Introduction to biology I. Nature of biology Studying biology makes us aware of the realms of the living world. (a) Nanobe- smallest organism (b) Blue whale- largest organism (c) Wola globosa- smallest ower (d) !a"esia arnoldii- largest ower #nowle #nowledg dge e of $hys $hysics ics%% mathe mathemat matics ics and chemi chemistr stry y hel$s us understand biology A. Biology as a science science of life life &t is through understanding of what makes such creature an organism Biolog Biologyy- the scienc science e of livin living g thing things' s' has becom become e a frontier frontier of science sciences' s' the study of life. life. &t is a scientic scientic eld eld that that is inte intere rest sted ed in the the form form%% func functi tion on%% and and behavior of all living things. B. Brief history of biology uman umans s began began studyin studying g biology biology in their their desire desire trium$h over creation' initially based on su$erstition
to
(a) i$$ocrates- wrote a book of diseases (b) *ristotle- listed +,, s$ecies of animals (c) heo$rhastus- founded botany and +,, s$ecies of $lants (d) alen- last real biologist of the ancient world (e) *ndrea *ndreas s /esalius esalius-- inaugur inaugurated ated the modern modern era of western medicine (f) 0eonardo da /inci- an artist studying $hysiological and anatomical details (g) *nton van 0eeuwenhoek- initiated microsco$y (h) 1harles 2arwin- on the origin of s$ecies C. Importance of Biology (a) discover the relationshi$s among humans% animals% and $lants (b) 0earn to value life (c) 0earn about sustainable develo$ment (d) 0earn about the need to conserve (e) 3nables us to reali4e economic im$ortance (f) 3nhances our interests and a$$reciation II. What is a living thing? What are the characteristics of life5 0iving organisms are a carbon- and water-based cellula cellularr form form with com$le6 com$le6 organi4 organi4ation ation and heritable heritable genetic information. hey undergo metabolism% $ossess a ca$acity to grow% res$ond to stimuli% re$roduce% and% through natural selection% ada$t to their environment in successive generations. A. Properties of life life 7. 0iving organisms are8 a carbon- and water-based cellular form. 1ell heory
(a) 1ells are basic structural and $hysiological units of all living organisms (b) 1ells are both distinct entities and building block of more com$le6 organisms 9. 0iving organisms8 undergo metabolism !e:uire 3nergy (a) 1ells use nutrients to su$$ly energy and build new structures (b) ;etabolism8 the sum total of chemical reactions that occur in an organism <. 0iving organisms8 res$ond to stimuli !es$ond (a) hel$s ensure the survival of an organism (b) allows an organism to carry on daily activities =. 0ivin 0iving g organ organism isms8 s8 $osses $ossess s a ca$aci ca$acity ty to grow> grow> re$roduce !e$roduce and 2evelo$8 (a) ase6ua ase6uall re$r re$rodu oducti ction on (clon (clonal al re$r re$rodu oducti ction on)8 )8 $roduce e6act re$lica of themselves (b) (b) se6u se6ual al re$r e$roduc oducti tion on (man (many y stra strate tegi gies es)8 )8 e6chang ange of gene enetic tic mate materrial betwe tween organisms +. 0iving organisms have8 heritab table genetic information> through natural selection% ada$t to their environment eredity (a) genome ? all 2N* molecules in a cell (b) ada$ta ada$tatio tion n ? an organ organism ism@s @s modic modicati ation on in structure% function% or behavior suitable to the environment natural natural selectionselection- When ada$tations ada$tations are so benecia beneciall that they are inherited in subse:uent generations A. 0iving organisms have8 com$le6 organi4ation 0ife Science (a) biology is the scientic study of life B. Characteristics of living things (a) cellular organi4ation (b) 0ocomotion (c) &rritability (d) ;atabolism (e) rowth (f) !e$roduction (g) *dustment% integration% ada$tation% coordination C. Life is complex 7. here are levels of life8 small molecules- large molecules- cells- tissues- organs - organ system- com$le6 organisms 9. here is diversity of life8 a. Crokaryotes8 single-celled organisms. each cell is an indi indivi vidu dual al orga organi nism sm that that can can live live and and func functi tion on inde$endently.
(7) 2omain Bacteriaorganisms
consists of all the bacterial
Kames Watson and Drancis 1rick ? discovered 2N* structure
(9) 2omain *rchaea- contains the descendants of the most $rimitive organisms on 3arth
C. !he !heory of 'ere$ity% (a) he genes of any organism are inherited as discrete units (b) hose genes are $ackaged u$ in chromosomes
b. 3ukaryotes8 multi-celled organisms (<) 2omain 3ukarya (a) #ingdom Crotistamulticellularity (b) #ingdom Clantae (c) #ingdom Dungi (d) #ingdom *nimalia
rst
grou$
to
develo$
<. here is ta6onomic order to life8 domain- kingdom- $hylum- class- order- family- genuss$ecies =. here is ecological order to life8 bios$here- region- landsca$e- ecosystem- community$o$ulation- individuals +. 0ife is interconnected and interde$endent8 a. Croducers b. 1onsumers c. 2ecom$osers III. !he scienti"c process o understand such a com$le6 subect% scientists develo$ed the scientic method8 (a) allows scientists to modify and correct their beliefs as new observations and information becomes available (b) if well su$$orted E theoryF Gbservationshy$othesisconclusion- scientic theory
e6$erimentHobservation-
regor ;endel ? ;endelian segregation' rst scientist to suggest how genes are inherited (. !he !heory of )volution% (a) Grganisms that can res$ond to the challenges of living will leave more oLs$ring (b) 2escent with modicationF 1harles 2arwin ? rst scientist to $resent this idea' living organisms are related to one another
#. *cienti"c +etho$ he Scientic ;ethod is a $rocess used to nd answers to :uestions about the world around us. he M-ste$ $rocess to scientic investigations (7) Dormulate a :uestion. What do you want to know or e6$lain5 se observations you have made to write a :uestion that addresses the $roblem or to$ic you want to investigate. (9) !esearch the :uestion. !esearching your :uestion lets you know if others have done this same e6$eriment before and if so% what their data suggests. &f they had a widely acce$ted conclusion% you may want to try a diLerent angle with your e6$eriment or test a diLerent variable. (<)Dorm a hy$othesis. What do you think will ha$$en5 * hy$othesis is your $rediction for the outcome of the e6$eriment. &t is based on your observations and should be testableF
I#. Core I$eas of Biology
here are four maor unifying themes in the study of life.
(=) 1onduct an e6$eriment to test your hy$othesis. 2esign a $rocedure that tests your hy$othesis to see if your $rediction is correct. !ecord all of your data and observations and $ut them into a table that is neat and organi4ed.
A. !he Cell !heory% (a) *ll organisms are com$osed of cells (b) *ll cells come from other cells
(+) *naly4e data. &s your data reliable5 2oes it make sense5 Cut your data into a chart or gra$h and look for any trends.
* theory is a unifying e6$lanation that has been well su$$orted time and time again' statement of fact that has not been dis$roven scientically.
!obert ooke? named cells' the rst scientist to identify a cell' honeycomb *nton van 0eeuwenhoek? the rst to identify bacterial cells% and he called them Iwee animalcules.J B. !he &ene !heory% (a) *ll organisms have a genome (b) *n organism@s genes determine what it will be like (secret codeF)
(A) 2raw 1onclusions. 2o your data and observations su$$ort your hy$othesis5 &f you cannot make a denite conclusion% you may need to try the e6$eriment again. his means you may either need to rewrite your $rocedure if it was not s$ecic enough' you may need to change your hy$othesis. (M) 1ommunicate results. !e$ort the results of your e6$eriment to let others know what you have learned. his will be
re$resented as either a lab re$ort% oral $resentation% or Science Dair dis$lay board. The Cell Theory and the Microscope
7. he cell contains hereditary information(2N*) which is $assed on from cell to cell during cell division. *ome ,an$om Cell -acts 9. *ll cells are basically the same in chemical com$osition (a) he average human being is com$osed of around 7,, and metabolic activities. rillion individual cells.. <. *ll basic chemical O $hysiological functions are carried (b) &t would take as many as +, cells to cover the area of a out inside the cells.(movement% digestion%etc) dot on the letter IiJ =. 1ell activity de$ends on the activities of sub-cellular structures within the cell(organelles% nucleus% $lasma membrane) (iscovery of Cells ow as he 1ell heory Been sed5 he basic discovered truths about cells% are the basis for8 !obert ooke- 7AA+' 3nglish Scientist% discovered cells 2iseaseHealthH;edical !esearch and 1ures(*&2S% while looking at a thin slice of cork' e described the 1ancer% /accines% 1loning% Stem 1ell !esearch% etc.) cells as tiny bo6es or a honeycomb' e thought that cells only e6isted in $lants and fungi *nton van 0euwenhoek- 7AM<' used a handmade microsco$e to observe $ond scum O discovered singlecelled organisms' e called them IanimalculesJ' e also observed blood cells from sh% birds% frogs% dogs% and humans' herefore% it was known that cells are found in animals as well as $lants Between the ookeH0euwenhoek discoveries and the mid 7Pth century% very little cell advancements were made. his is $robably due to belief in S$ontaneous eneration. 36am$les8 ;ice from dirty clothesHcorn husks' ;aggots from rotting meat 0ouis Casteurgeneration
1onclusively
dis$rove
)arly +icroscopes 3arly microsco$e lenses made images larger but the image was not clear Racharias Kanssen - made 7st com$ound microsco$e' a 2utch maker of reading glasses (late 7+,,@s) 0eeuwenhoek- made a sim$le microsco$e (mid 7A,,@s) magnied 9M, 0eeuwenhoekTs microsco$e
s$ontaneous
(evelopment of Cell !heory ;atthias Schleiden- 7Q
*) a screw for adusting the height of the obect being e6amined B) a metal $late serving as the body 1) a skewer to im$ale the obect and rotate it 2) the lens itself% which was s$herical +o$ern +icroscopes 0ens- makes an enlarged image O directs light towards you eye ;agnication- the change in a$$arent si4e $roduced by a microsco$e
!he Cell !heory Complete he < Basic 1om$onents of the 1ell heory were now com$lete8 7. he cell is the basic unit of life in all living things. (ooke)(7AA+) 9. *ll organisms are com$osed of one or more cells. (Schleiden O Schwann)(7Q
total magnication- $owers of the eye$iece (7,) multi$lied by obective lenses sim$le microsco$emagnifying glass
has
one
lens'
Similar
to
a
com$ound microsco$e- has multi$le lenses (eye$iece O obective lenses)
9. 3ukaryote- as several internal structures (organelles)' rue nucleus' 3ither unicellular or multicellular' unicellular e6am$le8 yeast' multicellular e6am$les8 $lants and animals
!he Parts of !he )u1aryotic Cell Stereomicrosco$e- creates a <2 image 3lectron microsco$e- ;ore $owerful' some can magnify u$ to 7%,,,%,,,' se a magnetic eld in a vacuum to bend beams of electrons' &mages must be $hotogra$hed or $roduced electronically Scanning 3lectron ;icrosco$e (S3;)- $roduces realistic <2 image ' only the surface of s$ecimen can be observed ransmission 3lectron ;icrosco$e (3;)- $roduces 92 image of thinly sliced s$ecimen' detailed cell $arts (only inside a cell) can be observed Scanning unneling ;icrosco$e (S;)- able to show arrangement of atoms A View of the Cell (7) (9) (<) (=) (+)
Cellular rgani/ation 1ell- basic unit of an organism issue ? grou$ of cells functioning together. Grgan ? grou$ of tissues functioning together. Grgan System ? grou$ of organs functioning together. Grganism ? grou$ of organ systems functioning together.
7. Boundaries (a) Clasma ;embrane- serves as a boundary between the cell and its e6ternal environment' *llows materials to $ass in and out of the cell. (b) 1ell Wall- surrounds the $lasma membrane of the cells of $lants% bacteria% and fungi' Clant cell walls contain cellulose while fungi cell walls contain chitin. 9. 1ontrols (a) Nucleus- !egulates cell function' Surrounded by a double-layered membrane (nuclear envelo$ed) with large $ores that allow materials to $ass in and out of the nucleus' 1ontains chromatin ? long tangles of 2N*. (b) Nucleolus- Dound in the nucleus and res$onsible for ribosome $roduction. !ibosomes are the sites of $rotein $roduction. <. *ssembly (a) 1yto$lasm- he elly-like material that surrounds the organelles. =. rans$ort
+icroscopes an$ Cells *nton van 0eeuwenhoek- 7A,,@s' rst described living cells as seen through a sim$le microsco$e. !obert ooke- used the rst com$ound microsco$e to view thinly sliced cork cells' was the rst to use the term IcellJ. ;athias Schleiden- 7Q<,@s' identied the rst $lant cells and concluded that all $lants made of cells. homas Schwann- made the same conclusion about animal cells.
Cell !heory% (7) *ll organisms are made u$ of one or more cells. (9) he cell is the basic unit of organi4ation of all organisms. (<) *ll cells come from other cells all ready in e6istence. !0o Basic Cell !ypes 7. Crokaryote- 0acks internal com$artments' No true nucleus' ;ost are single-celled (unicellular) organisms' 36am$les8 bacteria
(a) 3ndo$lasmic reticulum- Dolded membrane that acts as the cell@s delivery system. Smooth 3.!. contains en4ymes for li$id synthesis. !ough 3.!. is studded with ribosomes for $rotein synthesis. (b) olgi a$$aratus (or olgi body)- * series of attened sacs where newly made li$ids and $roteins from the 3.!. are re$ackaged and shi$$ed to the $lasma membrane. +. Storage (a) /acuoles- * sac of uid surrounded by a membrane used to store food% uid% or waste $roducts. (b) 0ysosomes- 1ontain a digestive en4yme' 1an fuse with vacuoles to digest food% or can digest worn cell $arts' *lso known as Isuicide sacsJ because they can also destroy the whole cell. A. 3nergy ransformers (a) ;itochondria- Croduce the energy for the cell' *lso known as the I$owerhouse of the cell' as a highly folded inner membrane (cristae). (b) 1hloro$lasts- Dound in $lant cells and some $rotists' ransforms light energy into chemical energy which is stored in food molecules'
1ontain chloro$hyll ? a green $igment that tra$s light energy and gives $lants their green color. M. Su$$ort (a) 1ytoskeleton- * network of thin% brous materials that act as a scaLold and su$$ort the organelles. ;icrotubules ? hollow laments of $rotein. ;icrolaments ? solid laments of $rotein.
dividing. his is mainly due to the synthesis of $roteins% !N* and 2N*. his is followed by division of the cell nucleus (karyokinesis) and nally the division of the cell cyto$lasm (cytokinesis). *ll these events collectively form a cell cycle.
Q. 0ocomotion (a) 1ilia- Short% numerous% hair-like $roections from the $lasma membrane' ;ove with a coordinated beating action. (b) Dlagella- 0onger% less numerous $roections from the $lasma membrane' ;ove with a whi$like action. P. 1ell 2ivision (a) 1entrioles- made of $rotein' $lay a role in the s$litting of the cell into two cells' found in animal and fungi cells.
he cell cycle% also called generation time% is the se:uence of events in the life of a cell. he cell cycle starts immediately after one cell division and ends with the com$letion of the ne6t division. !he cell cycle of eu1aryotic cells is classi"e$ into 7. &nter$hase- the $re$aratory $hase during which the cell is metabolically very active and $re$ares itself for the division. hree im$ortant $rocesses occur in inter$hase% a. re$lication of chromosomal 2N*% synthesis of !N* and the basic nuclear $roteins (histones) b. synthesis of energy rich com$ounds which $rovide energy for mitosis and c. in animal cells% division of the centriole.
Cell Division he cell is the structural and functional unit of life. New cells arise from the $ree6isting ones. he $rocess by which new cells are formed from the $re-e6isting cells is called cell division. &n unicellular organisms% the cell division directly $roduces two individuals and thus% re$resents a ty$e of re$roduction (multi$lication). &n multicellular organisms% there are two ty$es of cells' the somatic cells or the body cells (which form the body of the organism) and the re$roductive cells (such as gamete-$roducing cells and-s$ore $roducing cells). he somatic cells divide by mitosis (e:uational division) and the re$roductive cells divide by meiosis (reduction division). ;itosis hel$s in growth and develo$ment of an organism. ;eiosis $roduces gametes in se6ual re$roduction and s$ores in ase6ual re$roduction. *ll eukaryotic organisms% $lants as well as animals% show great regularity as well as similarity in the cell divisions. enerally% a cell increases in si4e before
Gn the basis of 2N* synthesis% inter$hase is subdivided into following three stages8 a. 7 (a$7) 8 &t starts immediately after the $revious division. herefore 7 is called ga$ $hase or rst growth $hase. Synthesis of $roteins and !N* takes $lace. he cell grows in volume. b. S $hase (Synthesis $hase) 8 &t is the $eriod during which 2N* synthesis occurs% i.e. re$lication of chromosomal 2N* takes $lace. his results in doubling of the chromosomal threads. c. 9 (a$ 9) 8 &t is the last $art of inter$hase and occurs ust before the new cell division. ence 9 is called $redivision ga$ $hase or second growth $hase. &t begins after com$letion of 2N* synthesis in the S $hase and ends when new division (karyokinesis) commences. 2uring 9% synthesis of $roteins and !N* takes $lace and the nuclear volume increases. 9. #aryokinesis- the division of the $arent nucleus into daughter nuclei. <. 1ytokinesis- the division of the cyto$lasm. &t occurs after karyokinesis and divides the $arent cell into daughter cells. #aryokinesis and cytokinesis together form the ; $hase (i.e. cell division). he total duration of a cell cycle varies greatly in diLerent organisms and under diLerent conditions% e.g. it may be as short as 9,-<, minutes in the bacterium
3scherichia coli or may take 79-9= hours as in most (a) 1hromosomes uncoil higher $lants and animals. (b) S$indle bres disintegrate (c) 1entrioles re$licate he time re:uired for com$letion of each $hase in the (d) Nucleur membrane forms cell cycle varies greatly. &n general% actual cell division (e) 1ell divides (;-$hase) occu$ies only a short s$an of the total cycle while the maor s$an is occu$ied by the inter$hase. *tages of mitosis Normally% time duration of S and 9 $hases is more or (7) 3arly $ro$hase- 2N* begins to condense less e:ual. he duration of 7 is longer in cells which do (9) 0ate $ro$hase- centriole $airs move a$art' nuclear not divide fre:uently% and is very short in cells which envelo$e starts to break u$ divide re$eatedly in close succession. (<) ransition to meta$hase- s$indle a$$aratus form , stage 8 &t is a stage during which cell cycle is (=) ;eta$hase- chromosomes line u$ at the s$indle e:uator. (+) *na$hase- sister chromatid (2N*) move a$art arrested for an indenite $eriod. (A) elo$hase- cyto$lasmic division occurs (M) &nter$hase- cytokinesis' after mitosis% two di$loid *igni"cance of cell cycle daughter cells have formed. (7) &n multicellular organism% the Tcycling ty$eT of cells (dividing cells) hel$ in re$roduction% growth and re$lacement of dead cells% healing of wounds% etc. (9) he inter$hase allows time for synthesis and growth of the dividing cell. (<) Cro$erly controlled and regulated cell cycle results in normal and $ro$ortionate growth of organisms. (=) 0oss of control over the cell cycle can lead to cancerous growth ;itosis-division of somatic (body) cells. ;eiosis-division of gametes (se6 cells) +itosis U;itosis is an e:uational division% dividing the mother cell into two daughter cells which are identical to each other and also to the original mother cell in every res$ect. &n mitosis% the chromosomes of the mother cell are du$licated and distributed e:ually to the two daughter cells.U Stages of ;itosis (&C;*) 7. &nter$hase- $hase of mitosis where the cell $erforms its normal activities for life' 2N* is in the chromatin state' &nteresting things ha$$enF (a) 1ell $re$aring to divide (b) enetic material doubles 9. Cro$hase- 1hromosome $air u$F (a) 1hromosomes thicken and shorten' become visible' 9 chromatids oined by a centromere (b) 1entrioles move to the o$$osite sides of the nucleus (c) Nucleolus disa$$ears (d) Nuclear membrane disintegrate <. ;eta$hase-1hromosomes meet in the middleF (a) 1hromosomes arrange at e:uator of cell (b) Become attached to s$indle bres by centromeres (c) omologous chromosomes do not associate =. *na$hase- 1hromosomes get $ulled a$art' S$indle bres contract $ulling chromatids to the o$$osite $oles of the cell +. elo$hase- Now there are twoF
*ummary of mitosis (7) &t can take $lace in ha$loid as well as di$loid cells. (9) Both the daughter cells formed through mitosis receive similar characters and number of chromosomes as that of the mother cell. (<) he original structure of the chromosomes remains unchanged in both the daughter nuclei. (=) ence% it is an e:uational division and the resulting daughter cells are identical :ualitatively and :uantitatively.
*igni"cance of +itosis (7) &t is an e:uational division which maintains e:ual distribution of the chromosomes after each cell cycle. (9) he resulting daughter cells inherit identical chromosomal material (hereditary material) both in :uantity (i.e.% number) and :uality (i.e.% genetic make u$ or characters). (<) ;itosis maintains a constant number of chromosomes in all body cells of an organism.
(=) &t hel$s to maintain the e:uilibrium in the amount of 2N* and !N* contents of a cell% as well as the nuclear and cyto$lasmic balance in the cell. (+) 2ead cells are re$laced by newly formed cells through mitosis. &t thus hel$s in the re$air of the body. (A) &t hel$s ase6ual re$roduction% growth and develo$ment of organisms. +eiosis &n the se6ually re$roducing organisms% two im$ortant $henomena regulate the number of chromosomes in the life cycle. hese are meiosis and fertili4ation. ;eiosis is the reduction division in which the di$loid (9n) number of chromosomes is reduced to ha$loid (n) during gamete formation (or s$ore formation). Whereas% in fertili4ation% the two ha$loid gametes fuse to form a di$loid 4ygote. &n this way% the di$loid condition is restored again in the life cycle.
<. he karyokinesis of meiosis consists of two com$lete nuclear divisions called rst meiotic division (;eiosis-& or ;-&) and second meiosis division (;eiosis-&& or ;-&&). =. ;-& is reduction division involving se$aration of homologous chromosomes. +. ;-&& is e:uational division like mitosis which involves du$lication of chromosomes. A. he four daughter nuclei are ha$loid due to the reduction division (;-&). ;oreover% they diLer from each other in the characters of chromosomes due to @crossing over@ during Cro$hase-& of ;-&. M. 1ytokinesis may be successive or simultaneous dividing the di$loid mother cell into four ha$loid daughter cells.
U;eiosis is a s$ecial ty$e of division characteristic of re$roductive cells in which the di$loid number of chromosomes is reduced to ha$loid in the daughter cells. &n meiosis% chromosomes divide once while the nucleus (and in some cases the cyto$lasm also) divides twice. Dour ha$loid daughter cells result from one di$loid mother cell. hese diLer from each other as well as from the mother cell.U ;eiosis- = daughter cells $roduced' 3ach daughter cell has half the chromosomes of the $arent' 9 sets of cell division involved
*ummary of 7. ;eiosis occurs in re$roductive cells only. 9. &t occurs in di$loid cells.
+eiosis
The Chemical Basis of Life
*G;S *N2 ;G03103S 9.7 he emergence of biological function starts at the chemical 3verything an organism is and does de$ends on chemistry 1hemistry is in turn de$endent on the arrangement of atoms in molecules &n order to understand the whole% biologists study the $arts (reductionism) ;olecules and ecosystems are at o$$osite ends of the biological hierarchy' -3ach level of organi4ation in the biological hierarchy builds on the one below it' - *t each level% new $ro$erties emerge
9.< 3lements can combine to form com$ounds 1hemical elements combine in 6ed ratios to form com$ounds' 36am$le8 sodium V chlorine sodium chloride 9.= *toms consist of $rotons% neutrons% and electrons he smallest $article of an element is an atom 2iLerent elements have diLerent ty$es of atoms *n atom is made u$ of $rotons and neutrons located in a central nucleus he nucleus is surrounded by electrons 3ach atom is held together by attractions between the $ositively charged $rotons and negatively charged electrons Neutrons are electrically neutral *toms of each element are distinguished by a s$ecic number of $rotons - he number of neutrons may vary - /ariant forms of an element are called isoto$es' Some isoto$es are radioactive
9.A 3lectron arrangement determines the chemical $ro$erties of an atom 3lectrons are arranged in shells -he outermost shell determines the chemical $ro$erties of an atom -&n most atoms% a full outer shell holds eight electrons *toms whose shells are not full tend to interact with other atoms and gain% lose% or share electrons
9.9 0ife re:uires about 9+ chemical elements * chemical element is a substance that cannot be broken down to other substances by ordinary chemical means *bout 9+ diLerent chemical elements are essential to life 1arbon% hydrogen% o6ygen% and nitrogen make u$ the bulk of living matter% but there are other elements necessary for life oiters are caused by iodine deciency
9.M &onic bonds are attractions between ions of o$$osite charge When atoms gain or lose electrons% charged atoms called ions are created - *n electrical attraction between ions with o$$osite charges results in an ionic bond Sodium and chloride ions bond to form sodium chloride% common table salt 9.Q 1ovalent bonds% the sharing of electrons% oin atoms into molecules Some atoms share outer shell electrons with other atoms% forming covalent bonds - *toms oined together by covalent bonds form molecules ;olecules can be re$resented in many ways - molecular formula% electron conguration% structural formula 9.P Water is a $olar molecule *toms in a covalently bonded molecule may share electrons e:ually% creating a non$olar molecule &f electrons are shared une:ually% a $olar molecule is created &n a water molecule% o6ygen e6erts a stronger $ull on the shared electrons than hydrogen - his makes the o6ygen end of the molecule slightly negatively charged - he hydrogen end of the molecule is slightly $ositively charged 9.7, Gverview8 Water@s $olarity leads to hydrogen bonding and other unusual $ro$erties
he charged regions on water molecules are attracted to the o$$ositely charged regions on nearby molecules - his attraction forms weak bonds called hydrogen bonds 0ike no other common substance% water e6ists in nature in all three $hysical states8 solid% li:uid% gas
9.7+ he chemistry of life is sensitive to acidic and basic conditions * com$ound that releases V ions in solution is an acid% and one that acce$ts V ions in solution is a base *cidity is measured on the $ scale8 ,-M is acidic % Q-7= is basic ' Cure water and solutions that are neither basic nor acidic are neutral% with a $ of M
9.77 ydrogen bonds make li:uid water cohesive 2ue to hydrogen bonding% water molecules can move from a $lant@s roots to its leaves &nsects can walk on water due to surface tension created by cohesive water molecules 9.79 Water@s hydrogen bonds moderate tem$erature &t takes a lot of energy to disru$t hydrogen bonds - herefore water is able to absorb a great deal of heat energy without a large increase in tem$erature - *s water cools% a slight dro$ in tem$erature releases a large amount of heat - * water molecule takes a large amount of energy with it when it eva$orates' this leads to eva$orative cooling 9.7< &ce is less dense than li:uid water ;olecules in ice are farther a$art than those in li:uid water - &ce is therefore less dense than li:uid water% which causes it to oat - &f ice sank% it would seldom have a chance to thaw - Conds% lakes% and oceans would eventually free4e solid 9.7= Water is a versatile solvent Solutes whose charges or $olarity allow them to stick to water molecules dissolve in water - hey form a:ueous solutions
1ells are ke$t close to $ M by buLers BuLers are substances that resist $ change - hey acce$t V ions when they are in e6cess and donate V ions when they are de$leted - BuLers are not fool$roof
9.7M 1hemical reactions rearrange matter &n a chemical reaction8 - reactants interact - atoms rearrange - $roducts result - 0iving cells carry out thousands of chemical reactions that rearrange matter in signicant ways