% 56 " of a< stock &c' 377 " of !ater% 67 " of a< stock &d' 376 " of !ater% 46 " of a< stock
2-15
*ndicate !hether the state"ents belo! are true or false. *f a state"ent is false% e(plain !hy it is false. A. Electron shells fill discrete regions around the nucleus of the ato" and li"it the nu"ber of electrons that can occupy a specific orbit. B. <% C% % and are the "ost co""on ele"ents in biological "olecules because they are the "ost stable. C. o"e ato"s are "ore stable !hen they lose one or t!o electrons% e#en though this "eans they !ill ha#e a net positi#e charge.
2-16
A co#alent bond bet!een t!o ato"s is for"ed as a result of the $$$$$$$$$$$$$$. &a' sharing of electrons. 2age 5 of
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An ionic bond bet!een t!o ato"s is for"ed as a result of the $$$$$$$$$$$$$$. &a' sharing of electrons. &b' loss of electrons fro" both ato"s. &c' loss of a proton fro" one ato". &d' transfer of electrons fro" one ato" to the other.
2-18
For each of the follo!ing sentences% fill in the blanks !ith the best !ord or phrase selected fro" the list belo!. ot all !ords or phrases !ill be usedD each !ord or phrase should be used only once. ,hereas ionic bonds for" a&n' $$$$$$$$$$$$$$$$$$% co#alent bonds bet!een ato"s for" a&n' $$$$$$$$$$$$$$$$$$. These co#alent bonds ha#e a characteristic bond $$$$$$$$$$$$$$$$$$ and beco"e stronger and "ore rigid !hen t!o electrons are shared in a&n' $$$$$$$$$$$$$$$$$$. E)ual sharing of electrons yields a&n' $$$$$$$$$$$$$$$$$$ co#alent bond. *f one ato" participating in the bond has a stronger affinity for the electron% this produces a partial negati#e charge on one ato" and a partial positi#e charge on the other. These $$$$$$$$$$$$$$$$$$ co#alent bonds should not be confused !ith the !eaker $$$$$$$$$$$$$$$$$$ bonds that are critical for the three-di"ensional structure of biological "olecules and for interactions bet!een these "olecules. charge co#alent double bond ionic
length "olecule nonco#alent nonpolar
polar salt single bond !eight
2-19
*ndicate !hether the state"ents belo! are true or false. *f a state"ent is false% e(plain !hy it is false. A. Electrons are constantly "o#ing around the nucleus of the ato"% but they can "o#e only in discrete regions. B. There is no li"it to the nu"ber of electrons that can occupy the fourth electron shell. C. Ato"s !ith unfilled outer electron shells are especially stable and are therefore less reacti#e.
2-20
Table -7 indicates the electrons in the first four ato"ic electron shells for selected ele"ents. n the basis of the infor"ation in the chart and !hat you kno! about ato"ic structure% !hich ele"ents are che"ically inert
2age 4 of
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Table Q2-20
&a' &b' &c' &d' 2-21
carbon% sulfur heliu"% neon sodiu"% potassiu" "agnesiu"% calciu"
Table -3 indicates the electrons in the first four ato"ic electron shells for selected ele"ents. n the basis of the infor"ation in the chart and !hat you kno! about ato"ic structure% !hich ele"ents !ill for" ions !ith a net charge of 3 in solution
Table Q2-21
&a' &b' &c'
carbon% sulfur heliu"% neon sodiu"% potassiu" 2age 6 of
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Table - indicates the electrons in the first four ato"ic electron shells for selected ele"ents. n the basis of the infor"ation in the chart and !hat you kno! about ato"ic structure% !hich ele"ents !ill for" ions !ith a net charge of in solution
Table Q2-22
&a' &b' &c' &d' 2-23
carbon% sulfur heliu"% neon sodiu"% potassiu" "agnesiu"% calciu"
Table -5 indicates the electrons in the first four ato"ic electron shells for selected ele"ents. n the basis of the infor"ation in the chart and !hat you kno! about ato"ic structure% !hich ele"ents for" stable but reacti#e diato"ic gases
2age 0 of
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nitrogen% o(ygen heliu"% neon sodiu"% potassiu" "agnesiu"% calciu"
2-24
*ndicate !hether the state"ents belo! are true or false. *f a state"ent is false% e(plain !hy it is false. A. There are four ele"ents that constitute 88 of all the ato"s found in the hu"an body. B. Copper% Ginc% and "anganese are a"ong 33 nonessential trace ele"ents that contribute less than 7.3 of all the ato"s in the hu"an body. C. Appro(i"ately 7.8 of the ato"s in the hu"an body co"e fro" se#en essential ele"entsHa% ;g% I% Ca% 2% % and ClHall of !hich for" stable ions in a)ueous solution.
2-25
,hich of the follo!ing factors do not influence the length of a co#alent bond &a' the tendency of ato"s to fill the outer electron shells &b' the attracti#e forces bet!een negati#ely charged electrons and positi#ely charged nuclei &c' the repulsi#e forces bet!een the positi#ely charged nuclei &d' the "ini"iGation of repulsi#e forces bet!een the t!o nuclei by the cloud of shared electrons
2-26
Jouble co#alent bonds are both shorter and stronger than single co#alent bonds% but they also li"it the geo"etry of the "olecule because they $$$$$$$$$$$$$$$$$$$$. &a' create a ne! arrange"ent of electron shells. &b' change the reacti#ity of the bonded ato"s. &c' li"it the rotation of the bonded ato"s. &d' pre#ent additional bonds fro" being for"ed !ith the bonded ato"s.
2-27
2olar co#alent bonds are for"ed !hen the electrons in the bond are not shared e)ually bet!een the t!o nuclei. ,hich one of these "olecules contains polar bonds &a' "olecular o(ygen &b' "ethane &c' propane &d' !ater
2-28
A. B.
2-29
(ygen% hydrogen% carbon% and nitrogen ato"s are enriched in the cells and tissues of li#ing organis"s. The co#alent bond geo"etries for these ato"s influence their
*n !hich scientific unit is the strength of a che"ical bond usually e(pressed *f 7.6 kilocalories of energy are re)uired to break 0 ? 375 bonds of a particular type% !hat is the strength of this bond
2age 9 of
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Figure Q2-29
A. B. C.
o(ygen carbon nitrogen
2-30
,hich co"bination of ans!ers best co"pletes the follo!ing state"ent: ,hen ato"s are held together by $$$$$$$$$$$ $$$$$$$$$$% they are typically referred to as $$$$$$$$$. &a' hydrogen bonds% "olecules. &b' ionic interactions% salts. &c' ionic interactions% "olecules. &d' double bonds% nonpolar.
2-31
Although co#alent bonds are 37K377 ti"es stronger than nonco#alent interactions% "any biological processes depend upon the nu"ber and type of nonco#alent interactions bet!een "olecules. ,hich of the nonco#alent interactions belo! !ill contribute "ost to the strong and specific binding of t!o "olecules% such as a pair of proteins &a' electrostatic attractions &b' hydrogen bonds &c' hydrophobic interactions &d' Lan der ,aals attractions
2-32
,hich of the follo!ing e(pressions accurately describes the calculation of p< &a' p< Klog37M<N &b' p< log37M<N &c' p< KlogM<N &d' p< Klog37M< K N
2-33
The p< of an a)ueous solution is an indication of the concentration of a#ailable protons.
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts &b' a""oniu" &c' chloride &d' hydroniu" 2-34
The relati#e strengths of co#alent bonds and #an der ,aals interactions re"ain the sa"e !hen tested in a #acuu" or in !ater.
2-35
*ndicate !hether the state"ents belo! are true or false. *f a state"ent is false% e(plain !hy it is false. A. Any co#alently bonded < ato" can participate in a hydrogen bond if it co"es in close pro(i"ity !ith an o(ygen ato" that for"s part of a !ater "olecule. B. 2rotons are constantly "o#ing bet!een !ater "olecules% !hich "eans there is an o#erall e)uilibriu" bet!een hydro(yl ions and hydroniu" ions in a)ueous solutions. C. A strong base is defined as a "olecule that can readily re"o#e protons fro" !ater.
2-36
arger "olecules ha#e hydrogen-bonding net!orks that contribute to specific% highaffinity binding. "aller "olecules such as urea can also for" these net!orks.
Figure Q2-36
2-37
&a' &b' &c' &d'
0 6 5 4
A.
ketch three different !ays in !hich three !ater "olecules could be held together by hydrogen-bonding. n a sketch of a single !ater "olecule% indicate the distribution of positi#e and negati#e charge &using the sy"bols O and O K '.
B. C.
2-38
A. B. C.
,hat is the p< of pure !ater ,hat concentration of hydroniu" ions does a solution of p< contain Co"plete the follo!ing reaction: 2age 8 of
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,ill the reaction in &C' occur "ore readily &be dri#en to the right' if the p< of the solution is high
2-39
Aro"atic carbon co"pounds such as benGene are planar and #ery stable. Jouble-bond character e(tends around the entire ring% !hich is !hy it is often dra!n as a he(agon !ith a circle inside. This characteristic is caused by electron $$$$$$$$$$. &a' resonance. &b' pairing. &c' partial charge. &d' stacking.
2-40
The a"ino acid histidine is often found in enGy"es. Jepending on the p< of its en#iron"ent% so"eti"es histidine is neutral and at other ti"es it ac)uires a proton and beco"es positi#ely charged. Consider an enGy"e !ith a histidine side chain that is kno!n to ha#e an i"portant role in the function of the enGy"e. *t is not clear !hether this histidine is re)uired in its protonated or its unprotonated state. To ans!er this )uestion% you "easure enGy"e acti#ity o#er a range of p<% !ith the results sho!n in Figure -47. ,hich for" of histidine is necessary for the acti#e enGy"e
Figure Q2-40 2-41
ilicon is an ele"ent that% like carbon% has four #acancies in its outer electron shell and therefore has the sa"e bonding che"istry as carbon. ilicon is not found to any significant degree in the "olecules found in li#ing syste"s% ho!e#er. Joes this difference arise because ele"ental carbon is "ore abundant than silicon ,hat other e(planations are there for the preferential selection of carbon o#er silicon as the basis for the "olecules of life
2-42
eleniu" &e' is an ele"ent re)uired in the hu"an body in trace a"ounts. eleniu" is obtained through the diet and le#els of seleniu" found in food depend greatly on the soil !here it is gro!n. nce ingested and absorbed as selenate% it can beco"e incorporated into a s"all nu"ber of polypeptides. These selenoproteins are for"ed !hen seleniu" 2age 37 of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts replaces an ele"ent that is found in t!o of the t!enty PstandardQ a"ino acids. 1sing your kno!ledge of ato"ic structure% the periodic table in Figure K9% and the structure of a"ino acids found in 2anel K6% deduce !hich t!o a"ino acids "ay be con#erted to PselenoQ a"ino acids and used to "ake selenoproteins.
Sm!"" M#"e'"e& i$ Ce""& 2-43
*ndicate !hether the "olecules belo! are inorganic &*' or organic &'. A. glucose B. ethanol C. sodiu" chloride J. !ater E. cholesterol F. adenosine R. calciu" <. glycine *. o(ygen S. iron I. phospholipid
2-44
,hich of the follo!ing "ono"er building blocks is necessary to asse"ble selecti#ely per"eable boundaries around and inside cells &a' sugars &b' fatty acids &c' a"ino acids &d' nucleotides
2-45
The #ariety and arrange"ent of che"ical groups on "ono"er subunits contribute to the confor"ation% reacti#ity% and surface of the "acro"olecule into !hich they beco"e incorporated. ,hat type of che"ical group is circled on the nucleotide sho!n in Figure -46
Figure Q2-45
&a' &b'
pyrophosphate phosphoryl 2age 33 of
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The a"ino acids gluta"ine and gluta"ic acid are sho!n in Figure -40. They differ only in the structure of their side chains &circled'. At p< 9% gluta"ic acid can participate in "olecular interactions that are not possible for gluta"ine. ,hat types of interactions are these
Figure Q2-46
&a' &b' &c' &d'
ionic bonds hydrogen bonds #an der ,aals interactions co#alent bonds
2-47
Cells re)uire one particular "onosaccharide as a starting "aterial to synthesiGe nucleotide building blocks. ,hich of the "onosaccharides belo! fills this i"portant role &a' glucose &b' fructose &c' ribulose &d' ribose
2-48
ligosaccharides are short sugar poly"ers that can beco"e co#alently linked to proteins and lipids through condensation reactions. These "odified proteins and lipids are called glycoproteins and glycolipids% respecti#ely. ,ithin a protein% !hich of the a"ino acids &sho!n in Figure -4' is the "ost probable target for this type of "odification
2age 3 of
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Figure Q2-48
&a' &b' &c' &d'
serine glycine phenylalanine "ethionine
2-49
,hich of the follo!ing are e(a"ples of iso"ers &a' glucose and galactose &b' alanine and glycine &c' adenine and guanine &d' glycogen and cellulose
2-50
A. B. C.
Figure Q2-50 2-51
;ost types of "olecules in the cell ha#e asy""etric &chiral' carbons. Conse)uently there is the potential to ha#e t!o different "olecules that look "uch the sa"e but are "irror i"ages of each other and therefore not e)ui#alent. These special types of iso"er are called stereoiso"ers. ,hich of the four carbons circled in Figure -63 is the asy""etric carbon that deter"ines !hether the a"ino acid &threonine in this case' is a ᴅ or an ʟ stereoiso"er
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Figure Q2-51
&a' &b' &c' &d'
3 5 4
2-52
*ndicate !hether the state"ents belo! are true or false. *f a state"ent is false% e(plain !hy it is false. A. A disaccharide consists of a sugar co#alently linked to another "olecule such as an a"ino acid or a nucleotide. B. The hydro(yl groups on "onosaccharides are reaction hot spots and can be replaced by other functional groups to produce deri#ati#es of the original sugar. C. The presence of double bonds in the hydrocarbon tail of a fatty acid does not greatly influence its structure.
2-53
n the phospholipid "olecule in Figure -65% label each nu"bered line !ith the correct ter" selected fro" the list belo!.
Figure Q2-53 2-54
;any types of cells ha#e stores of lipids in their cytoplas"% usually seen as fat droplets. ,hat is the lipid "ost co""only found in these droplets 2age 34 of
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Choose the ans!er that best fits the follo!ing state"ent: Cholesterol is an essential co"ponent of biological "e"branes. Although it is "uch s"aller than the typical phospholipids and glycolipids in the "e"brane% it is a&n' $$$$$$$$$$$$$$$$$ "olecule% ha#ing both hydrophilic and hydrophobic regions. &a' polar &b' o(ygen-containing &c' hydrophobic &d' a"phipathic
2-56
For each of the follo!ing sentences% fill in the blanks !ith the best !ord or phrase selected fro" the list belo!. ot all !ords or phrases !ill be usedD each !ord or phrase should be used only once. 2roteins are ______________ built fro" a"ino acids% !hich each ha#e an a"ino group and a _____________ group attached to the central _______________ . There are t!enty possible _______________ that differ in structure and are generally referred to as P.Q *n solutions of neutral p<% a"ino acids are _______________ % carrying both a positi#e and negati#e charge. ,hen a protein is "ade% a"ino acids are linked together through _______________ % !hich are for"ed by condensation reactions bet!een the carbo(yl end of the last a"ino acid and the ___________________ end of the ne(t a"ino acid to be added to the gro!ing chain. a"ino U-carbon carbon carbo(yl hydro(ide
ioniGed length nonco#alent peptide bonds
polypeptides protein group side chains
2-57
JA and A are different types of nucleic acid poly"er. ,hich of the follo!ing is true of JA but not true of A &a' *t contains uracil. &b' *t contains thy"ine. &c' *t is single-stranded. &d' *t has 6′-to-5′ directionality.
2-58
;atch each ter" related to the structure of nucleic acids &AK*' !ith one of the descriptions pro#ided. A. base B. glycosidic bond C. nucleoside J. nucleotide 2age 36 of
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2-59
$$$$ $$$$ $$$$ $$$$ $$$$ $$$$ $$$$ $$$$ $$$$
the linkage bet!een t!o nucleotides the linkage bet!een the 6′ sugar hydro(yl and a phosphate group the nitrogen-containing aro"atic ring fi#e-carbon sugar found in JA sugar unit linked to a base linkage bet!een the sugar and the base linkages bet!een phosphate groups sugar linked to a base and a phosphate fi#e-carbon sugar found in A
A.
,rite out the se)uence of a"ino acids in the follo!ing peptide% using the full na"es of the a"ino acids. 2ro-Lal-Thr-Rly-ys-Cys-Rlu ,rite the sa"e se)uence !ith the single-letter code for a"ino acids. According to the con#entional !ay of !riting the se)uence of a peptide or a protein% !hich is the C-ter"inal a"ino acid and !hich is the -ter"inal a"ino acid in the abo#e peptide
B. C.
2-60
The cell is able to har#est energy fro" #arious processes in order to generate AT2 "olecules. These AT2s represent a for" of stored energy that can be used later to dri#e other i"portant processes. E(plain ho! the cell can con#ert the che"ical energy stored in AT2 to generate "echanical energy% for e(a"ple changing the shape of a protein.
M!(#m#"e'"e& i$ Ce""& 2-61
Both JA and A are synthesiGed by co#alently linking a nucleoside triphosphate to the pre#ious nucleotide% constantly adding to a gro!ing chain. *n the case of JA% the ne! strand beco"es part of a stable heli(. The t!o strands are co"ple"entary in se)uence and antiparallel in directionality. ,hat is the principal force that holds these t!o strands together &a' ionic interactions &b' hydrogen bonds &c' co#alent bonds &d' #an der ,aals interactions
2-62
Each nucleotide in JA and A has an aro"atic base. ,hat is the principal force that keeps the bases in a poly"er fro" interacting !ith !ater &a' hydrophobic interactions &b' hydrogen bonds 2age 30 of
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Because there are four different "ono"er building blocks that can be used to asse"ble A poly"ers% the nu"ber of possible se)uence co"binations that can be created for an A "olecule "ade of 377 nucleotides is $$$$$$$. &a' 3774 &b' 4377 &c' 4 ? 377 &d' 377/4
2-64
There are 7377 different possible se)uence co"binations for a protein chain !ith 37 7 a"ino acids. *n addition to the a"ino acid se)uence of the protein% !hat other factors increase the potential for di#ersity in these "acro"olecules &a' free rotation around single bonds during synthesis &b' nonco#alent interactions sa"pled as protein folds &c' the directionality of a"ino acids being added &d' the planar nature of the peptide bond
2-65
*ndicate !hether the state"ents belo! are true or false. *f a state"ent is false% e(plain !hy it is false. A. Ponpolar interactionsQ is si"ply another !ay of saying P#an der ,aals attractions.Q B. Condensation reactions occur in the synthesis of all the "acro"olecules found in cells. C. All proteins and As pass through "any unstable confor"ations as they are folded% finally settling on one single% preferred confor"ation.
2-66
;acro"olecules in the cell can often interact transiently as a result of nonco#alent interactions. These !eak interactions also produce stable% highly specific interactions bet!een "olecules. ,hich of the factors belo! is the "ost significant in deter"ining !hether the interaction !ill be transient or stable &a' the siGe of each "olecule &b' the concentration of each "olecule &c' the rate of synthesis &d' surface co"ple"entarity bet!een "olecules
2-67
As a protein is "ade% the polypeptide is in an e(tended confor"ation% !ith e#ery a"ino acid e(posed to the a)ueous en#iron"ent. Although both polar and charged side chains can "i( readily !ith !ater% this is not the case for nonpolar side chains. E(plain ho! hydrophobic interactions "ay play a role in the early stages of protein folding% and ha#e an influence on the final protein confor"ation.
2-68
=ou are trying to "ake a synthetic copy of a particular protein but accidentally +oin the a"ino acids together in e(actly the re#erse order. ne of your class"ates says the t!o proteins "ust be identical% and bets you @7 that your synthetic protein !ill ha#e e(actly 2age 39 of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts the sa"e biological acti#ity as the original. After ha#ing read this chapter% you ha#e no hesitation in staking your @7 that it !on>t. ,hat particular feature of a p olypeptide chain "akes you sure your @7 is safe and that the pro+ect "ust be done again. 2-69
A protein chain folds into its stable and uni)ue three-di"ensional structure% or confor"ation% by "aking "any nonco#alent bonds bet!een different parts of the chain. uch nonco#alent bonds are also critical for interactions !ith other proteins and cellular "olecules. Fro" the list pro#ided% choose the class&es' of a"ino acids that are "ost i"portant for the interactions detailed belo!. A. for"ing ionic bonds !ith negati#ely charged JA B. for"ing hydrogen bonds to aid solubility in !ater C. binding to another !ater-soluble protein J. localiGing an Pintegral "e"braneQ protein that spans a lipid bilayer E. tightly packing the hydrophobic interior core of a globular protein acidic basic
nonpolar uncharged polar
2-70
*t is no! a routine task to deter"ine the e(act order in !hich indi#idual subunits ha#e been linked together in polynucleotides &JA' and polypeptides &proteins'.
2-71
=our lab director re)uests that you add ne! gro!th "ediu" to the "a""alian cell cultures before heading ho"e fro" the lab on a Friday night. 1nfortunately% you need to "ake fresh "ediu" because all the pre"i(ed bottles of "ediu" ha#e been used. ne of the ingredients you kno! you need to add is a "i( of the essential a"ino acids &those that cannot be "ade by the cells% but are needed in proteins'. n the shelf of dry che"icals you find the a"ino acids you need% and you "i( the" into your "ediu"% along !ith all the other necessary nutrients% and replace the old "ediu" !ith your ne! "ediu". n unday% you co"e in to the lab +ust to check on your cells and find that the cells ha#e not gro!n. =ou are sure you "ade the "ediu" correctly% but on checking you see that so"ebody !rote a note on the dry "i(ture of a"ino acids you used: Pote: this "i(ture contains only ᴅ-a"ino acids.Q A. ,hat is the "eaning of the note and ho! does it e(plain the lack of cell gro!th in your culture B. Are there any organis"s that could gro! using this "i(ture Sustify your ans!er.
2-72
Eukaryotic cells ha#e their JA "olecules inside their nuclei.
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts acetylation of lysines in histone proteins !ill affect the ability of a histone to perfor" its role &refer to your ans!er in part A'
Figure Q2-72
2age 38 of
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ANS)ERS 2-1 2-2
&d' A.
B. C.
2-3
&a'
2-4
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2-5
&c'
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A. B. C.
False. Although s"all "olecules are i"portant in "any processes% the che"ical reactions in li#ing syste"s are regulated by the coordinated action of large poly"eric "olecules. True. False. The che"ical reactions in li#ing syste"s are #ery tightly controlled% ensuring that e#ents occur at the proper ti"e and at the proper location inside the cell.
37 daltons. A "ole of a substance has a "ass e)ui#alent to its "olecular !eight e(pressed in gra"s. 46 g/ 0 ? 375 "olecules
2-10
&a' ulfur is the least abundant ele"ent a"ong the choices gi#en.
2-11
A#ogadro>s nu"ber% or 0 ? 375% is the nu"ber of ato"s &or units' in a "ole. *f you "ultiply the nu"ber of people on Earth by the nu"ber of cells in the hu"an body% then double it to account for the bacteria% you !ill calculate: &9 ? 378' ? &3 ? 3734' 9 ? 375. Thus% e#en !hen only considering the hu"an population and the associated "icrobial populations% you can esti"ate "ore than a "ole of li#ing cells on Earth. =ou !in @6.
2-12
&d'
2-13
&b'
2-14
&d'
2-15
A.
True. 2age 7 of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts B. False. <% C% % and are the "ost co""on ele"ents in biological "olecules because their outer shells are unfilled% "aking the" highly reacti#e. C. True. 2-16
&a'
2-17
&d'
2-18
,hereas ionic bonds for" a salt% co#alent bonds bet!een ato"s for" a molecule. These co#alent bonds ha#e a characteristic bond length and beco"e stronger and "ore rigid !hen t!o electrons are shared in a ouble bon. E)ual sharing of electrons yields a non!olar co#alent bond. *f one ato" participating in the bond has a stronger affinity for the electron% this produces a partial negati#e charge on one ato" and a partial positi#e charge on the other. These !olar co#alent bonds should not be confused !ith the !eaker nonco"alent bonds that are critical for the three-di"ensional structure of biological "olecules and for interactions bet!een these "olecules.
2-19
A. B. C.
2-20
&b'
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&c'
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&d'
2-23
&a' An o(ygen ato" !ith si( outer electrons needs t!o "ore to attain a stable outer shell. This can be achie#ed by for"ing t!o co#alent bonds !ith a second o(ygen% as sho!n on the right. i"ilarly% a nitrogen ato" needs three "ore electrons and "akes three co#alent bonds !ith another nitrogen ato".
True. False. The fourth electron shell has the capacity to hold 3 electrons. False. Ato"s that ha#e their outer electron shells filled are the "ost stable and least reacti#e. Ato"s !ith unfilled outer shells are "ore reacti#e because they tend to share or transfer electrons to fill and therefore stabiliGe the outer shell.
2age 3 of
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Figure #2-23 2-24
A. B. C.
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&a'
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&c'
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&d'
2-28
A. B.
True. False. Cu% Vn% and ;n are essential trace ele"ents in the hu"an body. False. a% ;g% I% Ca% and Cl for" ions in a)ueous solution% but 2 and for" co#alent bonds in order to fill their outer electron shells.
kilocalories per "ole &or kilo+oules per "ole' 7.6 kcal/"ole
2-29
Figure #2-29 2-30
&b' 2age of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts 2-31
&a'
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&a'
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&d'
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,e esti"ate bond strengths by "easuring the a"ount of energy needed to break the". As e(plained in 2anel K9 &p.9K98'% in an a)ueous solution% !ater can for" hydrogen bonds !ith any polar "olecules that are capably of for"ing hydrogen bonds !ith each other. This for"ation of bonds !ith !ater takes a!ay fro" the net energy that !ould be gained fro" the "olecules for"ing hydrogen bonds !ith each other% as they !ould in a #acuu". i"ilarly% !ater for"s fa#orable electrostatic interactions !ith ions% thereby greatly !eakening the ionic bonds that for" bet!een positi#e and negati#e ions in a #acuu" &see 2anel K9'. Thus% for e(a"ple% solid table salt &aCl' readily dissociates in !ater% producing separate a and Cl K ions as it dissol#es. *n contrast% co#alent bonds and #an der ,aals attractions ha#e an intrinsic bond strength that is independent of the a)ueous en#iron"ent% because changes in !ater "olecule associations are not in#ol#ed in the for"ation of these t!o types of bonds.
2-35
A.
B. C. 2-36
False.
&a' 1rea can for" at least si( hydrogen bonds in !ater: t!o fro" the o(ygen ato" and one fro" each hydrogen ato".
2-37
A. B. C.
ee Figure A-59A. ee Figure A-59B.
2age 5 of
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A. B. C. J.
p< 9 37 K ; C<5C K <5 =es. *f the p< is high% then the concentration of hydroniu" ions !ill be lo!. Therefore the right!ard reaction% !hich produces hydroniu" ions% !ill be fa#ored.
2-39
&a'
2-40
Assu"ing that the change in enGy"e acti#ity is due to the change in the protonation state of histidine% the enGy"e "ust re)uire histidine in the protonated% charged state. The enGy"e is acti#e only at lo!% acidic p<% !here the proton &or hydroniu" ion' concentration is highD thus% the loss of a proton fro" histidine !ill be disfa#ored so that histidine is likely to be protonated.
2-41
n the basis of Figure K4 in your te(tbook% silicon is actually "ore abundant in the Earth>s crust than carbon% so this is not likely to be the reason that carbon !as used preferentially. Carbon "ight ha#e been the ele"ent of choice in li#ing syste"s because it is lighter than silicon and for"s shorter co#alent bonds !ith other ele"ents. horter bonds are typically stronger and "ore stable.
2-42
ulfur is the only ele"ent found e(clusi#ely in t!o of the t!enty a"ino acids. This ele"ent is located directly abo#e seleniu" in the periodic table% indicating that these ele"ents ha#e the sa"e nu"ber of electrons in their outer shell and both prefer to for" bonds !ith other ato"s to fill their outer orbital. *f seleniu" instead of sulfur is incorporated into cysteine or "ethionine% the altered PselenoQ a"ino acids !ill be produced &selenocysteine and seleno"ethionine'. ,e can e(pect that this substitution !ill alter the nature of the proteins in !hich these a"ino acids are incorporated because seleniu" is a larger ato" than sulfur.
2-43
*ndicate !hether the "olecules belo! are inorganic &*' or organic &'. A. B. C. * J. * E. F. R. * <. *. * S. * I.
2-44
&b' 2age 4 of
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&b'
2-46
&a'
2-47
&d'
2-48
&a'
2-49
&a' Rlucose and galactose are both si(-carbon sugars and thus both ha#e the for"ula C0<30. They are therefore iso"ers of each other. Adenine and guanine are bases containing different nu"bers of nitrogen and o(ygen ato"s. Rlycogen and cellulose are different poly"ers of glucose. Alanine and glycine are a"ino acids !ith )uite different side chains: a "ethyl group and a hydrogen ato"% respecti#ely.
2-50
A. B. C.
7 carbon ato"s 53 hydrogen ato"s A fatty acid &Figure A-67 is arachidonic acid% an essential fatty acid re)uired by "ost "a""als'
Figure #2-50 2-51
&c' T!o of the carbon ato"s of threonine are asy""etric &nu"bered and 5 in Figure -63' but by con#ention it is the U-carbon &nu"ber 5' that deter"ines !hether the a"ino acid is the ᴅ or ʟ iso"er.
2-52
A. B. C.
False. A disaccharide consists of t!o sugar "olecules that undergo a condensation reaction to for" a co#alent bond &kno!n as a glycosidic linkage'. True. False. The presence of a double bond in the hydrocarbon chain of a fatty acid causes a kink in the chain% decreasing its fle(ibility and packing !ith neighboring hydrocarbon chains.
2-53
3HJD HAD 5HCD 4HSD 6H*D 0H
2-54
&d'
2-55
&d'
2-56
2roteins are !ol$!e!ties built fro" a"ino acids% !hich each ha#e an a"ino group and a carbo%$l group attached to the central &-carbon . There are t!enty possible sie chains 2age 6 of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts that differ in structure and are generally referred to as P.Q *n solutions of neutral p<% a"ino acids are ioni'e% carrying both a positi#e and negati#e charge. ,hen a protein is "ade% a"ino acids are linked together through !e!tie bons % !hich are for"ed by condensation reactions bet!een the carbo(yl end of the last a"ino acid and the amino end of the ne(t a"ino acid to be added to the gro!ing chain. 2-57
&b'
2-58
2-59
A. B. C.
2-60
The ter"inal phosphate group is typically hydrolyGed and the energy released fro" this che"ical bond is often Prein#estedQ to generate a ne! bond that links the phosphate group to a protein. This addition of a phosphate group can cause a change in the protein>s confor"ation. This confor"ational change is usually associated !ith change in function or transient interactions !ith other "acro"olecules% generating a do"ino effect !ithin the cell.
2-61
&b'
2-62
&a'
2-63
&b'
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&a'
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A.
B. C. 2-66
proline-#aline-threonine-glycine-lysine-cysteine-gluta"ic acid &or gluta"ate' 2LTRICE C-ter"inal is gluta"ic acid &or gluta"ate'D -ter"inal is proline
False. Lan der ,aals attractions describe the general attracti#e forces bet!een all ato"s. The contact distance bet!een any t!o nonbonded ato"s is the su" of the #an der ,aals radii. onpolar interactions are based on the e(clusion of hydrophobic "olecules fro" a hydrophilic en#iron"ent. True. True.
&d' 2age 0 of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts 2-67 ne reason that nonpolar groups are e(cluded fro" an a)ueous en#iron"ent is that a hydrophobic surface !ould organiGe !ater into a highly structured net!ork of hydrogen bonds% !hich is energetically unfa#orable. o% you !ould e(pect that nonpolar a"ino acids !ould group together early% for"ing Phydrophobic pockets%Q !hile the polar an d charged side chains re"ain at the interface of the surrounding solution. *n the final% folded protein% "ost of the nonpolar a"ino acids !ill re"ain buried inside the protein. This fold is "ore stable because nonpolar ato"s are pre#ented fro" contact !ith !ater and re"ain in contact !ith each other. 2-68
As a peptide bond has a distinct che"ical polarity% a polypeptide chain also has a distinct polarity &see Figure A-0'. The re#ersed protein chain cannot "ake the sa"e nonco#alent interactions during folding and thus !ill not adopt the sa"e threedi"ensional structure as the original protein. The acti#ities of these t!o proteins !ill definitely be different% because the acti#ity of a protein depends on its three-di"ensional structure. *t is unlikely that the re#erse chain !ill fold into an y !ell-defined% and hence functionally useful% structure at all% because it has not p assed the stringent selecti#e pressures i"posed during e#olution.
Figure #2-68 2-69
A. B. C. J. E.
2-70
ucleotides and a"ino acids ha#e an intrinsic directionality% and the "echanis" by !hich "ono"ers are added into a gro!ing poly"er is al!ays the sa"e. This yields a linear poly"er !ith the sa"e directionality as the "ono"ers. 2olysaccharides are produced by linking "onosaccharides together. The "onosaccharides can be either added directly or "odified to produce #arious deri#ati#es before addition. Beyond this% there are "ultiple sites on each "onosaccharide !here addition can occur% producing highly co"ple(% branched poly"ers.
2-71
A.
B.
basic uncharged polar uncharged polar% basic% and acidic nonpolar nonpolar
The note indicates that the "i(ture contains only one of the t!o possible stereoiso"ers &ʟ or ᴅ'. Because "a""alian cells use only the ʟ stereoiso"er% the ᴅ-a"ino acid "i(ture could not be used and therefore it is as though no a"ino acids !ere added at all. ot unless ʟ-a"ino acids !ere also "i(ed in. Certain types of bacteria use ᴅa"ino acids to produce their cell !alls% but they !ould still re)uire ʟ-a"ino acids for the rest of the proteins they "ake.
2age 9 of
Full file at http://testbankonline.eu/Test-Bank-for-Essential-Cell-Biology-4th-Edition-by-BruceAlberts JA is a nucleic acid poly"er in !hich each "ono"er has a negati#ely charged 2-72 A. phosphate group. The negati#e charges !ill naturally repel each other% so in order to !rap the high density of negati#e charges into a s"all space% positi#ely charged "olecules "ust be present. s net positi#e charge% !hich "akes it less effecti#e at buffering the negati#e charges on the JA backbone.
2age of
