Matriculation Biology - Molecule of Life

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TOPIC 1 : MOLECULES OF LIFE

Retold by,  Amran Md Said Matriculation College of Pahang SUBTOPIC : ! "ater  !# Carbohydrate$ !% &i'id$ !( Protein !) *ucleic acid$

1.1 WATER

 At the end end of thi$ thi$ to'ic, $tudent$ $tudent$ $hould $hould be able able to: •

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e+'lain the $tructure of ater molecule de$cribe the 'ro'ertie$ of ater and it$ im'ortance

Structure of a ater molecule •

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 A ater molecule molecule con$i$t con$i$t of an o+ygen atom atom and to hydrogen hydrogen atom$ atom$ The to hydrogen atom$ are combined ith the o+ygen atom by $haring of electron$ The three atom$ form a triangle, not a $traight line

The ater molecule i$ electrically neutral but there i$ a net negati-e charge on the o+ygen atom and a net 'o$iti-e charge on both hydrogen atom$!  A molecule carrying $uch an une.ual une.ual di$tribution di$tribution of electrical electrical charge charge i$ called called a 'olar 'olar molecule! The 'o$iti-ely charged hydrogen atom$ of one ater molecule are attracted to the negati-ely charged o+ygen atom$ of nearby ater molecule$ by force$ called hydrogen bond$!

Http://matriculation-biology.blogspot.com •

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/ydrogen bond$ largely account for the uni.ue 'ro'ertie$ of ater! ea0er than co-alent bond$! But 12 $trong enough to hold ater molecule$ together!

Becau$e of their hydrogen bond$, ater molecule$ are attracted to charged 'article$ or charged $urface$!

Pro'ertie$ of ater a$ -ital con$tituent of life 1. Water as a universal solvent •

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'oerful $ol-ent for 'olar $ub$tance$! The$e include ionic $ub$tance$ li0e $odium chloride 3*a 4 and Cl15, and al$o organic molecule$ ith ioni6ed The$e cation$ 3negati-ely charged ion$5 and anion$ 3'o$iti-ely charged ion$5 become $urrounded by a $hell of orientated ater molecule$! Thi$ ma0e$ them more reacti-e chemically than hen they form 'art of an undi$$ol-e $olid!  At the $ame $ame time, non1'olar non1'olar $ub$tance $ub$tance$ $ are re'elled re'elled by ater, ater, a$ in the the ca$e of oil on the $urface of ater! *on1'olar $ub$tance$ are hydro'hobic!

2. Low visosit! o" water  •

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Thi$ uni.ue 'ro'erty ma0e$ it $uitable medium of tran$'ortation in li-ing organi$m$! /el'$ in mo-ement of food $ub$tance$ It al$o can act a$ a lubricant$ in 7oint$

#. $i%& s'ei"i &eat a'ait!

Http://matriculation-biology.blogspot.com •

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/ydrogen bond$ largely account for the uni.ue 'ro'ertie$ of ater! ea0er than co-alent bond$! But 12 $trong enough to hold ater molecule$ together!

Becau$e of their hydrogen bond$, ater molecule$ are attracted to charged 'article$ or charged $urface$!

Pro'ertie$ of ater a$ -ital con$tituent of life 1. Water as a universal solvent •

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'oerful $ol-ent for 'olar $ub$tance$! The$e include ionic $ub$tance$ li0e $odium chloride 3*a 4 and Cl15, and al$o organic molecule$ ith ioni6ed The$e cation$ 3negati-ely charged ion$5 and anion$ 3'o$iti-ely charged ion$5 become $urrounded by a $hell of orientated ater molecule$! Thi$ ma0e$ them more reacti-e chemically than hen they form 'art of an undi$$ol-e $olid!  At the $ame $ame time, non1'olar non1'olar $ub$tance $ub$tance$ $ are re'elled re'elled by ater, ater, a$ in the the ca$e of oil on the $urface of ater! *on1'olar $ub$tance$ are hydro'hobic!

2. Low visosit! o" water  •

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Thi$ uni.ue 'ro'erty ma0e$ it $uitable medium of tran$'ortation in li-ing organi$m$! /el'$ in mo-ement of food $ub$tance$ It al$o can act a$ a lubricant$ in 7oint$

#. $i%& s'ei"i &eat a'ait!

Http://matriculation-biology.blogspot.com •

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 A lot of energy energy i$ re.uired to rai$e the tem'erature tem'erature of ater ater!! Becau$e, much energy i$ needed to brea0 the hydrogen bond$ ! The head ca'acity of ater i$ the amount of head re.uired to rai$e the tem'erature of g of ater by  oC 'er calorie 3cal5 or  cal8g of ater 'er oC Thi$ 'ro'erty of ater i$ 0non a$ it$ high $'ecific heat ca'acity! The $'ecific heat ca'acity of ater i$ the highe$t of any 0non $ub$tance!  A.uatic en-ironment$ en-ironment$ li0e $tream $tream , la0e$ la0e$ and $ea$ $ea$ are all -ery $lo $lo to change change tem'erature hen the $urrounding air tem'erature change$!

(. Latent &eat o" va'ori)ation o" water  •

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"hen 'ure ater i$ heated to 99 oC, it boil$ The ater molecule$ gain $ufficient 0inetic energy to e$ca'e into the air a$ ater -a'or  The heat energy that i$ being u$ed to 'roduce thi$ change i$ called the latent heat of -a'ori6ation "ater ha$ a high latent heat of -a'ori6ation Becau$e  the hydrogen bond$ beteen ater molecule$ ma0e it difficult for them to be $e'arated and -a'ori6ed Thi$ mean$ that much energy i$ needed to turn li.uid ater into ater -a'or! The amount of heat energy needed to melt ice i$ -ery high and the amount of heat that mu$t be remo-ed from ater to turn into ice i$ al$o great! Many li-ing organi$m u$e thi$ feature of ater a$ cooling mechani$m! ;or e+am'le, human $eat  the li.uid ater in $eat $eat ab$orb$ heat energy from the $0in or in tran$'iration from green lea-e$  to $to' the lea-e$< tem'erature from ri$ing

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too high on a hot day *. E""et o" te+'erature on water ,ensit! • •

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Mo$t li.uid$ contract on cooling, reaching their ma+imum den$ity at their free6ing 'oint! "ater i$ unu$ually reaching it$ ma+imum den$ity at (=C!  A$ ater free6e$, the ice formed i$ le$$ den$e than the the cold ater around it! The ice float$ on to'! The floating layer of ice in$ulate$ the ater belo!

Thi$ i$ hy the bul0 of 'ond$, la0e$ or the $ea rarely free6e $olid!  A.uatic life can generally $ur-i-e a free6e1u'!

-. $i%& Sur"ae Tension  a,&esive an, o&esive "ores •

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"ater adhere$ $trongly to mo$t $urface$ It can be dron u' into long column$ through narro tube$ li0e the +ylem -e$$el$ of 'lant $tem$, ithout the ater column brea0ing! Com'ared ith other li.uid$, ater ha$ e+tremely $trong adhe$i-e and cohe$i-e 'ro'ertie$ that 're-ent the column brea0ing under ten$ion! The outermo$t molecule$ of ater form hydrogen bond$ ith ater molecule$ belo them! Thi$ gi-e$ a -ery high $urface ten$ion to ater1 higher than that of any other li.uid e+ce't mercury! Surface $0ate! The in$ect