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Lecture BIOD 5: Eukaryotic Cell Structure &Function

- The cell is the basic unit of life.

- Based on their cellular structures, all living cells can be divided into 2 groups:

prokaryoticand eukaryotic.

- Only bacteriahave prokaryoticcell types.

- Animals, plants, fungi, protozoans, and algae all possess eukaryoticcell types.

- Fungi, protozoans, an algaeare Eukaryoticmicroorganisms.

-These microorganisms are very comple and prominent members of the ecosystem.

- !ungi "# some algae$ are useful in industrial microbiology.- %any fungi and protozoa are ma&or human pathogens' e.g. %alaria and African

sleeping sic(ness.

- )ro(aryotic cells are generally much smaller and more simple than eu(aryotic.

- )ro(aryotic cells are, in fact, able to be structurally more simple because of theirsmall size.

- *n the first part of this section, the focus is on the structure and function of the

eu(aryotic cell.

- At the end of the section, pro(aryotic and eucaryotic cells +ill be compared.

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Candida albicans

O!er!ie" o# Eucaryotic Cell Structure:

- The most obvious difference bet+een )ro. # uc. *s their use of membranes.

- ucaryotic cells have membrane-delimited nuclei, and have a variety of comple

membranous organellesin the cytoplasmic matri' "organellesare intracellular

structures that perform specific functions in cells$.

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Cytoplas$ic %atri:

- arge part of it is +ater "/0-13$.

- The 4environment5 of the organelles, and

location of important biochemical

processes.- 6ell is not 7&ust a bag in a bubble7. ots of

internal #ibers8 internal 4s(eleton5'

capable of being assembled, bro(en do+n in

minutes' involved in cell movement, shape

changes # division.- !ibers include $icro#ila$ents,

$icrotubules "e..g. form 6ilia and !lagella$

and Inter$eiate #ila$ents'

- Cell (allsalso, provide a rigid structure

around cells. %ade of cellulose in the case

of plants and fungi.

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Enoplas$ic )eticulu$ *E)+:

E)is a maze of parallel membranous tubules and

flattened sacs surrounding the nucleus that connects

+ith the nuclear membrane and runs throughout the

cytoplasm.- 9 provides a surface area for protein and lipid

synthesis'

- forms a path+ay for transporting molecules +ithi

n

the cell' and

- provides a storage area for molecules the cell has

synthesized.

- There are t+o distinct regions of the 9: the roug-

E)and the s$oot- E).

- 9 +ith riboso$es attac-eis called roug- E)

and is involved in protein synt-esis, prouction

o# ne" $e$brane, $oi#ication o# ne"ly #or$e

proteins, an transport o# t-ese proteins an

$e$brane to ot-er locations "it-in t-e cell.

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- 9 "it-out riboso$esis called s$oot-

E)and contains enzymes for lipi

biosynt-esis, especially the synthesis of

phospholipids and steroids.The smoothendoplasmic reticulum formstransition

!esicles to trans#er $olecules prouce in

t-e roug- E) to t-e .olgi apparatusan

ot-er parts o# t-e cell

.olgi /pparatus:

- The olgi apparatus "A$ consists of ;-20 flattened and stac(ed

sacli(e structures called cisternae. A comple net+or( of tubules

and !esiclesis located at the edges of the cisternae.

A sorts proteins and lipids received from the 9'

- modifies certain proteins and glycoproteins' and

- sorts and pac(ages these molecules into vesicles for transport to

other parts of the cell or secretion from the cell.

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Lysoso$es an Enocytosis:

- Lysoso$es, synthesized by the E)and the ./, are membrane-enclosed spheres

typically about 00 nm in diameter that contain po+erful igesti!e enzy$es.

- They function to igest materials that enter byenocytosis'

-

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%itoc-onria:

- %itochondria are rod-shaped structures ranging from 2 to

1 nm in length.

- !ound throughout the cytoplasm' up to 203 of the cell=s

volume.- %itochondria are surroune by t"o $e$branes.

- They have their o+n A and ribosomes

- !re?uently called the 4po+erhouses5 of the cell

- They are the centers forrespiratory catabolis$, during +hich oygen is combined

+ith chemicals to brea( do+n foods, and generate cell energy.

C-loroplasts:

- 6hloroplasts are dis(-shaped structures ranging from to

@0 m in length.

- i(e mitochondria, chloroplasts are surrounded by aninner and an outer membrane.

- 6ontain stac(s of t-ylakois, +here green pigmented

chlorophyll is embedded in membrane to trap lig-t.

- se lig-t energyto convert COand "aterto carbo-yratesand O, that is6-otosynt-esis.

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0ucleus: - is a membrane-delimited spherical body

filled +ith dense fibrous material called

c-ro$atin.

- A is organized as multiple chromosomes

located +ithin a nucleus.

- The nucleus is separated from the

cytoplasm by a nuclear $e$brane'

- The nuclear membrane has porest-at

connect "it- t-e E)'

- 0ucleolus is the most noticeable structure +ithin the nucleus, +here riboso$al

subunitsare assembled.

- The nucleus divides by $itosis, a process that ensures each daughter cell receives the

same number of chromosomes as the original parent cell.

- aploid se cellsare produced from diploid cells by $eiosis,

%eiosisis the nuclear division that occurs as a part of seual reproduction +herein

the daughter cell receives the haploid number of chromosomes.

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Flagella an Cilia:

- !lagella are long and fe+ in number

+hereas cilia are short and numerous.

- Both consist of 7 #use pairs o# protein

$icrotubules +ith side arms of the motormolecule dynein that originate from a

centriole.

- These #or$ a ring aroun an inner central pair of microtubules that arise from a

plate near the cell surface.

- !lagella and cilia function in loco$otion. 6ilia also function to move various material

that may surround a cell.

6rokaryotic *6+8s Eu9aryotic *E+ Cells:

- ): nuclear body is called nucleoid not bound by membrane' : bound by membrane

called nucleus.

- ): one circular chromosome composed of A Chistone-li(e proteins' : @ or more

paired linear chromosomes composed of A C histone proteins.

- ): no nucleolus' : nucleolus present.

- ): divide by binary fission' : divide by mitosis "diploid$ # se cells produced bymeiosis.

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- ): cytoplasmic membrane "6%$ is a fluid phospholipid bilayer +ithout carbohydrates,

contains sterol-li(e molecules called hopanoids, incapable of endocytosis # eocytosis.

- : 6% is a fluid phosphate bilayer, containing sterols # carbohydrates, capable of

endocytosis # eocytosis.

- ): 9ibosomes 0D # ;0D' : 9ibosomes E0D # F0D- ): %itochondria, 9, A, Gacuoles, ysosomes, chloroplasts are absent. >o

cytos(eleton.

- ): cell +alls composed of peptidoglycan' : 6H composed of cellulose or 6hitin.

- ): no cilia, flagella is composed of single rotating fibril' : flagella # cilia involved in

locomotion, consist of a distinct arrangement of sliding microtubules.

)epresentati!e organis$s:

- ): Bacteria "ubacteria # Archaebacteria$

- : Algae, )rotozoans, and !ungi. And of course Animals and )lants.