Cell Structure and Function.pptx

8/20/2019 Cell Structure and Function.pptx

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Cell structure andfunctionDoreen Alexis F VillanuevaIntroduction to Physiology


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Outline

• Introduction

• Membranes• Membrane Structure

• Membrane unctions

• Cell Organelles• !ucleus

• "ibosomes

• #ndo$lasmic "eticulum

• %olgi A$$aratus

• #ndosomes• Mitochondria

• &ysosomes

• Peroxisomes

• Cytos'eleton


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Outline

• Introduction• Membranes

• Membrane Structure



• "ibosomes


• %olgi A$$aratus


• &ysosomes

• Peroxisomes

• Cytos'eleton


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CellsSmallest living unit

Most are microsco$ic


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Characteristics of All Cells

• A surrounding membrane

• Proto$lasm ( cell contents in thic' )uid

• Organelles ( structures for cell function

• Control center *ith D!A


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+o* big is the cell,


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Cell -y$es

• Pro'aryotic

• #u'aryotic


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Pro'aryotic Cells

• First cell ty$e on earth

• Cell ty$e of .acteria and Archaea


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Pro'aryotic Cells

• !o membrane bound nucleus

• !ucleoid / region of D!A concentration

• Organelles not bound by membranes


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"e$resentative AnimalCell


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-he interior of a cell is divided into t*o regions1234 the nucleus, a s$herical or oval structureusually near the center of the cell0 and 254 the

cytoplasm, the region outside the nucleus


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-he interior of a cell is divided into t*o regions1234 the nucleus, a s$herical or oval structureusually near the center of the cell0 and 254 the

cytoplasm, the region outside the nucleus


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-he cyto$lasm contains t*o com$onents1 234 cellorganelles and 254 the )uid surrounding theorganelles 'no*n as the cytosol 2cyto$lasmic

solution46


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-he term intracellular fuid refers to all the )uid insidea cell7in other *ords0 cytosol $lus the )uid inside all theorganelles0 including the nucleus6 -he chemicalcom$ositions of the )uids in these cell organelles di8er

from that of the cytosol6 -he cytosol is by far the largestintracellular )uid com artment6


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Outline

• Introduction




• "ibosomes


• %olgi A$$aratus


• &ysosomes

• Peroxisomes

• Cytos'eleton


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Membranes

Membranes form a ma9or structural element incells6 Although membranes $erform a variety offunctions0 their most universal role is to act as aselective barrier to the $assage of molecules0

allo*ing some molecules to cross *hile excludingothers6


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-he Plasma Membrane

• -he $lasma membrane regulates the $assage ofsubstances into and out of the cell0 *hereas themembranes surrounding cell organelles allo*selective movement of substances bet*een the

organelles and the cytosol6• One of the ad: vantages of restricting the

movements of molecules across membranes iscon;ning the $roducts of chem: ical reactions tos$eci;c cell organelles6


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-he $lasma membrane0 in addition to acting as aselective barrier0 $lays an im$ortant role indetecting chemical signals from other cells and in

anchoring cells to ad9acent cells and to theextracellular matrix of connective:tissue $roteins


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Outline

• Introduction

• Membranes• Membrane Structure• Membrane unctions


• "ibosomes


• %olgi A$$aratus

• #ndosomes

• Mitochondria

• &ysosomes

• Peroxisomes

• Cytos'eleton


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Membrane Structure• All membranes consist of a double layer of li$id

molecules in *hich $roteins are embedded


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-he ma9or membrane li$ids are phospholipids.these are am$hi$athic molecules1 one end has acharged region0 and the remainder of the molecule0

*hich consists of t*o long fatty acid chains0 isnon$olar6


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Lipid Bilayer

Phospholipid

Phosphatidylcholine

Phosphatidylserine

Phosphatidylethanolamine

Phosphatidylinositol

Cholesterol

Sphingolipid


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Cholesterol

• -he $lasma membrane also contains cholesterol2about one molecule of cholesterol for eachmolecule of $hos$holi$id40 *hereas intracellularmembranes contain very little cholesterol6

Cholesterol0 a steroid0 is slightly am$hi$athicbecause of a single $olar hydroxyl grou$ on itsnon$olar ring structure6


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Membrane proteinsIntegral (intrinsic) proteins

Peripheral (extrinsic) proteins

Integral

protein Peripheral

protein


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• -here are t*o classes of membrane $roteins1integral and $eri$heral6 Integral membraneproteins are closely associated *ith themembrane li$ids and can: not be extracted from

the membrane *ithout disru$ting the li$id bilayer6• &i'e the $hos$holi$ids0 the integral $roteins are

am$hi$athic0 having $olar amino acid side chainsin one region of the molecule and non$o: lar sidechains clustered together in a se$arate region6


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.ecause they are am$hi$athic0 integral $roteins

are arranged in the membrane *ith the sameorientation as am$hi$athic li$ids7the $olarregions are at the surfaces in association *ith$olar *ater molecules0 andthe non$olar regions are in the interior in

association *ith non$olar fatty acid chains


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-ransmembrane $roteins

• Most integral$roteins s$anthe entiremembrane and

are referred toastransmembrane proteins.

• -hese

transmembrane$roteins crossthe li$id bilayerseveral times


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• -hese $roteins have $olar regions connected bynon$olar segments that associate *ith thenon$olar regions of the li$ids in the membraneinterior6

• -he $olar regions of transmembrane $roteinsmay extend far beyond the surfaces of the li$idbilayer6 Some transmembrane $roteins formchannels through *hich ions or *ater can crossthe membrane0 *hereas others are associated

*ith the transmission of chemical signals acrossthe membrane or the anchoring of extracellularand intracellular $rotein ;laments to the $lasmamembrane6


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Peri$heral MembraneProteinsPeripheral membrane proteins are notam$hi$athic and do not associate *ith the non$olarregions of the li$ids in the interior of themembrane6 -hey are located at the membrane

surface *here they are bound to the $olar regionsof the integral membrane $roteins

• Most of the $eri$heral $roteins are on thecytosolic surface of the $lasma membrane *herethey are associated *ith cytos'eletal elements

that in)uence cell sha$e and motility6


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Structure of cell membrane

!luid Mosaic Model (Singer " #icholson$ %&')


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Outline

• Introduction


• Membrane unctions• Cell Organelles

• !ucleus

• "ibosomes


• %olgi A$$aratus

• #ndosomes

• Mitochondria

• &ysosomes

• Peroxisomes

• Cytos'eleton


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) *

+ Ma,or !unctions -f Membrane

Proteins1. Transport. (left . protein that spans the membrane

may pro/ide a hydrophilic channel across the

membrane that is selecti/e for a particular solute0

(right -ther transport proteins shuttle a substance

from one side to the other by changing shape0 Some of

these proteins hydroly1e .2P as an energy ssource to

acti/ely pump substances across the membrane

!. "n#ymatic acti$ity. . protein built into the membrane

may be an en1yme 3ith its acti/e site exposed to

substances in the ad,acent solution0 In some cases$

se/eral en1ymes in a membrane are organi1ed as a

team that carries out se4uential steps of a metabolic

path3ay0

0 %ignal transduction. . membrane protein may ha/e a

binding site 3ith a specific shape that fits the shape of a

chemical messenger$ such as a hormone0 2he external

messenger (signal) may cause a conformational change

in the protein (receptor) that relays the message to the

inside of the cell0

.2P

5n1ymes

Signal

6eceptor


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) &

&ell-cell recognition. Some glyco7proteins ser/e as

identification tags that are specifically recogni1ed

by other cells0

Intercellular 'oining. Membrane proteins of ad,acent cells

may hoo8 together in /arious 8inds of ,unctions$ such asgap ,unctions or tight ,unctions

ttachment to the cytos)eleton and e*tracellular matri*

("&+. Microfilaments or other elements of the

cytos8eleton may be bonded to membrane proteins$

a function that helps maintain cell shape and stabili1es

the location of certain membrane proteins0 Proteins that

adhere to the 5CM can coordinate extracellular and

intracellular changes

.

.

.

9lyco7

protein

Cell Adhesion


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Cell Adhesion

%ycocalyx

:vecro:li'e ogliosaccharides that

bind and hold to other cells

-ight unctions

: seal


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Membrane Junctions

• Gap Junctions- These spaces allowchemicals,ions to pass through thereby allowingcell to cell communication. CONNEXONS are thetubes which are seen between gap junctions.

• Desmosomes !nchoring junctions" pre#ent cells$rom being pulle% apart.

• Tight Junctions- &mpermeable Junctions. 'hile

cells are boun% together they are lea(proo$ at these junctions.

l b


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)lasma Membrane

Speciali*ations• Membrane junctions

• Tight junctions

• +esmosomes

• ap junctions

Figure 3.3


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Desmosomes consist ofa regionbet*een t*oad9acentcells *herethe a$$osed$lasma

membranesarese$arated byabout 5= nmand have a

denseaccumulation of $roteinat thecyto$lasmic

surface of


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Tight Junctionis formed *hen the extracellular surfaces of t*oad9acent $lasma membranes are 9oined togetherso that there is no extracellular s$ace bet*een

them6 x


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gap unction

consists of $rotein channels lin'ing the cytosols of ad9acent cells

In the region of the ga$ 9unction0 the t*o o$$osing $lasma membranescome *ithin 5 to > nm of each other0 *hich allo*s s$eci;c $roteins fromthe t*o membranes to 9oin0 forming small0 $rotein: lined channels lin'ing

the t*o cells6

C ll : ti


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Cell :unctions

• Long7lasting or permanent connections bet3eenad,acent cells$ types of cell ,unctions

2ight ,unctions pre/ent

fluid from mo/ing

across a layer of cells

2ight ,unction

;0< =m

% =m

Space

bet3een

cellsPlasma membranes

of ad,acent cells

5xtracellular

matrix

9ap ,unction

Tight 'unctions

;0% =m

Intermediate

filamentsDesmosome

/ap

'unctions

.t tight 'unctions$ the membranes of

neighboring cells are /ery tightly pressed

against each other$ bound together by

specific proteins (purple)0 !orming continu7

ous seals around the cells$ tight ,unctions

pre/ent lea8age of extracellular fluid across

. layer of epithelial cells0

Desmosomes (also called anchoring

junctions) function li8e ri/ets$ fastening cells

2ogether into strong sheets0 Intermediate

!ilaments made of sturdy 8eratin proteins

.nchor desmosomes in the cytoplasm0

/ap 'unctions (also called communicating

junctions) pro/ide cytoplasmic channels from

one cell to an ad,acent cell0 9ap ,unctions

consist of special membrane proteins that

surround a pore through 3hich ions$ sugars$

amino acids$ and other small molecules may

pass0 9ap ,unctions are necessary for commu7

nication bet3een cells in many types of tissues$

including heart muscle and animal embryos0

2I9>2 :?#C2I-#S

@5SM-S-M5S

9.P :?#C2I-#S


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Outline

• Introduction




• "ibosomes


• %olgi A$$aratus


• &ysosomes

• Peroxisomes

• Cytos'eleton


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!tructure o"#nimal Cells

Cell Video


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Outline

• Introduction

• Membranes



• Cell Organelles• !ucleus• "ibosomes


• %olgi A$$aratus


• &ysosomes

• Peroxisomes

• Cytos'eleton


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Outline

• Introduction

• Membranes



• Cell Organelles• !ucleus• "ibosomes


• %olgi A$$aratus


• &ysosomes

• Peroxisomes

• Cytos'eleton

The 0ucleus nd The 0uclear "n$elope


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#ucleus

#ucleus#ucleolusChromatin

#uclear en/elopeInner membrane-uter membrane

#uclear pore

6ough 56

Pore

complex

%urface of nuclear

en$elope.

Pore comple*es (T"+. 0uclear lamina (T"+.

&lose-up of

nuclear

en$elope

6ibosome

% =m

% =m

;0< =m

The 0ucleus nd The 0uclear "n$elope

• 6epository for genetic material called chromatin - @#. and proteins• Nucleolus: holds chromatin and ribosomal subunits 7 region of intensi/e

ribosomal 6#. synthesis• Nuclear envelope Surface of nucleus bound by t3o phospholipid bilayer

membranes 7 @ouble membrane 3ith pores• Nucleoplasm semifluid medium inside the nucleus


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Cell $rganelles

• %ucleus

!ic'name1A -he Control Center

Function1 holds the D!AParts1

!ucleolus1 dar' s$ot in the middle of thenucleus that hel$s ma'e ribosomes

Chromatin1 loosely coiled D!A 2cells not dividing4t*o ty$es ( hetero?? (dar'

: eu?? : light


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Chromosomes• @#. of eu8aryotes is di/ided into linear chromosomes0• 5xist as strands of chromatin$ except during cell di/ision

• >istones associated pac8aging proteins


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•Mitochondria –Double membrane –Mitochondrial 2maternal4 D!A0 – re$licates inde$endently from the cell

APo*er +ouse of the cell• Food converted into energy

–Adenosine tri$hos$hate 2A-P4

• Consumes Oxygen0 $roduces CO5

+itochondria


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+itochondria• Sites of cellular respiration$ .2P synthesis

• Bound by a double membrane surrounding fluid7filled matrix0

• 2he inner membranes of mitochondria are cristae• 2he matrix contains en1ymes that brea8 do3n carbohydrates and

the cristae house protein complexes that produce .2P


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5ndomembrane System• Compartmentali1es cell$ channeling passage of molecules

through cells interior0• 5ndoplasmic reticulum• 6ough 56 7 studded 3ith ribosomes

• Smooth 56 7 fe3 ribosomes


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6ough 56

• 6ough 56 is especially abundant in cells that secrete proteins0

• .s a polypeptide is synthesi1ed on a ribosome attached to

rough 56$ it is threaded into the cisternal space through a

pore formed by a protein complex in the 56 membrane0

• .s it enters the cisternal space$ the ne3 protein folds into its

nati/e conformation0• Most secretory polypeptides are glycoproteins, proteins to

3hich a carbohydrate is attached0

• Secretory proteins are pac8aged in transport $esicles that

carry them to their next stage0


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6ough 56• 6ough 56 is also a membrane factory0

• Membrane7bound proteins are synthesi1ed directly into the

membrane0

• 5n1ymes in the rough 56 also synthesi1e phospholipids from

precursors in the cytosol0

• .s the 56 membrane expands$ membrane can be transferred

as transport /esicles to other components of theendomembrane system0


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Smooth 56

• 2he smooth 56 is rich in en1ymes and plays a role in a/ariety of metabolic processes0

• 5n1ymes of smooth 56 synthesi1e lipids$ including oils$

phospholipids$ and steroids0

• 2hese include the sex hormones of /ertebrates and adrenal

steroids0• In the smooth 56 of the li/er$ en1ymes help detoxify poisons

and drugs such as alcohol and barbiturates0

• Smooth 56 stores calcium ions0

• Muscle cells ha/e a speciali1ed smooth 56 that

pumps calcium ions from the cytosol and storesthem in its cisternal space0

• Dhen a ner/e impulse stimulates a muscle cell$

calcium ions rush from the 56 into the cytosol$

triggering contraction0


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"ibosomes-sites of $rotein synthesis6

-not membrane:bound

- consists of a small and larger subunit0

- consists of ribosomal "!A 2r"!A4 and some @=

structural $roteins6

-.ound ribsosomes ma'e $roteins for ex$ort0 non:boundribosomes ma'e $roteins for internal use

-

Most $lentiful organelle in the cell

6ibosomes

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossR.html%23ribosomal%20RNAhttp://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossR.html%23ribosomal%20RNA


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6ibosomes• 6ibosomes are 6#.7protein complexes composed of t3o

subunits that ,oin and attach to messenger 6#.0• Site of protein synthesis

• .ssembled in nucleoli

566ibosomes Cytosol

!ree ribosomes

Bound ribosomes

Largesubunit

Small

subunit

T"+ showing "R and ribosomes Diagram of a ribosome

;0< =m

5ndoplasmic reticulum (56)

&ysosomes1


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&ysosomes1

circular0 but bigger than ribosomes!ic'name1 AClean:u$ Cre*s

Function1 to brea' do*n food into $articles the rest of thecell can use and to destroy old cells

Intracellular digestion

"eleases nutrients

.rea'do*n of *aste


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%olgi Com$lex


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'essicles• Peroxisomes

• +ydrogen Peroxide generated and degraded todetoxify the cell

• Vessicles• Material trans$ort

•Vacuole7 stores *ater

• Plastids7 &euco$lasts0 a'a amylo$lasts store starch0 $rotein or

oils67 Chromo$lasts store bright color $igments

Microtubules


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–&arge0 hollo* tubes of tubulin$rotein1

attach to centrosomestrengthen cell and anchor organelles

change cell sha$e

move vesicles *ithin cell 2'inesin and

dynein4form s$indle a$$aratus

Form cilia and )agella

C i l i h


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Centrioles forms$indle

a$$aratus duringcell division

Centrosome1

cyto$lasmsurroundingcentriole

Centrioles in the

Centrosome


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Membrane Bound -rganelles

• Lysosomes E /esiclecontaining digesti/een1ymes that brea8 do3nfoodFforeign particles

• Gacuoles E food storageand 3ater regulation

• Peroxisomes 7 containen1ymes that cataly1e the

remo/al of electrons andassociated hydrogenatoms

(a Phagocytosis lysosome digesting food

% =m

Lysosome contains

acti/e hydrolytic

en1ymes

!ood /acuole

fuses 3ith

lysosome

>ydrolytic

en1ymes digest

food particles

@igestion

!ood /acuole

Plasma membrane

Lysosome

@igesti/e

en1ymes

Lysosome

#ucleus

C t 8 l t


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Cytos8eleton• 2he eu8aryotic cytos8eleton is a net3or8 of

filaments and tubules that extends from thenucleus to the plasma membrane that supportcell shape and anchor organelles0

• Protein fibers

• .ctin filaments

• cell mo/ement

• Intermediate filaments• Microtubules

• centrioles

&entrioles


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&entrioles

• Centrioles are shortcylinders 3ith a & H ;

pattern of microtubule

triplets0

• Centrioles may bein/ol/ed in microtubule

formation and

disassembly during cell

di/ision and in theorgani1ation of cilia and

flagella0

Cilia and !lagella


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Cilia and !lagella• Contain speciali1ed arrangements of microtubules• .re locomotor appendages of some cells• Cilia and flagella share a common ultrastructure

(a

(c

(b

-uter microtubule

doublet

@ynein arms

Central

microtubule

-uter doubletscross7lin8ing

proteins inside

6adial

spo8e

Plasma

membrane

Microtubules

Plasma

membrane

Basal body

;0< =m

;0% =m

;0% =m

Cross section of basal body

2riplet

2he 9olgi apparatus


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2he 9olgi apparatus• The Golgi apparatus is the shipping and receiving center for cell

products.•

Many transport /esicles from the 56 tra/el to the /olgi apparatus formodification of their contents0• 2he 9olgi is a center of manufacturing$ 3arehousing$ sorting$ and

shipping0• 2he 9olgi apparatus consists of flattened membranous sacscisternae

loo8ing li8e a stac8 of pita bread0• 2he 9olgi sorts and pac8ages materials into transport /esicles0


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!unctions -f 2he 9olgi .pparatus

25M of 9olgi apparatus

cis face(Arecei/ing side of

9olgi apparatus)

Gesicles mo/e

from 56 to 9olgi Gesicles alsotransport certain

proteins bac8 to 56

Gesicles coalesce to

form ne3 cis 9olgi cisternae

Cisternal

maturation

9olgi cisternae

mo/e in a cis7

to7trans

direction

Gesicles form andlea/e 9olgi$ carrying

specific proteins to

other locations or to

the plasma mem7

brane for secretion Gesicles transport specific

proteins bac83ard to ne3er

9olgi cisternae

Cisternae

trans face

(Ashipping side of

9olgi apparatus)

;0% ; =m1

!

2

9olgi

apparatus


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&ilia and 3lagella• Cilia (small and numerous) and flagella (large and single)

ha/e a & H pattern of microtubules and are in/ol/ed incell mo/ement0• Cilia and flagella mo/e 3hen the microtubule doublets

slide past one another0• 5ach cilium and flagellum has a basal body at its base0


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(a +otion of flagella. . flagellum

usually undulates$ its sna8eli8e

motion dri/ing a cell in the same

direction as the axis of the

flagellum0 Propulsion of a human

sperm cell is an example of

flagellatelocomotion (LM)0

% =m

@irection of s3imming

Cilia and !lagella

(b +otion of cilia. Cilia ha/e a bac87

and7forth motion that mo/es the

cell in a direction perpendicular

to the axis of the cilium0 . dense

nap of cilia$ beating at a rate of

about J; to +; stro8es a second$

co/ers this Colpidium, a

fresh3ater proto1oan (S5M)0

Cell Structure and Function.pptx

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