2012 RI Prelim Biology H1 P2_answers

RAFFLES INSTITUTION Higher 1 Biology Paper 1, !" An#$er# % Paper 1 an#$er#& 1% % "% )% *% +% % -% .% 1/%

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Paper  an#$er#& Se0ion A  Answer all the all the questions in this section. 1 In an experiment to study ATP ATP synthesis in plants, chloroplasts are isolated, and the pH levels in the vario various us compar compartme tments nts are monito monitored red.. The The graph graph below below shows shows the result results s of the experiment.

pH

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xplain the changes in pH seen in !ig."." upon illumination. #$% Illu4inaion o5 0hloropla## 0au#e# he e60iaion o5 he ele0ron# 5ro4 he rea0ion 0enre% Thi# iniiae# he ele0ron# 5lo$ 7o$n he ET(, energy lo# i# u#e7 o pu4p H8 5ro4 he #ro4a ino he hyla9oi7% Hen0e he in0rea#e in pH in he #ro4a an7 he 7e0rea#e in pH 2in0rea#e in H83 in he hyla9oi7 #pa0e

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2:3 escribe a similarity and a difference in the production of ATP in chloroplasts and in mitochondria. #(% /imilarity 1% Flo$ o5 ele0ron 7o$n he ele0ron ran#por 0hain o5 progre##ively in0rea#ing ele0ronegaiviy% % ;eneraion o5 proon 4oive 5or0e < ele0ro0he4i0al < H8  gra7ien "% 'i55u#ion o5 H8 5ro4 hrough ATP #ynha#e 0o4ple6, energy u#e7 5or he pho#phorylaion o5 A'P o ATP 2re5 o 0he4io#4o#i#, :u R&=u# 0he4io#4o#i# $ihou 7e#0ripion3 ifference

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Phoopho#phorylaion

O6i7aive pho#phorylaion

Ele0ron 7onor 

Rea0ion 0enre 0hlorophyll a  < $aer 

Re7u0e7 0oen>y4e, NA'Hy4e% ;enerae 0o4ple4enary #i09y en7# on :oh 'NA 4ole0ule# $hi0h 0an anneal via hy7rogen :on7# :y 0o4ple4enary :a#e pairing $hen hey are 4i6e7% Liga#e i# a77e7 o #eal ni09# :y 5or4ing 0ovalen pho#pho7ie#er  :on7# :e$een a7=a0en nu0leoi7e#% Thu# a re0o4:inan 'NA 4ole0ule i# 5or4e7 $hi0h i# 4a7e up o5  'NA 5or4  7i55eren #our0e#%  ["K

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3rite your answers on the separate answer paper provided. Gour answers should be illustrated by large, clearly labeled diagrams, where appropriate. Gour answers must be in continuous prose, where appropriate. Gour answers must be set out in sections 2a3, 2:3 etc., as indicated in the question. 2a3 xplain how glucagon differs from glycogen. #6% Poin o5  glu0agon gly0ogen (o4pari#on a3 Type o5 4a0ro4ole0ul

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;lu0agon i# a glo:ular proein%

;ly0ogen i# an e6en#ively :ran0he7 poly#a00hari7e

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e :3 Type o5 4ono4er  03 Type o5 :on7# :e$een 4ono4er 

73 Nu4:er o5 4ono4er per 4ole0ule e3 Solu:iliy in $aer 

4a7e o5 heli0al 0hain#% 2R& #pheri0aly4e3 ?ono4er# are a4ino a0i7 re#i7ue# $ih 7i55eren R group#% A4ino a0i7 re#i7ue#  =oine7 :y pepi7e :on7#%

Alpha glu0o#e =oine7 :y alpha 1) gly0o#i7i0 lin9age# $ih :ran0he7 alpha 1+ gly0o#i7i0 lin9age#%

Fi6e7 nu4:er o5 a4ino a0i7 per 4ole0ule%

aria:le nu4:er o5 glu0o#e per 4ole0ule%

Solu:le in $aer a# i i# glo:ular in #ru0ure%

In#olu:le in $aer a# i ha# a large 4ole0ular $eigh%

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?ono4er# 0on#i## o5 alpha glu0o#e only%

;lu0agon i# pro7u0e7 :y alpha 0ell# in he pan0rea# in he i#le# o5 Langerhan#% g3 Fun0ion ;lu0agon i# a hor4onee7 in liver an7 4u#0le 0ell# $hen :loo7 glu0o#e i# high% ;ly0ogen provi7e# an energy #ore in 4u#0le an7 liver%

". 'eplication begins at a specific site called origin o5 repli0aion. % Heli0a#e un>ip# an7 #eparae# he $o parenal #ran7# of  A double helix :y 7i#ruping he hy7rogen :on7# between complementary base pairs. $. Single#ran7 :in7ing proein# bind to single A strands  9eep he #ran7# apar, so that they can serve as templates for  the synthesis of new complementary A strands. )% ;n each of the parental A strands, a short RNA pri4er is added by an en>yme called pri4a#e% . 'NA poly4era#e adds 'NA nu0leoi7e# 8in the form of 7NTP#9 to the growing new strand in the * o " 7ire0ion. 6. A polymerase uses the parental strand as a e4plae and aligns the free a0ivae7 7NTP#  8deoxyribonucleoside triphosphates9 +. Through 0o4ple4enary :a#epairing with bases on the parental strand. a. A7enine base pairs with hy4ine, and vice versa b. ;uanine base pairs with 0yo#ine, and vice versa *. A polymerase catalyses the formation of pho#pho7ie#er  :on7# :e$een a7=a0en 'NA nu0leoi7e# of the newly synthesised strand. . A 7i55eren A polymerase then removes the 'A primer and repla0e# i $ih 'NA nu0leoi7e#% @ ").one of the daughter strands 0nown as the leading strand will be synthesised continuously from the * o " 7ire0ionJ "". the oher #ran7  0nown as the lagging strand is synthesi>ed discontinuously by 0o4:ining #hor 5rag4en#  called O9a>a9i 5rag4en# & 'I ()"(

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"(. 'NA liga#e catalyses the formation of pho#pho7ie#er :on7 between the O9a>a9i 5rag4en#, #ealing he ni09. "$.replication of A is #e4i0on#ervaive where the original strands of the double helix separates and act as templates for the synthesis of two new strands and each daughter cell inherits a A molecule that is a hybrid consisting of one original and one newly synthesised strandJ 203

xplain how gel electrophoresis can be used to provide evidence of molecular homology.

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1% 'NA poly4orphi#4 e6i## :e$een organi#4#  % 'NA 5rag4en# 5ro4 he 7i55eren organi#4 $a# 0u $ih he #a4e re#ri0ion en>y4e  "% 'NA #a4ple i# loa7e7 ino $ell# ogeher $ih loa7ing 7ye% The loa7ing 7ye i# 7en#e hu# i help# he 'NA #a4ple #in9 ino he $ell# OR a. (Teacher may want to point out that the dyes will  travel along the gel with the DNA but does not bind to the DNA.) :% 'NA #a4ple i# loa7e7 ino $ell# ogeher $ih loa7ing 7ye $hi0h 0onain#  loa7ing 7ye# o help 4onior he progre## o5 ele0rophore#i#, #in0e 'NA :an7# are no vi#i:le% )% The 5rag4en# o5 'NA are pipee7 ino he $ell# a he op o5  he gel in a po#iion 5urhe# 5ro4 he po#iive ele0ro7ee he 0he4i0al rea0ion So4e en>y4e# 0onain anoher #ie 2apar 5ro4 a0ive #ie3 5or  anoher 4ole0ule o :in7 o 20o5a0or#