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Summary AQA A level chemistry amino acids, proteins and DNA revision notes
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A helpful and comprehensive set of revision notes covering the entire amino acids, proteins and DNA unit of AQA A level chemistry
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Bomoleules30.1 AMINO ACIDS
Amno aads contan an amne (-NH,) and a Lauboxyle aud qro up ( C0OH)
conbOxyl
Thee arc 20 natwaly ocurna amino acids
cene al tormwiai
R - The group S valiable and s
H, N-C- Cc ditfe ent n each anno acd
0-H L
the ony achira amiaO ocid
H
glycine 1s
Amine auds n solutim
-CO0H has a tendeu to lose a proton (at as aa oacd]
- Nt has a
Tendlaay to gan a protun (act as a base)
ln neutrw solutn, ions hawe bo th a pemaneat posLtue cnaae c
pemaniat negative charge, thouah the compouad is neutra oueal.
aminO acicl exIst as zwitteiOAS
H R
H-N-c
At aud1c pH (b elow 7.00), At alkal1ne ph labove 7. co),
the amiao acid is protonatedi depotonated
R R
H
H-Nc
o-H H
Be awcr ot aminc auds with tuntiona qrouns on sidi
chaun
eg. cystene the presene of ethant and sulphurie aid
estenticatn reaction oclurs
H
sH
, 30. 2 PoLyPEPLDES
Folyplptide polymer tonved trom aunng acida whee the omine group
condensalion polyme isoton react on
e.g Dipcptide of alansn& and alycine
B,N-c- coOH + H, N-(-CcOH> N-C-C-N-C-C
OH
The revse ot Hh1s readin can as0 04cw- acid catalysedhycoyss
or base cataysed hydrolysis.
eg Ht R0
H,N-C-(-N-c-c H,0 2H,N-(y
H
l: the hydrolysis s atalys ed by oid conditious, Ehe resulting
amind acIds wil be tound in theu protonated form
Protein structure
Proteuns ace poypeph1des used in immunt system, branspo,eeizymes
Prinnesy structut - seguena ot amino acids in the chan
detemines tnad 30 shructurt ot protens.
Seondary structuwe held toqethe du to hudogen bDnda between
peptid (amide)lnles
6 torms K-helices cnd F- pleated sheets
H,N
HO0C
630 HG
letioy stru ctut - more tolding in the shrutut due to nteractios
between mino acd side chains - hydogn bondng, dpali- dipe,
Von de waads, ont inteactios leg.-(0O,-NH), hydophcaic
latuacons, sultur- sultur covaleat bonds betveen custene
o-(H,SH HS CH,
H H
HCoC
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