AP Biology Outline on Cell Unit

7/23/2019 AP Biology Outline on Cell Unit

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UNIT 3 – CELL BIOLOGY

THEMES COVERED:1. SCIENCE AS A PROCESS: The disc!e"# $%d e$"&# s'(d# )

ce&&s *"+"essed ,i'h 'he i%!e%'i% $%d i-*"!e-e%' )'he -ic"sc*es.

. EVOLUTION: The -$'chi%+ -$chi%e"# ) $&& e(/$"#'icce&&s e!ide%ces $ 0"$d e!&('i%$"# c%%ec'i% 0e',ee%e(/$"#'es.

. RELATIONSHIP O2 STRUCTURE TO 2UNCTION: M$%# ) 'hece&& "+$%e&&es sh, c&e$" c""e&$'i% 0e',ee% s'"(c'("e$%d )(%c'i%.

. SCIENCE AND TECHNOLOGY4 AND SOCIETY: Ad!$%ces i%c$%ce" "ese$"ch de*e%d % *"+"ess i% (" 0$sic(%de"s'$%di%+ ) h, ce&&s ,"/.

CHAPTER 5 – A TOUR O2 THE CELL

OB6ECTIVE 7UESTIONS:H, 8e S'(d# Ce&&s

1. Distinguish between magnifcation and resolving power.2. Describe the principles, advantages, and limitations o the lightmicroscope, transmission electron microscope, and scanningelectron microscope.

3. Describe the major steps o cell ractionation and explain why itis a useul techniue.

A P$%"$-ic Vie, ) 'he Ce&&!. Distinguish between pro"aryotic and eu"aryotic cells.#. $xplain why there are both upper and lower limits to cell si%e.&. $xplain the advantages o compartmentali%ation in eu"aryotic

cells

The N(c&e(s $%d Ri0s-es'. Describe the structure and unction o the nuclear envelope,

including the role o the pore complex.(. )rie*y explain how the nucleus controls protein synthesis in the

cytoplasm.+. $xplain how the nucleolus contributes to protein synthesis.



1. Describe the structure and unction o a eu"aryoticribosome.

11. Distinguish between ree and bound ribosomes in terms olocation and unction.

The E%d-e-0"$%e S#s'e-12. -ist the components o the endomembrane system, anddescribe the structure and unctions o each component.

13. ompare the structure and unctions o smooth and rough$/.

1!. $xplain the signifcance o the cis and trans sides o the0olgi apparatus.

1#. Describe three examples o intracellular digestion bylysosomes.

1&. ame three dierent "inds o vacuoles, giving the unctiono each "ind.

O'he" Me-0"$%(s O"+$%e&&es1'. )rie*y describe the energy conversions carried out by

mitochondria and chloroplasts.1(. Describe the structure o a mitochondrion and explain the

importance o compartmentali%ation in mitochondrial unction.1+. Distinguish among amyloplasts, chromoplasts, and

chloroplasts.2. dentiy the three unctional compartments o a chloroplast.

$xplain the importance o compartmentali%ation in chloroplastunction.

21. Describe the evidence that mitochondria and chloroplastsare semiautonomous organelles.

22. $xplain the roles o peroxisomes in eu"aryotic cells.

The C#'s/e&e'%23. Describe the unctions o the cytos"eleton.2!. ompare the structure, monomers, and unctions o

microtubules, microflaments, and intermediate flaments.2#. $xplain how the ultrastructure o cilia and *agella relates

to their unctions.

Ce&& S(")$ces $%d 6(%c'i%s2&. Describe the basic structure o a plant cell wall.2'. Describe the structure and list our unctions o the

extracellular matrix in animal cells.2(. $xplain how the extracellular matrix may act to integrate

changes inside and outside the cell.2+. ame the intercellular junctions ound in plant and animal

cells and list the unction o each type o junction.



I. OVERVIE8 9The Ce&& The"#:• 4ll organisms are made up o cells

• ells are the simplest collection o matter that can live 5 thebasic units o structure and unction in living organisms

• 4ll cells are related by their descent rom earlier cells, however,they were modifed in may dierent ways during the longevolutionary history o lie

II. MICROSCOPY AND OTHER TOOLSA. Li+h' -ic"sc*e:

• 6isible light is passed through the specimen and then through

glass lenses. 7he lenses reract the light that he image ismagnifed and projected into the eye or onto a photographic flmor digital sensor.

YOU MUST KNOW THE PARTS OF THE MICROSCOPE

• 7wo important parameters o light microscopes8o M$+%i;c$'i% 5 the ratio o an object9s image si%e to its

real si%e :to get it, multiply the magnifcation o theobjective lens and the eyepiece; 5 light microscopes aremost eective up to <1 o magnifcation

o Res&('i% 5 the measure o the clarity o the image :the

minimum distance that still distinguishes two points asseparate;. 7he maximum resolution o light microscopesis about 2 nm.

B. E&ec'"% -ic"sc*e 9EM

• =ocuses a beam o electrons through a specimen or onto itssurace and is able to have a resolution o about .2 nm.

• 7he two basic types o electron microscopes8o Sc$%%i%+ e&ec'"% -ic"sc*es 9SEM – excellent to

study the surace o the specimen that has to be coatedwith gold. >rovides a three dimensional images o dead

specimens.o T"$%s-issi% e&ec'"% -ic"sc*e 9TM – $xcellent

device to study the internal structure o the specimen thatmust be stained with heavy metals. 7he specimen alsomust be dead. 0ives two?dimensional images.

C. Ce&& 2"$c'i%$'i% 9Ce%'"i)(+es



• Ce&& 2"$c'i%$'i% 5 ta"ing cells apart and separate the majororganelles rom one another by their dierent densities and si%e.

• 7his procedure is done by centriuges. U&'"$ce%'"i)(+es arethe most powerul ones o these machines that can apply orcesthat are 1 million times the orce o gravity.

III. PRO<ARYOTES AND EU<ARYOTES

• 4ll cells contain the same general eatures such as a plasmamembrane, cytosol where the organelles are ound,

chromosomes that carry D4 and all o them have ribosomes toperorm protein synthesis.

• 7hree structural units are ound in every cell8o P&$s-$ -e-0"$%e o N(c&e(s 9%(c&eid o C#'*&$s-



• P"/$"#'es – single celled organisms in which the D4 isconcentrated around a %(c&eid region but they are lac"ing amembrane that separates the D4 rom the rest o the cell.@any other organelles are also missing. Ai%e8 1?1 Bm. 7wodomains o pro"aryotes are )acteria and 4rchaea.

• E(/$"#'es – have true nuclei that are bounded by a nuclearenvelope. 7he region between the nucleus and the cellmembrane is called c#'*&$s- :pro"aryotes also have it;. 7hese cells also have a large number o organelles. Ai%e8 1 51 Bm.

• 7he si%e dierences are the result o the various metabolicreuirements. ells cannot grow larger than the speed o gasexchange and nutrient 5 waste exchange between the borderand the inside o the cell. Crganelles9 compartmentali%ationhelps this process in eu"aryotes, so they can have a larger cell. 7he surace to volume ratio is a actor that will limit cell si%e.





6. 7$ E-$EA• 7he nucleus contains most o the genes o an eu"aryotic cells

:some genes are ound in the mitochondria and chloroplasts;• t is enclosed by the nuclear envelope 5 a double membrane,

each with a phospholipid bilayer and proteins. 7he envelope alsocontains pores that are lined with a pore complex o proteins. 7his complex regulates what enters and leaves the cell.

• 7he nuclear side o the envelope is lined by a %(c&e$" &$-i%$ :networ" o protein flaments; that extend inward into thenuclear matrix.

• Ch"-s-es 5 tightly pac"ed D4 are ound in the nucleus:!& or humans or 23 pairs, egg and sperm cells have hal;



• N(c&e&(s 5 densely stained granules and fbers in the center oa nondividing nucleus that assembles r/4 and its proteincomponents to orm the large and small subunit o ribosomes.

6. /)CAC@$A• 6ery small particles that are made up o r/4 and proteins. 7hey

are assembled rom a small and large subunit.• Aome ribosomes are ree *oating in the cytoplasm while others

are bound to the nuclear envelope or to the endoplasmicreticulum. =ree ribosomes ma"e proteins that unction in the

cytoplasm, while bound ribosomes ma"e proteins that either areattached to membranes or are pac"aged into membranestructures.



6. 7$ $DC@$@)/4$ AFA7$@• E%d-e-0"$%e s#s'e- – many dierent membranes in the

cytoplasm o an eu"aryotic cell that carry out a wide range ounctions. $ach membrane is related to the others by eitherdirect contact or by exchange o materials through !esic&es

• 7his system includes the endoplasmic reticulum, nuclearenvelope, 0olgi apparatus, lysosomes, vacuoles, and even the

cell membrane

4. 7he $ndoplasmic /eticulum



• 4n extensive networ" o tubules and sacs :cisternae; that iscontinuous with the nuclear envelope

• R(+h e%d*&$s-ic "e'ic(&(- 9RER 5 exists as *attened,*uid?flled, membrane sacs that are interconnected. tsappearance is due to the large number o ribosomes on itssurace. 4lmost all o the proteins o the cell are entered througha pore into the lumen o the /$/ where they are olded into their3D shape and other nonprotein parts are attached to them. /$/also provides catalytic suraces or some o the chemicalactivities o the cell. 7he proteins are than pac"aged into'"$%s*"' !esic&es and moved to various parts o the cell or outo the cells :secretory proteins;. 7he rough $/ is also the main



membrane actory o the cell where membrane proteins andphospholipids are made.

• S-'h e%d*&$s-ic "e'ic(&(- 9SER 5 lac"s ribosomes andhas a more tubular surace. >articipates in synthesis o lipids:oils, phospholipids, sterols;, metabolism o carbohydrates,

detoxifcation o drugs and poisons by ma"ing them more watersoluble so they can be easily *ushed through the body. A$/ isalso important in storing calcium ions that are vital or normalnerve and muscle unction.

). 7he 0olgi 4pparatus

• 6esicles ship many o the products o the endoplasmic reticulumhere or urther processing. 7his is the manuacturing, storingand shipping center o the cell. Aecretory cells are especiallyrich in 0olgi apparatus.

• t is made up o a stac" o *attened membranous sacs

:cisternae; that are surrounded by transport vesicles.• 7he 0olgi apparatus has a distinct polarity because o its

dierent molecular composition. 7he cis ace o the apparatus isthe receiving end that is located near the $/. 6esicles comingrom the $/ empty their contents on the cis end.

• @olecules are modifed during their trip rom the cis to the transend o the 0olgi apparatus. @olecules that are modifed hereinclude carbohydrates, phospholipids and membrane proteins.



4lso molecular identifcation tags are reuently added tomolecules here.

• 7he trans end is the shipping end o the 0olgi that gives rise tonew vesicles and ship molecules to various other parts o thecell.

• Aome polysaccharides :pectin; that are released by the cell arealso made here in the 0olgi apparatus.

. -ysosomes

• 4 &#ss-e is a membraneous sac o hydrolytic en%ymes thatan animal cell uses to digest all "inds o macromolecules. 7heseen%ymes wor" best in an acidic environment. -arge amount othese en%ymes lea"ing out into the cytoplasm can destroy thecell.

• -ysosomes carry out intracellular digestion or a variety o

reasons8o Digest ood particles ta"en in by *h$+c#'sis

o )rea" down old cell organelles and recycle some o theircomponents 5 $('*h$+#

• Aome diseases result when the lysosomes lac" hydrolyticdigestion en%ymes and the cell overcomes with indigestiblesubstances :7ay?Aachs disease;



D. 6acuoles

• Plant and fungi cells have one or several vacuoles.

• 2d !$c(&es 5 ormed by phagocytosis

• C%'"$c'i&e !$c(&es – pump excess water out o the cell tomaintain stable water and salt balance :unicellular animals canhave it as well;

• Ce%'"$& !$c(&es – ound in mature plant cells and enclosed bya membrane called '%*&$s'. 7he large central vacuole ormsrom the usion o smaller vacuoles. )ecause o the selectivepermeability o the tonoplast, the vacuole has a dierent solutecomposition than the cytoplasm. 7he central vacuole can act as

a storage compartment o organic or inorganic substances, canbe a pigment storage place and result in various colors o *owersor can assemble poisons to protect the plant. 7heir enlargementcan grow plant cells.

6. $$/0F >/C$AA0 C/04$--$A



• n eu"aryotic cells -i'ch%d"i$ and ch&"*&$s's are theorganelles that convert energy to orms that cells can use orwor". )oth o these organelles are enclosed by a doublemembrane system and most o their proteins are made by reemoving ribosomes that are not attached to the $/ or by

ribosomes that are inside o these organelles. 7hey both alsohave their own D4 that program the synthesis o their proteins.

• Pe"=is-es 5 oxidative organelles that are also not part o theendomembrane system

4. @itochondria

• =ound in almost all eu"aryotic cells, their numbers correlate tothe cell9s level o metabolic activity. 7hey are actively movingand dividing organelles that also change shape easily and

reuently.• Label and draw the structure by using the gure above

• 7he matrix o the mitochondrion contains many dierenten%ymes that are mostly related to cellular respiration including47> synthase, an en%yme that ma"es 47> molecules and isimbedded into the inner membrane.



). hloroplasts

• >art o the amily o *&$s'ids8o A-#&*&$s' 5 stores starch

o Ch"-*&$s' 5 stores colored pigments o ruits and*owers

o Ch&"*&$s' 5 contains the green pigment chlorophyll,photosynthetic en%ymes and other molecules that arenecessary or photosynthesis.

• Label and draw the structure by using the picture above

• 7he *uid outside the 'h#&$cids contains en%ymes, D4.

• hloroplasts are the main organs o photosynthesis.

• 7hey are also actively moving in the cell, changing shape anddivide.

. >eroxisomes• 4 single membrane organelle that contains powerul oxidative

en%ymes that transer hydrogen rom various substances tooxygen and produce hydrogen peroxide.

• 7hey can brea" atty acids down, beore the brea"down productsenter the mitochondria or cellular respiration, they can detoxiyalcohol and other poisons.



• 7hey contain catalase en%yme that brea"s down 2C2 toeventually produce water.

6. 7$ F7CAG$-$7C• C#'s/e&e'% is a networ" o fbers that extend throughout the

cytoplasm. t plays a major role in organi%ing the structures andactivities o the cell.

• t is composed o three "inds o structures8o @icrotubuleso @icroflamentso ntermediate flaments

• =unctions o the cytos"eleton8o Aupports the cell and maintains its shapeo >rovides anchorage or many cell organelles and en%yme

moleculeso

nvolved in many "inds o movements o the cell itsel orparts o it. 7hey wor" together with motor proteins toaccomplish this motion

o 7hey also perorm the streaming o the cytoplasmo /egulate biochemical processes in the cell

4. @icrotubules

• =ound in the cytoplasm o all eu"aryotic cells

• ollow rods, 2# nm in diameter and about 2nm 5 2# Bm inlength

• 7heir wall is constructed rom a globular protein called '(0(&i% that is composed o two dierent polypeptide chains :dimmers;

• 7hese tubulin dimmers can be ta"en apart and rearranged againin a new location in the cell

• @icrotubules shape and support the cell and orm trac"s to movemotor proteins



• Ce%'"s-es $%d ce%'"i&es 5 the centrosome is amicrotubule organi%ing center. n the centrosome o animal cellsare a pair o centrioles that are each composed o nine triplets omicrotubules 5 these duplicate beore the cell divides

• Ci&i$ 9si%+. Ci&i(- $%d 2&$+e&&$ 9si%+. 2&$+e&&(- – -ocatedoutside o the cells, these organelles move the cell or can movesubstances on the surace o the cell. =ound in many unicellularorganisms such as $uglena :*agellum; and >aramecium :cilia; orin many cells o multicellular organisms :sperm cells, cells o theoviduct, windpipe etc;. ilia are usually short and there aremany o them on the cell9s surace while *agella are ewer butlonger. ilia has a bac"?and?orce motion while *agella has anudulating motion.

• 7he ultrastructure o cilia and *agella are the same. 7hey have acore o + pairs H 2 single central microtubules that are coveredby an extension o the plasma membrane. 7his arrangement omicrotubules is uniorm in eu"aryotes but dierent inpro"aryotes. =lexible proteins connect the pairs o microtubulesto each other li"e wagon?wheels. 7he cilium and *agellum areanchored in the cell by a 0$s$& 0d# which is identicalstructurally to the centriole :it enters the egg rom the sperm andbecomes the centriole o the developing embryo;. 7he proteinthat extends rom one pair o microtubules to the next is calledd#%ei%, which is a complex protein with several polypeptide

chains. Dynein proteins bend the cilia and *agella microtubulesby using 47> and cause the movement o these organelles.



Watch:http://programs.northlandcollege.edu/biology/Biology1111/animations/agellum.html

B. Mic";&$-e%'s• Aolid rods, about ' nm in diameter

• 7hey are built o the globular protein called $c'i%

• 7he actin molecules orm two long chains that twist together.Aome other proteins can orm cross bindings between theactin molecules so this way microflaments can orm networ"sas well.

• 7he 3D networ" o actin flaments help to support the shapeo the cell. 7hey also ma"e up the core o microvilli that helpto enlarge the cell9s surace or ma"ing transport o materials

more eIcient.• @icroflaments also orm the contractile structure o muscles

where they are connected to a thic"er protein called -#si%.

• 7he contraction o the actin?myosin complex is also importantin amoeboid movement 9*se(d*ds and in cytoplasmicstreaming

http://programs.northlandcollege.edu/biology/Biology1111/animations/flagellum.html






!igure ".#$%ytoplasmic streaming: http://www.youtube.com/watch&v'"h()i)*+**, -moeboid movement: http://www.youtube.com/watch&v'$p$0()p-

C. I%'e"-edi$'e 2i&$-e%'s:

• 7heir diameter is ( 5 12 nm

• 7hey are speciali%ed or bearing tension, they reinorce the

structure o cells and "eep organelles in position, they also ma"eup the nuclear lamina

• 7hey are ormed rom a wider range o proteins and are morepermanent fxtures in the cell.

<. $<7/4$--E-4/ C@>C$7A4. ell Jalls o >lants• 7his extracellular structure is not ound in animals. n plants the

cell wall protects the cell, maintains its shape, preventsexcessive water upta"e. 7he cell wall also holds the entire plantagainst the orce o gravity

• =ungi, protists, pro"aryotes also have cell walls but they aredierent in composition

• 4lthough the composition o the plant cell wall can vary romspecies to species, the general structure is basically the sameamong all plants. @icrofbrils o cellulose are imbedded into amatrix that is made up o other polysaccharides and proteinscompose the main structure o the cell wall.

• P"i-$"# ce&& ,$&& 5 created in young cells that are still growing. 7hin wall that is airly *exible.

• 4djacent cells are held together by a -idd&e &$-e&&$ that is a

thin layer o polysaccharides called pectins. 7his middle lamellaglues cells together.

• Sec%d$"# ce&& ,$&& 5 produced when the cell stops growingand the cell deposits several layers o durable matrix :ormswood;.

!igure ".#2

). $xtracellular @atrix o 4nimal ells

http://www.youtube.com/watch?v=6hJ_i_-K--k

http://www.youtube.com/watch?v=7pR7TNzJ_pA

http://www.youtube.com/watch?v=6hJ_i_-K--k

http://www.youtube.com/watch?v=7pR7TNzJ_pA



• 4 networ" o glycoproteins that are excreted by the cells. 7ypeso glycoproteins8

o C&&$+e% 5 orms strong fbers outside the cells.o 2i0"%ec'i% 5 they attach to i%'e+"i%s :receptor proteins

in the plasmamembrane; and this complex will transmit

changes between the inside and outside o the cell. Jiththese interactions integrins and fbronectins regulate thecell9s behavior.

!igure ".#3

<. 7$/$--E-4/ KE7CA8• eighboring cells oten interact and communicate with each

other through special patches o direct physical contact.• >lants have *&$s-des-$'$ 5 thin channels o cytoplasm

between the cell walls. 7his continuous channel o cytoplasm

unifes the plant into one living organism. Jater and smallmolecules are able to pass through plasmodesmata reely, buteven some specifc proteins and /4 can also move through bymoving along fbers o the cytos"eleton.

• 4nimal cells have 'i+h' >(%c'i%s4 des-s-es $%d +$*

>(%c'i%s:o Ti+h' >(%c'i%s – specifc proteins tightly press the cell

membranes o neighboring cells togethero Des-s-es – intermediate "eratin flaments anchor

these rivers o cytoplasm togethero

G$* >(%c'i%s – pores orm by special proteins that allowvarious ions, sugars, amino acids and other smallmolecules pass through the cell membrane. 7hese poresare important in cell communication.

!igure ".41

4>7$/ ' 5 @$@)/4$ A7/E7E/$ 4D =E7CC)K$76$ LE$A7CA

Me-0"$%e S'"(c'("e1. $xplain why phospholipids are amphipathic molecules.2. Describe the *uidity o the components o a cell membrane and

explain how membrane *uidity is in*uenced by temperature andmembrane composition.



3. $xplain how cholesterol resists changes in membrane *uiditywith temperature change.

T"$?c Ac"ss Me-0"$%es:!. Distinguish between peripheral and integral membrane proteins.

#. -ist six major unctions o membrane proteins.&. $xplain the role o membrane carbohydrates in cell?cellrecognition.

'. $xplain how hydrophobic molecules cross cell membranes.(. Distinguish between channel proteins and carrier proteins.+. Defne diusion. $xplain why diusion is a spontaneous process.1. $xplain why a concentration gradient o a substance across

a membrane represents potential energy.11. Distinguish among hypertonic, hypotonic and isotonic

solutions.12. Defne osmosis and predict the direction o water

movement based on dierences in solute concentrations.13. Describe how living cells with and without cell walls

regulate water balance.1!. $xplain how transport proteins acilitate diusion.1#. Distinguish among osmosis, acilitated diusion, and active

transport.1&. Describe the two orces that combine to produce an

electrochemical gradient.1'. $xplain how an electrogenic pump creates voltage across a

membrane1(. Describe the process o cotransport.

1+. $xplain how large molecules are transported across a cellmembrane.

2. Distinguish between pinocytosis and receptor?mediatedendocytosis.

. C6$/6$J• 7he plasma membrane is the outer boundary o the cell that

separates the cell rom its nonliving environment. t controlstraIc into and out o the cell.

• t is se-i*e"-e$0&e so it allows some substances to crosseasily while does not allow others. Jith this ability, the cellmembrane creates a dierent environment inside the cell thanoutside.

. 7$ A7/E7E/$ C= 7$ $-- @$@)/4$8• 7he cell membrane is made up o phospholipids, proteins,

carbohydrates and sterols.



• )ecause phospholipids and many proteins are $-*hi*$'hic-&ec(&es :have both hydrophobic and hydrophilic areas; theyorm the main body o the cell membrane. 7he @(id -s$ic-de& describes the arrangement o phospholipids and proteinsin the cell membrane.

• 7he main body o the membrane is ormed by the hydrophobicattractions between the nonpolar parts o the phospholipidsmolecules that orm a double layer. Jithin this semi*uid doublelipid layer the protein molecules are imbedded by their similarhydrophobic attractions and are able to move sideways in it. t ishowever, very rare that the proteins move rom one layer to thenext.

4. >hospholipids• 7he phospholipids molecules can also move sideways rapidly and

can also *ip?*op rom one layer to the next but less reuently. 7he *uidity o the membrane depends on the temperature :thehigher the temperature the more *uid the membrane;, thenumber o unsaturated atty acids in the chain :the moreunsaturated atty acids the phospholipids have the more *uid themembrane is; and the concentration o cholesterol molecules :onmoderate temperatures, cholesterol ma"es the membrane less*uid, but on lower temperatures it slows down the solidifcationo the membrane;.



• 7he membrane has to be liuid to unction properly because itspermeability changes and en%ymes in the membrane becomeinactive. 7here are many animal adaptations that ma"e themresistant to low temperatures :higher unsaturated at andcholesterol concentrations;.



). @embrane >roteins• @embrane proteins are embedded in the *uid matrix. 7hese

proteins determine the membrane9s specifc unctions. 7here aretwo major types o proteins in the cell membrane8

o I%'e+"$& *"'ei%s – penetrate the hydrophobic part o themembrane completely and reach across the entiremembrane. 7hese proteins contain long stretches ononpolar amino acids to be able to ft into the nonpolarphospholipid layer. 7he outer edges o these proteins arehydrophilic so they can ft into the aueous environment o the cell.

o Pe"i*he"$& *"'ei%s – they are appendages that are onlyloosely bound to the surace o the cell membrane. Cn the

cytoplasmic side they may be held in place by thecytos"eleton, while on the outside o the cell membranethey are attached to fbers o the extracellular matrix.



• @embrane proteins have & major unctions8o T"$%s*"' *"'ei%s 5 provide hydrophilic channels or

ions or molecules to pass through or actively change shapeto shuttle a substance.

o E%#-$'ic $c'i!i'# 5 in some cases en%ymes areorgani%ed into a team that will cataly%e an entire metabolicpathway.

o Si+%$& '"$%sd(c'i% – 7he protein has abinding site that fts specifc messengermolecules and causes changes inside thecell.

o Ce&&ce&& "ec+%i'i% – glycoproteins that act asidentiying tags or the cell

o I%'e"ce&&(&$" >i%i%+ – @ay hoo" various cells together atintercellular junctions

o A''$ch-e%'s ) 'he c#'s/e&e'% $%d e='"$ce&&(&$"-$'"i= – anchoring proteins help to maintain the cell9sshape or stabili%e the location o the cell

. arbohydrates8• 7hese are usually short, branched chains o carbohydrates :1# or

ewer monosaccharides;



• Aome o the carbohydrates are covalently bonded to lipids,orming +&#c&i*ids, most are covalently bonded to proteinsorming +&#c*"'ei%s

• arbohydrates are responsible or tagging the cell. 7hese tagsare important or cell recognition, the proper speciali%ation o the

cell and or. the proper carbohydrate identifcation tags are notavailable on the surace o the cell, the immune system destroysthe cell.

• 7hese mar"ers vary rom organism to organism and rom speciesto species.

D. holesterol• holesterol provides rigidity to animal cell membranes. >lant cell

membranes usually do not contain cholesterol, because theyhave their cell wall

• http8MMwww.wiley.comMcollegeMprattM!'13+3('(MstudentManimationsMmembraneNtransportMindex.html

$. Aynthesis and Aidedness o @embranes8• 7he cell membrane has distinct inside and outside surace due to

a dierent lipid composition and the directional orientation o themembrane proteins.

• 6esicles use into the plasma membrane and their contents arereleased into the outside.

• 7he process o synthesi%ing, modiying and releasing plasmaproteins8

1. ribosomes ma"e polypeptides o the membraneproteins on the surace o the rough $/

2. >hospholipids are synthesi%ed and membraneproteins are modifed in the rough $/. @embraneproteins reuently get a carbohydrate chain andbecome glycoproteins.

3. 6esicles transport these proteins and phospholipidsinto the 0olgi apparatus

!. nside the 0olgi apparatus glycoproteins are urthermodifed and the lipids can gain carbohydrates andbecome glycolipids.

#. 4ll proteins and lipids are transported to the plasmamembrane in vesicles

&. 6esicles use with the membrane to releasesecretory proteins and to attach membraneglycoproteins and glycolipids to the cell membrane

http://www.wiley.com/college/pratt/0471393878/student/animations/membrane_transport/index.html






. 7$ A$@>$/@$4)-$ @$@)/4$• 4 steady traIc o small molecules and ions moves across the

plasma membrane in both directions. owever, these moleculesand ions move at a dierent rate.

• Augars, amino acids, nutrients and oxygen enter the cell, wasteproducts leave the cell. 6arious ion concentrations are alsoregulated by the cell membrane.

• 7he cell membrane is se-i*e"-e$0&e 5 because it acts as abarrier between the environment and the inside o the cell.

• ydrophobic molecules such as hydrocarbons, oxygen, and

carbon dioxide can easily cross the lipid bilayer without the aid o membrane proteins.

• >olar molecules cannot pass reely through the membrane.Augars, water and some other small polar molecules movethrough the membrane very slowly.

• 7he cell membrane is permeable to a variety o polar moleculeswith the help o '"$%s*"' *"'ei%s :orm a hydrophilicchannel;. =or example water molecules move through transport



proteins called $($*"i%s. Cther proteins are c$""ie"*"'ei%s that change shape and shuttles molecules across themembrane :ex. 0lucose carriers;.

6. >4AA6$ 7/4A>C/7•

P$ssi!e '"$%s*"' 5 the movement o substances across abiological membrane without a need rom the cell to expelenergy. 7he energy or the transport is ueled by potentialenergy rom the concentration gradient across the cellmembrane. During passive transport, particles move romhigher to lower concentration area.

• Di(si% 5 7he spreading out o molecules due to thermalmotion. 4lthough the movement o molecules may be random,the sum o the movement is directional rom the higher to thelower cc. area or down the c%ce%'"$'i% +"$die%'.

• mportant substance that moves by diusion through the cell

membrane is oxygen.



• Os-sis 5 the movement o water molecules across aselectively permeable membrane when the dissolved substancesare not allowed across the membrane. Csmosis moves waterdown the concentration gradient.



Diusion8Jatch the animation onhttp8MMbcs.whreeman.comMtheliewireMcontentMchp#M#21.htmlCsmosis8Jatch the animation on osmosis8http8MMwww.stola.eduMpeopleMgianniniM*ashanimatMtransportMosmosis.sw

•

Jhen considering the behavior o a cell in a solution, both thesolute concentration and the membrane permeability must beconsidered. T%ici'#, the ability o a solution to cause a cell togain or lose water, depends on both o the actors above.

• 4ccording to tonicity, solutions can be three "inds8o Is'%ic 5 a solution to a cell i the net water movement

across the plasma membrane is %ero

http://bcs.whfreeman.com/thelifewire/content/chp05/0502001.html

http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf







o H#*e"'%ic ?? a solution to the cell i the cell loses waterwhen inserted into this solution. n this solution the cellloses water, than shrivels and dies.

o H#*'%ic 5 a solution i the cell gains water rom thesolution, swells and bursts.

• 4nimal cells without rigid cells walls cannot tolerate variousenvironmental concentrations, unless they have variousadaptations to regulate their water concentration9s-"e+(&$'i%;. $x. ontractile vacuole o Paramecium.

• >lant cells have cell walls to prevent the bursting o the cell inhypotonic solutions. owever, they are not protected againstwater loss and the plant cell can also shrivel :*&$-s&#sis;.

• 2$ci&i'$'ed di(si% 5 7he transport o ions or polar

molecules across the cell membrane with the help o transportproteins. 7hese transport proteins are very specifc andtransport only certain molecules. =acilitated diusion can bedone with both carrier proteins and channel proteins.

• $xamples o channel proteins are i% ch$%%e&s or +$'edch$%%e&s 5 only opened by a certain stimulus. $x.eurotransmitters open gated sodium channels o theconnecting nerve cells to orward a nerve stimulus.



ompleting transport processes=acilitated diusion8 -oo" at the animations onhttp8MMbcs.whreeman.comMtheliewireMcontentMchp#M#21.html 4ctive transport8 Jatch the animation on

http8MMbcs.whreeman.comMtheliewireMcontentMchp#M#22.html$ndocytosis8 Jatch the animation onhttp8MMbcs.whreeman.comMtheliewire(eMcontentMcatN1M#!3.html

6. 476$ 7/4A>C/7• Ac'i!e '"$%s*"' 5 pumps molecules across the cell membrane

against the concentration gradient by using cellular energy in the

orm o 47>.• 4ctive transport mostly uses carrier proteins and not ion

channels.• 4ctive transport enables cells to maintain internal concentrations

o small molecules that dier rom the concentrations o theenvironment. :$x. igher G?ion concentration inside the cell thanoutside, but higher a?ion concentration outside the cell thaninside;.

• 47> uels active transport by attaching >i directly to the carrierproteins. 7he attached phosphate causes conormation changein the protein and moves attached ions or molecules across themembrane. $x. Sdi(-*'$ssi(- *(-*:



http://bcs.whfreeman.com/thelifewire8e/content/cat_010/0504003.html








• 4ll cells have !&'$+es :potential energy caused by separationo opposite charges; across the cell membrane. 7his voltageacross the membrane is called -e-0"$%e *'e%'i$& :it isnegative inside the cytoplasm compared to the environment;. 7his membrane potential avors the transport o positive ionsinto the cytoplasm by diusion and the transport o anions out o the cell. 7he combination o the two orces :chemical rom ionconcentration and electrical rom the dierence in charges; iscalled e&ec'"che-ic$& +"$die%' will determine the movemento ions.

• 4 transport protein that generates voltage across the cellmembrane is called an e&ec'"+e%ic *(-* :ex. >roton pumps;.



• C'"$%s*"' 5 the coupling o the OdownhillP diusion o onesubstance with the OuphillP diusion o an other substanceagainst its own concentration gradient. :ex. >lants9 couple protonpump with the transport o glucose or other substances;8

6. )E-G 7/4A>C/78• B(&/ '"$%s*"' 5 transport o larger particles across the cell

membrane by using vesicles.• E=c#'sis 5 usion o vesicles with the plasma membrane and

releasing various substances rom the cell into the environment:hormones, neurotransmitters, proteins, carbohydrates;.

• E%dc#'sis 5 the cell ta"es in macromolecules by ormingvesicles o the plasma membrane :moving cholesterol into the

cell;• 7hree main types o endocytosis are8

o Ph$+c#'sis

o Pi%c#'sis

o Rece*'"-edi$'ed e%dc#'sis



Documents

AP Biology Outline on Cell Unit